1

SUMMER TRAINING

REPORT ON

STUDY OF RADAR

Submitted By :-

Name : RAHUL ARORA

Enroll No. : 07814802811

Branch : 7ECE-123 (E-3)

PDF processed with CutePDF evaluation edition www.CutePDF.com

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CONTENTS

Page No.

1. Acknowledgement 3

2. Preface 4

3. Overview 5

Introduction

Corporate Mission

Corporate Objectives

Manufacturing Units

Customer Profile and Product Range

4. BEL Ghaziabad Unit 11

Formation

Product Ranges

5. Rotation Program 14

6. RADAR 18

Introduction

Basic Block Diagram of RADAR

Echo Shift

Doppler Effect

7. Principle Of Working of RADAR 21

Radar Transmitter

Radar Receiver

Free Space Radar Equations

8. Types of RADAR 25

Primary RADAR

Secondary RADAR

Continuous Wave RADAR

9. IFF Unit (Identification Friend or Foe) 28

10. Working of a Simple RADAR 30

11. Applications of RADAR 32

12. Other Uses of RADAR 33

13. Conclusion 34

14. References 35

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ACKNOWLEDGEMENT

First of all I would like to thank Mr. B.K.PANT ( MANAGER Human Resource Development Deptt.) for granting me

the permission to work as a Trainee in this esteemed company & for providing me all the facilities.

I also remain grateful to Mr. RAGHUNANDAN TYAGI (DM-Human Resource Development Department), who

granted us the permission to take this project. This project could be accomplished in the time span of weeks only due to

the kind co-operation of Manager. I am thankful to him and his colleagues.

I would also like to thank Mr. GIRISH KUMAR (Gen. Manager, RADAR and Unit Head) under whom I took this

project of Study of RADAR.

I pay my special thanks to Mr. AMIT VOHRA (Dep. Engineer) who guided me on my project and without who I was

not able to complete my project.

I am also thankful to other BEL staff that helped me during the summer training.

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PREFACE

With the ongoing revolution in electronics and communication where innovations are taking place at the blink of eye, it

is impossible to keep pace with the emerging trends.

This six weeks training is a part my 4-year degree course. Practical industrial training mainly aims at making one aware

of industrial environment, which means that, gets to know the limitation, constraint and freedom under which an

engineer works. One also gets opportunity to see from close quarter that indicates management relation. This training

mainly involves industrial and complete knowledge about designing, assembling and manufacturing of equipments.

Excellence is an attitude that the whole of the human race is born with. It is the environment that makes sure whether

the result of this attitude is visible or otherwise. A well planned, properly executed and evaluated industrial training

helps a lot in inculcating a professional attitude. It provides a linkage between the us and industry to develop an

awareness of industrial approach to problem solving, based on a broad understanding of process and mode of operation

of organization.

During this period, I got the real experience for working in the actual environment. Most of the theoretical knowledge

that has been gained during the course of my studies is put to test here. Apart from this, I get an opportunity to learn the

latest technology, which immensely helps them in building my career.

I had the opportunity to have a real experience on many ventures, which increased my sphere of knowledge to a great

extent. I got a chance to learn many new technologies and was also interfaced to many new instruments and all the

credit goes to organization BHARAT ELECTRONICS LTD.

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OVERVIEW

INTRODUCTION

Bharat Electronics Limited (BEL) was established in 1954 as a public-sector enterprise under the administrative control

of Ministry of Defense as the fountain head to manufacture and supply electronics components and equipment. BEL,

with a noteworthy history of pioneering achievements, has met the requirement of state-of-art professional electronic

equipment for defense, broadcasting, civil defense and telecommunications as well as the component requirement of

entertainment and medical X-Ray industry. Over the years, BEL has grown to a multi-product, multi-unit, and

technology driven company with track record of a profit earning PSU.

The company has a unique position in India of having dealt with all the generations of electronic component and

equipment. Having started with a HF receiver in collaboration with T-CSF of France, the companys equipment designs

have had a long voyage through the hybrid, solid state discrete component to the state of art integrated circuit

technology. In the component arena also, the company established its own electron valve manufacturing facility. It

moved on to semi-conductors with the manufacture of germanium and silicon devices and then on to manufacture of

integrated circuits. To keep in pace with the components and equipment technology, its manufacturing and product

assurance facilities have undergone sea change. From quality check control machines to multi-dimensional profile

measurement machines, Automatic testing machines, environmental labs to check extreme weather and other

operational conditions. All these facilities have been established to meet up the stringed requirements.

Today BELs infrastructure has spread over nine locations with 29 production divisions having ISO-9001/9002

accreditation. Product mix of company is spread over the entire Electro-magnetic (EM) spectrum ranging from tiny

audio frequency semiconductor to huge radar systems and X-Ray tubes o the upper edges of the spectrum .Its

manufacturing units have special focus towards the product ranges like defence communication, Radars, Optical &

Opto-electronics, Tele-communications, Sound and vision and broadcasting, Electronic components ,etc.

Besides manufacturing and supply of a wide variety of products, BEL offers a variety of services like Telecom and

Radar Systems Consultancy, Contract Manufacturing, Calibration of Test & Measuring Instruments, etc. At the

moment, the company is installing MSSR radar at important airports under the modernization of airports plan of

National Airport Authority (NAA).

BEL has nurtured and built a strong in-house R&D base by absorbing technologies from more than 50 leading

companies worldwide and DRDO Labs for a wide range of products. A team of more than 800 engineers is working in

R&D. Each unit has its own R&D Division to bring out new products to the production lines. Central Research

Laboratory (CRL) at Bangalore and Ghaziabad works as independent agency to undertake contemporary design work

on state-of-art and futuristic technologies. About 70% of BEL's products are of in-house design.

BEL was among the first Indian companies to manufacture computer parts and peripherals under arrangement with

International Computers India Limited (ICIL) in 1970s. BEL assembled a limited number of 1901 systems under the

arrangement with ICIL. However, following Government's decision to restrict the computer manufacture to ECIL, BEL

could not progress in its computer manufacturing plans. As many of its equipment were microprocessor based, the

company continued to develop computers based application, both hardware and software. Most of its software

requirements are in real time. EMCCA, software intensive naval ships control and command system is probably one of

the first projects of its nature in India and Asia.

\

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BEL has production units established at different parts of the country. The year of establishment and location are as

follows:

S.No Year of establishment

Location

1. 1954 Bangalore

2. 1972 Ghaziabad

3. 1979 Pune

4. 1979 Tajola(Maharashtra)

5. 1984 Hyderabad

6. 1984 Panchkula(Haryana)

7. 1985 Chennai

8. 1985 Machilipatnam(A.P)

9. 1986 Kotdwara(U.P)

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CORPORATE MISSION

To be the market leader in Defence Electronics and in other chosen fields and products.

CORPORATE OBJECTIVES

1. To become a customer-driven company supplying quality products at competitive prices at the expected time

and providing excellent customer support.

2. To achieve growth in the operations commensurate with the growth of professional electronics industry in the

country.

3. To generate internal resources for financing the investments required for modernization, expansion and growth

for ensuring a fair return to the investor.

4. In order to meet the nations strategic needs, to strive for self-reliance by indigenization of materials and

components.

5. To retain the technological leadership of the company in Defence and other chosen fields of electronics

through in-house Research and development as well as through collaboration/co-operation with

Defence/National Research Laboratories, International companies, Universities and Academic Institutions.

6. To progressively increase overseas sales of its products and services.

7. To create an organizational culture this encourages members of the organization to realize their full potential

through continuous learning on the job and through HRD initiatives.

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MANUFACTURING UNITS

Bangalore (Karnataka):

It was the first centre as already been given, being established in 1954. Since then, the Bangalore complex has grown to

specialize in communication and Radar/Sonar systems for army, navy, air force etc.

Ghaziabad (Uttar Pradesh):

Its the second largest unit to manufacture special types of Radars for the Air Defence Ground Environment System. It

provides Communication systems to the Defence forces and Microwave users.

Pune (Maharashtra):

This unit manufactures Image Converter tubes. Subsequently, Magnesium Manganese-dioxide batteries, Lithium

sulphur batteries and X-Ray Tubes/cables were added to the product range. At present unit manufactures Laser sub-unit

for tank fire control systems and Laser Range finders for the defence services.

Machilipatnam (Andhra Pradesh):

The product line includes Passive Night vision equipment, Binoculars, Goggles periscopes for tank fire control

systems. This unit also meets up demands of professional grade radio-communication equipment in VHF and UHF

ranges.

Chennai (Tamil Nadu):

It was established to manufacture gun control equipment required for the integration and installation in the Vijayanta

Tanks. The unit now is manufacturing Stabilizer systems for T-72 tanks, Infantry Combat Vehicles BMP-II etc.

Kotdwar (Uttar Pradesh):

This unit manufactures Tele-communication equipment for both defence and civilian.

Taloja (Maharashtra):

For the manufacture of B/W TV Glass bulbs, this plant was established in collaborating with coming, France in 1986.

The unit is now fully mobilized to manufacture 20 Glass bulbs indigenously.

Hyderabad (Andhra Pradesh):

To coordinate with the major Defence R&D Laboratories located in Hyderabad, DLRL, DRDL, and DMRL, BEL

established a unit in Hyderabad in 1986. Force Multiplier systems are manufactured here for the Defence services.

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Customer Profile & BEL Product Range

Defence

Army Tactical and Strategic Communication Equipment and Systems,

Secrecy Equipment, Digital Switches, Battlefield Surveillance

Radar, Air Defence and Fire Control Radar, Opto-Electronic

Instruments, Tank Fire Control Systems, Stabilizer Systems,

Stimulators and Trainers.

Navy Navigational, Surveillance, Fire Control Radar, IFF, SONAR

Systems, Torpedo Decoys, Display Systems, EW Systems,

Simulators, Communication Equipment and Systems.

Air Force Surveillance and Tracking Raiders, Communication Equipment

and Systems, IFF and EW Systems.

Non-Defence

Para-Military Communication Equipment and Systems.

Space Department Precision Tracking Radar, Ground Electronics, Flight and On-

Board Sub-systems.

All India Radio MW, SW & FM Transmitters.

Doordarshan

(TV Network)

Low, Medium and High Power Transmitters, Studio Equipment,

OB Vans, Cameras, Antennae, Mobile and Transportable Satellite

Uplinks.

NCERT TV Studios on Turnkey Basis for Educational Programs.

Department of

Telecommunications

Transmission Equipment (Microwave and UHF) and PCM

Multiplex, Rural and Main Automatic Exchanges, Flyaway Satellite

Terminals, Solar Panels for Rural Exchanges.

Videsh Sanchar

Nigam and other

Corporate Bodies

MCPC VSAT, SCPC VSAT, Flyaway Earth Stations. Hub Stations,

Up/Down Converters, LNA Modems

Civil Aviation Airport Surveillance Radar, Secondary Surveillance Radar.

Meteorological

Department

Cyclone Warning and Multipurpose Meteorological Radar.

Power Sector Satellite Communication Equipment.

Oil Industry Communication Systems, Radar.

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Forest Departments,

Irrigation &

Electricity Boards

Communication Systems.

Medical &

Health Care

Clinical and Surgical Microscope with Zoom, Linear Accelerators.

Railways Communication Equipment for Metros, Microwave Radio Relays,

And Digital Microwave Radio Relays.

Equipment Components

Defence Transmitting Tubes, Microwave Tubes, Lasers, Batteries,

Semiconductors-Discrete, Hybrid and Integrated Circuits.

Non-Defence

All India Radio,

Doordarshan(TV Network),

Department of

Telecommunications

Transmitting Tubes, Microwave Tubes, and Vacuum Tubes.

Entertainment Industry B/W TV Tubes, Silicon Transistors, Integrated Circuits,

Bipolar and CMOS, Piezo Electric Crystals, Ceramic

Capacitors and SAW Filters.

Telephone Industry Integrated Circuits, Crystals.

Switching Industry Vacuum Interrupters.

Instrumentation Industry Liquid Crystal Displays.

Medical &Health Care X-ray Tubes.

Systems/Network

Identity Card Systems Software, Office Automation

Software, LCD On-line Public Information Display Systems

and Communication Networks / VSAT Networks.

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BEL GHAZIABAD UNIT

The main equipment made by BEL includes: Radar, Antennas, Satellite Communication Equipment (for use in the

upcoming BELNET which all the units are being linked up) and other command & control support equipment.

The various department of BEL are:-

Human Resource & Development

Plant and Service

Work Maintenance

Test Equipment and Automation

Works Assembly

Magnetics

Microwave Component

Environment and Testing Laboratory

Personal and Administration

Finance and Account

Management Service

Production control

Material Management

Central Services

Antenna Fabrication

Machine Shop

Fabrication Shop

P.C.B Fabrication

Q.C Works

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Formation

In the mid 60s, while reviewing the defense requirement of the country, the government focused its attention to

strengthen the air defense system, in particular the ground electronics system support, for the air defense

network. This led to the formulation of a very major plan ADGES with Prime Minister as the presiding officer

of the apex review committee on the development and production of electronic equipment. The ministry of

defense immediately realized the need to establish production capacity for meeting the electronic equipment

requirements for its plan ADGES.

BEL was then entrusted with the task of meeting the development and production requirement for the plan

ADGES and in view of the importance of the project it was decided to create additional capacity at a second unit

of the company.

In December 1970 the Govt. sanctioned an additional unit for BEL. In 1971 the industrial license for

manufacture of radar and microwave equipment was obtained; 1972 saw the commencement of construction

activities and production was launched in 1974.

Over the years, the unit has successfully manufactured a wide variety of equipment needed for defense and civil

use. It has also installed and commissioned a large number of systems on turnkey basis. The unit enjoys a

unique status as manufacturer of IFF systems needed to match a variety of Primary Radars. More than 30

versions of IFF have already been supplied traveling the path from vacuum technology to solid state to latest

Microwave Component based system.

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PRODUCT RANGES

The product ranges today of the company are:

Radar Systems: 1) 3-Dimensional High Power Static and Mobile Radar for the Air Force.

2) Low Flying Detection Radar for both the Army and the Air force.

3) Tactical Control Radar Systems for the Army

4) Battlefield Surveillance Radar for the Army

5) IFF Mk-X Radar systems for the Defence and Export

6) ASR/MSSR systems for Civil Aviation.

7) Radar & allied systems Data Processing Systems.

Communications: 1) Digital Static Tropo scatter Communication Systems for the Air Force.

2) Digital Mobile Tropo scatter Communication System for the Air Force and Army.

3) VHF, UHF & Microwave Communication Equipment.

4) Bulk Encryption Equipment.

5) Turnkey Communication Systems Projects for defence & civil users.

6) Static and Mobile Satellite Communication Systems for Defence

7) Telemetry/Tele-control Systems.

Antennae: 1) Antennae for Radar, Terrestrial & Satellite Communication Systems.

2) Antennae for TV Satellite Receive and Broadcast applications.

3) Antennae for Line-of-sight Microwave Communication Systems.

Microwave Component: 1) Active Microwave components like LNAs, Synthesizer, Receivers etc.

2) Passive Microwave components like Double Balanced Mixers, etc

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ROTATION PROGRAM

Under this I was introduced to the company by putting them under a rotation program to various departments.

The several departments where I had gone under my rotational program are:

Test Equipment and Automation

P.C.B. Fabrication

Quality Control Works Radar

Works Assembly Communication

Magnetics

Microwave Lab

Rotation period was to give me a brief insight of the companys functioning and knowledge of the

various departments. A brief idea of the jobs done at the particular departments was given. The

cooperative staff at the various departments made the learning process very interesting, which

allowed me to know about the company in a very short time.

Test Equipment And Automation Testing equipment and automation laboratory is the most important laboratory of the BEL. Basically in this lab

testing, calibration, maintenance and repairing takes place. This lab is responsible for all these activities which

lead to the maintenance of all the instruments made by BEL. There are 300 equipments and they are of 16 types.

A calibration is basically testing of equipment with a standard parameter. It is done with the help of standard

equipment should be of some make, model and type.

BEL is basically recognized by the National Accreditation Board for Testing and Calibration Laboratories

(NABL). The testing lab of BEL has direct link with the National Physics Laboratory (NPL) i.e. some products

made in the NPL are also tested and calibrated here.

The national physical laboratory (NPL), New Delhi provides the standard values yearly. BEL follows

International Standard Organization (ISO) standard. The test equipments are calibrated either half yearly or

yearly. After testing different tags are labeled on the equipment according to the observations.

Green O.K , Perfect

Yellow Satisfactory but some trouble is present.

Red Cant be used, should be disposed off.

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P.C.B.Fabrication P.C.B. stands for Printed Circuits Board. Its an integral part of the Electronics equipment as well as all the

components are mounted on it. It consists of the fiberglass sheet having a layer of copper on both sides.

Types Of PCBs

1. Single Sided Board : Circuits on one side.

2. Double Sided Board : Circuit on Both sides.

3. Muti-layer Board : Several layers are interconnected through whole metallization.

BEL-Ghaziabad produces only single-sided and double-sided PCBs.

Fabrication of single sided PCBs:

1. A copper clad sheet is taken. It is cleaned and scrubbed.

2. The sheet is laminated with a photosensitive solution.

3. Positive photo paint of the required circuit is placed over the laminated sheet and it is subjected to the

UV light. As a result the transparent plate gets polymerized and the opaque part remains

unpolymerized.

4. The plate is dipped in solution in which the non-polymerized part gets dissolved.

5. Tin plating is done on the tracks obtained.

6. Lamination of the plate is removed.

7. The unwanted copper from the plate is also removed by dipping it in the solution that dissolves copper

but not tin (etching).

8. Now drilling is done on the paths where the components are to be mounted. This process fabricates

PCB.

Raw material for PCBs

Most common raw material used for manufacturing of PCBs is copper cladded glass epoxy resin sheet. The

thickness of the sheet may vary as 1.2, 2.4 and 3.2mm and the standard size of the board is 610mm to 675mm

QUALITY CONTROL According to some laid down standards, the quality control department ensures the quality of the product. The

raw materials and components etc. purchased and inspected according to the specifications by IG department.

Similarly QC work department inspects all the items manufactured in the factory. The fabrication department

checks all the fabricated parts and ensures that these are made according to the part drawing, painting , plating

and stenciling etc are done as per BEL standards.

The assembly inspection departments inspects all the assembled parts such as PCB , cable assembly ,cable form

, modules , racks and shelters as per latest documents and BEL standards.

The mistakes in the PCB can be categorized as:

1. D & E mistakes

2. Shop mistakes

3. Inspection mistakes

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The process card is attached to each PCB under inspection. Any error in the PC is entered in the process card by

certain code specified for each error or defect.

After a mistake is detected following actions are taken:

1. Observation is made.

2. Object code is given.

3. Division code is given.

4. Change code is prepared.

5. Recommendation action is taken

WORK ASSEMBLY

This department plays an important role in the production. Its main function is to assemble various components,

equipments and instruments in a particular procedure.

It has been broadly classified as:

WORK ASSEMBLY RADAR e.g. INDRA II, REPORTER.

WORK ASSEMBLY COMMUNICATION e.g. EMCCA, MSSR, MFC.

EMCCA: EQUIPMENT MODULAR FOR COMMAND CONTROL

APPLICATION.

MSSR: MONOPULSE SECONDARY SURVEILLANCE RADAR.

MFC: MULTI FUNCTIONAL CONSOLE.

The stepwise procedure followed by work assembly department is:

1) Preparation of part list that is to be assembled.

2) Preparation of general assembly.

3) Schematic diagram to depict all connections to be made and brief idea about all components

4) Writing lists of all components.

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MAGNETICS

In this department different types of transformers and coils are manufactured , which are used in the

various defense equipments i.e. radar , communication equipments.

This department basically consists of three sections:

1)PRODUCTION CONTROL:- Basic function of production control is to plan the production of

transformer and coils as per the requirement of respective division (Radar and Communication). This

department divided into two groups :

(a) Planning

(b) Planning store.

2)WORKS(PRODUCTION):- Production of transformers and coils are being carried out by the works

departments.

3)QUALITY CONTROL:- After manufacturing the transformer/coils the item is offered to the inspection

department to check the electrical parameters(DCR , No load current , full load current , dielectric

strength , inductance , insulation resistance and mechanical dimension as mentioned in the GA drawing

of the product.

MICROWAVE LABORATORY Microwave lab deals with very high frequency measurements or very short wavelength measurements. The

testing of microwave components is done with the help of various radio and communication devices. Phase and

magnitude measurements are done in this section. Power measurements are done for microwave components

because current and voltage are very high at such frequencies.

Different type of waveguides is tested in this department like rectangular waveguides, circular waveguides.

These waveguides can be used to transmit TE mode or TM mode. This depends on the users requirements. A

good waveguide should have fewer loses and its walls should be perfect conductors.

In rectangular waveguide there is min. distortion. Circular waveguides are used where the antenna is rotating.

The power measurements being done in microwave lab are in terms of S- parameters. Mainly the testing is done

on coupler and isolators and parameters are tested here.

There are two methods of testing:

1. Acceptance Test Procedure (ATP)

2. Production Test Procedure (PTP)

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RADAR

INTRODUCTION

RADAR is acronym for Radio Detection and Ranging.

Today, the technology is so common that the word has become standard English noun. The development of

RADAR accelerated and spread in middle and late 1930s with first successful demonstration in 1936. It uses

electromagnetic waves in microwave region to detect location, height, intensity and movements of targets. It

operates by radiating energy into space and detecting the echo signals reflected from an object, or target. The

reflected energy that is reflected to radar not only indicates the presence of target, but by comparing the received echo signals with the signals that were transmitted its location can be determined along with the other target

related information.

Radar is an active device. It utilizes its own radio energy to detect and track the target. It does not depend on

energy radiated by the target itself. The ability to detect a target at great distances and to locate its position with

high accuracy are two of the chief attributes of radar.

Earlier radar development was driven by military necessities. But now it enjoys wide range of application. One

of the most common is the police traffic radar used for enforcing speed limits. Another is color weather radar,

other most famous application is air traffic control system.

1)RADAR is an electromagnetic system for detection and location of reflecting objects such as aircraft,

ships, spacecraft, vehicles, people, and the natural environment.

2)It operates by radiating energy into space and detecting the echo signal reflected from an object or target.

3)The reflecting energy that is returned to the radar not only indicates the presence of a target, but also by

comparing the received echo signal with the signal that was transmitted, its location can be determined along

with other target-related information.

4)Radar can perform its function at long or short distances and under conditions impervious to optical and

infrared sensors.

5)Its can operate in darkness, haze, fog, rain, and snow.

6)Its ability to measure distances with high accuracy and in all weather is one of its most important attributes.

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TRANSMITTER

RECIEVER

DUPLEXER

A

N

T

E

N

N

A

The Basic Block Diagram Of Radar

Radar consists of a transmitter and a receiver each connected to a directional antenna.

A transmitter (in the upper left portion of the figure) is capable of sending out a large UHF or microwave power through the antenna.

A portion of transmitted energy is intercepted by the target and reradiated in many directions.

The receiver receives, analysis, and displays the information in the reflected echoes picked up by the antenna. There it is processed to detect the presence of the target and determine its location.

The single antenna is used for transmitter and reception with the help of a switch called duplexer.

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Echo Shift

In audio signal processing and acoustics, an echo (plural echoes) is a reflection of sound, arriving at the listener

sometime after the direct sound. Typical examples are the echo produced by the bottom of a well, by a building,

or by the walls of an enclosed room and an empty room. A true echo is a single reflection of the sound source.

The time delay is the extra distance divided by the speed of sound.

Echo is something you experience all the time. If you shout into a well or a canyon, the echo comes back a

moment later. The echo occurs because some of the sound waves in your shout reflect off from a surface (either

the water at the bottom of the well or the canyon wall on the far side) and travel back to your ears. The length of

time between the moments you shout and the distance between you and the surface that creates the echo

determines the moment that you hear the echo.

Doppler Effect

The Doppler effect (or Doppler shift), named after the Austrian physicist Christian Doppler, who proposed it in

1842 in Prague, is the change in frequency of a wave (or other periodic event) for an observer moving relative to

its source.

Doppler shift is a common phenomenon. Doppler shift occurs when sound is generated by, or reflected off of, a

moving object. Doppler shift in the extreme creates sonic booms. Heres how to understand Doppler shift

Lets say there is a car coming toward you at 60 miles per hour (mph) and its horn is blaring. You will hear the

horn playing one note as the car approaches, but when the car passes you the sound of the horn will suddenly

shift to a lower note. Its the same horn making the same sound the whole time. The change you hear is caused

by Doppler shift.

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PRINCIPLE OF WORKING OF BASIC RADAR Radar involves the transmission of pulses of electromagnetic waves by means of a directional antenna. A radar

system has a transmitter that emits radio waves called radar signals in predetermined directions. Some of the

pulses are reflected by objects that intercept them. When these come into contact with an object they are

usually reflected or scattered in many directions.

Transmitted signal

Antenna

Transmitter Target

Echo signal

Receiver

Range to target

Target detection and ranging The working of basic radar is shown in figure. Radar signals are reflected especially well by materials of

considerable electrical conductivity. The reflections are picked up by a receiver, processed electronically, and

converted into visible form by means of a cathode-ray tube. The range of the object is determined by measuring

the time it takes for the radar signal to reach the object and return. The object's location with respect to the radar

unit is determined from the direction in which the pulse was received. In most radar units the beam of pulses is

continuously rotated at a constant speed, or it is scanned (swung back and forth) over a sector, also at a constant

rate. If the object is moving either toward or away from the transmitter, there is a slight equivalent change in the

frequency of the radio waves, caused by the Doppler effect. The velocity of the object is measured by applying

the Doppler principle, if the object is approaching the radar unit, the frequency of the returned signal is greater

than the frequency of the transmitted signal, if the object is receding from the radar unit, the returned frequency

is less and if the object is not moving relative to the radar unit, the return signal will have the same frequency as

the transmitted signal

Radar receivers are usually, but not always, in the same location as the transmitter. Although the reflected radar

signals captured by receiving antenna are usually very weak, they can be strengthened by electronic amplifiers.

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More sophisticated method of signal processing are also used in order to recover useful radar signals.

The general requirement for any radar system is summarized as below:

1. The radar transmitter should remain silent during the echo period.

2. The transmitted pulse should be quite powerful to counter the attenuation during forward and return

journeys.

3. The received echo pulse being weak, the receiver should be extremely sensitive and at the same time

immune to noise signals. It should have necessary amplification, signal processing circuitry.

4. The radar antenna should be highly directive and have a large gain so it can radiate a strong signal and

receive a weak pulse.

5. Pulse repetition frequency (prf) of radar should be high.

Radar transmitter

The radar transmitter produces the short duration high-power RF pulses of energy that are radiated into space by

the antenna. The radar transmitter is required to have the following technical and operating characteristics:

1) The transmitter must have the ability to generate the required mean RF power and the required peak power.

2) The transmitter must have a suitable RF bandwidth. 3) The transmitter must have a high RF stability to meet signal processing requirements. 4) The transmitter must be easily modulated to meet waveform design requirements. 5) The transmitter must be efficient, reliable and easy to maintain and the life expectance and the cost of

the output device must be acceptable.

Radar receiver

The function of radar receiver is to detect the desired echo signals in the presence of noise, interference and

clutter, clutter is defined as any unwanted radar echo. These clutter make difficult the detection of wanted

signals. The design of radar receiver will depend not only on the type of waveform to be detected but also on the

nature of noise interference and clutter echoes.

The radar receiver is required to:

1) Amplify the received signals without adding noise or introducing any form of distortions.

2) Reject interfering signals so that the required can be optimally detected.

3) Receiver should be designed to have sufficient gain, amplification, stability.

4) Receiver should provide large dynamic range to accommodate large clutter signals.

5) Timing and reference signals are needed to properly extract target information.

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Free Space Radar Equations

The radar range equation relates the range of a radar to the characteristics of the transmitter, receiver, antenna,

target and the medium. Free space actually means that there are no obstacles between radar antenna and the

target. Also the free space medium is transparent and homogenous with respect to the refractive index at radar

frequency. If the power of a radar transmitter is denoted by Pt and if an isotropic antenna (one which radiates uniformly in

all the directions) then the power density at a distance R from the radar is equal to the transmitted power divided

by the surface area of sphere of radius R i.e. power density at a distance R from the isotropic source,

= Pt / 4R2watts/m2

Radar usually employ directive antennas to direct the transmitted power Pt into one particular direction. The

gain G of an antenna is a measure of the increased power radiated in the direction of the target as compared with

the power that would have been radiated from an isotropic antenna.

Power density at a distance R from directive antenna of power gain

= Pt G / 4R2 watts/m2

The target intercepts the portion of transmitted power and radiates it in various directions. A measure of the

incident power intercepted by the target and reradiated back in the direction of radar is denoted as the radar

cross-section of the target ().

The total power intercepted by a target having an area is,

= (Pt G / 4 R2). watts

Where is also defined as the area of the target as seen by the radar. It has units of area in m2. is a characteristic of a particular target and is a measure of its size and shape. The power density of echo signal at the radar station is

= (PtG / 4R2) . (1/4R2) = PtG/ (4R2)2 watts

The radar antenna captures the portion of of the echo power.if the effective area of the receiving antenna is denoted byAe, the power Pr received by the radar is given by,

Pr = PtGAe / (4R2)2watts

Maximum radar range is the distance beyond which the target cannot be detected. It occurs when the received echo signal power Pr, just equals the minimum detectable signal (Smin). i.e. when Pr = Smin, R = Rmax and when substituted in Eq. 11.5 we get,

Smin = PtGAe / (4)2 R4max

24

Rmax = [PtGAe /(4)2Smin]

1/4

From the antenna theory, we know that

G = 4Ae / 2

Where, = wavelength of the radiated energy,

Ae = effective area of receiving antenna,

G = transmitter gain

Since radar generally use the same antenna for both transmitter and receiver, the above expression for G can be substituted in Rmax relation. Then,

Rmax = [Pt

Ae / (4)2Smin]

1/4

Rmax = [PtAe2 / 42Smin]

1/4

Also, Ae = G2 / 4,

Rmax = [Pt(G2/4)2 / 42Smin]

1/4

Rmax = [Pt G2 / (4)2 Smin]

1/4

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TYPES OF RADAR Depending on the desired information, radar sets must have different qualities and technologies. One such different qualities and techniques radar sets are classified as shown.

PRIMARY RADAR:

A Primary Radar transmits high-frequency signals toward the targets. The transmitted pulses are

reflected by the target and then received by the same radar. The reflected energy or the echoes are further

processed to extract target information. This means, unlike secondary radar a primary radar unit receive

its own emitted signals as an echo again.

SECONDARY RADAR:

Secondary radar units work with active answer signals. In addition to primary radar, this type of radar

uses a transponder on the airborne target The ground unit, called interrogator, transmits coded pulses

(after modulation) towards the target. The transponder on the airborne object receives the pulse, decodes

it, induces the coder to prepare the suitable answer, and then transmits the interrogated information back

to the ground unit. The interrogator/ground unit demodulates the answer. The information is displayed on

the display of the primary radar. The secondary radar unit transmits and also receives high-frequency

impulses.

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CONTINUOUS WAVE RADAR:

Continuous wave radars continuously transmit a high-frequency signal and the reflected energy is also

received and processed continuously. These radars have to ensure that the transmitted energy doesnt leak into the receiver (feedback connection). CW radars measures radial velocity of the target using

Doppler Effect. If there is relative motion between the radar and the target, the shift in carrier frequency

(Doppler shift) of the reflected wave becomes a measure of targets relative velocity. The block diagram

of continuous wave radar is shown.

F o f o Target

CW Transmitter

F o f d

f0 f d

Detector f

Beat frequency

f

Indicator (mixer)

amplifier

The transmitter generates a continuous oscillations of frequency fo which is radiated by radar antenna. A portion

of this radiated energy is intercepted by target and reradiated energy is collected by the receiver antenna. If the

target is moving with the velocity vr relative to the radar, the received signal will be shifted in frequency from

the transmitted frequency fo by the amount fd. The plus sign for an approaching target and minus sign for a

receding target. The receivedecho signal (fofd) enters the radar via the antenna and is mixed in a detector mixer

with a portion of a transmitter signal fo to produce the Doppler frequency fd. The purpose of using a beat

frequency amplifier is to eliminate echo from stationary targets and to amplify the Doppler echo signal to a level

where it can operate an indicating device such as frequency meter.

ADVANTAGES:

1) It uses low transmitting power, low power consumption.

2) It has simple circuitry and it is small in size.

3) Unlike pulse radar CW radar is able to detect an aircraft inspite of fixed objects. DISADVANTAGES:

1) Practical application of CW radar is limited by the fact that several targets at a given bearing tend to

cause confusion.

2) Range discrimination can be achieved only by introducing very costly complex circuitry.

3) It is not capable of indicating the range of target an can show only its velocity.

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CW RADARS TYPES

Unmodulated

An example of unmodulated CW radar is speed gauges used by the police. The transmitted signal of these

equipments is constant in amplitude and frequency. CW radar transmitting unmodulated power can measure the

speed only by using the Doppler-effect. It cannot measure a range and it cannot differ between two reflecting

objects.

Modulated Unmodulated CW radars have the disadvantage that they cannot measure range, because run time measurements

is not possible (and necessary) in unmodulated CW-radars. This is achieved in modulated CW radars using the

frequency shifting method. In this method, a signal that constantly changes in frequency around a fixed

reference is used to detect stationary objects. Frequency is swept repeatedly between f1 and f2. On examining

the received reflected frequencies (and with the knowledge of the transmitted frequency), range calculation can

be done.

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IFF UNIT

IFF is basically radar bacon system employed for the purpose of general identification of military targets. The

bacon system when used for the control of civil air traffic is called SECONDARY SURVEILLANCE RADAR

(SSR).

The Identification Friend or Foe (IFF) system is a good example of a secondary radar system that is in wide use

in the military environment. A great deal of valuable information can be provided to the secondary radar by the

targets transponder. The transponder provides an identifying code to the secondary radar that then uses the code

and an associated data base system to look up aircraft origin and destination, flight number, aircraft type and

even the numbers of personnel onboard. This type of information is clearly not available from a primary radar

system.

Primary radar locates an object by transmitting a signal and detecting the reflected echo. A Secondary radar

system is basically very similar in operation to primary radar except that the return signal is radiated from a

transmitter on board the target rather than by reflection. In other words, secondary radar operates with a co-

operative active target while the primary radar operates with a passive target.

Secondary radar system consists of an INTERROGATOR and a TRANSPONDER. The interrogator transmitter

in the ground station interrogates transponder equipped aircraft, providing a two way data link to separate

transmit and receive frequencies. The transponder, on board the aircraft, on receipt of a chain of pulses from the

ground interrogator, automatically transmits a reply. The reply, coded for purposes of Identification is received

back at the ground interrogator where it is decoded and displayed on a radar type presentation.

ADVANTAGES OF SSR OVER PRIMARY RADAR

1.Reply pulses are stronger than the echo signals of primary radar.

2.Separate transmitting and receiving frequencies eliminate ground clutter and weather return problems.

3.Reply signal is independent of target cross section.

4.Interrogation and reply path coding provide discrete target identification and altitude data.

The interrogator transmitter operates in L Band at 1030 MHz and the airborne transponder operates at 1090

MHz.The SSR operates in the same frequency channel for both military and civil air traffic control by using

compatible airborne devices in the aircraft.

Operating Frequencies

The interrogator transmitter operates in L Band at 1030 MHz and the airborne transponder operates at 1090

MHz.

The SSR operates in the same frequency channel for both military and civil air traffic control by using

compatible airborne devices in the aircraft.

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Basic Radar System

A basic radar system is spilt up into a transmitter, switch, antenna, receiver, data recorder, processor

and some sort of output display. Everything starts with the transmitter as it transmits a high power

pulse to a switch, which then directs the pulse to be transmitted out an antenna. Just after the antenna

is finished transmitting the pulse, the switch switches control to the receiver, which allows the antenna

to receive echoed signals. Once the signals are received the switch then transfers control back to the

transmitter to transmit another signal. The switch may toggle control between the transmitter and the

receiver as much as 1000 times per second.

Any received signals from the receiver are then sent to a data recorder for storage on a disk or tape.

Later the data must be processed to be interpreted into something useful, which would go on a Pulse

Width and Bandwidth.

Some radar transmitters do not transmit constant, uninterrupted electromagnetic waves. Instead, they

transmit rhythmic pulses of EM waves with a set amount of time in between each pulse. The pulse

itself would consist of an EM wave of several wavelengths with some dead time after it in which there

are no transmissions. The time between each pulse is called the pulse repetition time (PRT) and the

number of pulses transmitted in one second is called the pulse repetition frequency (PRF). The time

taken for each pulse to be transmitted is called the pulse width (PW) or pulse duration. Typically they

can be around 0.1 microseconds long for penetrating radars or 10-50 microseconds long for imaging

radars (a display). Microsecond is a millionth of a second.

Mathematically,

PRT = 1 / PRF

Or

PRF = 1 / PRT

30

WORKING OF A SIMPLE RADAR

A simple RADAR system, as found on many merchant ships, has three main parts. These are:-

1) The antenna unit or the scanner.

2) The transmitter/receiver or transceiver and

3) The visual display unit.

The antenna is about 2 or 3 meters wide and focuses pulses of very high frequency radio energy into a narrow

vertical beam. The frequency of the radio waves is usually about 10,000 MHz. the antenna is rotated at the

speed of 10 to 25 revolutions per minute so that the radar beam sweeps through 300 degrees all around the ship

out to a range of about 90 kilometers.

In all RADARS it is vital that the transmitting and receiving in the transceiver are in close harmony. Everything

depends on accurate measurement of the time which passes between the transmission of the pulse and the return

of the ECHO about 1,000 pulses per second are transmitted. Though it is varied to suit requirements. Short

pulses are best for short-range work, longer pulses are better for long range.

An important part of the transceiver is the modulator circuit. This keys the transmitter so that it can oscillate, or

pulses, for exactly the right length of time. The pulses so generated are video pulses. These pulses are short

range pulses and hence cannot serve out purpose of long-distance communication. In order to modify these

pulses into radio frequency pulses or RF pulses, we need to generate power. The transmitted power is generated

in a device called magnetron, which can handle these very short pulses and very high oscillations.

Between each pulse, the transmitter is switched off and isolated. The weak echoes from the target are picked up

by the antenna and fed into the receiver. To avoid overlapping of these echoes with the next transmitted pulse,

another device called duplexer is used. Thus, by means of a duplexer, undisturbed, two-way communication is

established. The RF echoes emerging from the duplexer are now fed into the mixer where they are mixed with

pulses of RF energy. These pulses are generated by means of a local oscillator. Once the two are mixed, a signal

is produced in the output witch is of intermediate frequency range or IF range. The IF signals is received by a

receiver where it is demodulated to video frequency range, amplified, and then passed to the display unit.

The display unit usually carried all the controls necessary for the operation of the whole radar. It has a cathode

ray tube, which consist of an electron gun in its neck. The gun shoots a beam of electron at a phosphorescent

screen at the far end. The phosphorescent screen glows when hit by the electrons and, the resulting spot of light

can be seen through a glass surface. The screen is circular and is calibrated in degrees around its edge. The

electron beam travels out from the center to the edge. This random motion of the electron beam, known as the

trace, is matched with the rotation of the antenna. So, when the trace is at zero degrees on the tube calibration,

the antenna is pointing dead ahead. The beginning of each trace corresponds exactly which the moment at which

the radar energy is transmitted.

When an echo is received it brightens up the trace for a moment. This is a blip, and its distance from the center

of the tube corresponds exactly with the time taken for the radar pulse to travel to the target and return. So that

blip on the screen gives the range and bearing of the target. As the trace rotates, a complete picture is built up

from the coating of the tube. This type of display is called a PPI (plane position indicator) and is the most

common form of presenting radar information.

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RADAR EQUATION

The amount of power Pr returning to the receiving antenna is given by the radar equation:

Where,

Pt = transmitter power

Gt = gain of the transmitting antenna

Ar = effective aperture (area) of the receiving antenna

= radar cross section, or scattering coefficient, of the target

F = pattern propagation factor

Rt = distance from the transmitter to the target

Rr = distance from the target to the receiver.

In the common case where the transmitter and the receiver are at the same location, Rt = Rr and the term Rt2 Rr

2

can be replaced by R4, where R is the range. This yield:

This shows that the received power declines as the fourth power of the range, which means that the reflected

power from distant targets is very, very small.

The equation above with F = 1 is a simplification for vacuum without interference. The propagation factor

accounts for the effects of multipath and shadowing and depends on the details of the environment. In a real-

world situation, pathloss effects should also be considered.

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APPLICATIONS OF RADAR

Radar has been employed on the ground, in the air, on the sea and in space. Ground based radar has been

applied chiefly to the detection, location, and tracking of the aircraft or space target. Shipboard radar is used as a

navigation aid and safety device to locate buoys, shorelines and other ships as well as for observing aircraft.

Airborne radar may be used to detect other aircraft, ships, or land vehicles or it may be used for mapping of

land, storm avoidance, terrain avoidance and navigation. In space, radar has assist in the guidance of spacecraft

and for remote sensing of the land and sea.

The major use of radar, and contributor of the cost of almost all of its development, has been the military;

although there has been increasingly important civil application, chiefly for marine and air navigation. The

major areas of radar application are briefly described below:

Air Traffic Control (ATC): Radar is employed throughout the world for the purpose of safely controlling air

traffic route and in the vicinity of Airport. Aircraft and ground vehicular traffic at large airport are monitored by

means of high - resolution radar. Radar has been used with GCA (ground control approach) system to guide

aircraft to a safe landing in bad weather.

Ship Safety: Radar is used for enhancing the safety of ship travel by warning of ship potential collision with

other ships, and for detecting navigation buoys, especially in poor visibility. Automatic detection and tracking

equipment are commercially available for use with radar for the purpose of collision avoidance. Shore based

radar of moderately high resolution is also used for the surveillance of harbors as an aid to navigation.

Space: Space vehicles have used radar for rendezvous and docking and for landing on the moon. Some of the

largest ground based radar is for the detection and tracking of satellite.

Remote Sensing: All radar is a remote sensor. Radar has been used as a remote sensor of the weather. It is also

used to probe the moon and planets. The ionospheric sounder, an important adjunct for HF (short wave)

communications, is radar. Remote sensing with radar is also concerned with earth resources, which include the

measurement and mapping of sea condition, water resources, ice cover, agriculture, forestry condition,

geological information and environmental pollution.

Law Enforcement: In addition to the wide use of radar to measure the speed of automobile traffic by highway

police, radar has also been employed as a means for the detection of intruders.

Military: Many of the civilian application of the radar are also employed by the military. The traditional role of

radar for military application has been for surveillance, navigation and for the control and guidance of weapon.

33

OTHER USES OF RADAR

Apart from the above mentioned uses, radar may be employed for other purposes as well. Most missiles to their

respective destination by means of a radar mounted on their nose. Radars using continuous wave transmission

rather than pulses are fitted in devices such as the proximity fuse which causes the missile or shell to explode

when closed to the target.

Radars are also fitted on board of some aircraft to warn the pilot of air turbulence and thunderstorms. They now

play an important role in weather forecasting and are also found on board spacecraft, mapping the surface of the

earth below. Some of the radars that have been manufactured by Bharat Electronics Limited (BEL) listed below:

IRMA INDRA TRS -2215 PSM-33 FLYCATAHER REPORTER SRE CAR (RohniRewhti) TCR (Akash)

All the above are used for air traffic control and surveillance. Mark-I to Mark-XI is a series of radars used for

navigation purposes.

Another radar manufactured by BEL is the CWR or Cyclone Warning Radar.

GTC FUNCTION The GTC generator produces a discharging waveform which rises with GTC trigger and

discharge at a rate of 6 dB/octave.

Interrogate channel video is compared with GTC curve. The comparison gives an output only if the video is

greater than the GTC circuit.

RSLS FUNCTION The RSLS circuit compares the signals received from the two channels i.e., interrogate and

control, and gives the output if the level of the interrogate channel is higher than control channel. This

comparison is done only for a short time (RSLS stroke) started with rushed output of interrogate channel.

ECHO SUPRESSION Each reply pulse in the interrogate channel from a threshold that dies out at 3.5

dB/microsecond. This causes suppression of reflections with small levels.

34

CONCLUSION

The practical training aims at familiarizing the students with the working condition in a professional

firm as well as to apply their theoretical knowledge acquired in the institute into practice. This

training was helpful to me in various direct and indirect ways, like understanding of machines as well

as procedure followed in manufacturing a product. A good insight into inspection and Quality check

of products.

Through this internship, a well handled and followed way of professionalism as an engineer was

being experienced. BEL is one of the NAVRATNAS companies in India, and training in such

organization added a whole new dimension to my observation and practical approach as well as

introducing me to organizational hierarchy.

35

REFERENCES

Bharat Electronics Limited

www.bel-india.com

www.google.com

www.wikipedia.com

www.radartutorial.eu