Final Report

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

Department of ECE,PESSE

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.

Department of ECE,PESSE

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.

Department of ECE,PESSE

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.

Department of ECE,PESSE

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.

Department of ECE,PESSE

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.

Department of ECE,PESSE

NOTE : include contents, list of figures and list of tables.

CHAPTER 1

PREAMBLE

Department of ECE,PESSE

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

Department of ECE,PESSE

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

Department of ECE,PESSE

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.

Department of ECE,PESSE

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.

Department of ECE,PESSE

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.

Department of ECE,PESSE

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).

Department of ECE,PESSE

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.

Department of ECE,PESSE

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.

Department of ECE,PESSE

Fig : Different shapes of microstrip patches

Fig : Typicl MSA configuration.

Department of ECE,PESSE

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.

Department of ECE,PESSE

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.

Department of ECE,PESSE

Department of ECE,PESSE

Department of ECE,PESSE