Prateek Jainreport

8/4/2019 Prateek Jainreport

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TRAINING

REPORT

BHARAT

ELECTRONICS

SUBMITTED BY

NAME: NEETU SINGH

UPT NO.: UPT/ /2011

COLLEGE: SHAHEED RAJGURU COLLAGE OF APPLIED SCIENCE ONLY

FOR WOMEN (DELHI UNIVERSITY)

COURSE: B.A.SC (H) ELECTRONICS


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INDEX

CONTENTS PAGE

NO.

CERTIFICATE.

3

ACKNOWLEDGEMENT.

4

PREFACE.5

BHARAT ELECTRONICS LIMITED:

6

AN OVERVIEW.

MANUFACTURING UNITS.

BEL PRODUCT RANGE.

BEL GHAZIABAD UNIT.

11

ROTATION PROGRAMME:

14

TEST EQUIPMENT AND AUTOMATION.

PCB FABRICATION.

Q.C WORKS.

WORK ASSEMBLY.

MAGNETICS.

MICROWAVE LABORATORY.


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AN INTRODUTION TO BASIC RADAR.

26

THE IFF UNIT - MK XI.

28

BRIEF TECHNICAL DESCRIPTION OF IFF UNIT MK XI.

32

IFF MK X SYSTEM (BASIC PRINCIPLE)

34

APPLICATIONS OF RADAR

46 CONCLUSION

48

CERTIFICATE

This is to certify that, Mr. Sahil Sachdeva ( Enrollment Number: 0871042808) student of

B.TECH (Electronics and Communication) from Amity School Of Engineering and

Technology (Affiliated to Guru Gobind Singh Indraprastha University, Delhi ) has

completed his industrial training in BHARAT ELECTRONICS LIMITED,

GHAZIABAD from 13.06.11 to 23.07.11. During this training period he was

assigned PRODUCT ASSURANCE (RADAR) IFF TESTING.

He was involved in Studying and Testing of various components testing of IFF RADAR

System. In addition he also gained the knowledge and operation of other latest

testing/measuring equipments.

I wish him all the success in his life.


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PROJECT GUIDEMANAGER

(PA-R/IFF) (PA-

R/IFF)

ACKNOWLEDGEMENT

First of all I would like to thank Ms. VANEETA BHANDARI, (MANAGER) (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. RAGHUNANDAN TYAGI, (SR. Engineer-Human

Resource Development Department), 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


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only due to the kind co-operation ofMr. K.T.S MURTY (Manager). I am thankful to

him and his colleagues.

I pay my special thanks to Mr. JYOTI PRAKASH (Asst. Engineer) who guided me on

my project and without who I was not able to complete my project. I am also thankful to

other BEL staff that helped me during the summer training.

PREFACE

This six weeks training is a part my 4-year degree course. Practical industrialtraining mainly aims at making one aware of industrial environment, which means

that, gets to know the limitation, constraint and freedom under which an engineerworks. One also gets opportunity to see from close quarter that indicatesmanagement relation. This training mainly involves industrial and completeknowledge about designing, assembling and manufacturing of equipments.

Excellence is an attitude that the whole of the human race is born with. It is theenvironment that makes sure that whether the result of this attitude is visible orotherwise. A well planned, properly executed and evaluated industrial training


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helps a lot in inculcating a professional attitude. It provides a linkage between theme and industry to develop an awareness of industrial approach to problemsolving, based on a broad understanding of process and mode of operation oforganization.

During this period, the I get the real experience for working in the actualenvironment. Most of the theoretical knowledge that has been gained during thecourse of my studies is put to test here. Apart from this, I get an opportunity tolearn the latest technology, which immensely helps them in building my career.

I had the opportunity to have a real experience on many ventures, whichincreased my sphere of knowledge to a great extent. I got a chance to learnmany new technologies and was also interfaced to many new instruments and allthe credit goes to organization BHARAT ELECTRONICS LTD.

AN OVERVIEW

INTRODUCTION

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 noteworthyhistory of pioneering achievements, has met the requirement of state-of-art professional

electronic equipment for defence, broadcasting, civil defence and telecommunications as


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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 collaborationwith 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 valvemanufacturing facility. It moved on to semi-conductors with the manufacture of

germanium and silicon devices and then on to manufacture of integrated circuits. To keep

in pace with the components and equipment technology, its manufacturing and productassurance facilities have undergone sea change. From quality check control machines to

multi-dimensional profile measurement machines, Automatic testing machines,

environmental labs to check extreme weather and other operational conditions. All these

facilities have been established to meet up the stringed requirements.

Today BELs infrastructure has spread over nine locations with 29 production divisions

having ISO-9001/9002 accreditation. Product mix of company is spread over the entireElectro-magnetic (EM) spectrum ranging from tiny audio frequency semiconductor to

huge radar systems and X-Ray tubes o the upper edges of the spectrum .Its manufacturing

units have special focus towards the product ranges like defence communication,Radars, Optical & Opto-electronics, Tele-communications, Sound and vision and

broadcasting, Electronic components ,etc.

AWARDS WON BY BEL

R&D Divisions of BEL have been receiving number of National R&D awards, here is asmall list as its not possible to show out the same.

1. FICCI Award for Research in Science & Technology 1990

(For the corporate initiative of R&D)

2. DSIR National R&D Award 1992

(For successful commercialization of Public Funded R&D)(For D&E project handled at BEL-GAD)

3. DSIR National R&D Award 1993(For in house R&D efforts under Electronics & Electrical Industries Sector)


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(For D&E projects handled at BEL-Bangalore, Machilipatnam and Ghaziabad)

4. DSIR National R&D Award 1995(For in house R&D efforts under Electronics Industries Sector)

(For D&E projects handled at BEL-Bangalore & Ghaziabad)

5. Defence Technology Absorption 1998

(For successful commercialization of Public Funded R&D)

(For D&E project handled at BEL-Bangalore and Panchkula)

6. Award for excellence in R&D for the year 1998-2000-2001

(Sponsored by Ministry of Information Technology, Gol)(For BEL-Ghaziabads

development of various IFF-Systems)

AND MANY MORE AWARDS

BEL has production units established at different parts of country. The year ofestablishment and location are as follows:

S.No Year of establishment Location

1. 1954 Bangalore

2. 1972 Ghaziabad

3. 1979 Pune

4. 1979 Tajola(Maharashtra)

5. 1984 Hyderabad

6. 1984 Panchkula(Haryana)

7. 1985 Chennai

8. 1985 Machilipatnam(A.P)

9. 1986 Kotdwara(U.P)

MANUFACTURING UNITS


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CORPORATE MOTTO-------------------------------------------------------------------------------------

QUALITY, TECHNOLOGY and INNOVATION.


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CORPORATE MISSION

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

CORPORATE OBJECTIVES

1. To become a customer-driven company supplying quality products at competitiveprices at the expected time and providing excellent customer support.

2. To achieve growth in the operations commensurate with the growth of

professional electronics industry in the country.

3. To generate internal resources for financing the investments required for

modernization, expansion and growth for ensuring a fair return to the investor.

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

indigenization of materials and components.

5. To retain the technological leadership of the company in Defence and otherchosen fields of electronics through in-house Research and development as well

as through collaboration/co-operation with Defence/National Research

Laboratories, International companies, Universities and Academic Institutions.

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

7. To create an organizational culture this encourages members of the organization

to realize their full potential through continuous learning on the job and throughHRD initiatives.

MANUFACTURING UNITS:


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Bangalore (Karnataka): It was the first centre as already been given, being established

in 1954. Since then, the Bangalore complex has grown to specialize in communication

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

Ghaziabad (Uttar Pradesh): Its the second largest unit to manufacture special types ofRadars for the Air Defence Ground Environment System. It provides Communication

systems to the Defence forces and Microwave users.

Pune (Maharashtra): This unit manufactures Image Converter tubes. Subsequently,

Magnesium Manganese-dioxide batteries, Lithium sulphur batteries and X-Ray

Tubes/cables were added to the product range. At present unit manufactures Laser sub-unit for tank fire control systems and Laser Range finders for the defence services.

Machilipatnam (Andhra Pradesh): The product line includes Passive Night visionequipment, Binoculars, Goggles periscopes for tank fire control systems. This unit also

meets up demands of professional grade radio-communication equipment in VHF andUHF ranges.

Chennai (Tamil Nadu): It was established to manufacture gun control equipmentrequired for the integration and installation in the Vijayanta Tanks. The unit now is

manufacturing Stabilizer systems for T-72 tanks, Infantry Combat Vehicles BMP-II etc.

Kotdwar (Uttar Pradesh): This unit manufactures Tele-communication equipment for

both defence and civilian.

Taloja (Maharashtra): For the manufacture of B/W TV Glass bulbs, this plant wasestablished in collaborating with coming, France in 1986. The unit is now fully mobilized

to manufacture 20 Glass bulbs indigenously.

Hyderabad (Andhra Pradesh): To coordinate with the major Defence R&D

Laboratories located in Hyderabad, DLRL, DRDL, and DMRL, BEL established a unit in

Hyderabad in 1986. Force Multiplier systems are manufactured here for the Defenceservices.

BEL GHAZIABAD UNIT


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Formation

In the mid 60s, while reviewing the defense requirement of the country, the government

focused its attention to strengthen the air defense system, in particular the ground

electronics system support, for the air defense network. This led to the formulation of a

very major plan ADGES with Prime Minister as the presiding officer of the apex reviewcommittee on the development and production of electronic equipment. The ministry of

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

electronic equipment requirements for its plan ADGES.

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

requirement for the plan ADGES and in view of the importance of the project it was

decided to create additional capacity at a second unit of the company.

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

license for manufacture of radar and microwave equipment was obtained; 1972 saw the

commencement of construction activities and production was launched in 1974.

Over the years, the unit has successfully manufactured a wide variety of equipment

needed for defense and civil use. It has also installed and commissioned a large number

of systems on turnkey basis. The unit enjoys a unique status as manufacturer of IFF

systems needed to match a variety of Primary Radars. More than 30 versions of IFF have

already been supplied traveling the path from vacuum technology to solid state to latest

Microwave Component based system.

PRODUCT RANGES:

The product ranges today of the company are:


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1. Radar systems:

(a) 3-Dimensional High power static and mobile Radar for the Air force.(b) Low flying detection Radar for both the Army and the Air force.

(c) Tactical control Radar systems for the Army.

(d) Battlefield Surveillance Radar for the Army.(e) IFF-MKX Radar systems for the defence and export.

(f) Radar allied systems Data Processing systems.

2. Communications:

(a) Digital Static Tropo Scatter Communications systems for the Air force.

(b) Digital Mobile Tropo Scatter Communication system for the Air force.(c) Bulk encryption equipment.

(d) Telemetry/Tele control systems.

(e) VHF, UHF and Microwave Communication equipment.

3. Antenna:(a) Antennae for Terrestrial, Radar and Satellite Communication systems.

(b) Antennae for TV Satellite Receive and Broadcast applications.

(c) Antennae for line-of-sight Microwave Communication systems.

4. Microwave components

(a) Active Microwave components like LNAs, Synthesizer, Receivers etc.(b) Passive 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 BELsown design and development efforts.

Organization:


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The operations at BEL Ghaziabad are headed by General Manager with

Additional/Deputy General Manager heading various divisions as follows:

Design & Engineering Divisions:

Development and Engineering Radars

Development and Engineering-Communication Development and Engineering-Antenna

1. Equipment Manufacturing Divisions:

Radars

Communication

Antenna

Systems

Microwave components.

2. Support Divisions:

Material Management

Marketing and Customer Co-ordination

Quality Assurance & Torque

Central Services

PCB & Magnetics

Information Systems

Finance & Accounts

Personnel & Administration

Management Services.


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ROTATION PROGRAM

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

various departments. The several departments where I had gone under my rotationalprogram are:

Test Equipment and Automation

P.C.B. Fabrication

Quality Control Works Radar

Works Assembly

Communication

Magnetics

Microwave Lab

Environmental Lab

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

knowledge of the various departments. A brief idea of the jobs done at the

particular departments was given. The cooperative staff at the various

departments made the learning process very interesting, which allowed me to

know about the company in a very short time.


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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 verycostly, 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.


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Green O.K , Perfect

Yellow Satisfactory but some trouble is present.

Red Cant be used, should be disposed off.

The standards 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 StandardAfter 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.


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P.C.B. FABRICATION

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

as well as all the components are mounted on it. It consists of the fiberglass sheet having

a layer of copper on both sides.

TYPES OF PCBs

1. Single Sided Board : Circuits on one side.

2. Double Sided Board : Circuit on Both sides.

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

metallization.

BEL-Ghaziabadproduces only single-sided and double-sided PCBs.

Fabrication of single sided PCBs:

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

2. The sheet is laminated with a photosensitive solution.

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

it is subjected to the UV light. As a result the transparent plate gets polymerized

and the opaque part remains unpolymerized.

4. The plate is dipped in solution in which the non-polymerized part gets dissolved.5. Tin plating is done on the tracks obtained.

6. Lamination of the plate is removed.

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

that dissolves copper but not tin (etching).

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

process fabricates PCB.

Raw material for PCBsMost 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


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Operation in processFollowing 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

But these PCBs have the following disadvantages:

>> Due to very narrow spacing between adjacent tracks, there may be a chance of short

circuit if the soldering is done by hands between components on opposite side.

>> Moisture or dust between gaps may disrupt smooth soldering.

These disadvantages are overcome by soldered mask PCBs. In the later one an additionalfilm is put on the earlier fabricated PCB, leaving points where components are to be

soldered.


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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 BELstandards.

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 enteredin 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


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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 RADARe.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.

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.


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


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MAGNETICS

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

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

equipments.

This department basically consists of three sections:

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

production of transformer and coils as per the requirement of respective division

(Radar and Communication). This department divided into two groups :

(a) Planning 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) Molding type transformers

iv) P.C.B Mounting transformers :-

(a) Impedance matching transformers

(b) RF transformers

(c) IF transformers


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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 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 plastic layer is inserted between two

consecutive layers.

The various types of windings are as follows:

i) Layer Winding

ii) Wave Windingiii) 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.


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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 thissection. 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. Theinstruments used for this purpose are as follow:

1. Filters

2. Isolators

3. Reflectors

4. Network Analyzers

5. Spectrum Analyzers

6. Amplifiers and Accessories

ENVIRONMENTAL LAB


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Various tests are conducted in the environmental lab in BEL in order to

ensure reliability. Reliability is defined as the probability of a device performing its

purpose adequately for the period intended under the given operating condition. In a

given reliability is given as

The standards available here are:

JSS55555- Joint services specifications (Military Standard of India)

MII Standards U.S Military standers

QM333 Civil Aviation and police

VARIOUS TESTS:-

1. Thermal Shock Test

2. High Temperature Operate and Storage

3. Low Temperature Operate and Storage

4. Altitude Test

5. Bump / Vibrations Test

6. Salt Spray Test

7. Tropical Exposure Test

8. Rain Test

9. Humidity Test

10. Dust Test

11. Transportation Test


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TRANSMITTER

RECIEVER

DUPLEXER

A

NT

E

N

N

A

INTRODUCTION TO RADAR

RADAR BASIC

RADAR STANDS FOR RADIO DETECTION AND RANGING.

RADAR is an electromagnetic system for detection and location of reflecting

objects such as aircraft, ships, spacecraft, vehicles, people, and the natural

environment.

It operates by radiating energy into space and detecting the echo signal reflected

from an object or target.

The reflecting energy that is returned to the radar not only indicates the presence of

a target, but also by comparing the received echo signal with the signal that was

transmitted, its location can be determined along with other target-relatedinformation.

Radar can perform its function at long or short distances and under conditions

impervious to optical and infrared sensors.

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

Its ability to measure distances with high accuracy and in all weather is one of itsmost important attributes.

THE BASIC PRINCIPLE OF RADAR


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

antenna.

A transmitter (in the upper left portion of the figure) is capable of sending out a

large UHF or microwave power through the antenna.

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

directions.

The receiverreceives, analysis, and displays the information in the reflected echoes

picked up by the antenna. There it is processed to detect the presence of the target

and determine its location.

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

called duplexer

Figure showing: Principle of radar operation. The transmitted pulse hasalready passed the target, which has reflected a portion of theradiated energy back toward the radar unit.

According to the block diagram, the transmitter generates a short, rectangular pulse.

As soon as the pulse enters the duplexer disconnected the receiver from antenna andconnects the transmitter to the antenna.

Antenna Beam

width

Target

Radar

Antenna

Transmitted signal

beam


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As soon as, transmitted pulse terminates, the duplexer disconnects the transmitterfrom the antenna and connects echoes received by the antenna are fed to the receiver,

where they are amplified, demodulated and fed to a display device.

The distance to the target is determined by measuring the time taken for the radarsignal to travel to the target and back.

d=vtWhere, d=distance/range

v=velocity

t=time

The targets 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

target is in motion, there is a shift in the frequency of the echo signal due to the

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

radar. The Doppler frequency shift is widely used in radar as the basis for separatingdesired moving targets from fixed (unwanted) clutterechoes reflected from thenatural environment such as land, sea, or rain.

Range or distance of radar is measured in nautical miles.

1 nautical miles=1852m.

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. Heres how to

understand Doppler shift Lets say there is a car coming toward you at 60 miles perhour (mph) and its horn is blaring. You will hear the horn playing one note as the car

approaches, but when the car passes you the sound of the horn will suddenly shift to a

lower note. Its the same horn making the same sound the whole time. The change you

hear is caused by Doppler shift.


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TYPES OF RADAR

Basis on its function radar is classified as:

1. Primary radar.2. Secondary radar.

PRIMARY RADAR:

A PRIMARY RADAR locates an object by transmitting a signal and detecting the

reflected echo. A SECONDARY RADAR SYSTEM is similar in operation to primary

radar except that the return signal is radiated from a transmitter on board the target ratherthan by reflection. In other words, secondary radar operates with a co-operative ACTIVE

TARGET while the primary radar operates with a PASSIVE TARGET. But in cases such

as controlling of air traffic, the controller must be able to identify the air craft and know

whether it is of a friend or a foe. It is also desired to know the height of the aircraft, sothat on the same source but flying at different levels can be kept apart.

To give the controller this information, a second radar called a secondarysurveillance 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.

SECONDARY RADAR SYSTEM:

The secondary radar system consists of an INTERROGATOR and aTRANSPONDER. The interrogator transmitter in the ground station interrogatestransponder 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 forpurposes of Identification is received back at the ground interrogator where it is decoded

and displayed on a radar type presentation.

The secondary radar gives the aircraft identity code and height data derived froma pressure capsule in the aircraft. In the Secondary Surveillance Radar (SSR), by

providing the interrogation pulses above the minimum triggering level, the transponder

makes a powerful reply. This enables the interrogator transmitters to be of lower powerand the ground equipment simpler.


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IFF UNIT

IFF is basically radar bacon system employed for the

purpose of general identification of military targets.The bacon system when used for the control of civil air

traffic is called SECONDARY SURVEILLANCE

RADAR (SSR).

Primary radar locates an object by

transmitting a signal and detecting the reflected echo. A Secondary radarsystem 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.


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Basic Radar System

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

recorder, processor and some sort of output display. Everything starts with the

transmitter as it transmits a high power pulse to a switch, which then directs the pulse to

be transmitted out an antenna. Just after the antenna is finished transmitting the pulse,

the switch switches control to the receiver, which allows the antenna to receive echoed

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

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

transmitter and the receiver as much as 1000 times per second.

Any received signals from the receiver are then sent to a data recorder for

storage on a disk or tape. Later the data must be processed to be interpreted into

something useful, which would go on a Pulse Width and Bandwidth.

Some radar transmitters do not transmit constant, uninterrupted electromagnetic

waves. Instead, they transmit rhythmic pulses of EM waves with a set amount of time in

between each pulse. The pulse itself would consist of an EM wave of several

wavelengths with some dead time after it in which there are no transmissions. The time

between each pulse is called the pulse repetition time (PRT) and the number of pulses

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


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Or

PRF = 1 / PRT

WORKING OF A SIMPLE RADAR

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

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 ofabout 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. Thepulses 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.


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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 thecoating 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 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 =

Rr and the termRt2Rr2 can be replaced byR4, whereR 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.
http://en.wikipedia.org/wiki/Radar_cross_sectionhttp://en.wikipedia.org/wiki/Radar_cross_section


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The equation above with F = 1 is a simplification for vacuum without

interference. The propagation factor accounts for the effects ofmultipath and shadowing

and depends on the details of the environment. In a real-world situation,pathloss effects

should also be considered.

IFF (MK-XI) UNITPURPOSE

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

1Nos.

b) RF Switch Unit

1Nos.

c) Interrogator - Decoder

1Nos.

d) Remote Control Panel

1Nos.

e) Control Units

2Nos.

f) Voltage Stabiliser
http://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Multipathhttp://en.wikipedia.org/wiki/Pathlosshttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Multipathhttp://en.wikipedia.org/wiki/Pathloss


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1Nos.

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


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IFF ANTENNA

RF SWITCH UNIT

TRANSMITTER

RECEIVER

MK X DECODER

MODE S DRAWER

REMOTE

CONTROL PANEL

CONTROL UNIT

PPI(INTERROGATOR DECODER)

GROUND / SHIPINTERROGATOR


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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 replycomprises 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 ofreplies by function.

IFF Mk-X SYSTEM

BASIC PRINCIPLE


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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 automaticallywhenever 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

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 fedto the display unit of primary radar for displaying the IFF responses. The system also

includes Mode `S drawer.

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


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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 P1and 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.

NOTE: the control pulse P2 does not carry any significance to thedecoding equipment (video processor).

INTERROGATION SIGNALP1 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

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

2

s Depends on

working mode


41/53

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 Figure next.

1. Modes 1 and 2 are used for Military Interrogations.

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

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

transponder 3S

2S

MODE 1

P2 P3P1

5S

2S

MODE 2

P2 P3P1

8S

2S

MODE 3/A

P2 P3P1

21S

2S

MODE C

P2 P3P1

24 S TO 1023 S

IN STEP 1 S

2S

MODE `S

P2 PS1P1

MODES OF INTERROGATION


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TRANSPONDER REPLY

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

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

the pulses and their designations is illustrated in Figures here. Every reply includes two

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


43/53

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

unit of the transponder.

The different types of reply received are:

a) NORMAL REPLY

The normal reply consists of the F1; F2 frame pulses bracketed the code pulses

appropriate to that particular aircraft for the mode of interrogation

b) MODE 1 REPLY

When an aircraft is interrogated in mode 1, which consists of P1 and P3 pulses spaced

3 microseconds apart, the transponder sends back accede train with the characteristics ofthe SI code train. SI is another designation for mode 1 and is the abbreviation for

SECURITY IDENTIFICATION .The returning SI code train is the basic FRIENDAND FOE identification.

The reply signal consists of the framing pulses F1 and F2 spaced at 20.3 microseconds

apart with all the pulses having pulse duration of 0.45 microseconds and 1.45microseconds apart.

c) MODE 2 REPLY

When the IFF ground interrogator transmits a mode 2 interrogation, consisting

of P1, P3 spaced at five microseconds apart, the aircraft transponder replies with aPERSONAL IDENTITY (PI) code train. Different aircraft return different codes, and thedesignation of the PI codes for specific aircraft varies in different areas or zones.

The code train consists of the two frame pulses F1, F2 spaced at 20.3 microseconds apart,

with pulse duration of 0.45 microseconds.The IFF MK 10 with SIF (SELECTIVE IDENTIFICATION FEATURE) has the ability

to change operating frequencies for security and also has complex coded replies to

positively identify the aircraft as friendly. It would be practically impossible for any

unfriendly aircraft to know the frequency and codes with which we were expecting thefriendly aircraft to reply. Besides distinguishing the aircraft as friendly, the SIF reply

codes tell its type and mission.

d) MODE 3 REPLY

The aircraft transponders response to mode 3 interrogation, consisting of P1, P3 spaced at

8 micro second apart is a T1 code train. The T1 is abbreviation for TRAFFIC IDENTITY

Each aircraft on a different flight schedule or mission can be assigned a different T1reply. The mode 3 reply is assigned differently in certain areas or zones.


44/53


45/53

EXAMPLE 2: CODE 6375

SIDE LOBE SUPPRESSIONA 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 interrogates and control patterns. When target is in

position `A', the amplitude of P1 & P3 pulses is more than the level of P2 pulse, the


46/53

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 alongwith 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.

OMNI ANTENNA PATTERN [P2]

DIRECTIONAL ANTENNA PATTERN [P

P3]

A

FOR `A

P1 P2 P3

FOR `B

P1 P2 P3

3 PULSES SIDE LOBE

SUPPRESSION


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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 thumbwheelswitch 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

All Aircraft

Signal (AA)

Primary

Radar Echo

Emergency andCommunication

Failure

Mode Smatch

Special Position

Identification

Passive CodeMatch


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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

The Interrogator Decoder Rack is made of high grade Aluminium 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

RECEIVER PROCESSOR

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

Mk-X system. The major drawbacks are:

1. 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


49/53

was not able to interact with a single (or a particular/

selected) aircraft with whom interaction is required.

2. 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.

3. 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 nameMk-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 respectto a pulse which is generated after a random delay between 1 s to 1023 s after pre-

trigger.

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

P1 PS4PS3PS2P2 PS1


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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 1s 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 variablePoly 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.

In this manner, the variable reply code was generated and which was being transmitted to

the ground system and therefore ensuring that no leaking of the code can happen.

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,


51/53

storm avoidance, terrain avoidance and navigation. In space, radar has assist in the

guidance of spacecraft and for remote sensing of the land and sea.

The major use of radar, and contributor of the cost of almost all of its

development, has been the military; although there has been increasingly important civil

application, chiefly for marine and air navigation. The major areas of radar application

are briefly described below:

Air Traffic Control (ATC): Radar is employed throughout

the world for the purpose of safely controlling air traffic

route and in the vicinity of Airport. Aircraft and ground

vehicular traffic at large airport are monitored by means of

high - resolution radar. Radar has been used with GCA

(ground control approach) system to guide aircraft to a safe

landing in bad weather.

Ship Safety: Radar is used for enhancing the safety of shiptravel 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 environmentalpollution.

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.


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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.

OTHER USES OF RADAR

Apart from the above mentioned uses, radar may be employed for other

purposes as well. Most missiles to their respective destination by means of a radar

mounted on their nose. Radars using continuous wave transmission rather than pulses are

fitted in devices such as the proximity fuse which causes the missile or shell to explode

when closed to the target.

Radars are also fitted on board of some aircraft to warn the pilot of air

turbulence and thunderstorms. They now play an important role in weather forecasting

and are also found on board spacecraft, mapping the surface of the earth below. Some ofthe radars that have been manufactured by Bharat Electronics Limited (BEL) and their

functions are listed below:

Flycatcher

Indra

Reporter

All the three are used for air traffic control and surveillance. Mark-I to Mark-XI is a

series of radars used for navigation purposes.

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

GTC FUNCTION The GTC generator produces a discharging waveform which rises

with GTC trigger and discharge at a rate of 6 dB/octave.

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

only if the video is greater than the GTC circuit.

RSLS FUNCTION The RSLS circuit compares the signals received from the two

channels i.e., interrogate and control, and gives the output if the level of the interrogatechannel is higher than control channel. This comparison is done only for a short time

(RSLS stroke) started with rushed output of interrogate channel.

ECHO SUPRESSION Each reply pulse in the interrogate channel from a threshold that

dies out at 3.5 dB/microsecond. This causes suppression of reflections with small levels.


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CONCLUSION

The practical training aims at familiarizing the students with the working

condition in a professional firm as well as to apply their theoretical knowledge acquiredin the institute into practice. This training was helpful to me in various direct and indirect

ways, like understanding of machines as well as procedure followed in manufacturing a

product. A good insight into inspection and Quality check of products.

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

engineer was being experienced. BEL is one of the NAVRATNAS companies in India,

and training in such added a whole new dimension to my observation and practicalapproach as well as introducing me to organizational hierarchy.

Prateek Jainreport

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