VISVESVARAYA TECHNOLOGICAL UNIVERSITY
Belgaum-590014
PROJECT WORK REPORTOn
“DESIGN OF A COMPACT BROADBAND BROADBEAM MICROSTRIP ANTENNA FOR SSR APPLICATIONS”
Submitted in partial fulfillment of the requirements for the VIII Semester
Bachelor of EngineeringIN
ELECTRONICS AND COMMUNICATION ENGINEERINGFor the Academic year
2011-2012
BYRAMYA KANNA . P 1PE08EC074CHANDAN.K.A 1PE08EC121PREMSHANKAR ROUSHAN 1PE08EC122DEEPAK CHANDRASEKHARAN 1PE07EC024
Under the guidance ofMRS. SANDHYA . P C
MR.A.K.SINGHAssistant professor
Scientist "D"Dept. of ECE, PESSE.
CABS, DRDO
Department of Electronics and communication EngineeringPES SCHOOL OF ENGINEERING
HOSUR ROAD , BANGALORE-56010
PES SCHOOL OF ENGINEERINGHOSUR ROAD
BANGALORE-560100
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
CERTIFICATEThis is to certify that the project work entitled “DESIGN OF A COMPACT, BROADBAND, BROADBEAM MICROSTRIP ANTANNA FOR SSR APPLICATIONS” is a bonafide work carried out by RAMYA KANNA. P bearing register number 1PE08EC074 in partial fulfillment for the award of Degree of Bachelors (Bachelors of Engineering) in Electronics and communication Engineering of Visvesvaraya Technological University, Belgaum during the year 2011-2012.
Signatures:
Seminar Guide Head of the dept.MRS. SANDHYA . P C PROF. AJEY SNR
Assistant professor HOD, ECE PES SCHOOL OF ENGINEERING
BANGALORE - 560010
EXAMINERS :
1.
2.
ORGANISATION PROFILE
INTRODUCTION
BACKGROUND :
Centre for Air Borne Systems (CABS) , Bangalore is dedicated to design and development of Airborne Early Warning and Control (AEW&C) System for airborne surveillance and control of Indian airspace and sea surface.
The importance of developing an indigenous AWACS to increase its electronic force multiplication effect was felt by the IAF in the early 80’s. To realise the indigenous technological capabilities, a precursor to our own full-fledged AWACS programme, Airborne Surveillance Warning and Control (ASWAC) programme was launched in July 1985 with limited scope and objectives. ASWAC , the lead project organisation was formed to pursue R&D activities related to indigenous AEW System development. A project called ‘Guardian’ was sanctioned to carry out the certain vital but long-lead activities.
Centre for Air Borne Systems (CABS) was formed on 1st February 1991on completion of project ‘Guardian’. CABS essentially acts a system house and an integration agency, utilising all available infrastructure and expertise in the country for the development of electronic force multiplier technology focusing attention on AEW/AWACS related technologies.
ASP PROGRAMME :
In pursuant with the above objective , a structurally modified HS-748 AVRO aircraft was integrated with primary radar and its sub-systems. The aircraft used the conventional mechanical scanning with a rotating antenna placed inside a huge (24 ft x 5 ft) composite rotodome. It had undergone extensive flight trials for evaluating the Air Borne Surveillance Radar and its sub-systems.
AEW&C PROGRAMME :
The expertise developed and core competencies achieved along with the assets created remained to be harnessed. IAF owing to their urgent operational requirements placed order for procurement of three AWACS based on IL-76 aircraft from Israel. At the same time , the requirement of an indigenous AEW&C system, based on smaller executive jet, was also felt by the IAF to act as a gap filler and to achieve operationally more agile solution. A joint DRDO-IAF team finalized the requirements of such a system based on an executive jet aircraft namely EMB-145 of Brazil. After a thorough feasibility study and peer review, the prestigious AEW&C programme was sanctioned on
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October 4th for a cost of Rs. 1800 crores. CABS is the nodal agency for execution of the programme with the help of other DRDO laboratories, PSU’s and Indian industries.
VISION AND MISSION STATEMENTS
The vision and mission of the centre is as follows :
VISION
Meet Technological challenges of Airborne Surveillance Systems.
MISSION
Develop key technologies and infrastructure for building efficient and cost effective indigenous Airborne Surveillance System.
QUALITY POLICY
Centre for Airborne Systems is committed to design and develop Airborne Force Multipliers in cost effective ways to meet user requirements and continuously improve the systems / products through an efficient quality management system.
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CORE COMPETENCIES / STRENGTHSDESIGN AND DEVELOPMENT OF AIRBORNE SURVEILLANCE SYSTEM :
- Aircraft structural modifications for mounting of systems.
- System Integration including High level Design, Avionics integration and thermal management.
- Flight test planning and evaluation of indigenous systems.
INFRASTRUCTURE :
- Lightning Test Facility.
- GPS Simulator.
- Anechoic Chambers.
- Thermal Rig.
- Ground Rig.
- Vector and Pulsed Network Analyzers.
- Vx-Works Integrated Software Development Environment.
- Simulation Tools (Catia, Matlab, Flowtherm, Labview ).
- Tools for Visualization and Ergonomics.
- Radar Target/ Scenario Generators.
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ACKNOWLEDGEMENT
"Wit beyond measure is man's greatest treasure."
The satisfaction and euphoria that accompanies the successful completion of any task would be incomplete without the mention of people who made it possible.
I would like to express my sincere gratitude to each and every one of them who helped me complete this seminar report. Clearly , every good outcome has a very good backing.
My sincere thanks to Dr. J. Suryaprasad, Director/Principal of PES school of engineering for providing a congenial environment to work in.
I would also like to thank Mr. Ajey SNR , HOD , Electronics and Communication department, PESSE , for his constant support and encouragement. He has always been a source of inspiration to me.
I am deeply indebted to my project/seminar guide , Mrs. Sandhya . P C , Assistant Professor, Electronics and Communication department, PESSE , for her genuine interest , valuable suggestions and constructive criticism during the seminar work.
To top it all, it was CENTRE FOR AIRBORNE SYSTEMS (CABS), DRDO which gave us an opportunity to realize our dream of carrying out the project in their prestigious organization under the noble guidance of Mr. A.K. Singh, Senior scientist, CABS , DRDO.
Further , it was the technical team of CABS , DRDO; namely Ms. Uma and Mr. Sanjay Manjhi who were of immense help in carrying out the project.
I will always be grateful to Mr. Prashanth.V and Mr. Ananda.M ; project co-ordinaters for giving their thoughtful insights and motivating me to give my best.
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RAMYA KANNA. P
ABSTRACT
Since the earliest days of conflict, warriors have sought the highest possible
position. This was not only to provide an advantage in fighting, but also to see
better, see early enough and then to shoot down the enemy. Be it anything, early
warning, surveillance, eavesdropping, the aim was clear – “Forewarned is
forearmed”. The enemy needs to be observed to determine the strength of his
forces, disposition, movement, and other such information. Observation from
height might have started from high towers of castles, but soon it led to use of hot-
air balloons , airships, and aircraft for surveillance with varied sensors like
RADAR , long-range camera’s and so on.
In this project we design and develop a compact broad-band , light weight, broad-
beam radiating element of electronically scanned secondary surveillance radar
antenna for airborne applications.
Microstrip antennas (MSAs) have several advantages, including that they are
lightweight and small-volume and that they can be made conformal to the host
surface. In addition, MSAs are manufactured using printed-circuit technology, so
that mass production can be achieved at a low cost. MSAs, which are used for
defense and commercial applications, are replacing many conventional antennas.
However, the types of applications of MSAs are restricted by the antennas’
inherently narrow bandwidth (BW). Accordingly, increasing the BW of the MSA
has been a primary goal of research in the field.
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PREFACE
This report is organized into 5 chapters.
CHAPTER 1 : Preamble to the project describing the aim of the project, scope of the project work, limitations and methodology .
CHAPTER 2 : Theory behind the project work : technology of microstrip antenna and feeding techniques.
CHAPTER 3 : Design and Implementation. This chapter describes the calculations involved while designing the microstrip antenna , various design techniques incorporated, simulation and practically measured results.
CHAPTER 4 : Conclusion-final results.
CHAPTER 5 : Bibliography - references made during the course of the project.
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NOTE : include contents, list of figures and list of tables.
CHAPTER 1
PREAMBLE
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1.1 INTRODUCTION
The field of Antenna design and technology is vigorous and dynamic. Over the
last 50 years, Antenna technology has been an indispensable partner of the
communication revolution. They are everywhere ; at our home and workplace, on
our cars and aircrafts, while our ships, satellites and spacecrafts bristle with them.
Antennas are electronic eyes and ears on the world. They are our links with space.
They are an essential and integral part of our civilization. Antennas are the
essential communication link for aircrafts and ships. With mankind activities
expanding into space, the need for antenna will grow up to an unprecedented
degree.
A radio antenna may be defined as the structure associated with the region of
transition between a guided wave and a free space wave , or vice-versa. Antennas
convert electrons to photons or vice versa. The function of an antenna is to radiate
RF energy developed in the transmitter and act as impedance matching device for
matching the impedance of the transmission line with the impedance of space and
to radiate energy in specified directions and suppress the radiation in unwanted
directions.
FIELDS AND RADIATIONS
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The antenna is characterized by its radiation pattern or patterns involving
field quantities. An electromagnetic wave consists of electric and magnetic
fields propagating through space, a field being a region where electric and
magnetic forces act. These fields in a free space wave travelling outwards
at a large distance from the antenna convey energy called RADIATION.
ANTENNA PATTERNS
To completely specify the radiation pattern with respect to field intensity
and polarization requires three patterns :
1. The θ component of the electric field as a function of the angles θ
and ɸ or (θ,ɸ) (v/m) as in the figure.
2. The ɸ component of the electric field as a function of the angles θ
and ɸ or (θ,ɸ) (v/m) .
3. The phases of the fields as a function of the angles θ and ɸ :
δθ(θ,ɸ) and δɸ(θ,ɸ) (radians or degrees ).
Any field pattern can be presented in three- dimensional spherical co-ordinates as
shown in the figure below
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Fig :Antenna Radiation Pattern.
BEAM AREA or BEAM SOLID ANGLE
Beam area of an actual pattern is equivalent to the same solid angle subtended by
the spherical cap of the cone-shaped (triangular cross section) pattern. The solid
angle can often be described approximately in terms of the angles subtended by
the half -power points of the main lobe in the two principal planes.
RADIATION INTENSITY and BEAM EFFICIENCY
The power radiated from an antenna per unit solid angle is called the radiation
intensity U (watts per steradian or per square degree). The total beam area or
beam solid angle consists of the main beam area (or solid angle) plus the minor
lobe area.
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The ratio of the main beam area to the total beam area is called the "MAIN
BEAM EFFICIENCY".
The ratio of the minor lobe area to the total beam area is called the "MINOR
BEAM EFFICIENCY".
DIRECTIVITY
The directivity of an antenna is given by the ratio of the maximum radiation
intensity (power per unit solid angle) to the average radiation intensity. (OR) At a
certain distance from the antenna , the directivity may be expressed as the ratio of
the maximum to the average pointing vector. Both the radiation intensity and
pointing vector values should be measured in the far field of the antenna.
GAIN and RESOLUTION
The gain of an antenna (referred to as a lossless isotropic source) depends on both
its directivity and its efficiency. When gain is used as a single valued quantity
(like directivity) its maximum noise-on-main beam value is implied in the same
way that the power rating of an engine implies its maximum value. The resolution
of an antenna may be defined as equal to half the beam width between the first
nulls. Thus, when the antenna beam maximum is aligned with one satellite, the
first null coincides with the other satellite.
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1.2 AIM OF THE PROJECT
To design, simulate and develop a compact, broad-band , light weight, broad-
beam radiating element (microstrip antenna) of electronically scanned secondary
surveillance radar antenna in L- band for airborne applications.
1.3 OBJECTIVES
The main aim of this project is to design an Antenna array for successful
transmission and reception in L-band (1-2 Ghz).
A single microstrip antenna is designed for the desired specifications. The
size and structure of the antenna are designed in accordance with the
specifications.
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Since we are designing a single antenna / radiating element and not
employing an array of them, we optimise our results to the best by a
certain trade off between essential antenna design parameters.
We employ co-axial feeding technique and also adjust the design
(specifications) to obtain optimal response at the centre frequency (1.06
Ghz).
1.4 SCOPE OF THE PROJECT :
The Secondary Surveillance Radar (SSR) System, also called as Identification of
Friend or Foe (IFF) operates independently and in conjunction with the primary
radar. It comprehends the decision making about a target detected by primary
radar to be a friend or foe. The SSR operates as per the recommendations of
Annexure 10 of International Civil Aviation Organization (ICAO).
It consists of two sub-systems, namely the Interrogator and a Transponder. The
Interrogator transmits pulsed signal with suitable spacing as per the desired mode
of interrogation in a specified direction.
Aircraft fitted with compatible transponder receives the interrogator signal and
replies back in the form of another coded signal. These coded replies are received
by the interrogator and processed for identification by comparing the response
received from the interrogated target with its own database. However in modern
trend of warfare the interrogator is made airborne.
It provides additional target details such as height, range, and azimuth. In
addition, it can extract target status like communication failure, emergency and
hijack.
The SSR Interrogator system consists of a compact broad-band, broad-beam, light
weight radiating element (micro strip antenna) of electronically scanned
secondary surveillance radar antenna, Transmitter – Receiver unit and signal
processor (IFF – SP).
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ILLUSTRATION
Fig :ILLUSTRATION OF SECONDARY SURVEILLANCE RADAR
In the interrogator on the ground:
The secondary radar unit needs a synchronous impulse of the (analogous) primary
radar unit to the synchronization of the indication.
The chosen mode is encoded in the Coder. (By the different modes different
questions can be defined to the airplane.)
The transmitter modulates these impulses with the RF frequency. Because
another frequency than on the replay path is used on the interrogation path, an
expensive duplexer can be renounced.
The antenna is usually mounted on the antenna of the primary radar unit and
turns synchronously to the deflection on the monitor therefore.
In the aircrafts transponder:
A receiving antenna and a transponder are in the airplane.
The receiver amplifies and demodulates the interrogation impulses.
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The decoder decodes the question according to the desired information and
induces the coder to prepare the suitable answer.
The coder encodes the answer.
The transmitter amplifies the replay impulses and modulates these with the
RF reply-frequency.
Again in the interrogator on the ground:
The receiver amplifies and demodulates the replay impulses. Jamming or
interfering signals are filtered out as well as possible at this. signals
From the information’s Mode and Code the decoder decodes the answer.
The monitor of the primary radar represents the additional interrogator
information. Perhaps additional numbers must be shown on an extra display.
1.5 AN INSIGHT TO MICROSTRIP ANTENNA
Deschamps first proposed the concept of the MSA in 1953. However, practical
antennas were developed by Munson and Howell in the 1970s. The numerous
advantages of MSA, such as its low weight, small volume, and ease of fabrication
using printed-circuit technology, led to the design of several configurations for
various applications . With increasing requirements for personal and mobile
communications, the demand for smaller and low-profile antennas has brought the
MSA to the forefront.
An MSA in its simplest form consists of a radiating patch on one side of a
dielectric substrate and a ground plane on the other side. The top and side views of
a rectangular MSA (RMSA) are shown in the figure. However, other shapes, such
as the square, circular, triangular, semicircular, sectoral, and annular ring shapes ,
are also used.
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Fig : Different shapes of microstrip patches
Fig : Typicl MSA configuration.
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Radiation from the MSA can occur from the fringing fields between the periphery
of the patch and the ground plane. The length L of the rectangular patch for the
fundamental TM10 mode excitation is slightly smaller than l /2, where l is the
wavelength in the dielectric medium. The value of εe is slightly less than the
dielectric constant εr of the substrate because the fringing fields from the patch to
the ground plane are not confined in the dielectric only, but are also spread in the
air. To enhance the fringing fields from the patch, which account for the radiation,
the width W of the patch is increased. The fringing fields are also enhanced by
decreasing the εr or by increasing the substrate thickness h. Therefore, unlike the
microwave integrated circuit (MIC) applications, MSA uses microstrip patches
with larger width and substrates with lower εr and thicker h. For MSA
applications in the microwave frequency band, generally h is taken greater than or
equal to1/16th of an inch (0.159 cm).
CHARACTERISTICS OF MSA's
The MSA has proved to be an excellent radiator for many applications because of
its several advantages, but it also has some disadvantages. The advantages and
disadvantages of the MSA are as follows :
ADVANTAGES :
MSAs have several advantages compared to the conventional microwave
antennas. The main advantages of MSAs are listed as follows:
They are lightweight and have a small volume and a low-profile planar
configuration.
They can be made conformal to the host surface.
Their ease of mass production using printed-circuit technology leads to a
low fabrication cost.
They are easier to integrate with other MICs on the same substrate.
They allow both linear polarization and CP.
They can be made compact for use in personal mobile communication.
They allow for dual- and triple-frequency operations.
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DISADVANTAGES
MSAs suffer from some disadvantages as compared to conventional microwave
antennas. They are the following:
Narrow BW
Lower gain
Low power-handling capability.
APPLICATIONS OF MSA's
The advantages of MSAs make them suitable for numerous applications.
The telemetry and communications antennas on missiles need to be thin
and conformal and are often MSAs.
Radar altimeters use small arrays of microstrip radiators.
Other aircraft-related applications include antennas for telephone and
satellite communications.
Microstrip arrays have been used for satellite imaging systems.
Patch antennas have been used on communication links between ships or
buoys and satellites.
Smart weapon systems use MSAs because of their thin profile.
Pagers, the global system for mobile communication (GSM), and the
global positioning system (GPS) are major users of MSAs.Mobile
communication, satellite communication, direct broadcast satellite
services.
Wireless applications due to their low profile structure.
Military aircraft, defense vehicles, rockets and missiles.
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