Low Cost Em Signal Direction Estimation With Two Element Time Modulated Array System For Military/Police Search

7/27/2019 Low Cost Em Signal Direction Estimation With Two Element Time Modulated Array System For Military/Police Search

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International Journal of Computer Trends and Technology (IJCTT) – volume 4 Issue 7–July 2013

ISSN: 2231-2803 http://www.ijcttjournal.org Page 2113

Low Cost Em Signal Direction Estimation With Two Element

Time Modulated Array System For Military/Police Search

Operations

B.Gayathri#1

, M.Devendra*2

Department of ECE( M.tech), G.P.R Engg College, Kurnool.

Associate Professor, M.S., (Ph.D), G.P.R Engg College, Kurnool.

ABSTRACT-

Today homeland secuiry could be a huge matter of concern.

The current day wireless technology is accessible to anti-

social components that measure mistreatment this in manyundesirable manners. By knowing the direction of the

source of magnetism waves it becomes possible to find such

anti-social teams and take offensive action. In military

applications additionally finding the direction of the signal

supply becomes valuable information. The direction finding

systems can do this goal.

Conventional radio direction finding (RDF) systems usually

use associate degree array of 2 or additional antennas and

use either phase-comparison or amplitude-comparison of

the received signals to work out direction of arrival data. In

each of those techniques directional data springs by process array information at the receive signal frequency.

In this project, to seek out the direction by mistreatment the

strategy of time-switched array system is enforced. The

time-switched array system uses straightforward signal

process techniques to produce a directional main beam and

pattern nulls at harmonic frequencies. To see 2 dimensional

angles are 3 parts, the system price has been largely

minimised. We have a tendency to currently take into

account the matter of mistreatment our low price system to

find and estimate the direction of arrival of a desired signal within the presence of array antenna.

The projected theme is value effective technique as

compared with the prevailing schemes.

MATLAB/GNU OCTAVE simulation tool are going to be

used for simulation. The simulation results, applications,

deserve and demerits of projected approach are going to be

analyzed and can be documented.

Index Terms-antenna, array, direction finding.

I. INTRODUCTION

Time modulated arrays (TMAs) are unit antenna

systems wherever a group of frequency (RF) switches is

employed within the beam forming network to modulate the

static excitation weights of a standard phased array. The on-

off commutation of the switches are controlled by periodic

pulse sequences, generates harmonics, known as sideband

radiation (SR), that are unit spaced within the frequency

domain by multiple of the heartbeat repetition frequency.

Until today, most of the analysis activities are dedicated to

the synthesis of a desired pattern at the antenna operating

frequency and therefore the joint minimisation of the ability

losses within the SR that incapably cut back the antenna

directionality and gain. During this framework, TMAs are

used to get ultra-low facet lobe patterns and formed beams

with component excitations characterised by reduced

dynamic vary quantitative relation. The synthesis of pulse

Doppler radio location and sum-difference patterns for

monopulse applications has been thought-about, as well.

More modern used instead thought-about the exploitation of

the harmonics generated by the modulation method. Among

them, multiple harmonic patterns directed on totally different

angular directions are used for electronic beam scanning





applications, the estimation of the direction of arrival, and in

psychological feature radio systems.

It has been exploited in numerous applications (e.g., radar,

sonar, wireless communications, seismic exploration, speech

processing, medical imaging, radio astronomy).

0°

90°

12

1

1

2

2

Fig 1: Two Element Time-Switched Array and definition of switching wave

forms.

Time switched array systems

The received signal from every component of the array is

time switching wave and combined to produce a part

modulated output. The shape of the time modulation is said

to each of the switching waves and therefore the direction of

arrival of the incident signal. The angular response at the

primary higher and lower harmonic frequencies exhibits one

deep null which may be scanned in angle over a full ninety

vary by dominant the component shift wave. The time-

switched array so achieves active electronic null steering

while not the necessity for part shift, or time, delays,

network.

An inherent disadvantages associated with time-

modulated arrays is that they generate unwanted harmonics,

or sidebands, at multiples of the change frequency and most

analysis into time-modulated arrays has focused on

minimizing or dominant these harmonics. A lot of recently

work has been administrated to analyze the utilization of part

centre motion to manage aspect lobe levels and therefore the

application of time-modulated arrays in Doppler radio

location.

During this contribution we tend to describe a prototype

2 component time-switched array system and gift measured

knowledge may be the performance of the array.

Direction of Arrival

We have seen that there a matched relationship between the

direction of a signal and therefore the associated received

steering vector. It ought to so be attainable to invert the link

and estimate the direction of a signal from the received

signals. An antenna array so ought to be able to give for

direction of arrival estimation. We’ve got additionally seen

that there's a Fourier relationship between the beam pattern

and (DOA) estimation drawback to be treated as resembling

spectral estimation.

∅∅∅

D

Fig 2: The DOA estimation problem

The problem created is shown in Fig. 1. Many (M) signals

collide with a linear, equispaced, array with N parts, every

with direction φi. The goal of DOA estimation is to use the

information received at the array to estimate φi, i = 1 . . . M.

it's usually assumed that M < N, although there exist

approaches (such as most chance estimation) that don't place

this constraint.

∑





II. SYSTEM DESCRIPTION

The time-switched array system is shown schematically in

Fig.1 and consists of 2 antenna parts separated by a distance

d. every component is assumed to exhibit omnidirectional

radiation within the plane of the diagram. The output fromevery component is connected to the array output via a

switch within the feed line the component change amount is

additionally outlined in Fg.1. a complete analysis the system

is also found and except for the aim of this contribution we'll

going to assume that the weather are alternately switched on

and off with an equal mark-space magnitude relation sq.

wave change perform such t1= t2 = T/2.

If we tend to assume that the spacing between thecomponents is a half wavelength, the output from the array is

also represented by

A (θ, t) = cos,where

={

п θ; ()

;

}.

Time-switched array

Mounted on turntable

Receive antenna

Fig 3: Details of the measurement set-up.

Hence the output of the array is part modulated and

therefore the depth of modulation depends on the angle of

arrival of the incident signal. For illumination broadside to

the array, the array output isn’t modulated. However, because

the illumination angle will increase the depth of modulation

will increase till at finish hearth illumination (θ = 90deg) the

array output exhibits 180 deg part shift modulation. A plot of

the array receive pattern at the example frequency, ω, is

given in Fig.2 and shows a directional response with a peak

on broadside and a null response at ±90deg. The directional

pattern happens as a result of because the depth of PM will

increase energy is decentralized from the carrier into

sidebands, and at finish hearth there's zero energy at the at

the carrier frequency. If we have a tendency to currently

examine the output of the time-switched array at the primary

harmonic.

Multiple Signal Classification Algorithms:

MUSIC is perhaps the foremost standard technique. MUSIC,

as square measure several adaptation techniques, depends on

the matrix of the information. Using

The matrix S may be an N ×M matrix of the M steering

vectors. Forward that the diff erent signals to be uncorrelated,

the matrix of x may be written as

Signalsource

Spectrumanalyzer





Where

The signal variance matrix, Rs, is clearly an N × N matrix

with rank M. It thus has N−M eigenvectors like the zero

eigenvalue. Let qm be such associate eigenvector. Therefore,

Where this final equation is valid since the matrix A is clearly

positive definite. It implies that every one N −M eigenvectors

(qm) of Rs in to the zero eigenvalues are orthogonal. To any

or all M signal steering vectors. This can be the idea for

MUSIC. Decision Qn the N × (N −M) matrix of those

eigenvectors. Note that since the eigenvectors creating up Qn

orthogonal to the signal steering vectors, the divisor becomes

zero once φ may be a signal direction.

BLOCK DIAGRAM

Table1

Algorithm overview

Step1: First we tend to think about AN L formed antenna

array system on the Z axis with the gap of separation aszero.5 λ and letter as 360 deg.

Step2: To calculate the output radiated from the three

antennas.

Step3: Upon calculating the magnitude of the output, we tend

to plot the magnitude (in decibel) against the angle (in deg).

Step4: To calculate the angle of arrival, we find out the peak

value wherever the output is most. The angle of arrivals is

found to be 90 and 270 degrees severally.

step5: we tend to next calculate 2 of the foremost necessary

properties i.e., Array issue and Array part.

step6: we tend to then create polar plots of each Array issue

and Array part with an angle of 360 degrees.

Step7: The last step is to calculate and plot spectral analysis

victimisation MUSIC rule.

Step8: To perform the analysis, we tend to initial produce a

steering vector matrix with the assistance of DOA’s found.

Step9: Generate BPSK symbols and add uncorrelated noise

to the present knowledge to come up with an information

matrix.

Step10: To form a variance matrix and realize all the Eigen

values and Eigen vectors from this matrix.

Step11: Sort these Eigen vectors to separate signal Eigen

vectors in Qs and noise Eigen vectors in Qn.

L shaped 3

antenna

array

Output

radiated

Angle of

arrival

Array element

&array factor

calculation

Spectral analysis

using MUSIC

al orithm





Step12: we tend to then type a steering vector matrix from

every of the angles from one to 360 in a1.

Step13: Finally we tend to plot the spectral values against the

angles in degrees.

A spectrum instrument measures the magnitude of input

signal versus frequency among the complete frequency vary

of the instrument. The first use is to live the ability of the

spectrum of far-famed and unknown signals. The signal a

spectrum instrument measures is electrical, however, spectral

compositions of different signals, like acoustic pressure

waves and optical light-weight waves, may be through the

applicable electrical device. By analyzing the spectra of

electrical signals, dominant frequency, power, distortion,

harmonics, bandwidth, and different spectral elements of an

indication may be determined that don't seem to be simply

detectable in time domain waveforms. These parameters

square measure helpful within the characterization of

electronic devices, like wireless transmitters. The show of a

spectrum instrument has frequency on the horizontal axis and

also the amplitude on the vertical axis. To the casual

observer, a spectrum instrument appears like AN scope and,

in fact, some work instruments will perform either as AN

scope or a spectrum instrument.

Fig 6: Spectral Analysis using MUSIC Algorithm

Fig 7: Measured Angle of Fig Arrival shown at precisely 90 and 270 deg

Fig 5: Array Factor and Array Element

The measured results are plotted in Fg.5 along with

practical predictions obtained from a simple model based on

array factor and array element.

III. CONCLUSION

While in the presence of a two element time-switched

array system has been implemented. The signals to each

element of the array are time switched to provide a phase

modulated output signal in which the depth of modulation is

dependent on the angle of arrival of the received signal. The

angular response to the array at the fundamental frequency of

0 50 100 150 200 250 300 350 400-25

-20

-15

-10

-5

0

5

10Output

Angle (deg)

G a

i n

( d B )

0.5

1

30

210

60

240

90

270

120

300

150

330

180 0

0.5

1

30

210

60

240

90

270

120

300

150

330

180 0





the received signal exhibits a directional response at

broadside, while the response at the first harmonic of the

switching frequency exhibits a deep null.

REFERENCES

[1] M.J.Wilson and B.S.Halo, the ARRL Handbook for the Radio mateur, 65 th

ed.Washington, DC: American Radio Relay League, 1988.

[2] A.Tennant and B.chambers, “A two-element time-modulated array with

direction finding properties,”IEEE Antennas Wireless propag. Lett, vol. 6,

pp.64-65, 2007.

[3] A.Tennant and B.chambers “Direction finding using a four element. Time-

switched array,” presented at the Loughborough Antennas and propagation

conf, Loughborough, U, K, Mar.17-18, 2008.

[4]H.E.Shanks and R.W.Bckmoree,”Four-dimensional electromagneticradiators, “canard J.phys, vol. 37, p.263, 1959.

[5] W.H. Kummel, A. T. Villenuve,T.S.Fong and F.G. Terrio,”ultra- low side

lobes from time-modulated arrays”IEEE Trans Antennas propag., vol.

11,pp.633-69,1963.

[6] S.Yang, Y.B.Gan,Z, and A. Qing,” Sideband suppression in time-

modulated linear arrays by the differential evolution algorithm,”IEEE

Antennas Wireless Propag.Lett.,vol. 1,pp. 173-175,2002.

[7] S.Yang, Y.B.Gan, and P.k.Tan,”A new technique for Power- pattern

synthesis in time-modulated linear arrays,”IEEE Antennas Wireless propag.

Lett, vol.3, p.298-300, 2004.

Author Biographies

Mr.M.DEVENDRA obtained his

M.S. in Electronics and Control from

BITS Pilani in 1996.He is currently

pursuing Ph.D degree from GITAM

University, Hyderabad, India. He

published 3 papers in International

journals and presented 4 papers in

National conferences and 1 paper in

International conference. He is

presently working as Associate

Professor in ECE Department,

G.Pulla Reddy Engineering, College, Kurnool, India. His research interests

include VLSI and Signal processing.

Ms.B.GAYATHRI is pursuing her

M.Tech in communication and signal

processing(C.S.P) at G.Pulla Reddy

Engineering, College, Kurnool,India. She

published 1 paper in International

conference and 1 paper in national

conference.. Her area of Interests is in the field of Antennas and signal processing.

Low Cost Em Signal Direction Estimation With Two Element Time Modulated Array System For Military/Police Search

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