report on bel

8/4/2019 Report on Bel

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CHAPTER 1

BHARAT ELECTRONICS LIMITED

Figure 1.1

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 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 Enterprises (PSE) was mooted. With telecom and electronics recognized

among the core sectors, Indian Telephone Industry, now renamed as ITI 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.

COMPANY PROFILE


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

Enterprise under the administrative control of Ministry of Defence as the

fountainhead 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 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 value 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 technology, its

manufacturing and products assurance facilities have also undergone sea change.

The design groups have CADD facility; the manufacturing has CNC machines and a

Mass Manufacture Facility. 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 BELs infrastructure is spread over nine locations with 29 production

divisions having ISO-9001/9002 accreditation. Product mix of the company are

spread over the entire Electro-magnetic (EM) sp 3ectrum 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 products

ranges like Defence Communication, Raders, Optical & Opto-electronics,


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Telecommunication, 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 Rader 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 BELs 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 Governments 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 navel 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 Rattans (Category II) by the

Government of India, 49th among Asias top 100 worldwide Defence Companies by

the Defence News, USA.


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CORPORATE MOTTO , MISSION AND OBJECTIVES

The passionate pursuit of excellence at BEL is reflected in a reputation with its

customers that can be described in its motto, mission and objectives:

CORPORATE MOTTO

Quality, Technology and Innovation.

CORPORATE MISSION

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

products.

CORPORATE OBJECTIVES

To become a customer-driven company supplying quality products at

competitive prices at the expected time and providing excellent customer

support.

To achieve growth in the operations commensurate with the growth of

professional electronic industry in the country.

To generate internal resources for financing the investments required formodernization, expansion and growth for ensuring a fair return to the investor.

In order to meet the nations strategic needs, to strive for self-reliance by

indigenization of materials and components.

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

To create an organizational culture which encourages members of the

organization to real and through continuous learning on the job


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MANUFACTURING UNITSMANUFACTURING UNITS

BANGALORE (KANARATAKA)

BEL started its production activities in Bangalore on 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.

BELs 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 DoT, VSNL, AIR and

Doordarshan, Meteorological Dept., ISRO, 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 (UTTER 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 Units 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 Laser Range

Finders for the Defence services.


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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 and Goggles, Periscopes, Gun Sights, SurgicalMicroscope and Optical Sights and Mussel 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 and the Vijay anta

tanks. The Unit is now manufacturing Stabilizer Systems for T-72 tanks, Infantry

Combat Vehicles BMP-II; Commanders Panoramic Sights & Tank Laser Sights are

among others.

KOTDWARA (UTTER 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 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

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


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Multiplier Systems are manufactured here for the Defence services 20 glass bulbs

indigenously.

BEL GHAZIABAD UNIT

Formation

In the mid 60s, 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 for an integrated Air Defence Ground Environment

System known as the plan ADGES with Prime Minister as the presiding officer of

the apex review committee .At about the same time, Public attention was focused onthe report of the Bhabha 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 inserted 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 manufacture

of IFF systems needed to match a variety of primary raiders. More than 30 versions

of IFFs 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

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 System for the Army.

Battlefield Surveillance Rader 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 scatters Communication Systems for the Air Force.

Digital Mobile Tropo scatters 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.

ANTENNA

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, and Receivers etc.

Passive Microwave components like Double Balanced Mixers, etc.


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SERVICES OF BHARAT ELECTRONICS LIMITED (BEL):-

DEFENCE PRODUCTS:-

Naval System

Military Communication Equipment

Radars

Tele Communication & Broadcasting Services

Opto Electronics

Electronic Warfare

Tank Electronics

NON-DEFENCE PRODUCTS:-

Electronic Voting Machine

Solar Products

Simputer

DTH


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CHAPTER 2

INTRODUCTION

ROTATION PROGRAM

Under this students are 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:

1. Test Equipment and Automation

2. P.C.B. Fabrication

3. Quality Control Works-Radar

4. Work Assembly- Communication

5. Magnetics

6. Microwave lab

Rotation period was to give us 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.

2.1 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.


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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 Defence 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.

1. Green O.K , Perfect

2. Yellow Satisfactory but some trouble is present.3. Red Cant be used, should be disposed off.

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

1. WS 102

2. WS 104

3. PS 520

4. PS 8095. PS 811


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6. PS 369

Where, WS = Workmanship & PS = Process Standard

After the inspection of cables, PCBs 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 department

which is rectified there.

2.2 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.

2.3 TYPES OF PCBs

Single Sided Board : Circuits on one side.

Double Sided Board : Circuit on Both side.

Muti-layer Board : Several layers are interconnected through hole

metallization.


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2.4 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.

2.5 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


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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.

2.6 Procedure for through hole metallizationLoading-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 onit. 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.


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2.7 There are three types of solder marking done in BEL:

2.7.1Wet 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.

2.7.2Dry pin solder mask: Due to wastage of films about 30% this method

is also not used now.

2.7.3 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


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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 temp. Of 20degree C is done. After

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

2.8 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:

D & E mistakes

Shop mistakes


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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

2.9 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:

o Preparation of part list that is to be assembled.

o Preparation of general assembly.

o Schematic diagram to depict all connections to be made and brief idea about all

components.


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o Writing lists of all components.

In work assembly following things are done :

Material 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 dont 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.


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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.

CHAPTER 3

MAGNETICS

In this department different types of transformers and coils are manufactured ,

which are used in the various Defence equipments i.e. radar , communication

equipments.

This department basically consists of three sections :

3.1 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 .


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3.2 WORKS (PRODUCTION) :- Production of transformers and coils are

being carried out by the works departments.

3.3 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.

3.4 Types of transformers

The various types of transformers are as follows :

3.4.1 Air cored transformers

3.4.2 Oil filled transformers

3.4.3 Moulding type transformers

3.4.4 P.C.B Mounting transformers :-

(a) Impedance matching transformers

(b) RF transformers

(c) IF transformers

3.5 Types of cores

The various types of cores are as follows :

a)E type

b)C type

c)Lamination

d)Ferrite core

e)Toroidal core

3.6 Steps involved in the process of manufacturing of

transformer/coils:


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3.6.1 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.

3.6.2 Winding : It is done with different material and thickness of wire.

The winding has specified number of layers with each layers 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.

3.7 Types of windings

The various types of windings are as follows :

Layer Winding

Wave Winding

Bank Winding

Insulation: For inter-winding and inter layer , various types of insulation

sheets viz. Craft paper , paper , leather , oil paper , polyester film are beingused.

Protection : To protect the transformer from the external hazards ,

moisture , dust and to provide high insulation resistance , they are

impregnated.

3.8 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


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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.

4.1 Methods of testing

There are two methods of testing:

4.1.1 Acceptance Test Procedure(ATP)

4.1.2 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:

i) Filters

ii) Isolators

iii) Reflectors

iv) Network Analyzers

v) Spectrum Analyzer

vi) Amplifiers and Accessories

CHAPTER 4

RADAR

4.1 History of RADAR

Nobody can be credited with "inventing" radar. The idea had been around for a long

time--a spotlight that could cut through fog. But the problem was that it was too

advanced for the technology of the time. It wasn't until the early 20th century that a

radar system was first built. One of the biggest advocators of radar technology was

Robert Watson-Watt, a British scientist.
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Great Britain made a big effort to develop radar in the years leading up to World

War Two. Some people credit them with being pioneers in the field. As it was, the

early warning radar system (called "Chain Home") that they built around the BritishIsles warned them of all aerial invasions. This gave the outnumbered Royal Air

Force the edge they needed to defeat the German Luftwaffe during the Battle of

Britain.

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

4.2 Introduction

The term RADAR was coined in 1941 as an acronym for Radio Detection and

Ranging. This acronym of American origin replaced the previously used British

abbreviationRDF(Radio Direction Finding).

Radar is a system that uses radio waves to detect, determine the distance or speed,

objects such as aircraft, ships, rain and map them. Speed detection is measured by

the amount ofDoppler Effect frequency shift of the reflected signal. A transmitter

emits radio waves, which are reflected by the target, and detected by a receiver,

typically in the same location as the transmitter. Although the radio signal returned

is usually very small, radio signals can easily be amplified, so radar can detect

objects at ranges where other emission, such as sound orvisible light, would be too

weak to detect. Radar is used in many contexts, including meteorological detection

ofprecipitation, air traffic control, police detection ofspeeding traffic, and by the

military.

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 Hlsmeyer, who demonstratedthe feasibility of detecting the presence of ships in dense fog and received a patent
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for radar as Reichspatent Nr. 165546. Another of the first working models was

produced by Hungarian Zoltn Bay in 1936 at the Tungsram laboratory

4.3 BASIC PRINCIPLE

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 (see below). Here's

how to understand Doppler shift (you may also want to try this experiment in an

empty parking lot). 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.
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4.4 HOW RADAR WORKS

A radar system, as found on many merchants ships, has three main parts:

1. The antenna unit or the scanner

2. The transmitter receiver or transceiver and

3. the visual display unit

The antenna is two or three meter wide and focuses pulses off very high frequency

radio energy into a narrow vertical beam. The frequency of the radio waves is

basically about 10,000 Mhz. The antenna is rotated at the rate of 10 to 25 rpm so

that radar beam swaps through 300degree Celsius all around the shiout to a range of

about 90 kms.

In all radar it is vital that the transmitting and the receiving in a transceiver are in

close harmony. Every thing depends on accurate measurement of the time that

passes between the transmission of pulse and the return of the echo. About 1000,

pulses per second are transmitted. Though it is varied to suit the requirements. Short

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

An important part of transceiver circuit is modular circuit. This keys the

transmitter so that it oscillates, or pulses for the right length of time. The pulses so

designed are video pulses. These pulses are short range pulses hence cant serve out

the purpose of long range work .In order to modify these pulses to long range pulses

or the RF pulses, we need to generate the power. The transmitted power is generated

in a device called the magnetron which can handle all these short pulses and very

high oscillations.

The display system usually carried out the control necessary for the operation of

whole radar .It has a cathode ray gun, which consists of a electron gun in its neck.

The gun shouts electron to the phosphorescent screen at the far end. Phosphorescent

screen glows when hit by an electron and the resulting spot can be seen through the

glass face.

The basic idea behind radar is very simple: a signal is transmitted, it bounces off anobject and some type of receiver later receives it. They use certain kinds of


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electromagnetic waves called radio waves and microwaves. This is where the name

RADAR comes from (Radio Detection And Ranging). Sound is used as a signal to

detect objects in devices called SONAR (Sound Navigation Ranging). Another type

of signal used that is relatively new is laser light that is used in devices called

LIDAR (Light Detection And Ranging).

Once the radar receives the returned signal, it calculates useful

information from it such as the time taken for it to be received, the

strength of the returned signal, or the change in frequency of the signal.

4.5 Basic Radar System:

Figure 4.1

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. 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:


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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).

In math language, the above can be said...

PRT = 1 / PRF

or

PRF = 1 / PRT

And for all you visual learners out there, this is what it looks like...

Figure 4.2

4.6 RT means repetition time.

However, the above diagram is not quite realistic for several reasons. One reason

why it is not realistic is that the frequency in waves of the pulses is the same. In real

life the frequency of the waves are not the same and they change as time goes on.

This is called frequency modulation, which means the frequency changes or

modulates.


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It looks something like this...

Figure 4.3

Think of this as one pulse. All the pulses will look something like this.

On the above diagram, the frequency of the wave is low on the left and it slowly

increases, as you look right. The different frequencies of the wave will lie in a range

called bandwidth. Radars use bandwidth for several reasons regarding the resolution

of a data image, memory of the radar and overuse of the transmitter. For instance, a

high bandwidth can yield a finer resolution but take up more memory. When an EM

wave hits a surface, it gets partly reflected away from the surface and refracted into

the surface. The amount of reflection and refraction depends on the properties of the

surface and the properties of the matter, which the wave was originally travelingthrough. This is what happens to radar signals when they hit objects. If a radar

signal hits a surface that is perfectly flat then the signal gets reflected in a single

direction (the same is true for refraction). If the signal hits a surface that is not

perfectly flat (like all surfaces on Earth) then it gets reflected in all directions. Only

a very small fraction of the original signal is transmitted back in the direction of the

receiver. This small fraction is what is known as backscatter. The typical power of

a transmitted signal is around 1 kilowatt and the typical power of the backscatter can

be around 10 watts.

4.7 TYPES OF RADAR

Based on function radar can be divided into two types:

4.7.1 PRIMARY RADAR

4.7.2 SECONDRY RADAR


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

section. But in cases as controlling of air traffic, the controller must be able to

identify the aircraft and find whether it is a friend or foe. It is also desired to know

the height of aircraft.

To give controller this information second radar called the secondary surveillance

radar (SSR) is used. This works differently and need the help of the target aircraft it

sance out a sequence of pulses to an electronic BLACK BOX called the

TRANSPONDER, fitted on the aircraft. The transponder is connected to the

aircrafts altimeter (the device which measures the planes 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 secrete code to make sure that it is friend or foe, a

hostile aircraft does not know what code to transmit back to the ground station for

the corresponding receiver code.

4.8 IFF UNIT

IFF is basically a 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 as SECONDARY SURVEILLANCE RADAR (SSR).

Primary radar locates an object by transmitting signal and detecting the reflected

echo. A secondary radar system is basically very similar to primary radar system

except that the returned signal is radiated from the transmitter on board the target

rather then by reflection, i.e. it operates with a cooperative active target while the

primary radar operates with passive target.

Secondary radar system consists of an interrogative and a transponder. The

interrogator transmitter in the ground station interrogates transponder equipped

aircraft, providing two way data communication on different transmitter and

receiver frequency .The transponder on board the aircraft on receipt of a chain of

pulses from ground interrogator, automatically transmit the reply, coded for the

purpose of identification, is received back to the ground interrogator where it is

decoded and displayed on a radar type presentation.


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4.9 RADAR EQUATION

The amount of powerPr 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 =Rrand the termRt2Rr

2 can be replaced byR4, whereR is the range.

This yields:

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.

4.10 RADAR SIGNAL PROCESSING
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Distance measurement

Transit time

Figure 4.4Principle of radar distance measurement using pulse round trip time.

One way to measure the distance to an object is to transmit a short pulse of radio

signal, and measure the time it takes for the reflection to return. The distance is one-

half the product of round trip time (because the signal has to travel to the target and

then back to the receiver) and the speed of the signal.2

cRange = where c is the

speed of light in a vacuum, and is the round trip time. For radar, the speed of signal

is the speed of light, making the round trip times very short for terrestrial ranging.

Accurate distance measurement requires high-performance electronics.

The receiver cannot detect the return while the signal is being sent out there is no

way to tell if the signal it hears is the original or the return. This means that a radar

has a distinct minimum range, which is the length of the pulse multiplied by the

speed of light, divided by two. In order to detect closer targets one must use a

shorterpulse length.

A similar effect imposes a specific maximum range as well. If the return from the

target comes in when the next pulse is being sent out, once again the receiver cannot

tell the difference. In order to maximize range, one wants to use longer times

between pulses, the inter-pulse time.

These two effects tend to be at odds with each other, and it is not easy to combine

both good short range and good long range in a single radar. This is because the
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short pulses needed for a good minimum range broadcast have less total energy,

making the returns much smaller and the target harder to detect. This could be offset

by using more pulses, but this would shorten the maximum range again. So each

radar uses a particular type ofsignal. Long range radars tend to use long pulses with

long delays between them, and short range radars use smaller pulses with less time

between them. This pattern of pulses and pauses is known as the

Pulse Repetition Frequency (orPRF), and is one of the main ways to characterize a

radar. As electronics have improved many radars now can change their PRF.
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4.11 DIFFERENT TYPES OF RADARS

4.11.1 3D Mobile Radar (PSM 33 Mk II)4.11.1 3D Mobile Radar (PSM 33 Mk II)

3-D mobile radar employs monopulse technique for height estimation and using

electronic scanning for getting the desired radar coverage by managing the RF

transmission energy in elevation plane as per the operational requirements. It can be

connected in air defence radar network. The Radar is configured in three transport

vehicles, viz., Antenna, Transmitter cabin, Receiver and Processor Cabin. The radar

has an autonomous display for stand-alone operation.

Figure 4.5

FEATURES

Frequency agility

Monopulse processing for height estimation

Adaptive sensitivity time control

Jamming analysis indication, pulse compression, plot filtering / tracking

data remoting

Comprehensive BITE facility

4.11.2 Low Flying Detection Radar (INDRA II)4.11.2 Low Flying Detection Radar (INDRA II)

The low-level radar caters to the vital gap filling role in an air defence environment.

It is a transportable and self-contained system with easy mobility and deployment


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features. The system consists mainly of an Antenna, Transmitter cabin and Display

cabin mounted on three separate vehicles.

Figure 4.6

4.11.2.1. SYSTEM CHARACTERISTICS

Range up to 90 km (for fighter aircraft)

Height coverage 35m to 3000m subject to Radar horizon

Probability of detection: 90% (Single scan)

Probability of false alarm: 10E-6

Track While Scan (TWS) for 2D tracking

Capability to handle 200 tracks

Association of primary and secondary targets

Automatic target data transmission to a digital modem/networking of radars

Deployment time of about 60 minutes

4.11.2.2 FEATURES

Fully coherent system

Frequency agility

Pulse compression

Advanced signal processing using MTD and CFAR Techniques

Track while scan for 2-D tracking

Full tracking capabilities for maneuverings targets

Multicolor PPI Raster Scan Display, presenting both MTI and Synthetic Video

Integral IFF


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4.11.3 Tactical Control Radar4.11.3 Tactical Control Radar

This is an early warning, alerting and cueing system, including weapon control

functions. It is specially designed to be highly mobile and easily transportable, by air

as well as on the ground. This radar minimizes mutual interference of tasks of both

air defenders and friendly air space users. This will result in an increased

effectiveness of the combined combat operations. The command and control

capabilities of the RADAR in combination with an effective ground based air

Defence provide maximum operational effectiveness with a safe, efficient and

flexible use of the airspace.

Figure 4.7

FEATURESAll weather day and night capability

40 km ranges, giving a large coverage

Multiple target handling and engagement capability

Local threat evaluation and engagement calculations assist the commander's

decision making process, and give effective local fire distribution

Highly mobile system, to be used in all kinds of terrain, with short into and out of

action times (deployment/redeployment)

Clutter suppression


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4.12 RADAR APPLICATION

Air traffic control uses radar to trackplanes both on the ground and in the

air, and also to guide planes in for smooth landings.

Police use radar to detect the speed of passing motorists.

NASA uses radar to map the Earth and other planets, to track satellites and

space debris and to help with things like docking and maneuvering.

The military uses it to detect the enemy and to guide weapons.
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4.134.13RADARRADAR TRANSMITTERTRANSMITTER

The radar transmitter produces the short duration high-power of pulses of energy

that are radiated into space by the antenna. The radar transmitter is required to have

the following technical and operating characteristics:

The transmitter must have the ability to generate the required mean RF

power and the required peak power

The transmitter must have a suitable RF bandwidth.

The transmitter must have a high RF stability to meet signal processing

requirements

The transmitter must be easily modulated to meet waveform design

requirements.

The transmitter must be efficient, reliable and easy to maintain and the life

expectancy and cost of the output device must be acceptable.

The radar transmitter is designed around the selected output device and most of the

transmitter chapter is devoted to describing output devices therefore:


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Figure 4.8

One main type of transmitters is the keyed-oscillator type. In this transmitterone stage or tube, usually a magnetron, produces the rf pulse. The oscillator

tube is keyed by a high-power dc pulse of energy generated by a separate

unit called the modulator. This transmitting system is called POT (Power

Oscillator Transmitter). Radar units fitted with an POT are either non-

coherent orpseudo-coherent.

Power-Amplifier-Transmitters (PAT) are used in many recently developed

radar sets. In this system the transmitting pulse is caused with a small

performance in a waveform generator. It is taken to the necessary power with

an amplifier flowingly (Amplitron, klystron orSolid-State-Amplifier). Radar

units fitted with an PAT are fully coherent in the majority of cases.

o A special case of the PAT is the active antenna.

Even every antenna element

or every antenna-group is equipped with an own amplifier

here.
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Pictured is a keyed oscillator transmitter of the historically russian radar set P-37

(NATO-Designator: Bar Lock). The picture shows the typical transmitter system

that uses a magnetron oscillator and a waveguide transmission line. The magnetron

at the middle of the figure is connected to the waveguide by a coaxial connector.

High-power magnetrons, however, are usually coupled directly to the waveguide.

Beside the magnetron with its magnetes you can see the modulator with its

thyratron. The impulse-transformer and the pulse-forming network with the charging

diode and the high-voltage transformer are in the lower bay of this rack.
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4.14 BRIEF DESCRIPTION OF THE RADAR SUBSYSTEM

4.14.1 Main Circuit of Radar Subsystem

High Tension Unit

Transmitter Unit

Lo+Afc Unit

Receiver Unit

Antenna

Video Processor

4.14.2 High Tension Unit-

The high tension unit converts the 115v 400Hz 3 Phase mains voltage into a d.c

supply voltage of about 4.2kv for the transmitter unit.

The exact value of the high voltage depends on the selected PRF(low,high or

extra)to Prevent the dissipation of the magnetron from becoming too high PRF thelower the supplied high voltage

4.14.3 Transmitter Unit

The transmitter unit Comprises

Submodulator

Modulator

Magnetron

Afc control Unit

The magnetron is a self oscillating RF Power generator. It supplied by the

modulator with high voltage Pulses of about 20kvdc, whereupon it Produces X-band

Pulses with a duration of about 0.35us. The generated RF Pulses are applied to the

receiver unit.


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The Pulse repetition frequency of the magnetron pulses is determined by the

synchronizations circuit in the video Processor, Which applies start pulses to the sub

modulator of the transmitter unit. This sub modulator issues start Pulses of suitable

amplitude to trigger the thyraton in the modulator. Which is supplied by the high

tension unit, Produces high voltage Pulses of about 20kvDC.As a magnetron is self-

oscillating some kind of frequency control is required. The magnetron is provided

with a tunning mechanism to adjust the oscillating frequency b/w certain limits. This

tunning mechanism is operated by an electric motor being part of the Afc control

circuit. Together with circuits in the Lo+Afc units, a frequency control loop is

created thus maintaining a frequency of the SSLO and the magnetron output

frequency.

4.14.4 LO+AFC Unit

The Lo+Afc unit determines the frequency of the transmitted radar pulses. It

comprises-

Lock Pulses mixer

Afc discriminator

Solid state local oscillator(SSLO)

Coherent oscillator(COHO)

The Afc lock Pulses are Pulses are also applied to the COHO. The COHO outputs

signals with a freq. of 30Hz, and it is synchronized with the pulse of each transmitter

Pulse. In this way a phase reference signal is obtained, required by the Phase

sensitive detector in the receiver unit.

4.14.5 Receiver unit

The Rx unit converts the received RF echo signal to IF level and detects the IF

signals in two different ways, two receiver channel are obtained, called MTI channel

and linear channel.

The RF signal received by the radar antenna pass the circulator and are applied to a

low noise amplifier. The image rejection mixer mixes the amplified signals with the


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SSLO signals, to obtain a 30MHz IF signal is split into two branches.viz, an MTI

channel and a linear channel.via directional coupler, a fraction of the low noise

amplifier output is branch offer and applied to the broadband jamming detector. The

BJD is a wideband device, which amplifies and detects the signal applied. The

resulting signal is passed on the SJI-STC circuit (Search jamming indication

sensitivity time control) in the video Processor , if jamming occurs, it is used to

prevent a polar diagram of a jamming on the PPI Screen, Which shows the direction

of the jamming source.

In the MTI channel, the IP signal is amplified again by the MTI main amplifier

and applied to the phase sensitive detector. The second signal applied to the phase

sensitive detector PSD is the phase reference signal from the COHO. The output

signal of the PSD consists of video pulse, the amplitudes of which are a function of

the phase difference between the two input signal of the PSD. The polarity of the

video pulse indicate whether the phase difference is positive or negative.

The phase differences between the corlo signal and if echo signals from a fixed

target are constant whereas those between the COHO signal and if echo signals from

a moving target are subject to change.

The PSD output signal is applied to the canceller in the video processor.

The linear detector outputs positive video signals which are passed on to the colour

PPI drive unit.

4.14.6 Antenna

The antenna is a cosecant square parabolic reflector, rotating with a speed of about

48 r.p.m. in the focus of the reflector is a radiator, which emits the RF pulses from

the circulartor and which receives RF echo Pulses.

In the waveguide is Polarisation shifter, which causes the polarization of the RF

energy to the either horizontally or circularly. The polarization shifter is controlled

by the system operator.

4.14.7 Video Processor


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The video processor processes the MTI receiver channel, to make the video suitable

for presentation on the colour PPI screen and for use by the video extractor.

The main circuit comprised by the video processor are :

Synchronization circuit.

Canceller

Floating level circuit

Correlator

4.14.8 Synchronization circuit

The synchronization circuit develops the start pulse for the sub modulator in the

transmitter unit, and accordingly it generates the timing pulses required by the

canceller.

The repetition time of the start pulses depends on the PRF is staggered Pseudo-

randomly : 32 point stagger is used for low and high PRF and 64 point stagger is

used for extra PRF. The 64 point stagger for extra PRF is actually is compound of a

32 point staggered short PRT and 32 point staggered long PRT and a 32 point

staggered long PRT.

4.14.9 Canceller

The canceller is a circuit used to suppress the echos of fixed targets or very slow

moving targets. The canceller makes use of the difference in phase behavior moving

and fixed targets with moving target and phase differs from pulse to pulse, but with

fixed targets the phase is constant (i.e. the PSD output is constant). The suppression

by the canceller is limited. The higher the PRF of the radar pulses, the better thesuppression factor; a further cancellation improvement can be obtained by using a

triple canceller instead of a double canceller; here a compromise is to found.

The operation of the canceller depends on the selected PRF :

Low and high PRF ;

The canceller is swithched as double canceller.

Extra PRF :

The PRF jumps from pulse to pulse between low PRF and high PRF.


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The canceller switched to double is a digital three pulse comparison

canceller.

Videos are :

Undelayed video (V0)

Video delayed by one PRT (V1)

Video delayed by two PRTs (V2)

By addition, multiplication and subtraction these video are combined to obtained a

canceller output according to the following formula.

V out (double) = 2 V1 (V 0 + V 2)

The canceller switched to triple is digital four pulse comparison canceller.

This circuit the following videos are obtained : Undelayed Video (V0)

Video delayed by one PRT (V1)

Video delayed by two PRT (V2)

Video delayed by three PRTs (V3)

Canceller output according to the following formula :

V out (triple) = V0 3 V1 + 3 V2 V3


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CHAPTER 5

SIGNAL PROCESSING UNIT

5.1 INTRODUCTION

The signal processing unit constitutes a very important functional block with vital

roles to perform in overall system configuration of receiver radar returns under

normal operating conditions are initially processed by the analogue processing

stages (such as LNA, IF, VIDEO DETECTOR etc.) and then processed by signal

processor.

This type of signal processor is known as MOVING TARGET DETECTOR.

To improve the radar resolution in range, without the need for transmitting narrow

pulse, a technique called PULSE COMPRESSION is employed. This will avoid the

need for the transmission of a narrow pulse with high peak power, thus simplifying

the transmitter chain.


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5.2 PRINCIPLE OF OPERATION

The signal processor consists of Digital Pulse Compression system followed by the

prewhitening clutter cancellation filter in the form of three pulses in MTI. The MTIoutput is then processed by a sixteen point FFT processor with frequency domain

windowing feature. Final stage of data processing is detection. In detection block

Cell Averaging (CACFAR) with programmable threshold setting features in

range/Doppler domain is used.

The MTI, FFT and CFAR are collectively known as MTD.

Similarly, in order to enable detection of tangentially moving (or low Doppler )

targets under noise limited, and weak to moderate ground clutter conditions, the

Zero Velocity Filter(ZVF) and its associated clutter map are used. PRF staggering

scheme on scan-to-scan and CPI-to-CPI basis is employed to ensure better

performance against blind speed conditions.

Signal Processor receives digital data from if processor. The data is received and

offset corrected (if AUTO OFFSET is ON SP control panel) and passed on toDigital Pulse Compression (DPC) block.

The Digital Pulse Compression block carries out the matched filtering and

correlation of the returns with the transmitted phase codes. However, to enable the

detection of weak signals under noise and clutter backgrounds, and extraction of

signal parameters such as Doppler content, strength, range and azimuthal positions

etc. further processing needs to be carried out using clutter cancellation, filtering and

integrations, and detection techniques.

Moving Target Detector (MTD) technique, facilitate optimal detection under

conditions of heavy clutter especially in Radars used for low looking surveillance

role. Keeping in view, the environment under which the INDRA-II is expected to

perform its role for the given specifications, the MTD technique naturally turns out

to be the ideal choice of its implementation.


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Timing and control signals required by various functional blocks of the Signal

Processor and also the transmitter system are catered for as part of the Signal

Processor design feature. To facilitate the validation and testing of the signal

processor, a swept Doppler BITE is also provided. Similarly, to monitor on

Oscilloscope outputs of MTI, FFT and ZVF blocks, the necessary circuits in the

form of D/A converters are also provided.

Interface circuits for MTD processed video on PPI as well for MTD data transfer to

centroid/RDP processor also form part of the design features.

5.3 HARDWARE ORGANISATION

The Signal Processor is realized on multiple, multilayer PCBs. The PCBs are

grouped into functions are packed into a single card cage. Each card cage is capable

of housing up to 15 PCBs, along with a power supply module. The power supply

takes ac input and caters for the +5V, +15V and -15V supply needs of that card

cage.

Two such card cages are put together in a card enclosure called Card Panel. Two

such card panels are being used to realize total signal processing hardware.

Each of the card panel is mounted on rails, to be able to pull out for maintenance

purpose.

5.4 FUNCTIONAL ORGANISATION

All the functions performed by Signal Processor can be organized under following

groups:

5.4.1 SIGNAL PROCESSING FUNCTIONS:

These are the main functions that process the radar echo, and hence form the main

functional chain.


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DIGITAL PULSE COMPRESSION

AUTO OFFSET CORRECTION

MATCHED FILTER

MOVING TARGET INDICATOR

FFT PROCESSING

ZERO VELCITY FILTER (ZVF)

ADAPTIVE THRESHOLDING (CFAR)

5.4.2 INTERFACE FUNCTIONS:

These are the functions enabling the signal processor to communicate with other

units in the radar. Following are realized as dedicated interface on separate PCBs.

Other interfaces are part of their respective hardware.

DISPLAY INTERFACE

CENTROIDER INTERFACE

5.4.3 SYSTEM FUNCTIONS:

These functions receive controls (if any), and generate control for some functions

performed by other units of radar.

SYSTEM TIMING (also contain circuits for internal timing requirements of

SP).

SYSTEM BITE Generates control for simulated target generation by

Receiver.

ADAPTIVE MSC (AMSC) Adaptive map generation and transfer to

receiver for Adaptive Microwave Sensitive Control.

ECCM Analyze and generate control for optimum frequency selection and

jammer indication on PPI.

5.4.4 MONITORING FUNCTIONS:

For parameter control and quick check on health of Signal Processor following

functions are performed:

RPM monitoring.

SP output monitoring.


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Control Panel Function.

5.5 FUNCTIONAL DESCRIPTION

The following are detailed description of each functional block.

5.5.1 DIGITAL PULSE COMPRESSION (DPC) BLOCK

DPC card module performs the following functions:

I/Q channel Digital Matched Filtering.

Automatic DC offset correction for I/Q ADC data.

Adaptive Microwave Sensitivity Control.

Online JAM sensing with real time ECCM controls.

Systems BITE control for generation of simulated targets for on-line injection at

RF & IF levels.

PD /Pfa / Antenna RPM monitoring & Indication.

The Digital Card Module houses 13 nos. of extended double Euro Multi-layer PCBs

as part of the Signal Processing Rack of INDRA-PC RADAR.

This card module receives theINPHASEand QUADRATURE channel ADC data

(12+12 bits) from the 30 MHz IF processor. Automatic DC offset correction is

applied to this data and inputted to the digital matched filter. The I & Q channel

pulse compressed signal is then fed to the corner turning memory of the MTD

processor in the next card module. The received ADC data also goes after buffering

to the Adaptive Microwave Sensitivity Control (AMSC) card and ECCM control

card.


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5.5.2MATCHED FILTER FUNCTION BLOCK

DPC CONTROL CARD # 1, DPC CONTROL CARD # 2, I-CH matched filter and

Q-CH matched filter together constitutes the matched filter block.

I/Q ADC data from IF unit, offset corrected in Auto Offset Correction Card enters

DPC CNTL CARD # 1.Here I/Q ADC data is added to I/Q clutter BITE (CLUT).

The clutter BITE is initiated with the help of CLUT PULSE trigger when needed

only.

I/Q ADC + CLUT data is multiplexed with I/Q SIM data and the selected data goes

to I/Q matched filters. SIM data is used for on-line diagnostics and fault indication.

Under normal operating conditions, ADC data is present during radar operational

range and DPC SIM data is injected during the dead range of the radar. There is an

over-riding switch control DPC BITE ON/OFF by which only DPC SIM data can be

selected as input to I/Q matched filters for diagnostics purposes.

I and Q matched filters look for the correlation in the code between the transmitted

pulse and that of received echo pulse. The peaking of the signal occurs whenever the

correlation exists. There are two banks in the matched filter performing the similar

filtering operation and the selection of a particular bank for operation is decided by

the signature analysis circuit in DPC CNTL CARD # 2.

Signature analysis is carried out on-line during the dead range. The matched filter

output patterns for I & Q DPC SIM data are stored in EPROMs. A signature analysis

gate is opened during which the on-line matched filter outputs are compared with

the signatures stored and the error condition if any is detected

With BANK # 1 selected, I-DPC data is selected for signature analysis for 8 sweeps

and then Q-DPC data for the next 8 sweeps. The same sequence is followed when

BANK # 2 is selected. If there is any error in BANK # 1 or BANK # 2 of I-MF or

BANK # 1 or BANK # 2 of Q-MF, an appropriate LED is switched on. The

signature analysis logic automatically switches to alternate bank when one bank is

found faulty.


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The codes used in operation are stored in a PROM band can be selected manually

using DIP-switch on the card or automatically when code agility mode is selected.

DPC CONTROL CARD # 1 generates the various control signals for signature

analysis.

Code generation and distribution to the other subunits/subsystems, is done, in DPC

CONTROL CARD # 2. This card also receives various signals and distributes them.

DPC output analog video is generated for monitoring purposes in DPC CONTROL

CARD # 1 & # 2.

5.5.3 AUTO OFFSET CORRECTION FUNCTION

Auto offset correction block comprises

Auto offset correction hardware card, and

AMSC- Master Card.

The estimation of offset value in I/Q ADC data is done on-line every scan using

ADSP processor in AMSC-Master Card. This offset data is subtracted (with proper

sign) from the real time I/Q data for every range cell in following scan.

During the dead CPI period, when there is no transmission, I/Q samples are taken at

3microsec. interval over several range cells. This way samples are collected over

several dead CPIs in a scan. The mean of these samples is computed to get the offset

value in each of the channels. These I/Q offset values are passed on to the Auto

Offset Correction Card, where the hardware corrects the offset in the two channelson-line in the following scan.

Auto Offset Correction Card receives I-ADC and Q-ADC data from IF processor

unit corrects the offset in the two channels and passes on to DPC CONTROL CARD

# 1. It also buffers and distributes the I-ADC and Q-ADC data to AMSC and ECCM

CARD #1.

5.5.4 BULK MEMORY FUNCTION BLOCK


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As the processing requirement is in the batch mode for MTD, the radar real time

data has to be reordered and to processing block. This reordering is done in the bulk

memory. This circuit consists of two PCBs. The first PCB is the Bulk Memory

Control Card. In this PCB, the address generations for both read and write

operations; control generation and BITE generation are implemented. In the second

card mainly the memory and the corresponding switching buffer is available. The

memory in the second board is organized in such a way that while DPC output data

is written in one of the memories called bank A, the other memory called bank B,

outputs the previous CPI data for processing block. The clock used for the read

operation is gated Rck, generated in system timing card. The bank switching is done

after every CPI.

5.5.5 MOVING TARGET DETECTOR PROCESSOR BLOCK

MTD is an example of an MTI processing system that takes the advantage of the

various capabilities offered by digital techniques to produce improved detection of

moving targets.

Infact,

The MTI, FFT and CFAR are collectively known as MTD.

5.5.6 MOVING TARGET INDICATOR FUNCTION BLOCK

It is possible to remove from the radar display the majority of clutter, that is, echoes

corresponding to stationary targets, showing only the moving targets. This is often

required, although of course not in such applications as radar used in mapping or

navigational applications. One of the methods of eliminating clutter is the use of

MTI, which employs the DOPPLER EFFECT in its operation.

5.5.6.1 DOPPLER EFFECT

The apparent frequency of electromagnetic sound waves depends on the relative

radial motion of the source and the observer. If source and observer are moving

away from each other, the apparent frequency will decrease, while if they are

moving towards each other, the apparent frequency will increase.


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The Doppler effect is observed only for radial motion, not for tangential motion.

Thus no Doppler effect will be noticed if a target moves across the field of view of

radar.

A Doppler shift will be apparent if the target is rotating, and the resolution of the

radar is sufficient to distinguish leading edge from its trailing edge.

5.5.6.2 FUNDAMENTALS OF MTI

Basically, the moving-target indicator system compares a set of received echoes

with those received during the previous sweep. Those echoes whose phase has

remained constant are then cancelled out. This applies to echoes due to stationary

objects, but those due to moving targets do show a phase change; they are thus not

cancelled-nor is noise, for obvious reasons.

The fact that the clutter due to stationary targets is removed makes it easier to

determine which targets are moving and reduces the time taken by an operator to

take in the display.

It also allows the detection of moving targets whose echoes are hundreds of times

smaller than those of nearby stationary targets and which would otherwise have been

completely masked.

The phase difference between the transmitted and received signals will be constant

for fixed targets, whereas it will vary for moving target.

The advantage offered by digital MTI processing:

Compensation for blind phases, which cause a loss due to the difference in

phase between the echo signal and the MTI reference signal. This is achieved

by use of I & Q processing, something that was always known to be of value for

MTI processing, but which was not convenient to implement with analog

methods.


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Greater dynamic range can be obtained than was possible with acoustic delay

lines.

Digital processor can be made reprogrammable.

Digital MTI is more stable and reliable than analog MTI, and requires lessadjustments during operation in the field.


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5.5.7 FFT PROCESSOR FUNCTION BLOCK

5.5.7.1 FAST FOURIER TRANSFORM (FFT)

Digital filtering involves the use of Fourier transform. The FFT requires less

computational effort, and it has been popular for many applications. It has some

limitations, however compared to. The number of samples has to be expressed as 2 n

if a filter bank is being generated, all filters have identical responses, they will be

uniformly spaced frequencies, and the weighting coefficients are not optimum since

they cannot be chosen independently for each filter. The filters possible with a non-

FFT filter bank also can achieve greater attenuation of moving clutter (such as rain

or chaff) because of the greater flexibility available in their design. There are times,

therefore, when the classical Fourier transform may be more advantageous than the

FFT even though the FFT might be quicker and require less complexity.

5.5.7.2 HARDWARE

FFT processor has been realized on 12 multilayer PCBs. The PCBs are as follows:

FFT Timing and Control

Cascade Buffer for FFT

Processor 1 ALE

Processor 1 Feedback

Processor 1 Feed forward

Complex multiplier

Processor 2 ALE (Architecture same as Processor 1 ALE)

Processor 2 Feedback (Architecture same as Processor 1 Feedback)

Processor 2 Feed forward (Architecture same as Processor 1 Feed forward)

Frequency Domain Window (Real)

Frequency Domain Window (Imag.)

Magnituder


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ZERO VELOCITY FILTER FUNCTIONThe MTD also uses a new concept of Zero Velocity filter (ZVF) to overcome the

probability of missing the targets which have a velocity falling in the zero Doppler

zone. This will be the case of targets which are flying tangential radar and low

velocity radial targets, whos Doppler is such hat they fall in zeroeth filter. Also

since the response of the DMTI is rather poor for low Doppler targets, there is every

chance that these targets may go under. ZVF performs its function by forming a

clutter map.

Clutter map: A conventional MTI processor eliminates stationary clutter, but it

also eliminates aircraft moving on a crossing trajectory (one perpendicular to the

radar line of sight) which causes the aircrafts radial velocity to be zero. This is

unfortunate since the radar cross-section of an aircraft is relatively large when

viewed at the broadside aspect presented by a crossing trajectory. The MTD took

advantage of this large cross-section to detect the targets that normally would be lost

to a simple MTI radar. It did this with the aid of a clutter map that stored the

magnitude of the clutter echoes in a digital memory. The clutter map established the

thresholds used for detecting those aircraft targets which produce zero radial

velocity.

There may be many range cells which may not contain clutter, or contain low

clutter, but due to the poor response of MTI. These may be the implementation of

the ZVF will allow the detection of targets whose return exceeds that of the clutter

in that particular range azimuth cell. The ZVF is implemented by integrating all

the 18 returns of a CPI, and whose response extends to the frequency band covered

by the zeroeth filter.

In the zeroeth Doppler cell, the clutter is generally due to the ground echoes.

To estimate the average backscatter signal level, the entire range azimuth space is

divided into fine grain resolution cells and the returns are stored in the form of a

map. To build up the map accurately, each antenna resolution is broken into 256

CPIs and there are 2560 range cells. The ZVF is made up of magnitude of 18


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samples, which are formed by first adding 9 samples and then adding the next 9

samples coherently and non-coherently adding up the sums.


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5.5.8 CFAR PROCESSOR BLOCK

CFAR is used in radars to maintain effectiveness when there are too many

extraneous crossings of a fixed threshold caused by clutter or noise. Automatic

tracking of targets can be seriously degraded if excessive false alarms occur.

CONSTANT FALSE ALARM RATE (CFAR) processor block is one of the

major functional blocks of digital signal processor. The output of the FFT filtering

block is further processed to facilitate the following

Generation of adaptive threshold levels using Moving Window concept.

Detection of signals and extraction of primitive (primary) data information

pertaining to the detected signals.

The output of the FFT magnituder forms the main data input to the CFAR Processor

block. Functional sub-blocks such as the running sum computation, Pipeline

memory storage, Mode Selection Multiplier and threshold detection constitute the

hardware blocks of the CFAR processor. In the CFAR processo

report on bel

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