BHARAT ELECTRONICS LIMITED

INTRODUCTION

India, as a country, has been very lucky with regard to the introduction of telecom

products. The first telegraph link was commissioned between Calcutta and Diamond

Harbor in the year 1852, which was invented in 1876. first wireless communication

equipment were introduced in Indian Army in the year 1909 with the discovery of Radio

waves in 1887 by Hertz and demonstration of first wireless link in the year 1905 by

Marconi and Vacuum tube in 1906. Setting up of radio station for broadcast and other

telecom facilities almost immediately after their commercial introduction abroad followed

this. After the independence of India in 1947 and adoption of its constitution in 1950, the

government was seized with the plans to lay the foundations of a strong, self- sufficient

modern India. On the industrial front, Industrial Policy Resolution (IPR) was announced in

the year 1952. It was recognized that in certain core sectors infrastructure facilities require

huge investments, which cannot be met by private sector and as such the idea of Public

Sector Enterprise was mooted. With telecom and electronics recognized among the core

sectors, Indian Telephone Industry, now renamed as TI Limited, was formed in 1953 to

undertake local manufacture of telephone equipment, which were of electro-mechanical

nature at that stage. Hindustan Cable Limited was also started to take care of telecom

cables.

Bharat Electronics Limited (BEL) was established in 1954 as a Public Sector Enterprise

under the administrative control of Ministry of Defence 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 Defence, broadcasting, civil Defence 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 company's 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 semiconductors with the manufacture of

germanium and silicon devices and then to the manufacture of Integrated circuits. To keep

in pace with the component and equipment technology, its manufacturing and product

assurance facilities have also undergone sea change. The design groups have CADDs

facility, the manufacturing has CNC machines and a Mass Manufacture Facility, and

Quality Control (QC) checks are preformed with 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 the stringent

requirements of MIL grade systems.

Today BEL's infrastructure is spread over nine locations with 29 production

divisions having ISO-9001/9002 accreditation. Product mix of the company is spread over

the entire Electro-magnetic (EM) spectrum ranging from tiny audio frequency

semiconductor to huge radar systems and X-ray tubes on the upper edge of the spectrum.

Its manufacturing units have special focus towards the product ranges like Defence

Communication, Radars, Optical & Opto-electronics, Telecommunications, Sound and

Vision 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.

BEL has won a number of national and international awards for Import Substitution,

Productivity, Quality, Safety Standardization etc. BEL was ranked no.1 in the field of

Electronics and 46th overall among the top 1000 private and public sector undertakings in

India by the Business Standard in its special supplement "The BS 1000 (1997-98)". BEL

was listed 3rd among the Mini Ratanas (category II) by the Government of India, 49 th

among Asia's top 100 Electronic Companies by the Electronic Business Asia and within the

top 100 worldwide Defence Companies by the Defence News, USA.

MANUFACTURING UNITS

BANGALORE (KARNATAKA)

BEL started its production activities in Bangalore in 1954 with 400W high frequency (HF)

transmitter and communication receiver for the Army. Since then, the Bangalore Complex

has grown to specialize in communication and Radar/Sonar Systems for the Army, Navy

and Air Force. BEL's in-house R&D and successful tie-ups with foreign Defence

companies and Indian Defence Laboratories has seen the development and production of

over 300 products in Bangalore alone. The Unit has now diversified into manufacturing of

electronic products for the civilian customers such as D.O.T., V.S.N.L., A.I.R. and

Doordarshan, Meteorological Dept., I.S.R.O., Police, Civil Aviation, and Railways. As an

aid to Electorate, the unit has developed Electronic Voting Machines that are produced at

its Mass Manufacturing Facility (MMF).

GHAZIABAD (UTTAR PRADESH)

The second largest Unit at Ghaziabad was set up in 1974 to manufacture special types of

radar for the Air Defence Ground Environment Systems (Plan ADGES). The Unit provides

Communication Systems to the Defence Forces and Microwave Communication Links to

the various departments of the State and Central Govt. and other users. The Unit's product

range included Static and Mobile Radar, Tropo scatter equipment, professional grade

Antennae and Microwave components.

PUNE (MAHARASHTRA)

This Unit was started in 1979 to manufacture Image Converter Tubes. Subsequently,

Magnesium Manganese-dioxide Batteries, Lithium Sulphur Batteries and X-ray

Tubes/Cables were added to the product range. At the present the Unit manufactures Laser

Sub-unit for tank fire control systems and Laser Range Finders for the Defence services.

MACHILIPATNAM (ANDHRA PRADESH)

The Andhra Scientific Co. at Machilipatnam, manufacturing optics/Opto-electronic

equipment was integrated with BEL in 1983. The product line includes Passive Night

Vision Equipment, Binoculars, Binoculars and Goggles, Periscopes, Gun Sights, Surgical

Microscope and Optical Sights and Mussle Reference Systems for tank fire control

systems. The Unit has successfully diversified to making the Surgical Microscope with

zoom facilities.

PANCHKULA (HARYANA)

To cater the growing needs of Defence Communications, this Unit was established in 1985.

Professional grade Radio-communication Equipment in VHF and UHF ranges entirely

developed by BEL and required by the Defence services are being met from this Unit.

CHENNAI (TAMIL NADU)

In 1985, BEL established another Unit at Chennai to facilitate manufacture of Gun Control

Equipment required for the integration and installation in the Vijayanta tanks. The Unit is

now manufacturing Stabilizer Systems for T-72 tanks, Infantry Combat Vehicles BMP-II;

Commander's Panoramic Sights & Tank Laser Sights are among others.

KOTDWAR (UTTAR PRADESH)

In 1986, BEL started a Unit at Kotdwara to manufacture Telecommunication Equipment

for both Defence and civilian customers. Focus is being given on the requirement of the

Department of Telecommunications to manufacture Transmission and Switching

Equipment.

TALOJA (MAHARASHTRA)

For the manufacture of B/W TV Glass bulbs, this plant was established in collaboration

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 at Hyderabad in 1986. Force Multiplier Systems

are manufactured here for the Defence services.

BEL GHAZIABAD UNIT

Formation

In the mid 60’s, while reviewing the defence requirement of the country, the

government focused its attention to strengthen the air defence system, in particular the

ground electronics system support, for the air defence 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 defence 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 defence 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.

PRODUCT RANGE

The product ranges today of the company are:

Radar Systems

3-Dimensional High Power Static and Mobile Radar for the Air Force.

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

Tactical Control Radar Systems for the Army

Battlefield Surveillance Radar for the Army

IFF Mk-X Radar systems for the Defence and Export

ASR/MSSR systems for Civil Aviation.

Radar & allied systems Data Processing Systems.

Communications

Digital Static Tropo scatter Communication Systems for the Air Force.

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

VHF, UHF & Microwave Communication Equipment.

Bulk Encryption Equipment.

Turnkey Communication Systems Projects for defence & civil users.

Static and Mobile Satellite Communication Systems for Defence

Telemetry/Tele-control Systems.

Antennae

Antennae for Radar, Terrestrial & Satellite Communication Systems.

Antennae for TV Satellite Receive and Broadcast applications.

Antennae for Line-of-sight Microwave Communication Systems.

Microwave Component

Active Microwave components like LNAs, Synthesizer, Receivers etc.

Passive Microwave components like Double Balanced Mixers, etc

Most of these products and systems are the result of a harmonious combination of

technology absorbed under ToT from abroad, Defence R&D Laboratories and BEL's own

design and development efforts.

ORGANIZATION

The operations at BEL Ghaziabad are headed by General Manager with Additional / Deputy General Manager heading various divisions as follows:

1. Design & Engineering Divisions

Development and Engineering-R

Development and Engineering-C

Development and Engineering-Antenna.

2. Equipment Manufacturing Divisions

Radar

Communication

Antenna

Systems

Microwave Components.

3. Support Divisions

Material Management

Marketing & Customer Co-ordination

Quality Assurance & Torque

Central Services

PCB & Magnetics

Information Systems

Finance & Accounts

Personnel & Administration

Management Services.

ROTATION PROGRAM

Under this students are introduced to th 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 us a brief insight of the company’s 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 :

This department deals with the various instruments used in BEL. There are 300

equipments and they are of 16 types.

Examples of some test equipments are:

Oscilloscope(CRO)

Multimeter

Signal Analyzer

Logical Pulsar

Counter

Function Generator etc.

Mainly the calibration of instruments is carried out here. They are

compared with the standard of National Physical Laboratory (NPL). So, it is said to

be one set down to NPL. As every instrument has a calibration period after which

the accuracy of the instrument falls from the required standards. So if any of the

instruments is not working properly, it is being sent here for its correct calibration.

To calibrate instruments software techniques are used which includes the program

written in any suitable programming language. So it is not the calibration but

programming that takes time .For any industry to get its instrument calibrated by

NPL is very costly, so it is the basic need for every industry to have its own

calibration unit if it can afford it.

Test equipment and automation lab mainly deals with the equipment that is used for

testing and calibration .The section calibrates and maintains the measuring instruments

mainly used for Defense purpose.

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.

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 – Can’t be used, should be disposed off.

The standard for QC, which are followed by BEL are:

WS 102

WS 104

PS 520

PS 809

PS 811

PS 369

Where, WS = Workmanship & PS = Process Standard

After the inspection of cables, PCB’s and other things the defect found are given in

following codes.

A --- Physical and Mechanical defects.

B --- Wrong Writing

C --- Wrong Component / Polarity

D --- Wrong Component / Mounting

E --- Bad Workmanship/ Finish

F --- Bad Soldering

G --- Alignment Problem

H --- Stenciling

I --- Others (Specify)

J --- Design & Development

After finding the defect, the equipment is sent to responsible departmentwhich is rectified there.

P.C.B. FABRICATION

P.C.B. stands for Printed Circuits Board. It’s 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 PCBs1. Single Sided Board : Circuits on one side.

2. Double Sided Board : Circuit on Both side.

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

metalization.

Raw material for PCB’s

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.

Operation in process

Following steps are there for PCB manufacturing :-

CNC Drilling

Drill Location

Through Hole Plating

Clean Scrub and Laminate

Photo Print

Develop

Cu electroplate

Tin electroplate

Strip

Etching and cleaning

Tin Stripping

Gold plating

Liquid Photo Imageable Solder Masking (LPISM)

Photo print

Develop

Thermal Baking

Hot Air leaving

Non Plated Hole Drilling

Reverse Marking

Sharing & Routing

Debarring & Packing

P.C.B. is a non-conducting board on which a conductive board is made. The base

material, which is used for PCB plate are Glass Epoxy, Bakelite and Teflon etc.

Procedure for through hole metallization

Loading-Cleaner-Water Rinse-Spray Water-Rinse-Mild Etch-Spray Water-Rinse-

Hydrochloric Acid-Actuator-Water Rinse-Spray Water-Rinse-Accelerator Dip-Spray

Water- Rinse- Electrolyses Copper-Plating-Plating- Spray water-Rinse-Anti Tarnish Dip-

Hot Air Drying- Unloading.

After through hole metallization, photo tool generation is done which is followed by

photo printing. In this the PCB is kept b/w two blue sheets and the ckt. is printed on it. A

negative and a positive of a ckt. are developed. To identify b/w the negative and positive,

following observation is done. If the ckt. is black and the rest of the sheet is white, it is

positive otherwise negative.

Next, pattern plating is done. The procedure for pattern plating follows :

Loading- Cleaner- Water rings- Mild etch- Spray- Water Rinse-Electrolytic- Copper

plating- Water rinse- Sulfuric acid-Tin plating- Water rinse- Antitarnic dip- Hot air dry-

Unloading. To give strength to the wires so that they can not break. This is done before

molding. Varnishing is done as anti fungus prevention for against environmental hazard.

After completion of manufacturing proceeds it is sent for testing. This is followed

by resist striping and copper etching. The unwanted copper i.e. off the tracks is etched by

any of the following chemicals. After this, tin is stripped out from the tracks.

After this solder marking is done. Solder marking is done to mark the tracks to get

oxidized & finally etch. To prevent the copper from getting etched & making the whole

circuit functionally done.

There are three types of solder marking done in BEL :

Wet solder mask: Due to some demerits this method is totally ruled out. The demerit

was

non- alignment, which was due to wrong method applied or wrong machine.

Dry pin solder mask : Due to wastage of films about 30% this method is also not used

now.

Liquid photo imaginable solder mask (LPISM): In this first presoaking is at 80 degree

Celsius for 10 to 20 minutes. Next, screen preparation is done. The board is covered by a

silk cloth whose mesh is T-48. The angle to tilt of the board is 15 degree to 22.5 degree.

The next is ink preparation:

Ink + Hardener

71 % : 29 %

(150 gms.) : (300gms.)

+

Butyrate solo solve 50gms/kg.

Ink preparation-

It uses :-

Ink-----100gm

Catalyst----10% of total weight

Reducer-----10% of total weight

The catalyst is used as binder and prevents the following, while reducer is used as

thinner. The three things are then fully mixed.

For wash out, following procedure takes place.

Water-Lactic acid-Water-Bleaching power-Water-caustic Soda-Water-Air dry-TCE.

After wash out, final baking for one hour at the temt. of 20degree C is done. After this

shearing or routing is done which is followed by debarring and packing.

QUALITY CONTROL (WORK ASSEMBLY )

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

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.

In work assembly following things are done :

M aterial Receive :

Preparation- This is done before mounting and under takes two procedures.

Tinning- The resistors ,capacitors and other components are tinned with the help of

tinned lead solution .The wire coming out from the components is of copper and it is

tinned nicely by applying flux on it so that it does not tarnished and soldering becomes

easy.

Bending- Preparation is done by getting the entire documents , part list drawing and

bringing all the components before doing the work.

Mounting- It means soldering the components of the PCB plate with the help of

soldering tools. The soldering irons are generally of 25 W and are of variable

temperature, one of the wires of the component is soldered so that they don’t move from

their respective places on the PCB plate. On the other hand of the component is also

adjusted so that the PCB does not burn.

Wave Soldering- This is done in a machine and solder stick on the entire path, which are

tinned.

Touch Up- This is done by hand after the finishing is done.

Cleaning:

Inspection- This comes under quality work.

Heat Ageing- This is done in environmental lab at temperature of 40 degree C for 4 hrs

and three cycles.

Testing:

Lacquering- This is only done on components which are not variable.

Storing- After this variable components are sleeved with Teflon. Before Lacquering

mounted plate is cleaned with isopropyl alcohol. The product is then sent to store.

MAGNETICSIn 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 and (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.

The D&E department provides all the information about manufacturing a coil and

the transformer.

The various types of transformers are as follows :

i) Air cored transformers

ii) Oil filled transformers

iii) Moulding type transformers

iv) P.C.B Mounting transformers :-

(a) Impedance matching transformers

(b) RF transformers

(c) IF transformers

The various types of cores are as follows :

i) E type

ii) C type

iii) Lamination

iv) Ferrite core

v) Toroidal core

Steps involved in the process of manufacturing of transformer/coils:

a.) Preparation of former : Former is made of plastic bakelite comprising a male

and female plates assembled and glued alternately to form a hollow rectangular

box on which winding is done.

b.) Winding : It is done with different material and thickness of wire. The winding

has specified number of layers with each layer’s having a specified number of

turns. The distance between the two turns should be maintained constantly that is

there should be no overlapping. The plasatic layer is inserted between two

consecutive layers.

The various types of windings are as follows :

i) Layer Winding

ii) Wave Winding

iii) Bank Winding

c.) Insulation : For inter-winding and inter layer , various types of insulation sheets

viz. Craft paper , paper , leather , oil paper , polyester film are being used.

d.) Protection : To protect the transformer from the external hazards , moisture , dust

and to provide high insulation resistance , they are impregnated.

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)

Drawing of various equipments that are to be tested is obtained and testing is

performed on manufactured part. In the antenna section as well as SOHNA site

various parameters such as gain ,bandwidth ,VSWR , phase ,return loss, reflection

etc. are checked. The instruments used for this purpose are as follow:

1. Filters

2. Isolators

3. Reflectors

4. Network Analyzers

5. Spectrum Analyzers

6. Amplifiers and Accessories

RADAR(RADIO DETECTION AND RANGING)

INTRODUCTION

Radar is an electromagnetic system for the detection and location of reflecting objects such

as aircrafts, ships, spacecraft, vehicles, peoples and the natural environment. It operates by

radiating energy into space and detecting the reflected echo signal from an object or target.

The reflected energy to the radar not only indicates the presence of a target, but by

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

determined along with other target related information. Radar can perform its function at

long or short distances and under conditions impervious to optical and infrared sensors. It

can operate in darkness, haze, fog, rain and snow. Its ability to measure the distance with

high accuracy and in all weather is one of its most important attributes. Although most of

the radar units use microwave frequencies, the principle of radar is not confine to any

particular frequency range. There are some radar units that operate on frequencies well

below 100 MHz and others operate in the infrared range and above.

RADAR DEVELOPMENT

Although the development of radar as a full-fledged technology did not occur until World

War-II, the basic principle of radar detection is almost as old as the subject of

electromagnetism itself. Heinrich Hertz, in 1886, experimentally tested the theories of

Maxwell and demonstrated the similarity between radio and light waves. Hertz showed that

radio waves could be reflected by metallic and dielectric bodies. It is interesting to know

that although Hertz’s experiments were performed with relatively short wavelength ration

(66 cm), later work in radio engineering was almost entirely at longer wavelengths. The

shorter wavelengths were not actively used to any extent until the late thirties. One of the

biggest advocators of radar technology was Robert Watson-Watt, a British scientist.

Several inventors, scientists, and engineers contributed to the development of radar. The

use of radio waves to detect "the presence of distant metallic objects via radio waves" was

first implemented in 1904 by Christian Hülsmeyer, who demonstrated the feasibility of

detecting the presence of ships in dense fog and received a patent for radar as Reichspatent

Nr. 165546. Another of the first working models was produced by Hungarian Zoltán Bay in

1936 at the Tungsram laboratory.

While radar development was pushed because of wartime concerns, the idea first came

about as an anti-collision system. After the Titanic ran into an iceberg and sank in 1912,

people were interested in ways to make such happenings avoidable.

The term RADAR was coined in 1941 as an acronym for RAdio Detection And Ranging.

The name reflects the importance placed by the workers in this field on the need for a

device to detect the presence of a target and to measure its range. This acronym of

American origin replaced the previously used British abbreviation RDF (Radio Direction

Finding).

Although modern radar can extract more information from a target’s echo signal

than its range, the measurement of range is still one of its most important functions. There

are no competitive techniques that can accurately measure long ranges in both clear and

adverse weather as well as can radar.

BASIC PRINCIPLE

An elementary form of radar consists of a transmitting antenna emitting

electromagnetic radiation generated by an oscillator of some sort, a receiving antenna, and

an energy detecting device or receiver. A transmitter generates an electromagnetic signal

(such as a short pulse of sine wave) that is radiated into space by an antenna. A portion of

the transmitted signal is intercepted by a reflecting object (target) and is re-radiated in

many directions. The reradiation directed back towards the radar is collected by the radar

antenna, which delivers it to a receiver. There it is processed to detect the presence of the

target and determine its location. A single antenna is usually used on a time shared basis for

both transmitting and receiving when the radar waveform is a repetitive series of pulses.

The range, or distance, to a target is found by measuring the time it takes for the radar

signal to travel to the target and return back to the radar (Radar engineers use the term

range to mean distance). The target’s location in angle can be found from the direction the

narrow-beamwidth radar antenna points when the received echo signal is of maximum

amplitude. If the target is in motion, there is a shift in the frequency of the echo signal due

to Doppler Effect. This frequency shift is proportional to the velocity of the target relative

to the radar (also called the radial velocity). The Doppler frequency shift is widely used in

radar as the basis for separating desired moving targets from fixed (unwanted) “clutter”

echoes reflected from the natural environment such as land, sea, or rain. Radar can also

provide information about the nature of the target being observed.

ECHO AND DOPPLER SHIFT

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 of 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 shift is also common. You probably experience it daily (often without

realizing it). Doppler shift occurs when sound is generated by, or reflected off of, a moving

object. Doppler shift in the extreme creates sonic booms. Here’s how to understand

Doppler shift – Let’s 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. It’s the

same horn making the same sound the whole time. The change you hear is caused by

Doppler shift.

TYPES OF RADAR

Based on its functions, RADAR can be divided into two types:

PRIMARY OR SIMPLE RADAR

SECONDARY RADAR

Primary radar or the simple radar locates a target by procedure described in section. But in

cases as controlling of aircrafts, the controller must be able to identify the air craft and find

whether it is a friend or a foe. It is also desired to know the height of the aircraft, so that on

the same source but flying at different levels can be kept apart.

To give the controller this information, second radar called a ‘SECONDARY

SURVEILLANCE RADAR’ (SSR) is used. This works differently and needs the help of

the target aircraft. It senses out the sequence of pulses to an electronic black box, called a

transponder fitted on the aircraft. The transponder is connected to the aircrafts altimeter

(the device which measures the plane’s altitude) to transmit back the coded message to the

radar about its status and altitude. Military aircrafts uses a similar kind of radar system with

secret code to transmit back to the ground station for the corresponding receiver code.

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).

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.

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

WORKING OF A SIMPLE RADAR

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

are:-

The antenna unit or the scanner.

The transmitter/receiver or transceiver and

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.

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

σ = 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.

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 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.

IFF (MK-XI) UNIT

PURPOSE

The Identification Friend or Foe Mk-XI (IFF - Mk XI) Ground Equipment is used to

interrogate and identify the ship/aircraft (target) fitted with compatible transponder. The

coded replies from the interrogated target are received back, processed and displayed on a

PPI in a convenient form to the operator.

EQUIPMENT DESIGN

The IFF Mk-XI Ground Equipment - GRL 541 (Here in after called only IFF Mk-XI) has

been designed for operation in association with `FREGAT-M2EM’ Primary Radar and

PODBEREZOVIK-ET1 on board GORSHKOV ships to give a range coverage

compatible to Primary Radar which is approximately 180 Km. However IFF System

GRL541 is designed to provide range coverage of 280 KM.

MAJOR SUBSYSTEMS

IFF Mk-XI has following major subsystems:-

a) 3.5 m IFF Mono Pulse Antenna 1 Nos.

b) RF Switch Unit 1Nos.

c) Interrogator - Decoder 1 Nos.

d) Remote Control Panel 1 Nos.

e) Control Units 2 Nos.

f) Voltage Stabiliser 1 Nos.

COMPOSITION

IFF MK-XI Interrogator Equipment (only IFF MK-XI hereafter) has a Selective

Address Interrogation Mode called Mode `S', in addition to all standard operating

modes and features of a IFF MK-X System. Therefore IFF MK-XI has two parts as

follows:

a) IFF MK-X System

b) Selective Address Interrogation (Mode `S') Feature

BASIC CONSIDERATIONS

The SSR interrogate transponder equipped aircraft with coded pulses train whose spacing

denotes whether identity or altitude replies are being requested. The elicited reply comprises up

to 15 pulses, spaced at multiples of 1.45 microseconds. Two pulses in this code train define the

pulse train and the other pulses contain the code data these positions provide up to 4096

discrete identify codes including the altitude.

The position of the scanning antenna and the elapsed time between the interrogation and

receipt of the transponder reply give the azimuth and range. Thus range, azimuth and altitude

are derived. Special code provisions enable to declare an emergency or communication failure,

special identification of a particular aircraft when the same identify code has been used by two

or more aircraft.

OPERATION

The SSR system can operate in association with both static and mobile primary radar or

independently with its own monitor display. The transmitter can be triggered either internally

or externally. Interrogations are pre-triggered with respect to the primary radar pulse

transmission (external triggering) to provide for a timing match between radar echoes and SSR

replies at the PPI display. The PRF of the interrogation transmission is either the same as the

primary radar or counted down to maintain a nominal value as the case may be. The

interrogation modes provide for separation of replies by function. For e.g., mode C is the

automatic altitude mode. Interlacing of two modes is done to update identity and altitude data

on each scan of the ground based antenna.

IFF Mk-X SYSTEM

BASIC PRINCIPLE

IFF Mk-X system basically operates on the principle of a Secondary Radar as per

recommendations of Annexure 10 of International Civil Aviation Organization (ICAO)

advisory circular on SSRs. The Ship borne Ground Interrogator together with an Air/Ship

borne transponder, constitute the IFF system. The Interrogator sends out RF pulses, called

mode pulses with suitable spacing as per the desired mode of interrogation. The

transponder receives these pulses and sends out suitable replies. The RF reply pulses from

transponder are received, amplified and detected in ground receiver chain. The detected

reply code and corresponding mode information are then `Passed on' to the MK-X Decoder

unit for further decoding and establishing the identity of the aircraft. This is done by

looking for a match between the received reply code and the preset expected codes. Such

targets whose codes are matched are displayed on the PPI near the respective primary radar

echo in the form of two slashes. The expected codes can be preset from the front panel of

the Control Unit supplied as part of IFF equipment. Special codes like Emergency,

Communication Failure and Hijack are decoded automatically whenever targets are

interrogated on mode 3/A irrespective of setting for active decoding and passive decoding

(code match) and are indicated on Control unit.

OPERATIONAL DESCRIPTION (Refer Figure 2.1)

The output of the IFF Interrogator consists of three RF pulses P1, P2 and P3 at 1030 MHz.

The R.F. output is applied to an IFF Antenna through a RF switch unit. The transmitted

pulses P1 & P3 are received by the transponder fitted in the aircraft/ship. The coded replies

at 1090 MHz from the transponder are received, amplified, detected and fed to Mk-X

Decoder. The Decoder decodes the replies for identity and its output is fed to the display

unit of primary radar for displaying the IFF responses. The system also includes Mode `S’

drawer.

P1, P2, P3

P2P1, P3

REPLY PULSE (1090 MHz)

FIG. No. 2-1IFF MK-XI SYSTEMBASIC PRINCIPLE

F2F1

(1030 MHz)

P3P2P1

(INTERROGATION PULSES)

RF SWITCH UNIT

TRANSMITTER

RECEIVER

MK-X DECODER

MODE `S’ PROCESSOR

IFF ANTENNA

REMOTE CONTROL

PANEL

CONTROL UNIT

PPI(INTERROGATOR – DECODER)

GROUND/SHIP INTERROGATOR

IFF INTEROGATION SIGNAL

The interrogation signal of the IFF ground equipment consists of a signal consisting of 3

pulses are designated as P1, P2 and P3 as shown in the figure above. The P1 and P3 pulses

are known as the INTERROGATE PULSES and pulse P2 is known as the CONTROL

PULSE.

The three pulses viz P1, P2, P3 are produced to achieve the 3 pulse side lobe suppression.

The pulses P1, P2 and P3 are of same width viz 0.8 microseconds each.

The P1 and P3 pulses occur at discrete pulse intervals and the P1, P3 combination is known

as MODE. The aircraft transponder on receipt of the mode pulses P1and P3 recognizes the

mode and responds with its suitable reply code.

The pulse P2, control pulse, is always positioned at 2 microseconds from P1 and is used for

achieving the 3 pulse side lobe suppression. The P2 pulse determines whether the

interrogation is true or false. If the interrogation is false, the aircraft transponder uses side

lobe suppression technique to inhibit the reply. In this technique, P1, P2 and P3 are

transmitted in succession in different directions in such a manner that amplitude of P1 and

P3 are greater than that of P2 only along the direction of the main beam of the signal. In all

other directions, amplitude of P2 is greater than that of the other pulses. The target is

required to respond only when it finds the amplitude of the P1 and P3 greater than that of

P2.

INTERROGATION SIGNAL

P1 P2 P3

MODES OF INTERROGATION

The IFF Mk-X Interrogator has four types of interrogation modes to accommodate its

various uses. Each mode of interrogation consists of a pair of pulses P1 and P3. An

2sPRT depends on working mode

additional pulse P2 is transmitted 2 microseconds after initial P1 pulse. This pulse is

used for achieving Interrogation Side Lobe Suppression (ISLS). Each pulse is of 0.8

microsecond duration.

The mode is designated by the P1-P3 inter pulse interval. The intervals for each mode are

shown in Fig. 2.2.

Modes 1 and 2 are used for Military Interrogations.

Mode 3/A is common to both Military and civil systems, and

Mode C is used for eliciting the digitally encoded altitude from the airborne

transponder.

3µS

2µSMODE 1

P2 P3P1

5µS

2µSMODE 2

P2 P3P1

8µS

2µSMODE 3/A

P2 P3P1

21µS

2µSMODE C

P2 P3P1

24 µS TO 1023 µS

IN STEP 1 µS

2µSMODE `S’

P2 PS1P1

MODES OF INTERROGATION

TRANSPONDER REPLY

The transponder reply normally consists of a sequence of upto 14 pulses on 1090

MHz each of duration 0.45 µs. The basic reply format showing the spacing between

the pulses and their designations is illustrated in Fig. 2.3 & Fig. 2.4. Every reply includes

two brackets or framing pulses F1 and F2 spaced at 20.3 µs. Twelve pulses with their

positions defined can be selected for transmission by means of switches in the control

unit of the transponder.

Special codes are allotted to recognise situations such as emergency,

communication failure, hijack etc. The special codes sent by transponder in such

situations are:-

a) Hijack : Code X1 on Mode 3/A

b) Communication Failure : Code X2 on Mode 3/A

c) Emergency (Military):

I. Mode 1 and Mode 2: Repetition of three frame pulse pairs in addition to

the first frame. The first frame carries the normal code on Mode 1 and 2.

II. Mode 3: Same as above except that the first frame contains code X3.

d) Special Position Identification (SPI):

The SPI reply is transmitted on instructions from the interrogating station and consists of

additional frame pulse pair, transmitted at 4.35 s from F2 of first frame pulse pair

(Special pulse).

EXAMPLE 1 : CODE 7777

0.5 µS

2.0 µS

1.45 µS

0.45 µS

2.0 µS

20.3 µS

A4C4A2C2A1C1F1 F2D4B4D2B2D1B1

A4C4A2C2C1F1 F2D4B2D1B1

0.5 µS

8.0 µS

F2B1B2B4A1A2A4F1 D1D2D4C1C2C4 E1E2E4

REPLY CODE FORMATNORMAL REPLY PULSES

EXAMPLE 2 : CODE 6375

MODE `S’ REPLY

SIDE LOBE SUPPRESSION

A three pulse side lobe suppression technique during interrogation (ISLS) is employed to

avoid false responses through side lobes when the responding air-craft is in close vicinity

to RADAR. This is achieved by the use of a RF Switch unit and special IFF antenna with

distinct patterns namely interrogate and control patterns. When target is in position `A',

the amplitude of P1 & P3 pulses is more than the level of P2 pulse, the interrogated

target will respond. When the target is in position `B', the amplitude of P2 pulse is more

than that of P1 & P3 pulses and the target will not respond.

PASSIVE DECODING AND DISPLAY

The coded replies from the transponder after detection and amplification are fed along

with the mode information to the Decoder Unit which identifies the mode of interrogation

& coded replies and feeds the output to the primary radar displays. The Control Units of

Decoder are located near the primary radar displays. Whenever a standard bracket pulse

pair F1-F2 is detected a single slash known as "All Aircraft" or "AA" slash is generated

on the PPI coincident with the primary radar target echo.

For passive decoding the operator sets the mode and code combination on the thumb

wheel switches (code match) provided in the Control Units. Whenever an incoming IFF

reply matches with the mode and code combination set on any one of these passive

channels, two slashes are generated on the PPI. Three slashes are generated whenever a

SPI pulse is received and four slashes indicate a situation of emergency or

communication failure report from the target. The `slash' patterns for different situations

are shown in Fig.

DISPLAY OF IFF SYMBOLS ON PPI

ACTIVE DECODING

With the help of a designation pulse generated from Primary Radar Display the actual

code of the designated target can be read out on Control Unit by means of active

decoding. The mode for active decoding can be selected with the help of a thumbwheel

switch provided in the Control Units. The code is displayed on a 4 digit numeric

indicator. 5th digit displays the validity of the incoming code. Altitude of Aircraft also

can be displayed on Control Unit when IFF is operated in Mode `C'.

DIFFERENCE BETWEEN ACTIVE DECODING & PASSIVE DECODING

In case of active decoding the code received from the target is displayed on control unit.

If the mode of active decoding is one out of the three modes of interrogation (set on

RCP). In case mode `S’ the active decoding is not applicable.In case of passive decoding

the code received from the target is compared with preset code on thumbwheel switches

of channel 1, channel 2 and channel 3 and two slashes are generated on PPI.

INTERROGATOR - DECODER

All Aircraft Signal (AA)

Primary Radar Echo

Emergency and Communication Failure

Mode ‘S’ match

Special Position Identification

Passive Code Match

The Interrogator Decoder Rack is made of high grade Aluminum extruded profiles. For

ease of maintenance all RF and digital hardware has been placed in four drawers which

slide on the rails inside the rack. Major RF modules and digital PCBs are again plug-in

type within the drawers. This modular concept reduces the down time to minimum since

all plug-in type modules and PCBs are given as carried spares.

The Interrogator-Decoder rack consists mainly of four drawers, namely:-

a) TX-Rx drawer

b) MK-X decoder drawer

c) Mode `S' Processor drawer

d) Blower Drawer

MODE `S' PROCESSOR

The concept of Mode ‘S’ was introduced because of the drawbacks encountered in the

Mk-X system. The major drawbacks are:

a) Whenever the ground system asks a question from an aircraft, the answer comes

from that aircraft as well as from the other aircrafts also which are there within that

region. It was not able to interact with a single (or a particular/ selected) aircraft

with whom interaction is required.

b) It did not prove to be a full-proof system, as the unknown (or enemy) aircrafts were

able to decode the reply sent by the friend aircrafts to the IFF ground systems and

then by sending the same code to the ground systems and therefore able to escape

easily.

c) It was not able to counteract the jamming being introduced by the enemy aircrafts.

Mode ‘S’ processor was then invented to avoid the abovementioned drawbacks in the Mk-

X decoder system and then came the advance version of the IFF system which was a

modification over the Mk-X system as it comprises both the Mk-X system as well as the

Mode ‘S’ processor which was given the name Mk-XI SYSTEM.

In the Mode ‘S’ system the concept of POLY COEFFICIENT called POLY and KEY

was introduced to achieve (or generate) VARIABLE REPLY CODE to avoid spoofing.

BASIC CONCEPT OF WORKING

As in MK-X for interrogation P1, P2, P3 are generated in Mode `S' P3 pulse is generated

at varying distance depending on the address of target which are set in storage card. In this

four targets addresses can be selected according to which generated pulses called as PS1,

PS2, PS3, PS4. These address, are stored in the storage card through Mode `S’ Local

Control Panel. The pulses P1, P2, PS1, PS2, PS3, PS4 are generated with respect to a

pulse which is generated after a random delay between 1 µs to 1023 µs after pretrigger.

At the Transponder Reply the frame consist of 15 bit varying code which is generated by

ExoRing the 15 bit varying code (dependent on poly coefficient called poly) with key code.

From reply frame defruited AA is generated in Decoder & Defruiter Card and code is

decoded. Time of Arrival (TOA), range are also latched in latch register in the decoder card

at arrival of AA pulse. The range of incoming frame is compared with previous range

stored in RAM of processor card. If ranges are same then incoming code is compared with

code generated from previous code with help of poly and key combination stored at first

address. If these codes are matched then a video match pulse is generated otherwise

comparison of incoming code with code generated from previous code with help of poly

and key combination stored at second address is compared. Then third and fourth are

compared respectively and when a match of code is there matched video pulse is generated.

Matched address is decremented from the range and at new range which is delay of AA

pulse with PS1 or PS2 or PS3 or PS4 depending on the matched address is given for

display of PPI.

GENERATION OF THE VARIABLE REPLY

At the Transponder the reply codes are generated by ANDing a 15-bit initially set data

called Poly coefficient and then this data is sent to a odd parity generator which generates a

parity bit a 1 or 0, according to the no. of 1’s in the data is even or odd, and then this parity

bit is inserted in the Poly coefficient from left such that the initial data is shifted to right

with the 15th bit being the parity bit. So, by continuing in this manner a variable Poly has

been generated at a rate of 500 KHz (or 2 sec) for the generation of the reply code. Now,

as mentioned earlier the reply code is generated by XORing the 15-bit variable poly code

with KEY.

P1 PS4PS3PS2P2 PS1

SUBMITTED BYNAME : ANKUR GARG (06102331)UPT NO. : UPT/192/B.TECH/2009

COLLEGE : JAYPEE INSTITUTE OF INFORMATION

TECHNOLOGY UNIVERSITY NOIDA (U.P.)

COURSE OF STUDY : B.TECH(ELECTRONICS AND

COMMUNICATION)

CERTIFICATE

This is to certify that, Mr.ANKUR GARG student of B.TECH (ECE) from J.I.I.T.U NOIDA, in BHARAT ELECTRONICS LIMITED, GHAZIABAD from 01.06.09 to 11.07.09. During this training period he was assigned PRODUCT ASSURANCE RADAR – IFF TESTING.

He was involved in Studying and Testing of DIGITAL PCB’s cards, Sub System of IFF RADAR System. In addition he also gained the knowledge and operation of other latest testing/measuring equipments.

His performance during the Training was found

I wish him all the success in his life.

PROJECT GUIDE MANAGER(PA-C/IFF) (PA-C/IFF)

ACKNOWLEDGEMENT

First of all I would like to thank Mr. TAPASH BOSE, (D.G.M-Human Resource Development Department) 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. S.ERANDE (D.G.M), who granted us the permission to take this project. The aim at the project was testing of flycatcher radar and study & analysis of Tx module, Rx Module & RF Switch Unit. This could be accomplished in the time span of weeks only due to the kind co-operation of Mr. K.T.S MURTY(Manager). I am thankful to him and his colleagues.

I pay my special thanks to Mr. JYOTI PRAKASH who guided us on our project and with whom help I am able to complete my report. I am also thankful to other BEL staff who helped us during the summer training.

PREFACE

This six weeks training is a part our 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 indicate management relation. This training mainly involve industrial and complete knowledge about designing, assembling and manufacturing of equipments.

With the ongoing revolution in electronics where innovations are taking place at the blink of an eye, it is impossible to keep the pace with the emerging trends.

Excellence is an attitude that the whole of the human race is born with. It is the environment that makes sure that 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 student 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, the students get the real experience for working in the actual environment. Most of the theoretical knowledge that has been gained during the course of their studies is put to test here. Apart from this, the students get an opportunity to learn the latest technology, which immensely helps them in building their 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.

CONTENTS

PREFACE.

ACKNOWLEDGEMENT.

CERTIFICATE.

BHARAT ELECTRONICS LIMITED.

AN OVERVIEW.

MANUFACTURING UNITS.

FINANCIAL PERFORMANCE.

BEL PRODUCT RANGE.

BEL GHAZIABAD UNIT.

ROTATION PROGRAMME.

PCB FABRICATION.

TEST EQUIPMENT AND AUTOMATION.

WORK ASSEMBLY

Q.C.WORKS.

MAGNETICS.

MICROWAVE LABORATORY.

AN INTRODUTION TO BASIC RADAR.

THE IFF UNIT - MK XI.

BRIEF TECHNICAL DESCRIPTION OF IFF UNIT MK XI.

BRIEF TECHNICAL DESCRIPTION OF MAJOR SUB-SYSTEMS OF IFF MK XI.

MK-X TRANSMITER AND RECIEVER UNIT.