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Summer Training Project Report On Phased Array Radar Study And Modelling Submitted to: Submitted by: Pranav Kumar Ankita Singh Scientist ‘C’ Roll no. 110207 ISSA, DRDO, Delhi B.Tech- 7 th Semester 1 | Page
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DRDO Presentation

Dec 27, 2015

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IT is summer training report at DRDO which was performed for 6 weeks at Civil Lines, New Delhi. It helps to understand the basic principle of Antenna & its arrays.. It also helps to analyse the basic principle of Electronics & Communication Engineering..
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Transcript
Page 1: DRDO Presentation

Summer Training Project Report

On

Phased Array Radar Study And Modelling

Submitted to Submitted by

Pranav Kumar Ankita Singh

Scientist lsquoCrsquo Roll no 110207

ISSA DRDO Delhi BTech- 7th Semester

2014

1 | P a g e

Acknowledgement

Through this acknowledgment I express my sincere gratitude to all

those people who have been associated with this project and have

helped me with it and made it a worthwhile experience

Firstly I extend my thanks to the various people who have shared

their opinions and experiences through which I received the required

information crucial for our report

I am highly indebted to Mr Pranav Kumar (Scientist lsquoCrsquo) our project

guide and his team for their guidance and constant supervision as

well as for providing necessary information regarding the project amp

also for their support in completing the project

My thanks and appreciations also go to my colleagues in developing

the project and people who have willingly helped me out with their

abilities

Finally I express my thanks to A Kumar who guided me and gave me

valuable suggestions regarding the project environment

2 | P a g e

ABSTRACT

The technologies keep generating new ways of improving on the performance of the old systems Array antennas one of the continuously improving technologies brought many benefits to our life The superiorities of array antennas remove the disadvantages of the old technology radars such as great sidelobes vulnerability to the jammers and degradation effect of the clutter Array antennas find many applications on different areas

If the radiating elements of the array are excited by the relatively phased currents the array is called a phased array The main beam of these types of arrays can scan the desired field continuously Phased arrays are particularly used in radars but are gaining wider use in communications applications

A single phased array can serve several systems This feature of phased arrays removes the need for individual antennas for each system and reduces the RCS arising from the extensions on the ship mast and structure Radars can search the airspace and then track the desired targets in order to extract the azimuth elevation course and speed information from the movement of the targets It enables the operator to predict where the target will be next

The search radars detect the target via their wide beamwidth and once the target is designated the tracking radar which could be another mode of the same radar system tracks the target with its narrow beamwidth (ie pencil beam) of the tracking antenna

Phased array radars can track many targets on a time-shared basis with a higher data rate than the types of tracking radar The purpose of this research is to track the target through Phased Array Radar

3 | P a g e

C O N T E N T S

1 INTRODUCTION 11 ISSA 812 Antenna array 1013 Radar Fundamentals 14

2 PROJECT DESCRIPTION

21 Phased Array Radar 18

22 Multifunction Radar 18 23 Bandwidth of Phased Array Radar 19

24 Tracking Errors 22

3 FUNCTIONALITY

31 Tracking Techniques 27

32 Determining the design parameters 30

33 GUI in matlab 34

4 CONCLUSION AND REFERENCES 41 Conclusion 36

42 Future Scope for Modification 37

43 ReferencesBibliography 38

4 | P a g e

LIST OF FIGURES

Figure No Description

1 Array of two point source

2 The sum and difference patterns of array

antenna

3 Basic principle of RADAR

4 Centre Fed Series Feed

5 Sequential Lobing

6 Conical Scanning

7 Geometry of multi-path tracking

8 Element spacing vs scan angle

9 Gain vs number of element

5 | P a g e

LIST OF TABLES

Table No Description

1 Parameters for use in computing the

directivity of uniform current amplitude

LIST OF ABBREVIATIONS

Abbreviation Description

MB MegabyteRAM Random Access MemoryEM Electro Magnetic

6 | P a g e

CHAPTER 1

INTRODUCTION

11 Introduction about the Company

12 Antenna Array

13 Radar Fundamentals

7 | P a g e

CHAPTER 1 INTRODUCTION

11 Introduction about the Company

Defence Research amp Development Organisation (DRDO) works under

Department of Defence Research and Development of Ministry of

Defence DRDO dedicatedly working towards enhancing self-reliance

in Defence Systems and undertakes design amp development leading to

production of world class weapon systems and equipment in

accordance with the expressed needs and the qualitative

requirements laid down by the three services

DRDO is working in various areas of military technology which

include aeronautics armaments combat vehicles electronics

instrumentation engineering systems missiles materials naval

systems advanced computing simulation and life sciences DRDO

while striving to meet the Cutting edge weapons technology

requirements provides ample spinoff benefits to the society at large

thereby contributing to the nation building

DRDO has various RampD labs working on different technologies The

lab under which I am working is Institute for Systems Studies amp

Analyses (ISSA)

8 | P a g e

ISSA specializes in systems analysis modeling amp simulation of

defense systems using state-of-the-art info-technologies such as

Computer Networking Software Engineering Distributed Database

Distributed Simulation Web Technologies Situational Awareness

and Soft-Computing techniques in development of complex

simulation products

Its activities include

Evolution and evaluation of strategic and tactical plans

Threat analysis Force mix studies and Strategic decision

making

Design trade-off and performance evaluation of systems

Cost-effectiveness analysis Weapon selection and acquisition

Development of computer war games for teaching amp training

Integrated software for mission planning tactical training and

operational planning

Development of software as decision aid with Military GIS

System reliability studies

Vision

Transform ISSA into centre of excellence in system analysis

modelling amp simulation of defence systems to meet the challenges of

the present and future requirements of the armed forces

Mission

Conduct system study and develop high quality integrated software

for system analysis amp decision support in application areas of Sensors

9 | P a g e

amp Weapons Electronic Combat Land amp Naval Combat Air-to-Air

Combat and Air Defence for effective use by DRDO and Services for

Design

Mission Planning Tactics development and Training

12 ANTENNA ARRAYS

A single-element antenna is usually not enough to achieve technical needs That happens because its performance is limited A set of discrete elements which constitute an antenna array offers the solution to the transmission andor reception of electromagnetic energy The geometry and the type of elements characterize an antenna array For simplicity implementation and fabrication reasons the elements are chosen in such a way so as to be identical and parallel For the same reasons uniformly spaced linear arrays are mostly encountered in practice In the following paragraphs the properties of various antenna arrays will be presented

An array consisting of identical and identically oriented elements

A uniform linear array is one in which elements are fed with equal magnitude of current and with equal phase shift along the line

VARIOUS TYPES OF ANTENNA ARRAY

1 Broadside ArrayIn this a number of identical parallel antennas are set up along a line drawn perpendicular to their respective axes Each element is fed with equal magnitude all in the same phase

2 End Fire ArrayEnd fire is nothing but broadside array except that individual elements are fed in out of phase (usually 180) Thus in the end fire array a number of identical antennas are spaced equally along a line and individual elements are fed with current of equal magnitude and their phases varies progressively

3 Collinear Array

10 | P a g e

In collinear array the antennas are arranged co-axially that is antennas are mounted end to end in a single line In other words one antenna is stacked over other antenna

4 Parasitic ArrayParasitic element is not fed directly instead a parasitic element derives power by the radiation from nearby driven element Array with a number of parasitic elements is called ldquoParasitic Arrayrdquo

Figure 1- Array of two point source

To distant point lsquoPrsquo

11 | P a g e

theta

d

Path difference = dcos(theta)lamda

Phase angle = 2piPath differenceΨ

= dcos(theta)Ψ βE = E1e-j 2Ψ + E2e+j 2Ψ

E = 2E0( dcos(theta)2)β1 Equal amplitude and same phaseE = cos(π2cosθ) Maxima is at θ=90270hellipMinima is at θ=0360hellip2 Equal amplitude and opposite phaseE = sin(π 2cos θ)Maxima is at θ=0360hellipMinima is at θ=90270hellip3 Unequal amplitude and any phase In this amplitude transmitted by point sources is different and they have phase difference

ARRAY OF lsquonlsquo POINT SOURCES

12 | P a g e

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 2: DRDO Presentation

Acknowledgement

Through this acknowledgment I express my sincere gratitude to all

those people who have been associated with this project and have

helped me with it and made it a worthwhile experience

Firstly I extend my thanks to the various people who have shared

their opinions and experiences through which I received the required

information crucial for our report

I am highly indebted to Mr Pranav Kumar (Scientist lsquoCrsquo) our project

guide and his team for their guidance and constant supervision as

well as for providing necessary information regarding the project amp

also for their support in completing the project

My thanks and appreciations also go to my colleagues in developing

the project and people who have willingly helped me out with their

abilities

Finally I express my thanks to A Kumar who guided me and gave me

valuable suggestions regarding the project environment

2 | P a g e

ABSTRACT

The technologies keep generating new ways of improving on the performance of the old systems Array antennas one of the continuously improving technologies brought many benefits to our life The superiorities of array antennas remove the disadvantages of the old technology radars such as great sidelobes vulnerability to the jammers and degradation effect of the clutter Array antennas find many applications on different areas

If the radiating elements of the array are excited by the relatively phased currents the array is called a phased array The main beam of these types of arrays can scan the desired field continuously Phased arrays are particularly used in radars but are gaining wider use in communications applications

A single phased array can serve several systems This feature of phased arrays removes the need for individual antennas for each system and reduces the RCS arising from the extensions on the ship mast and structure Radars can search the airspace and then track the desired targets in order to extract the azimuth elevation course and speed information from the movement of the targets It enables the operator to predict where the target will be next

The search radars detect the target via their wide beamwidth and once the target is designated the tracking radar which could be another mode of the same radar system tracks the target with its narrow beamwidth (ie pencil beam) of the tracking antenna

Phased array radars can track many targets on a time-shared basis with a higher data rate than the types of tracking radar The purpose of this research is to track the target through Phased Array Radar

3 | P a g e

C O N T E N T S

1 INTRODUCTION 11 ISSA 812 Antenna array 1013 Radar Fundamentals 14

2 PROJECT DESCRIPTION

21 Phased Array Radar 18

22 Multifunction Radar 18 23 Bandwidth of Phased Array Radar 19

24 Tracking Errors 22

3 FUNCTIONALITY

31 Tracking Techniques 27

32 Determining the design parameters 30

33 GUI in matlab 34

4 CONCLUSION AND REFERENCES 41 Conclusion 36

42 Future Scope for Modification 37

43 ReferencesBibliography 38

4 | P a g e

LIST OF FIGURES

Figure No Description

1 Array of two point source

2 The sum and difference patterns of array

antenna

3 Basic principle of RADAR

4 Centre Fed Series Feed

5 Sequential Lobing

6 Conical Scanning

7 Geometry of multi-path tracking

8 Element spacing vs scan angle

9 Gain vs number of element

5 | P a g e

LIST OF TABLES

Table No Description

1 Parameters for use in computing the

directivity of uniform current amplitude

LIST OF ABBREVIATIONS

Abbreviation Description

MB MegabyteRAM Random Access MemoryEM Electro Magnetic

6 | P a g e

CHAPTER 1

INTRODUCTION

11 Introduction about the Company

12 Antenna Array

13 Radar Fundamentals

7 | P a g e

CHAPTER 1 INTRODUCTION

11 Introduction about the Company

Defence Research amp Development Organisation (DRDO) works under

Department of Defence Research and Development of Ministry of

Defence DRDO dedicatedly working towards enhancing self-reliance

in Defence Systems and undertakes design amp development leading to

production of world class weapon systems and equipment in

accordance with the expressed needs and the qualitative

requirements laid down by the three services

DRDO is working in various areas of military technology which

include aeronautics armaments combat vehicles electronics

instrumentation engineering systems missiles materials naval

systems advanced computing simulation and life sciences DRDO

while striving to meet the Cutting edge weapons technology

requirements provides ample spinoff benefits to the society at large

thereby contributing to the nation building

DRDO has various RampD labs working on different technologies The

lab under which I am working is Institute for Systems Studies amp

Analyses (ISSA)

8 | P a g e

ISSA specializes in systems analysis modeling amp simulation of

defense systems using state-of-the-art info-technologies such as

Computer Networking Software Engineering Distributed Database

Distributed Simulation Web Technologies Situational Awareness

and Soft-Computing techniques in development of complex

simulation products

Its activities include

Evolution and evaluation of strategic and tactical plans

Threat analysis Force mix studies and Strategic decision

making

Design trade-off and performance evaluation of systems

Cost-effectiveness analysis Weapon selection and acquisition

Development of computer war games for teaching amp training

Integrated software for mission planning tactical training and

operational planning

Development of software as decision aid with Military GIS

System reliability studies

Vision

Transform ISSA into centre of excellence in system analysis

modelling amp simulation of defence systems to meet the challenges of

the present and future requirements of the armed forces

Mission

Conduct system study and develop high quality integrated software

for system analysis amp decision support in application areas of Sensors

9 | P a g e

amp Weapons Electronic Combat Land amp Naval Combat Air-to-Air

Combat and Air Defence for effective use by DRDO and Services for

Design

Mission Planning Tactics development and Training

12 ANTENNA ARRAYS

A single-element antenna is usually not enough to achieve technical needs That happens because its performance is limited A set of discrete elements which constitute an antenna array offers the solution to the transmission andor reception of electromagnetic energy The geometry and the type of elements characterize an antenna array For simplicity implementation and fabrication reasons the elements are chosen in such a way so as to be identical and parallel For the same reasons uniformly spaced linear arrays are mostly encountered in practice In the following paragraphs the properties of various antenna arrays will be presented

An array consisting of identical and identically oriented elements

A uniform linear array is one in which elements are fed with equal magnitude of current and with equal phase shift along the line

VARIOUS TYPES OF ANTENNA ARRAY

1 Broadside ArrayIn this a number of identical parallel antennas are set up along a line drawn perpendicular to their respective axes Each element is fed with equal magnitude all in the same phase

2 End Fire ArrayEnd fire is nothing but broadside array except that individual elements are fed in out of phase (usually 180) Thus in the end fire array a number of identical antennas are spaced equally along a line and individual elements are fed with current of equal magnitude and their phases varies progressively

3 Collinear Array

10 | P a g e

In collinear array the antennas are arranged co-axially that is antennas are mounted end to end in a single line In other words one antenna is stacked over other antenna

4 Parasitic ArrayParasitic element is not fed directly instead a parasitic element derives power by the radiation from nearby driven element Array with a number of parasitic elements is called ldquoParasitic Arrayrdquo

Figure 1- Array of two point source

To distant point lsquoPrsquo

11 | P a g e

theta

d

Path difference = dcos(theta)lamda

Phase angle = 2piPath differenceΨ

= dcos(theta)Ψ βE = E1e-j 2Ψ + E2e+j 2Ψ

E = 2E0( dcos(theta)2)β1 Equal amplitude and same phaseE = cos(π2cosθ) Maxima is at θ=90270hellipMinima is at θ=0360hellip2 Equal amplitude and opposite phaseE = sin(π 2cos θ)Maxima is at θ=0360hellipMinima is at θ=90270hellip3 Unequal amplitude and any phase In this amplitude transmitted by point sources is different and they have phase difference

ARRAY OF lsquonlsquo POINT SOURCES

12 | P a g e

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 3: DRDO Presentation

ABSTRACT

The technologies keep generating new ways of improving on the performance of the old systems Array antennas one of the continuously improving technologies brought many benefits to our life The superiorities of array antennas remove the disadvantages of the old technology radars such as great sidelobes vulnerability to the jammers and degradation effect of the clutter Array antennas find many applications on different areas

If the radiating elements of the array are excited by the relatively phased currents the array is called a phased array The main beam of these types of arrays can scan the desired field continuously Phased arrays are particularly used in radars but are gaining wider use in communications applications

A single phased array can serve several systems This feature of phased arrays removes the need for individual antennas for each system and reduces the RCS arising from the extensions on the ship mast and structure Radars can search the airspace and then track the desired targets in order to extract the azimuth elevation course and speed information from the movement of the targets It enables the operator to predict where the target will be next

The search radars detect the target via their wide beamwidth and once the target is designated the tracking radar which could be another mode of the same radar system tracks the target with its narrow beamwidth (ie pencil beam) of the tracking antenna

Phased array radars can track many targets on a time-shared basis with a higher data rate than the types of tracking radar The purpose of this research is to track the target through Phased Array Radar

3 | P a g e

C O N T E N T S

1 INTRODUCTION 11 ISSA 812 Antenna array 1013 Radar Fundamentals 14

2 PROJECT DESCRIPTION

21 Phased Array Radar 18

22 Multifunction Radar 18 23 Bandwidth of Phased Array Radar 19

24 Tracking Errors 22

3 FUNCTIONALITY

31 Tracking Techniques 27

32 Determining the design parameters 30

33 GUI in matlab 34

4 CONCLUSION AND REFERENCES 41 Conclusion 36

42 Future Scope for Modification 37

43 ReferencesBibliography 38

4 | P a g e

LIST OF FIGURES

Figure No Description

1 Array of two point source

2 The sum and difference patterns of array

antenna

3 Basic principle of RADAR

4 Centre Fed Series Feed

5 Sequential Lobing

6 Conical Scanning

7 Geometry of multi-path tracking

8 Element spacing vs scan angle

9 Gain vs number of element

5 | P a g e

LIST OF TABLES

Table No Description

1 Parameters for use in computing the

directivity of uniform current amplitude

LIST OF ABBREVIATIONS

Abbreviation Description

MB MegabyteRAM Random Access MemoryEM Electro Magnetic

6 | P a g e

CHAPTER 1

INTRODUCTION

11 Introduction about the Company

12 Antenna Array

13 Radar Fundamentals

7 | P a g e

CHAPTER 1 INTRODUCTION

11 Introduction about the Company

Defence Research amp Development Organisation (DRDO) works under

Department of Defence Research and Development of Ministry of

Defence DRDO dedicatedly working towards enhancing self-reliance

in Defence Systems and undertakes design amp development leading to

production of world class weapon systems and equipment in

accordance with the expressed needs and the qualitative

requirements laid down by the three services

DRDO is working in various areas of military technology which

include aeronautics armaments combat vehicles electronics

instrumentation engineering systems missiles materials naval

systems advanced computing simulation and life sciences DRDO

while striving to meet the Cutting edge weapons technology

requirements provides ample spinoff benefits to the society at large

thereby contributing to the nation building

DRDO has various RampD labs working on different technologies The

lab under which I am working is Institute for Systems Studies amp

Analyses (ISSA)

8 | P a g e

ISSA specializes in systems analysis modeling amp simulation of

defense systems using state-of-the-art info-technologies such as

Computer Networking Software Engineering Distributed Database

Distributed Simulation Web Technologies Situational Awareness

and Soft-Computing techniques in development of complex

simulation products

Its activities include

Evolution and evaluation of strategic and tactical plans

Threat analysis Force mix studies and Strategic decision

making

Design trade-off and performance evaluation of systems

Cost-effectiveness analysis Weapon selection and acquisition

Development of computer war games for teaching amp training

Integrated software for mission planning tactical training and

operational planning

Development of software as decision aid with Military GIS

System reliability studies

Vision

Transform ISSA into centre of excellence in system analysis

modelling amp simulation of defence systems to meet the challenges of

the present and future requirements of the armed forces

Mission

Conduct system study and develop high quality integrated software

for system analysis amp decision support in application areas of Sensors

9 | P a g e

amp Weapons Electronic Combat Land amp Naval Combat Air-to-Air

Combat and Air Defence for effective use by DRDO and Services for

Design

Mission Planning Tactics development and Training

12 ANTENNA ARRAYS

A single-element antenna is usually not enough to achieve technical needs That happens because its performance is limited A set of discrete elements which constitute an antenna array offers the solution to the transmission andor reception of electromagnetic energy The geometry and the type of elements characterize an antenna array For simplicity implementation and fabrication reasons the elements are chosen in such a way so as to be identical and parallel For the same reasons uniformly spaced linear arrays are mostly encountered in practice In the following paragraphs the properties of various antenna arrays will be presented

An array consisting of identical and identically oriented elements

A uniform linear array is one in which elements are fed with equal magnitude of current and with equal phase shift along the line

VARIOUS TYPES OF ANTENNA ARRAY

1 Broadside ArrayIn this a number of identical parallel antennas are set up along a line drawn perpendicular to their respective axes Each element is fed with equal magnitude all in the same phase

2 End Fire ArrayEnd fire is nothing but broadside array except that individual elements are fed in out of phase (usually 180) Thus in the end fire array a number of identical antennas are spaced equally along a line and individual elements are fed with current of equal magnitude and their phases varies progressively

3 Collinear Array

10 | P a g e

In collinear array the antennas are arranged co-axially that is antennas are mounted end to end in a single line In other words one antenna is stacked over other antenna

4 Parasitic ArrayParasitic element is not fed directly instead a parasitic element derives power by the radiation from nearby driven element Array with a number of parasitic elements is called ldquoParasitic Arrayrdquo

Figure 1- Array of two point source

To distant point lsquoPrsquo

11 | P a g e

theta

d

Path difference = dcos(theta)lamda

Phase angle = 2piPath differenceΨ

= dcos(theta)Ψ βE = E1e-j 2Ψ + E2e+j 2Ψ

E = 2E0( dcos(theta)2)β1 Equal amplitude and same phaseE = cos(π2cosθ) Maxima is at θ=90270hellipMinima is at θ=0360hellip2 Equal amplitude and opposite phaseE = sin(π 2cos θ)Maxima is at θ=0360hellipMinima is at θ=90270hellip3 Unequal amplitude and any phase In this amplitude transmitted by point sources is different and they have phase difference

ARRAY OF lsquonlsquo POINT SOURCES

12 | P a g e

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 4: DRDO Presentation

C O N T E N T S

1 INTRODUCTION 11 ISSA 812 Antenna array 1013 Radar Fundamentals 14

2 PROJECT DESCRIPTION

21 Phased Array Radar 18

22 Multifunction Radar 18 23 Bandwidth of Phased Array Radar 19

24 Tracking Errors 22

3 FUNCTIONALITY

31 Tracking Techniques 27

32 Determining the design parameters 30

33 GUI in matlab 34

4 CONCLUSION AND REFERENCES 41 Conclusion 36

42 Future Scope for Modification 37

43 ReferencesBibliography 38

4 | P a g e

LIST OF FIGURES

Figure No Description

1 Array of two point source

2 The sum and difference patterns of array

antenna

3 Basic principle of RADAR

4 Centre Fed Series Feed

5 Sequential Lobing

6 Conical Scanning

7 Geometry of multi-path tracking

8 Element spacing vs scan angle

9 Gain vs number of element

5 | P a g e

LIST OF TABLES

Table No Description

1 Parameters for use in computing the

directivity of uniform current amplitude

LIST OF ABBREVIATIONS

Abbreviation Description

MB MegabyteRAM Random Access MemoryEM Electro Magnetic

6 | P a g e

CHAPTER 1

INTRODUCTION

11 Introduction about the Company

12 Antenna Array

13 Radar Fundamentals

7 | P a g e

CHAPTER 1 INTRODUCTION

11 Introduction about the Company

Defence Research amp Development Organisation (DRDO) works under

Department of Defence Research and Development of Ministry of

Defence DRDO dedicatedly working towards enhancing self-reliance

in Defence Systems and undertakes design amp development leading to

production of world class weapon systems and equipment in

accordance with the expressed needs and the qualitative

requirements laid down by the three services

DRDO is working in various areas of military technology which

include aeronautics armaments combat vehicles electronics

instrumentation engineering systems missiles materials naval

systems advanced computing simulation and life sciences DRDO

while striving to meet the Cutting edge weapons technology

requirements provides ample spinoff benefits to the society at large

thereby contributing to the nation building

DRDO has various RampD labs working on different technologies The

lab under which I am working is Institute for Systems Studies amp

Analyses (ISSA)

8 | P a g e

ISSA specializes in systems analysis modeling amp simulation of

defense systems using state-of-the-art info-technologies such as

Computer Networking Software Engineering Distributed Database

Distributed Simulation Web Technologies Situational Awareness

and Soft-Computing techniques in development of complex

simulation products

Its activities include

Evolution and evaluation of strategic and tactical plans

Threat analysis Force mix studies and Strategic decision

making

Design trade-off and performance evaluation of systems

Cost-effectiveness analysis Weapon selection and acquisition

Development of computer war games for teaching amp training

Integrated software for mission planning tactical training and

operational planning

Development of software as decision aid with Military GIS

System reliability studies

Vision

Transform ISSA into centre of excellence in system analysis

modelling amp simulation of defence systems to meet the challenges of

the present and future requirements of the armed forces

Mission

Conduct system study and develop high quality integrated software

for system analysis amp decision support in application areas of Sensors

9 | P a g e

amp Weapons Electronic Combat Land amp Naval Combat Air-to-Air

Combat and Air Defence for effective use by DRDO and Services for

Design

Mission Planning Tactics development and Training

12 ANTENNA ARRAYS

A single-element antenna is usually not enough to achieve technical needs That happens because its performance is limited A set of discrete elements which constitute an antenna array offers the solution to the transmission andor reception of electromagnetic energy The geometry and the type of elements characterize an antenna array For simplicity implementation and fabrication reasons the elements are chosen in such a way so as to be identical and parallel For the same reasons uniformly spaced linear arrays are mostly encountered in practice In the following paragraphs the properties of various antenna arrays will be presented

An array consisting of identical and identically oriented elements

A uniform linear array is one in which elements are fed with equal magnitude of current and with equal phase shift along the line

VARIOUS TYPES OF ANTENNA ARRAY

1 Broadside ArrayIn this a number of identical parallel antennas are set up along a line drawn perpendicular to their respective axes Each element is fed with equal magnitude all in the same phase

2 End Fire ArrayEnd fire is nothing but broadside array except that individual elements are fed in out of phase (usually 180) Thus in the end fire array a number of identical antennas are spaced equally along a line and individual elements are fed with current of equal magnitude and their phases varies progressively

3 Collinear Array

10 | P a g e

In collinear array the antennas are arranged co-axially that is antennas are mounted end to end in a single line In other words one antenna is stacked over other antenna

4 Parasitic ArrayParasitic element is not fed directly instead a parasitic element derives power by the radiation from nearby driven element Array with a number of parasitic elements is called ldquoParasitic Arrayrdquo

Figure 1- Array of two point source

To distant point lsquoPrsquo

11 | P a g e

theta

d

Path difference = dcos(theta)lamda

Phase angle = 2piPath differenceΨ

= dcos(theta)Ψ βE = E1e-j 2Ψ + E2e+j 2Ψ

E = 2E0( dcos(theta)2)β1 Equal amplitude and same phaseE = cos(π2cosθ) Maxima is at θ=90270hellipMinima is at θ=0360hellip2 Equal amplitude and opposite phaseE = sin(π 2cos θ)Maxima is at θ=0360hellipMinima is at θ=90270hellip3 Unequal amplitude and any phase In this amplitude transmitted by point sources is different and they have phase difference

ARRAY OF lsquonlsquo POINT SOURCES

12 | P a g e

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 5: DRDO Presentation

LIST OF FIGURES

Figure No Description

1 Array of two point source

2 The sum and difference patterns of array

antenna

3 Basic principle of RADAR

4 Centre Fed Series Feed

5 Sequential Lobing

6 Conical Scanning

7 Geometry of multi-path tracking

8 Element spacing vs scan angle

9 Gain vs number of element

5 | P a g e

LIST OF TABLES

Table No Description

1 Parameters for use in computing the

directivity of uniform current amplitude

LIST OF ABBREVIATIONS

Abbreviation Description

MB MegabyteRAM Random Access MemoryEM Electro Magnetic

6 | P a g e

CHAPTER 1

INTRODUCTION

11 Introduction about the Company

12 Antenna Array

13 Radar Fundamentals

7 | P a g e

CHAPTER 1 INTRODUCTION

11 Introduction about the Company

Defence Research amp Development Organisation (DRDO) works under

Department of Defence Research and Development of Ministry of

Defence DRDO dedicatedly working towards enhancing self-reliance

in Defence Systems and undertakes design amp development leading to

production of world class weapon systems and equipment in

accordance with the expressed needs and the qualitative

requirements laid down by the three services

DRDO is working in various areas of military technology which

include aeronautics armaments combat vehicles electronics

instrumentation engineering systems missiles materials naval

systems advanced computing simulation and life sciences DRDO

while striving to meet the Cutting edge weapons technology

requirements provides ample spinoff benefits to the society at large

thereby contributing to the nation building

DRDO has various RampD labs working on different technologies The

lab under which I am working is Institute for Systems Studies amp

Analyses (ISSA)

8 | P a g e

ISSA specializes in systems analysis modeling amp simulation of

defense systems using state-of-the-art info-technologies such as

Computer Networking Software Engineering Distributed Database

Distributed Simulation Web Technologies Situational Awareness

and Soft-Computing techniques in development of complex

simulation products

Its activities include

Evolution and evaluation of strategic and tactical plans

Threat analysis Force mix studies and Strategic decision

making

Design trade-off and performance evaluation of systems

Cost-effectiveness analysis Weapon selection and acquisition

Development of computer war games for teaching amp training

Integrated software for mission planning tactical training and

operational planning

Development of software as decision aid with Military GIS

System reliability studies

Vision

Transform ISSA into centre of excellence in system analysis

modelling amp simulation of defence systems to meet the challenges of

the present and future requirements of the armed forces

Mission

Conduct system study and develop high quality integrated software

for system analysis amp decision support in application areas of Sensors

9 | P a g e

amp Weapons Electronic Combat Land amp Naval Combat Air-to-Air

Combat and Air Defence for effective use by DRDO and Services for

Design

Mission Planning Tactics development and Training

12 ANTENNA ARRAYS

A single-element antenna is usually not enough to achieve technical needs That happens because its performance is limited A set of discrete elements which constitute an antenna array offers the solution to the transmission andor reception of electromagnetic energy The geometry and the type of elements characterize an antenna array For simplicity implementation and fabrication reasons the elements are chosen in such a way so as to be identical and parallel For the same reasons uniformly spaced linear arrays are mostly encountered in practice In the following paragraphs the properties of various antenna arrays will be presented

An array consisting of identical and identically oriented elements

A uniform linear array is one in which elements are fed with equal magnitude of current and with equal phase shift along the line

VARIOUS TYPES OF ANTENNA ARRAY

1 Broadside ArrayIn this a number of identical parallel antennas are set up along a line drawn perpendicular to their respective axes Each element is fed with equal magnitude all in the same phase

2 End Fire ArrayEnd fire is nothing but broadside array except that individual elements are fed in out of phase (usually 180) Thus in the end fire array a number of identical antennas are spaced equally along a line and individual elements are fed with current of equal magnitude and their phases varies progressively

3 Collinear Array

10 | P a g e

In collinear array the antennas are arranged co-axially that is antennas are mounted end to end in a single line In other words one antenna is stacked over other antenna

4 Parasitic ArrayParasitic element is not fed directly instead a parasitic element derives power by the radiation from nearby driven element Array with a number of parasitic elements is called ldquoParasitic Arrayrdquo

Figure 1- Array of two point source

To distant point lsquoPrsquo

11 | P a g e

theta

d

Path difference = dcos(theta)lamda

Phase angle = 2piPath differenceΨ

= dcos(theta)Ψ βE = E1e-j 2Ψ + E2e+j 2Ψ

E = 2E0( dcos(theta)2)β1 Equal amplitude and same phaseE = cos(π2cosθ) Maxima is at θ=90270hellipMinima is at θ=0360hellip2 Equal amplitude and opposite phaseE = sin(π 2cos θ)Maxima is at θ=0360hellipMinima is at θ=90270hellip3 Unequal amplitude and any phase In this amplitude transmitted by point sources is different and they have phase difference

ARRAY OF lsquonlsquo POINT SOURCES

12 | P a g e

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 6: DRDO Presentation

LIST OF TABLES

Table No Description

1 Parameters for use in computing the

directivity of uniform current amplitude

LIST OF ABBREVIATIONS

Abbreviation Description

MB MegabyteRAM Random Access MemoryEM Electro Magnetic

6 | P a g e

CHAPTER 1

INTRODUCTION

11 Introduction about the Company

12 Antenna Array

13 Radar Fundamentals

7 | P a g e

CHAPTER 1 INTRODUCTION

11 Introduction about the Company

Defence Research amp Development Organisation (DRDO) works under

Department of Defence Research and Development of Ministry of

Defence DRDO dedicatedly working towards enhancing self-reliance

in Defence Systems and undertakes design amp development leading to

production of world class weapon systems and equipment in

accordance with the expressed needs and the qualitative

requirements laid down by the three services

DRDO is working in various areas of military technology which

include aeronautics armaments combat vehicles electronics

instrumentation engineering systems missiles materials naval

systems advanced computing simulation and life sciences DRDO

while striving to meet the Cutting edge weapons technology

requirements provides ample spinoff benefits to the society at large

thereby contributing to the nation building

DRDO has various RampD labs working on different technologies The

lab under which I am working is Institute for Systems Studies amp

Analyses (ISSA)

8 | P a g e

ISSA specializes in systems analysis modeling amp simulation of

defense systems using state-of-the-art info-technologies such as

Computer Networking Software Engineering Distributed Database

Distributed Simulation Web Technologies Situational Awareness

and Soft-Computing techniques in development of complex

simulation products

Its activities include

Evolution and evaluation of strategic and tactical plans

Threat analysis Force mix studies and Strategic decision

making

Design trade-off and performance evaluation of systems

Cost-effectiveness analysis Weapon selection and acquisition

Development of computer war games for teaching amp training

Integrated software for mission planning tactical training and

operational planning

Development of software as decision aid with Military GIS

System reliability studies

Vision

Transform ISSA into centre of excellence in system analysis

modelling amp simulation of defence systems to meet the challenges of

the present and future requirements of the armed forces

Mission

Conduct system study and develop high quality integrated software

for system analysis amp decision support in application areas of Sensors

9 | P a g e

amp Weapons Electronic Combat Land amp Naval Combat Air-to-Air

Combat and Air Defence for effective use by DRDO and Services for

Design

Mission Planning Tactics development and Training

12 ANTENNA ARRAYS

A single-element antenna is usually not enough to achieve technical needs That happens because its performance is limited A set of discrete elements which constitute an antenna array offers the solution to the transmission andor reception of electromagnetic energy The geometry and the type of elements characterize an antenna array For simplicity implementation and fabrication reasons the elements are chosen in such a way so as to be identical and parallel For the same reasons uniformly spaced linear arrays are mostly encountered in practice In the following paragraphs the properties of various antenna arrays will be presented

An array consisting of identical and identically oriented elements

A uniform linear array is one in which elements are fed with equal magnitude of current and with equal phase shift along the line

VARIOUS TYPES OF ANTENNA ARRAY

1 Broadside ArrayIn this a number of identical parallel antennas are set up along a line drawn perpendicular to their respective axes Each element is fed with equal magnitude all in the same phase

2 End Fire ArrayEnd fire is nothing but broadside array except that individual elements are fed in out of phase (usually 180) Thus in the end fire array a number of identical antennas are spaced equally along a line and individual elements are fed with current of equal magnitude and their phases varies progressively

3 Collinear Array

10 | P a g e

In collinear array the antennas are arranged co-axially that is antennas are mounted end to end in a single line In other words one antenna is stacked over other antenna

4 Parasitic ArrayParasitic element is not fed directly instead a parasitic element derives power by the radiation from nearby driven element Array with a number of parasitic elements is called ldquoParasitic Arrayrdquo

Figure 1- Array of two point source

To distant point lsquoPrsquo

11 | P a g e

theta

d

Path difference = dcos(theta)lamda

Phase angle = 2piPath differenceΨ

= dcos(theta)Ψ βE = E1e-j 2Ψ + E2e+j 2Ψ

E = 2E0( dcos(theta)2)β1 Equal amplitude and same phaseE = cos(π2cosθ) Maxima is at θ=90270hellipMinima is at θ=0360hellip2 Equal amplitude and opposite phaseE = sin(π 2cos θ)Maxima is at θ=0360hellipMinima is at θ=90270hellip3 Unequal amplitude and any phase In this amplitude transmitted by point sources is different and they have phase difference

ARRAY OF lsquonlsquo POINT SOURCES

12 | P a g e

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 7: DRDO Presentation

CHAPTER 1

INTRODUCTION

11 Introduction about the Company

12 Antenna Array

13 Radar Fundamentals

7 | P a g e

CHAPTER 1 INTRODUCTION

11 Introduction about the Company

Defence Research amp Development Organisation (DRDO) works under

Department of Defence Research and Development of Ministry of

Defence DRDO dedicatedly working towards enhancing self-reliance

in Defence Systems and undertakes design amp development leading to

production of world class weapon systems and equipment in

accordance with the expressed needs and the qualitative

requirements laid down by the three services

DRDO is working in various areas of military technology which

include aeronautics armaments combat vehicles electronics

instrumentation engineering systems missiles materials naval

systems advanced computing simulation and life sciences DRDO

while striving to meet the Cutting edge weapons technology

requirements provides ample spinoff benefits to the society at large

thereby contributing to the nation building

DRDO has various RampD labs working on different technologies The

lab under which I am working is Institute for Systems Studies amp

Analyses (ISSA)

8 | P a g e

ISSA specializes in systems analysis modeling amp simulation of

defense systems using state-of-the-art info-technologies such as

Computer Networking Software Engineering Distributed Database

Distributed Simulation Web Technologies Situational Awareness

and Soft-Computing techniques in development of complex

simulation products

Its activities include

Evolution and evaluation of strategic and tactical plans

Threat analysis Force mix studies and Strategic decision

making

Design trade-off and performance evaluation of systems

Cost-effectiveness analysis Weapon selection and acquisition

Development of computer war games for teaching amp training

Integrated software for mission planning tactical training and

operational planning

Development of software as decision aid with Military GIS

System reliability studies

Vision

Transform ISSA into centre of excellence in system analysis

modelling amp simulation of defence systems to meet the challenges of

the present and future requirements of the armed forces

Mission

Conduct system study and develop high quality integrated software

for system analysis amp decision support in application areas of Sensors

9 | P a g e

amp Weapons Electronic Combat Land amp Naval Combat Air-to-Air

Combat and Air Defence for effective use by DRDO and Services for

Design

Mission Planning Tactics development and Training

12 ANTENNA ARRAYS

A single-element antenna is usually not enough to achieve technical needs That happens because its performance is limited A set of discrete elements which constitute an antenna array offers the solution to the transmission andor reception of electromagnetic energy The geometry and the type of elements characterize an antenna array For simplicity implementation and fabrication reasons the elements are chosen in such a way so as to be identical and parallel For the same reasons uniformly spaced linear arrays are mostly encountered in practice In the following paragraphs the properties of various antenna arrays will be presented

An array consisting of identical and identically oriented elements

A uniform linear array is one in which elements are fed with equal magnitude of current and with equal phase shift along the line

VARIOUS TYPES OF ANTENNA ARRAY

1 Broadside ArrayIn this a number of identical parallel antennas are set up along a line drawn perpendicular to their respective axes Each element is fed with equal magnitude all in the same phase

2 End Fire ArrayEnd fire is nothing but broadside array except that individual elements are fed in out of phase (usually 180) Thus in the end fire array a number of identical antennas are spaced equally along a line and individual elements are fed with current of equal magnitude and their phases varies progressively

3 Collinear Array

10 | P a g e

In collinear array the antennas are arranged co-axially that is antennas are mounted end to end in a single line In other words one antenna is stacked over other antenna

4 Parasitic ArrayParasitic element is not fed directly instead a parasitic element derives power by the radiation from nearby driven element Array with a number of parasitic elements is called ldquoParasitic Arrayrdquo

Figure 1- Array of two point source

To distant point lsquoPrsquo

11 | P a g e

theta

d

Path difference = dcos(theta)lamda

Phase angle = 2piPath differenceΨ

= dcos(theta)Ψ βE = E1e-j 2Ψ + E2e+j 2Ψ

E = 2E0( dcos(theta)2)β1 Equal amplitude and same phaseE = cos(π2cosθ) Maxima is at θ=90270hellipMinima is at θ=0360hellip2 Equal amplitude and opposite phaseE = sin(π 2cos θ)Maxima is at θ=0360hellipMinima is at θ=90270hellip3 Unequal amplitude and any phase In this amplitude transmitted by point sources is different and they have phase difference

ARRAY OF lsquonlsquo POINT SOURCES

12 | P a g e

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 8: DRDO Presentation

CHAPTER 1 INTRODUCTION

11 Introduction about the Company

Defence Research amp Development Organisation (DRDO) works under

Department of Defence Research and Development of Ministry of

Defence DRDO dedicatedly working towards enhancing self-reliance

in Defence Systems and undertakes design amp development leading to

production of world class weapon systems and equipment in

accordance with the expressed needs and the qualitative

requirements laid down by the three services

DRDO is working in various areas of military technology which

include aeronautics armaments combat vehicles electronics

instrumentation engineering systems missiles materials naval

systems advanced computing simulation and life sciences DRDO

while striving to meet the Cutting edge weapons technology

requirements provides ample spinoff benefits to the society at large

thereby contributing to the nation building

DRDO has various RampD labs working on different technologies The

lab under which I am working is Institute for Systems Studies amp

Analyses (ISSA)

8 | P a g e

ISSA specializes in systems analysis modeling amp simulation of

defense systems using state-of-the-art info-technologies such as

Computer Networking Software Engineering Distributed Database

Distributed Simulation Web Technologies Situational Awareness

and Soft-Computing techniques in development of complex

simulation products

Its activities include

Evolution and evaluation of strategic and tactical plans

Threat analysis Force mix studies and Strategic decision

making

Design trade-off and performance evaluation of systems

Cost-effectiveness analysis Weapon selection and acquisition

Development of computer war games for teaching amp training

Integrated software for mission planning tactical training and

operational planning

Development of software as decision aid with Military GIS

System reliability studies

Vision

Transform ISSA into centre of excellence in system analysis

modelling amp simulation of defence systems to meet the challenges of

the present and future requirements of the armed forces

Mission

Conduct system study and develop high quality integrated software

for system analysis amp decision support in application areas of Sensors

9 | P a g e

amp Weapons Electronic Combat Land amp Naval Combat Air-to-Air

Combat and Air Defence for effective use by DRDO and Services for

Design

Mission Planning Tactics development and Training

12 ANTENNA ARRAYS

A single-element antenna is usually not enough to achieve technical needs That happens because its performance is limited A set of discrete elements which constitute an antenna array offers the solution to the transmission andor reception of electromagnetic energy The geometry and the type of elements characterize an antenna array For simplicity implementation and fabrication reasons the elements are chosen in such a way so as to be identical and parallel For the same reasons uniformly spaced linear arrays are mostly encountered in practice In the following paragraphs the properties of various antenna arrays will be presented

An array consisting of identical and identically oriented elements

A uniform linear array is one in which elements are fed with equal magnitude of current and with equal phase shift along the line

VARIOUS TYPES OF ANTENNA ARRAY

1 Broadside ArrayIn this a number of identical parallel antennas are set up along a line drawn perpendicular to their respective axes Each element is fed with equal magnitude all in the same phase

2 End Fire ArrayEnd fire is nothing but broadside array except that individual elements are fed in out of phase (usually 180) Thus in the end fire array a number of identical antennas are spaced equally along a line and individual elements are fed with current of equal magnitude and their phases varies progressively

3 Collinear Array

10 | P a g e

In collinear array the antennas are arranged co-axially that is antennas are mounted end to end in a single line In other words one antenna is stacked over other antenna

4 Parasitic ArrayParasitic element is not fed directly instead a parasitic element derives power by the radiation from nearby driven element Array with a number of parasitic elements is called ldquoParasitic Arrayrdquo

Figure 1- Array of two point source

To distant point lsquoPrsquo

11 | P a g e

theta

d

Path difference = dcos(theta)lamda

Phase angle = 2piPath differenceΨ

= dcos(theta)Ψ βE = E1e-j 2Ψ + E2e+j 2Ψ

E = 2E0( dcos(theta)2)β1 Equal amplitude and same phaseE = cos(π2cosθ) Maxima is at θ=90270hellipMinima is at θ=0360hellip2 Equal amplitude and opposite phaseE = sin(π 2cos θ)Maxima is at θ=0360hellipMinima is at θ=90270hellip3 Unequal amplitude and any phase In this amplitude transmitted by point sources is different and they have phase difference

ARRAY OF lsquonlsquo POINT SOURCES

12 | P a g e

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 9: DRDO Presentation

ISSA specializes in systems analysis modeling amp simulation of

defense systems using state-of-the-art info-technologies such as

Computer Networking Software Engineering Distributed Database

Distributed Simulation Web Technologies Situational Awareness

and Soft-Computing techniques in development of complex

simulation products

Its activities include

Evolution and evaluation of strategic and tactical plans

Threat analysis Force mix studies and Strategic decision

making

Design trade-off and performance evaluation of systems

Cost-effectiveness analysis Weapon selection and acquisition

Development of computer war games for teaching amp training

Integrated software for mission planning tactical training and

operational planning

Development of software as decision aid with Military GIS

System reliability studies

Vision

Transform ISSA into centre of excellence in system analysis

modelling amp simulation of defence systems to meet the challenges of

the present and future requirements of the armed forces

Mission

Conduct system study and develop high quality integrated software

for system analysis amp decision support in application areas of Sensors

9 | P a g e

amp Weapons Electronic Combat Land amp Naval Combat Air-to-Air

Combat and Air Defence for effective use by DRDO and Services for

Design

Mission Planning Tactics development and Training

12 ANTENNA ARRAYS

A single-element antenna is usually not enough to achieve technical needs That happens because its performance is limited A set of discrete elements which constitute an antenna array offers the solution to the transmission andor reception of electromagnetic energy The geometry and the type of elements characterize an antenna array For simplicity implementation and fabrication reasons the elements are chosen in such a way so as to be identical and parallel For the same reasons uniformly spaced linear arrays are mostly encountered in practice In the following paragraphs the properties of various antenna arrays will be presented

An array consisting of identical and identically oriented elements

A uniform linear array is one in which elements are fed with equal magnitude of current and with equal phase shift along the line

VARIOUS TYPES OF ANTENNA ARRAY

1 Broadside ArrayIn this a number of identical parallel antennas are set up along a line drawn perpendicular to their respective axes Each element is fed with equal magnitude all in the same phase

2 End Fire ArrayEnd fire is nothing but broadside array except that individual elements are fed in out of phase (usually 180) Thus in the end fire array a number of identical antennas are spaced equally along a line and individual elements are fed with current of equal magnitude and their phases varies progressively

3 Collinear Array

10 | P a g e

In collinear array the antennas are arranged co-axially that is antennas are mounted end to end in a single line In other words one antenna is stacked over other antenna

4 Parasitic ArrayParasitic element is not fed directly instead a parasitic element derives power by the radiation from nearby driven element Array with a number of parasitic elements is called ldquoParasitic Arrayrdquo

Figure 1- Array of two point source

To distant point lsquoPrsquo

11 | P a g e

theta

d

Path difference = dcos(theta)lamda

Phase angle = 2piPath differenceΨ

= dcos(theta)Ψ βE = E1e-j 2Ψ + E2e+j 2Ψ

E = 2E0( dcos(theta)2)β1 Equal amplitude and same phaseE = cos(π2cosθ) Maxima is at θ=90270hellipMinima is at θ=0360hellip2 Equal amplitude and opposite phaseE = sin(π 2cos θ)Maxima is at θ=0360hellipMinima is at θ=90270hellip3 Unequal amplitude and any phase In this amplitude transmitted by point sources is different and they have phase difference

ARRAY OF lsquonlsquo POINT SOURCES

12 | P a g e

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 10: DRDO Presentation

amp Weapons Electronic Combat Land amp Naval Combat Air-to-Air

Combat and Air Defence for effective use by DRDO and Services for

Design

Mission Planning Tactics development and Training

12 ANTENNA ARRAYS

A single-element antenna is usually not enough to achieve technical needs That happens because its performance is limited A set of discrete elements which constitute an antenna array offers the solution to the transmission andor reception of electromagnetic energy The geometry and the type of elements characterize an antenna array For simplicity implementation and fabrication reasons the elements are chosen in such a way so as to be identical and parallel For the same reasons uniformly spaced linear arrays are mostly encountered in practice In the following paragraphs the properties of various antenna arrays will be presented

An array consisting of identical and identically oriented elements

A uniform linear array is one in which elements are fed with equal magnitude of current and with equal phase shift along the line

VARIOUS TYPES OF ANTENNA ARRAY

1 Broadside ArrayIn this a number of identical parallel antennas are set up along a line drawn perpendicular to their respective axes Each element is fed with equal magnitude all in the same phase

2 End Fire ArrayEnd fire is nothing but broadside array except that individual elements are fed in out of phase (usually 180) Thus in the end fire array a number of identical antennas are spaced equally along a line and individual elements are fed with current of equal magnitude and their phases varies progressively

3 Collinear Array

10 | P a g e

In collinear array the antennas are arranged co-axially that is antennas are mounted end to end in a single line In other words one antenna is stacked over other antenna

4 Parasitic ArrayParasitic element is not fed directly instead a parasitic element derives power by the radiation from nearby driven element Array with a number of parasitic elements is called ldquoParasitic Arrayrdquo

Figure 1- Array of two point source

To distant point lsquoPrsquo

11 | P a g e

theta

d

Path difference = dcos(theta)lamda

Phase angle = 2piPath differenceΨ

= dcos(theta)Ψ βE = E1e-j 2Ψ + E2e+j 2Ψ

E = 2E0( dcos(theta)2)β1 Equal amplitude and same phaseE = cos(π2cosθ) Maxima is at θ=90270hellipMinima is at θ=0360hellip2 Equal amplitude and opposite phaseE = sin(π 2cos θ)Maxima is at θ=0360hellipMinima is at θ=90270hellip3 Unequal amplitude and any phase In this amplitude transmitted by point sources is different and they have phase difference

ARRAY OF lsquonlsquo POINT SOURCES

12 | P a g e

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 11: DRDO Presentation

In collinear array the antennas are arranged co-axially that is antennas are mounted end to end in a single line In other words one antenna is stacked over other antenna

4 Parasitic ArrayParasitic element is not fed directly instead a parasitic element derives power by the radiation from nearby driven element Array with a number of parasitic elements is called ldquoParasitic Arrayrdquo

Figure 1- Array of two point source

To distant point lsquoPrsquo

11 | P a g e

theta

d

Path difference = dcos(theta)lamda

Phase angle = 2piPath differenceΨ

= dcos(theta)Ψ βE = E1e-j 2Ψ + E2e+j 2Ψ

E = 2E0( dcos(theta)2)β1 Equal amplitude and same phaseE = cos(π2cosθ) Maxima is at θ=90270hellipMinima is at θ=0360hellip2 Equal amplitude and opposite phaseE = sin(π 2cos θ)Maxima is at θ=0360hellipMinima is at θ=90270hellip3 Unequal amplitude and any phase In this amplitude transmitted by point sources is different and they have phase difference

ARRAY OF lsquonlsquo POINT SOURCES

12 | P a g e

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 12: DRDO Presentation

theta

d

Path difference = dcos(theta)lamda

Phase angle = 2piPath differenceΨ

= dcos(theta)Ψ βE = E1e-j 2Ψ + E2e+j 2Ψ

E = 2E0( dcos(theta)2)β1 Equal amplitude and same phaseE = cos(π2cosθ) Maxima is at θ=90270hellipMinima is at θ=0360hellip2 Equal amplitude and opposite phaseE = sin(π 2cos θ)Maxima is at θ=0360hellipMinima is at θ=90270hellip3 Unequal amplitude and any phase In this amplitude transmitted by point sources is different and they have phase difference

ARRAY OF lsquonlsquo POINT SOURCES

12 | P a g e

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 13: DRDO Presentation

For Linear Array

Et=Eo(1+ejψ+e2j ψ +e3j ψ +helliphellipe(n-1)j ψ) After manipulations Et=Eo (sin nψ2)(sin ψ2) ψ= βcosθ +α For Broadside antennas α=0 For End fire antennas αne0

For BroasdsideDirection of pattern maxima

sin(nψ2)=1 nψ2=(2N+1)π2 After manipulations θmmax=cos-1(βd)-1[(2N+1) π n -α ] Direction of pattern minima sin(nψ2)=0 nψ2=Nπ After manipulations θmmin=cos-1(βd)-1[(2Nπ n) -α ]

For End Fire

Ψ=0α=-βd and Ψ= β dcosθ- β d

Direction of pattern maximasin (nΨ2)=1 n Ψ2=(2N+1)π2βdcosθ -βd=(2N+1)πnθmminor=cos-1[(2N+1)πnd]+1

Direction of pattern minima

13 | P a g e

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 14: DRDO Presentation

Similarly βdcos- βd=2Nπnθmin=cos-1[(Nλnd)+1]

FIGURE- 2 The sum and difference patterns of array antenna

13 Radar fundamentals

The word ldquoRADARrdquo is an acronym for Radio Detection and Ranging It is basically means of gathering information about distant objects or targets by sending electromagnetic (EM) waves to them and thereafter analyzing reflected waves or the echo signals

Advantages

14 | P a g e

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 15: DRDO Presentation

1 Radars can see through darkness haze fog rain and snow2 They can determine the range and angle ie the location of the

target very accurately

Limitations

1 Radars cannot resolve in detail like the human eye especially at short distances

2 They cannot recognize the colour of the target

Applications

1 Navigational aid on ground and sea2 Radar altimeters for determining the height of plane above

ground3 Airborne radar for satellite surveillance

Radar range equation

R max =[PtAe2 4 σ π λ2Pr]

Where Pt = transmitted power

Ae = capture area of the receiving antenna

= radar cross-section of targetσ

= wavelength of radiated energyλ

Pr = power received

Factors affecting Range of a Radar

1 Transmitted power2 Frequency

15 | P a g e

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 16: DRDO Presentation

3 Target cross sectional areas4 Minimum received signal (Pr(min))

Basic principle of RADAR

Figure 3- Radar Principle

16 | P a g e

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 17: DRDO Presentation

CHAPTER 2

Project Dsecription

21 Phased Array Radar

22 Multifunction Radar

23 Bandwidth of Phased Array Radar

24 Tracking Errors

Chapter-2 PROJECT DESCRIPTION

21 PHASE ARRAY RADARS

17 | P a g e

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 18: DRDO Presentation

Early radar systems used antenna arrays formed by the combination of individual radiators Antenna characteristics are determined by the geometric position of the radiators and the amplitude and phase of their excitation As radars progressed to shorter wavelengths arrays were displaced by simpler antennas such as parabolic reflectors But now days electronically controlled phase shifter switches and transmitreceive modules are used to steer beam rather than rotating antenna mechanically These types of radars are known as ldquoPhase Array Radarsrdquo

Advantages of Phase Array Radar

1 Flexibility in beam steering2 Less time to steer the beams (in microseconds)

22 Multifunction RadarsThe capability of rapidly and accurately switching beams permits multiple radar function to be performed interlaced in time An Electronically steered array radar may track a great multiplicity of targets illuminate a number of targets with RF energy and guide missiles toward them and perform complete hemispherical search with automatic target selection and handover to tracking Phase array are very expensive

Phased Array Antennas

The phased array antenna has an aperture that is assembled from a great many similar radiating elements such as slots dipoles or patches each element being individually controlled in phase and amplitude

Elements are spaced by 2λ (λ = wavelength) distance to avoid the generation of multiple beams

18 | P a g e

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 19: DRDO Presentation

The number of radiating elements N for a pencil beam is approximately related to the beam width by

N = 10000 ( θB )2

Where θB is the 3-dB beam width in degrees

The antenna gain when the beam points broadside to the aperture is

G0 = N π η

Where accounts for antenna losses and reduction in gainη

23 BANDWIDTH OF PHASED ARRAYS

The phenomenon of focusing an array is a result of the energy of each element adding in phase at some desired point within the antenna When energy is incident normally to the array each element receives the same phase independent of frequency When energy is incident from some angle other than normal the phase difference from the planar phase front to each element is the function of frequency and most phased array with phase shifter becomes frequency dependant This same phenomenon can be viewed in the time domain When pulse of energy is incident at an angle other than normal the energy is received earlier at one edge of the array than at the other edge and a period of time must elapse before energy appears in all element

The bandwidth of phased array is composed of two effects namely

1 Aperture Effect2 Feed Effect

In both effects it is the path length difference that contribute to the bandwidth sensitivity of the phased array

For a parallel-fed array (equal line length) the feed network does not contribute to a change with frequency and so only the aperture effect remains

19 | P a g e

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 20: DRDO Presentation

APERTURE EFFECT

When energy is incident on an array at angle other than broadside the phase required on the edge element

= 2 L sinψ π λ θ

This indicates that required phase is frequency dependant

If frequency is changed and the phase shifters are not changed the beam will move For an equal-line-length feed the beam shape will be undistorted and the beam will move towards broadside as the frequency is increased If the phase shifters are replaced by time delay networks than the phase through time delay network will change with frequency and the beam will remain stationary

As the frequency is increased the beam scans toward broadside by an angle that is independent of aperture size or beamwidth The angle that beam actually scans is related to bandwidth

Bandwidth factor K = Bandwidth() Beamwidth(degree)

Permissible amount that a beam may scan with frequency is related to the beamwidth since pattern and gain deteriorations are a function of fractional beamwidth scanned

Above is valid for antenna operating at a single (CW) frequency However most radars are pulsed and radiate over a band of frequencies

And in above explanations it was assumed that we are using equal path length feed but practically it is nit possible to have the path lengths within one wavelength

FEED EFFECT

20 | P a g e

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 21: DRDO Presentation

When an equal-path-length feed is not in use feed networks will produce a change in phase with frequency In some cases the feed can actually compensate for the aperture effect and produce a beam direction which is independent of frequency

Types of feed

1 End fed series feed2 Centre fed series feed

End fed series feed

The radiating elements are in series and progressively farther removed from the feed point When the frequency is changed the phase at the radiating element changes proportionally to the length of the feed line so that the phase at the aperture tilts in a linear and beam is scanned

his effect is used for frequency scanning technique

But in case of phased array it is undesirable and reduces the bandwidth

Centre ndash Fed Series Feed

Figure- 4

21 | P a g e

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 22: DRDO Presentation

A Centre ndash Feed array can be considered as two end feeds Each feed controls an aperture which is half the total and therefore has the twice beam width

As the frequency is changed each half of t he aperture scans in opposite direction This initially creates a broader beam with reduced gain As frequency continues to change the two beams will eventually split apart At broadside the centre fed antenna has poorer performance the a parallel feed since each half scans However at 600 scan the compensation on one ndash half of the array assists in keeping the gain comparable to that of a parallel feed From the view point of gain reduction the criterion for a centre fed is

Bandwidth () = ( beam width (degree)) λ λg

24TRACKING ERRORS

The measure of error is the root mean square (rms) of the difference between the measured angle (estimated) values and the true values The tracking errors can be divided into two main groups range tracking errors and angle tracking errors Thermal noise angular glint (angle noise) scintillation manufacturing qualities and alignment are factors contributing to angular tracking errors There are some more errors caused by external factors

1 Thermal Noise

Thermal noise is a very important factor degrading the performance of the system and limiting the accuracy of the angle measurements

22 | P a g e

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 23: DRDO Presentation

Noise is a function of probability as well If the Friis equation is divided by the noise power the signal to noise ratio (SNR) is obtained It is seen that the signal-to-noise ratio is inversely proportional to the square of range This relationship in the well-known Friis equation gives the limiting effect of noise on radar in terms of range The angular rms error in a tracking radar due to thermal noise can be calculated with the general formula

where k=1 for a monopulse and 14 for a conical-scan θB is the half-power beamwidth SN the signal-to-noise ratio fp pulse repetition frequency and βn servo bandwidthThe product of B (bandwidth) and τ (pulse width) is approximately equal to unity and 2 f p βn gives the number of pulses integrated The constant k s seen in the denominator is the monopulse slope constant which is approximately equal to 17 for monopulse radarsand 13 for conical-scan radar However its exact value must be determined for the specific antenna used in tracking

2 Angular GlintA source of angle tracking error is angular glint also called angular noise angle scintillation angle fluctuations or target noise The tracker determines the direction of the vector sum of all signals arriving Glint is the difference in the apparent location compared to the actual Sometimes it can even result in tracking points off the target The tracker angle-sensing devices sense the phase front of the transmitted wave and indicate the source to be in a direction normal to the wavefrontFor a single source the wave arrives at the antenna in the form of a uniform planar wave Thus the incident wavefront is tilted with respect to the antenna base line The spread of the scatterers leads to multipath and the angle measurement gets worse The vector sum of these incident wavefronts give a wavefront whose amplitude and phase is not uniform across the antenna aperture Glint can be a major problem in angle measurements especially for short rangesAngle noise is an issue on the performance of all the continuous tracking radars with closed-loop angle tracking whatever tracking

23 | P a g e

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 24: DRDO Presentation

type it has The rms error of the angular location of the point on the target with respect to the center of the scatterer can be calculated by-

where the error is in radians L i is the distance to the ith scattering point and 1 ki 1048595 is the ratio of the ith signal component amplitude to that of the main element

3 Total ErrorAssuming independent error sources that are normally distributed the total errorof the system is the sum of the variances-

24 | P a g e

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 25: DRDO Presentation

Figure- 7

25 | P a g e

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 26: DRDO Presentation

CHAPTER 3

Functionality

31 Tracking Techniques

32 Determining the design parameters

26 | P a g e

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 27: DRDO Presentation

Chapter 3Functinality

31TRACKING TECHNIQUES

There are three major methods that can be used to track a target sequential lobing conical scan and monopulse tracking

1 Sequential LobingThis technique involves sequential switching between two beams with overlapping but offset patterns Figure 5 shows the antenna output when a target is present and the beam switched between two positions Each position of the target on the beam corresponds to a voltage value The rectangles A and B in Figure 5 are the beam position 1 and 2 returns respectively The goal is to bring the target on the antenna boresight The difference of the voltage amplitudes between the two positions gives the angular measurement error The beam is moved to the direction in which the amplitude of the voltage is largerIf the amplitude of the voltages corresponding to the two positions of the target are the same then the target is said to be on the switching axis

27 | P a g e

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 28: DRDO Presentation

Figure-5

2 Conical Scanning

Conical scanning takes its name from the shape that a pencil beam makes by rotating the beam around an axis as seen in Figure 6 The angle between the rotating axis and the beam axis where the gain of the antenna is greatest is called a squint angle The amplitude of the echo signal is modulated at a frequency called conical scan frequency Conical scan frequency is actually the beam rotation frequency This modulation occurs due to the rotation of the squinted beam and the targetrsquos offset from the rotation axis The phase of conical scan modulation gives the location of the target The error signal obtained from the modulated signal combines the elevation-angle error and azimuth angle error These error signals are applied to elevation and azimuth servo

28 | P a g e

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 29: DRDO Presentation

motors to position the antenna If the antenna is on target the amplitude of conical-scan modulation is zero

Figure-6

3 Monopulse Scanning

Monopulse scanning is the most efficient and robust tracking technique Thetracking techniques discussed above need more than one signal sample theoretically four target returns two of which are for the vertical direction and two for the horizontal direction to determine the tracking error The signals returning from the target will have different phase and amplitude due to the signal fluctuations The fluctuations in the signal results in tracking errors As evident from its name monopulse scanning radars use only one pulse to determine the tracking error Using one pulse (single sample) eliminates theproblem of signal fluctuation Several samples can be used to improve the accuracy of the angle estimate

Monopulse systems can be divided into two types amplitude comparison monopulse systems and phase comparison monopulse systems

29 | P a g e

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 30: DRDO Presentation

32Determining the design parameters

This chapter addresses the overall tracking antenna design

Figure- 8 element spacing vs scan angle

30 | P a g e

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 31: DRDO Presentation

The gain of the linear array can be calculated with the following formula

Figure- 9 Gain vs number of elements

31 | P a g e

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 32: DRDO Presentation

Table 1 Parameters for use in computing the directivity of uniform current amplitude Equally spaced linear arrays

33 GUI in matlab

Purpose- To check target is in the range of radar or not and to show the distance of target if it is in the range

CODE

functionvarargout = one(varargin)gui_Singleton = 1gui_State = struct(gui_Name mfilename gui_Singleton gui_Singleton gui_OpeningFcn one_OpeningFcn gui_OutputFcn one_OutputFcn gui_LayoutFcn [] gui_Callback [])ifnarginampampischar(varargin1)gui_Stategui_Callback = str2func(varargin1)end

ifnargout [varargout1nargout] = gui_mainfcn(gui_State varargin)elsegui_mainfcn(gui_State varargin)end End initialization code - DO NOT EDIT

--- Executes just before one is made visiblefunctionone_OpeningFcn(hObject eventdata handles varargin)

32 | P a g e

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 33: DRDO Presentation

handlesoutput = hObject

Update handles structureguidata(hObject handles)

functionvarargout = one_OutputFcn(hObject eventdata handles)varargout1 = handlesoutput

--- Executes on button press in pushbutton1function pushbutton1_Callback(hObject eventdata handles)textstring = get(handlestext1string) x = randi([0100]11)if(xlt50)textstring = target in rangeelsetextstring = nothing in rangeend

set(handlestext1stringtextstring)

--- Executes on button press in pushbutton2function pushbutton2_Callback(hObject eventdata handles) hObject handle to pushbutton2 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA) y = randi([0100]11)textstring = get(handlestext1string)

textstring = y100 textstring = eval(textstring)set(handlestext1stringtextstring)

function edit1_Callback(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles structure with handles and user data (see GUIDATA)

Hints get(hObjectString) returns contents of edit1 as text str2double(get(hObjectString)) returns contents of edit1 as a double

--- Executes during object creation after setting all propertiesfunction edit1_CreateFcn(hObject eventdata handles) hObject handle to edit1 (see GCBO) eventdata reserved - to be defined in a future version of MATLAB handles empty - handles not created until after all CreateFcns called

Hint edit controls usually have a white background on Windows See ISPC and COMPUTERifispcampampisequal(get(hObjectBackgroundColor) get(0defaultUicontrolBackgroundColor))set(hObjectBackgroundColorwhite)end

33 | P a g e

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 34: DRDO Presentation

GUI figure

34 | P a g e

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 35: DRDO Presentation

CHAPTER 4

CONCLUSION AND REFERENCES

41 Conclusion

42 Limitations

43 Future Scope for Modification

44 Reference

35 | P a g e

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 36: DRDO Presentation

CHAPTER 4 CONCLUSION AND REFERENCES

41 CONCLUSION

As a part of an ongoing project this research aimed to track a signal transmitted continuously by a target via an array of antennas Tracking this signal will be the first step towards maintaining a data link between a target and ground station for any kind data transfer such as video image or audio This research has covered the design and development of the tracking array beginning with background about tracking systems and techniques and the causes of tracking errors

MATLAB programs and GUI designed for this research made the tracking of the signal possible

36 | P a g e

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 37: DRDO Presentation

42 FUTURE SCOPE FOR MODIFICATION

1 Circularly Polarized AntennasThe dipoles that are set in the array are linearly polarized The antennas should preferably be circularly polarized for the best performance

2 Acquisition SystemThe array system designed for this research project does not have the capability of acquiring the target Hence the target is acquired manually Sweeping the sum and difference beams simultaneously the signal transmitted continuously from the target can be acquired and tracked

3 Operational TestingAfter the array has been tested it should be taken to the field and its operability with a real target should be checked This last step will reveal the vulnerabilities of the system and lead to further improvements

37 | P a g e

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals
Page 38: DRDO Presentation

43 REFRENCE

1 Radar Handbook ndash Merrill Skolnik

2 Radar Engineering ndash M Kulkarni

3 Antenna Fundamentals ndash KDPrasad

4 Electromagnetic Waves and radiating system ndash EC Jordan KG Balmain

5 Introduction to Airborne Radar(SciTech-1998)

6 wwwradar tutorialscom

7 Matlab help guide

38 | P a g e

  • C O N T E N T S
  • 1 INTRODUCTION
    • 2 PROJECT DESCRIPTION
    • 21 Phased Array Radar 18
    • 22 Multifunction Radar 18
    • 4 CONCLUSION AND REFERENCES
      • LIST OF ABBREVIATIONS
        • 11 Introduction about the Company
          • 12 ANTENNA ARRAYS
          • 13 Radar fundamentals