SUMMER TRAINING REPORT

STUDY OF RADARTRANSMITTER

FROM

BHARAT ELECTRONICS LIMITED, GHAZIABAD

BY

RAVI PRAKASH

ECE, 4TH YEAR (MSIT)

ROLL NO.- 0951502808

BEL UPT NO.- 774/B.TECH/2011

21st JUNE – 30th JULY, 2011

CONTENTS

1 : CERTIFICATE

2 : ACKNOWLEDGEMENT

3 : PREFACE

4 : BHARAT ELECTRONICS INDUSTRY

5 : B E: SALES ANS SERVICES

6 : FORMATION OF UNIT

7 : PROJECT : ROTATION

8 : PROJECT : RADAR

9 : TRANSMITTER

10 : CONCLUSION

CERTIFICATE

THIS IS TO CERTIFY THAT MR. RAVI PRAKASH OF B.TECH 4TH YEAR STUDENT

OF BRANCH ELECTRONICS & COMMUNICATION FROM MSIT,DELHI HAS

SUCCESSFULLY COMPLETED HIS INDUSTRIAL TRAINING UNDER THE

GUIDANCE OF MR. A.K. SAXENA MANAGER (PA-RADAR) AND MR. K.V.

SINGH IN BHARAT ELECTRONICS LIMITED, GHAZIABAD FROM 21st JUNE TO

30th JULY.

A PROJECT TITLED –“STUDY OF TRANSMITTER OF RADAR”

THE STUDY OF TRANSMITTR OF RADAR WAS ASSIGNED TO HIM IN THIS

PERIOD. HE WORKED HARD DILIGENTLY, &, COMPLETED HIS PROJECT IN

TIME. HE TOOK INITIATIVES IN LEARNING ABOUT RADAR SYSTEM &

VARIOUS TEST INSTRUMENTS METHOD. HIS OVERALL PERFORMANCE

DURING THIS PERIOD WAS EXCELLENT. WE WISH HIM ALL SUCCESS IN HIS

CAREER.

MR.K.V.SINGH MR. A.K. SAXENA (ASSISTANT ENGINEER PA-RADAR) (MANAGER)

ACKNOWLEDGEMENT

I WISH TO EXPRESS MY SINCERE THANKS TO THE MANAGEMENT OF BHARAT ELECTRONICS LIMITED (BEL), BHARAT NAGAR, GHAZIABAD INCLUDING THE HEAD OF THE HUMAN RESOURCE DEVELOPMENT DEPARTMENT MR. TYAGI (DGM, HRD) FOR PROVIDING ME AN OPPORTUNITY TO RECEIVE TRAINING IN THIS IMPORTANT INDUSTRIAL UNIT MANUFACTURING ELECTRONICS EQUIPMENT IN OUR COUNTRY.

I AM DEEPLY INDEBTED TO MR. A.K. SAXENA, MANAGER, RADAR DIVISION (PA-RADAR) FOR SPARING HIS MOST SPECIAL TIME IN PROVIDING GUIDANCE TO ME IN TRAINING. WITHOUT HIS WISE COUNSEL, INESTIMABLE ENCOURAGEMENT, IT WOULD HAVE BEEN DIFFICULT FOR ME TO HAVE KNOWLEDGE OF THE FUNCTIONING OF VARIOUS TYPES OF ELECTRONICS EQUIPMENT PARTICULARLY RADARS. GRATITUDE IS ALSO DUE TO HIM FOR HIS CONSTANT GUIDANCE AND DIRECTION IN WRITING THIS PIECE OF WORK.

SPECIAL THANKS TO MR. K V SINGH (DEPARTMENT OF RADAR TRANSMITTER) FOR THEIR VALUABLE GUIDANCE, HELP AND COOPERATION.

IT IS A GREAT PLEASURE TO EXPRESS MY HEART FULL THANKS TO STAFF OF BEL WHO HELPED ME DIRECTLY OR INDIRECTLY THROUGHOUT THE SUCCESSFUL COMPLETION OF MY TRAINING. THERE IS NO SUBSTITUTION TO ‘TEAM WORK’; THIS IS ONE OF THE LESSONS I LEARNT DURING MY TRAINING IN BHARAT ELECTRONICS LIMITED.

PREFACE

WITH THE ONGOING REVOLUTION IN ELECTRONICS AND COMMUNICATION WHERE INNOVATIONS ARE TAKING PLACE AT THE BLINK OF EYE, IT IS IMPOSSIBLE TO KEEP PACE WITH THE EMERGING TRENDS.

EXCELLENCE IS AN ATTITUDE THAT THE WHOLE OF THE HUMAN RACE IS BORN WITH. IT IS THE ENVIRONMENT THAT MAKES SURE THAT WHETHER THE RESULT OF THIS ATTITUDE IS VISIBLE OR OTHERWISE. A WELL PLANNED, PROPERLY EXECUTED AND EVALUATED INDUSTRIAL TRAINING HELPS A LOT IN CULCATING A PROFESSIONAL ATTITUDE. IT PROVIDES A LINKAGE BETWEEN A STUDENT AND INDUSTRY TO DEVELOP AN AWARENESS OF INDUSTRIAL APPROACH TO PROBLEM SOLVING, BASED ON A BROAD UNDERSTANDING OF PROCESS AND MODE OF OPERATION OF ORGANIZATION.

DURING THIS PERIOD, THE STUDENT GETS THE REAL EXPERIENCE FOR WORKING IN THE INDUSTRY ENVIRONMENT. MOST OF THE THEORETICAL KNOWLEDGE THAT HAS BEEN GAINED DURING THE COURSE OF THEIR STUDIES IS PUT TO TEST HERE. APART FROM THIS THE STUDENT GETS AN OPPORTUNITY TO LEARN THE LATEST TECHNOLOGY, WHICH IMMENSELY HELPS IN THEM IN BUILDING THEIR CAREER.

I HAD THE OPPORTUNITY TO HAVE A REAL EXPERIENCE ON MANY VENTURES, WHICH INCREASED MY SPHERE OF KNOWLEDGE TO GREAT EXTENT. I GOT A CHANCE TO LEARN MANY NEW TECHNOLOGIES AND ALSO INTERFACED TOO MANY INSTRUMENTS. AND ALL THIS CREDIT GOES TO ORGANIZATION BHARAT ELECTRONICS LIMITED.

INTRODUCTION OF BEL

BHARAT ELECTRONICS LIMITEDINDUSTRY

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

Enterprise under the administrative control of Ministry of Defence as the fountain head to manufacture and supply electronics components and equipment. BEL, with a noteworthy history of pioneering achievements, has met the requirement of state-of-art professional electronic equipment for Defence, broadcasting, civil Defence and telecommunications as

well as the component requirement of entertainment and medical X-ray industry. Over the years, BEL has grown to a multi-product, multi-unit, and technology driven company with track record of a profit earning PSU.

Today BEL's infrastructure is spread over nine locations with 29 production divisions having ISO-9001/9002 accreditation. Product mix of the company is spread over the entire Electro-magnetic (EM) spectrum ranging from tiny audio frequency semiconductor to huge radar systems and X-ray tubes on the upper edge of the spectrum. Its manufacturing units have special focus towards the product ranges like Defence Communication, Radar's, Optical & Opto-electronics, Telecommunications, Sound and Vision Broadcasting, Electronic Components, etc.

BEL has nurtured and built a strong in-house R&D base by absorbing technologies from more than 50 leading companies worldwide and DRDO Labs for a wide range of products. A team of more than 800 engineers is working in R&D. Each unit has its own R&D Division to bring out new products to the production lines. Central Research Laboratory (CRL) at Bangalore and Ghaziabad works as independent agency to undertake contemporary design work on state-of-art and futuristic technologies. About 70% of BEL's products are of in-house design.

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

Serial no.

Year of establishment

Location

1.

2.

3.

4.

5.

6.

7.

8.

9.

1954

1972

1979

1979

1984

1984

1985

19851986

Bangalore

Ghaziabad

Pune

Taloja (Maharashtra)

Hyderabad

Panchkula (Haryana)

Chennai

Machhilipathnam (A.P.)Kotdwara (U.P.)

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:

Customer Profile & BEL Product Range

CORPORATE MOTTO

"Quality, Technology and Innovation."

CORPORATE MISSIONTo 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 electronics industry in the country.

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

In order to meet the nation's 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.

T progressively increase overseas sales of its products and services.

To create an organizational culture which encourages members of the organization to realize their full potential through continuous learning on the job and through other HRD initiatives?

Equipment

Components

Defence Transmitting Tubes, Microwave Tubes, Lasers, Batteries, Semiconductors-Discrete, Hybrid and Integrated Circuits.

DefenceArmy Tactical and Strategic Communication Equipment and

Systems, Secrecy Equipment, Digital Switches, Battlefield Surveillance Radar, Air Defence and Fire Control Radar, Opto-Electronic Instruments, Tank Fire Control Systems, Stabilizer Systems, Stimulators and Trainers.

Navy Navigational, Surveillance, Fire Control Radar, IFF, SONAR Systems, Torpedo Decoys, Display Systems, EW Systems, Simulators, Communication Equipment and Systems.

Air Force Surveillance and Tracking Raiders, Communication Equipment and Systems, IFF and EW Systems.

Non-DefencePara-Military Communication Equipment and Systems.Space Department Precision Tracking Radar, Ground Electronics, Flight and

On-Board Sub-systems.All India Radio MW, SW & FM Transmitters.Doordarshan(TV Network)

Low, Medium and High Power Transmitters, Studio Equipment, OB Vans, Cameras, Antennae, Mobile and Transportable Satellite Uplinks.

NCERT TV Studios on Turnkey Basis for Educational Programs.Department ofTelecommunications

Transmission Equipment (Microwave and UHF) and PCM Multiplex, Rural and Main Automatic Exchanges, Flyaway Satellite Terminals, Solar Panels for Rural Exchanges.

Videsh SancharNigam and otherCorporate Bodies

MCPC VSAT, SCPC VSAT, Flyaway Earth Stations. Hub Stations, Up/Down Converters, LNA Modems

Civil Aviation Airport Surveillance Radar, Secondary Surveillance Radar.Meteorological Department

Cyclone Warning and Multipurpose Meteorological Radar.

Power Sector Satellite Communication Equipment.Oil Industry Communication Systems, Radar.Forest Departments,Irrigation &Electricity Boards

Communication Systems.

Medical &Health Care

Clinical and Surgical Microscope with Zoom, Linear Accelerators.

Railways Communication Equipment for Metros, Microwave Radio Relays, And Digital Microwave Radio Relays.

Non-DefenceAll India Radio,Doordarshan(TV Network),Department of TelecommunicationsAnd Civil Industries

Transmitting Tubes, Microwave Tubes, and Vacuum Tubes.

EntertainmentIndustry

B/W TV Tubes, Silicon Transistors, Integrated Circuits, Bipolar and CMOS, Piezo Electric Crystals, Ceramic Capacitors and SAW Filters.

Telephone Industry Integrated Circuits, Crystals.Switching Industry Vacuum Interrupters.Instrumentation Industry Liquid Crystal Displays.Medical &Health Care X-ray Tubes.

Systems/Network

Identity Card Systems Software, Office Automation Software, LCD On-line Public Information Display Systems and Communication Networks / VSAT Networks.

Product Range

The product ranges today of the company are:

Radar Systems:

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

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

Tactical Control Radar Systems for the Army

Battlefield Surveillance Radar for the Army

IFF Mk-X Radar systems for the Defence and Export

ASR/MSSR systems for Civil Aviation.

Radar & allied systems Data Processing Systems.

Communications:

Digital Static Tropo scatter Communication Systems for the Air Force.

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

VHF, UHF & Microwave Communication Equipment.

Bulk Encryption Equipment.

Turnkey Communication Systems Projects for defence & civil users.

Static and Mobile Satellite Communication Systems for Defence

Telemetry/Tele-control Systems.

Antennae:

Antennae for Radar, Terrestrial & Satellite Communication Systems.

Antennae for TV Satellite Receive and Broadcast applications.

Antennae for Line-of-sight Microwave Communication Systems.

Microwave Component:

Active Microwave components like LNAs, Synthesizer, Receivers etc.

Passive Microwave components like Double Balanced Mixers, etc

Most of these products and systems are the result of a harmonious combination of technology absorbed under ToT from abroad, Defence R&D Laboratories and BEL's own design and development efforts.

Organization

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

Design & Engineering Divisions :

Development and Engineering-R

Development and Engineering-C

Development and Engineering-Antenna.

1. Equipment Manufacturing Divisions :

Radar

Communication

Antenna

Systems

Microwave Components.

2. Support Divisions:

Material Management

Marketing & Customer Co-ordination

Quality Assurance & Torque

Central Services

PCB & Magnetics

Information Systems

Finance & Accounts

Personnel & Administration

Management Services.

Design & Engineering:

The pace of development and technological obsolescence in their field of electronics necessitates a strong Research and Development base. This is all the more important in the area of Defence Electronics. BEL Ghaziabad has since its inception laid a heavy emphasis on indigenous research and development. About 70% of its manufacture today relate to items developed in-house. For the development and production of the Mobile Tropo scatter System and the IFF equipment, BEL was awarded the Gold Shield for Import Substitution.

Design facilities are also constantly being modernized and substantial computer-aided design facilities are being introduced including installation of mini- and micro-computers and dedicated design application. About 170 graduate and post-graduate engineers are working on research and development and indication of the importance R&D has in BEL's growth.

Three Design and Engineering groups are product based viz. Communication, Radar and Antenna. These divisions are further divided into different departments to look after products of a particular nature. Each of them has a drawing office attached to them, which are equipped with latest drafting and engineering software. The PCB layout and PCB master making is done at CADDs Center. A central Records & Printing section takes care of the preserving the engineering documents and distribution thereof. Most of the engineering documents are available online.

Equipment Manufacturing Divisions:

As a supplier of equipment to the Defence services and professional user, strict adherence to specifications and tolerances has to be in-built into the design and manufacturing process. For this BEL Ghaziabad has well defined standards and processes for as well as manufacturing and testing activities. Activities are divided into various departments like Production Control, Works Assembly, and QC WORKS. The manufacture and control of production is through a central system, BELMAC, BEL's own homegrown ERP system.

Apart from conventional machines, BEL Ghaziabad has been equipped with several Computer Numerical Control (CNC) machines for ensuring repeat occurrences and increased throughput. A separate NC programming cell has been set up to develop the programs for execution on the CNC machines.

Microwave Component Group:

Frequencies greater than 1 GHz is termed as Microwaves. Microwaves Integrated Circuits (MIC) used extensively in the production of subsystems for Radar and Communication equipment constitutes a very vital part of the technology for these systems and is generally imported. Owing to the crucial and building block nature of the technology involved, BEL is currently setting up a modern MIC manufacturing facility at a planned expenditure of Rs. 2 crore. When in full operation, this facility will be the main center for the MIC requirements of all the units of the company.

The manufacturing facilities of hybrid microwave components available at BEL, Ghaziabad includes facility for preparation of substrates, assembly of miniaturized component viz. directional couplers, low noise amplifiers, phase shiftier, synthesizers etc. involves scalar as well as vector measurements. For this state of the network analysis are used.

Material Management:

Material Management division is responsible for procurement, storage handling, issue of purchased parts as well as raw materials required to manufacture various equipment and spares. It also takes care of disposal of unused or waste material.

The division is divided into Purchase, Component store, Raw material store, Chemical store, Inwards good store, Custom clearance Cell, Inventory management & disposal.

Marketing and Customer Co-ordination:

This division is responsible for acquisition and execution of customer orders and customer services. Marketing department looks after order acquisition. Commercial department looks after order execution. Shipping takes care of packing and dispatch of material to customer.

Quality Assurance & Torque:

In the area of professional Defence electronics, the importance of Quality and Reliability is of utmost importance. BEL has therefore established stringent processes and modern facilities and systems to ensure product quality- from the raw material to the finished product. IGQA, Environmental Labs, Test Equipment Support and QA departments are grouped under this division.

All material for consumption in the factory passes through stringent inward goods screening in IGQA department before being accepted for use.

Subsequent to manufacture and inspection, the end product is again put through a rigorous cycle of performance and environmental checks in Environmental Labs.

The testing, calibration and repair facility of test Instruments used in the factory is under the control of Test Equipment Support. All the instruments come to this department for periodic calibration.

Quality Assurance department facilitates ISO 9000 certification of various divisions. All production divisions of BEL Ghaziabad are ISO9000 certified. The microwave division is ISO9001 certified whereas the remaining three division viz. Radar, Communication and Antennae are also ISO9002 certified.

Central Services:

Central services Division looks after plant and maintenance of the estate including electrical distribution, captive power generation, telephones, transport etc.

PCB Fabrication & Magnetics:

PCB Fabrication, Coil and Magnetics, Technical Literature, Printing Press and Finished Goods are the areas under this division.

Single sided PCB blanks- having circuit pattern only on one side of the board and double sided - having circuit pattern on both sides of the board are manufactured in house. However, Multi-layered PCBs, having many layers of circuit, are obtained from other sources.

Magnetic department makes all types of transformers & coils that are used in different equipment. Coils and transformers are manufactured as per various specifications such as number of layers, number of turns, types of windings, gap in core,

dielectric strength, insulation between layers, electrical parameters, impedance etc. laid down in the documents released by the D&E department.

Information Systems:

IS Department is responsible for BEL's own home grown manufacturing and control system called BELMAC. It comprises of almost all modules a modern ERP system but is Host and dumb terminal based.

Finance & Accounts:

The F&A division is divided into Budget & Compilation, Cost and Material Accounts, Bills Payable, Bill Receivable, Payrolls, Provident Fund, Cash Sections

Personnel & Administration:

There are at present about 2300 employees at BEL Ghaziabad, of which more than 400 are graduate and post graduate engineers.

P&A Division is divided into various departments like Recruitment, Establishment, HRD, Welfare, Industrial Relations, Security and MI Room.

Management Services:

This department deals with the flow of information to or from the company. It is broadly classified into three major sub-sections - Management Information System, Industrial engineering department and Safety.

Production Control

The main goals of the production control are:

To improve the profits of the company by better resource management

To ensure on-time delivery products

To improve the quality of product

To reduce the capital investment

To reduce working capital needs by better inventory management

Production control is responsible for producing the products, right from the stage engineering.

Drawings are received to the stage where it is store credited as finished product. It’s basic function is to identify the parts/operations to be made, the best way of making them, the time when they have to be made and to arrange the production resources to the optimum.

The commercial department obtains orders from equipments through quotations. The equipment stock order (ESO) is released by commercial department. Then the

management services department issues work order for the quantity of equipment to be made. This is for the calculation for the cost of the project then D&E department develops the equipment and releases the following engineering documents:

KS : Key Sheet

PL : Part List

GA : General Assembly Diagram

CL : Connection List

WL : Wiring Diagram

Now the production control takes the responsibility of manufacturing the equipment. PC decides for items to be purchased from outside, for items to be manufactured by other companies and prepares documents for items to be made inside the company.

Documents issued by the PC:

I. Process sheet (fabrication): This process sheet indicates the process and the sequence of operation to be followed in various work cells and work centers. Every item is timed by productivity services.

II. Process sheet (Assembly): This is similar to PS (fabrication) except that it is used in electronics assembly, PCB assemblies, cable form and cable assemblies.

III.Process sheet (coils): This indicates operation analysis for transformer and coils.

IV. Schedule for RM, fasteners and PPs: This gives the gross requirements for raw materials, purchased parts, fasteners etc. Based on this material control department initiates procurement action and store requisitions are released with reference to this schedule.

Tool Planning

1. Some of the items while under fabrication require the use of some jigs and fixtures.

2. The cost estimation, revenue and budget plans are got approved by the board of management

3. Standard hour is approved by the department. This is the time, which is decided to complete the job by a worker in a stipulated time, which is decided on the previous records of the shop, type of machine used and the nature of work.

4. Report on production value is evaluated for each unit.

My Training in BEL, was attended in two phases. In first phase, I was given a schedule to visit all the departments in BEL, relevant to my field of Electronics and Communication. In this period of orientation, I visited different departments and was introduced to the current technology used and the various industrial processes under practice. In the second phase I was allotted a Project under Project Manager, MR.A.K.SAXENA (CAR- RADAR).

I am briefing my experience and observation about various departments of the company in next paragraphs.

ROTATION

ABOUT VARIOUS DEPARTMENTS

MICROWAVE INTEGRATED CIRCUITS

Frequencies greater than 1 GHz are termed as Microwaves. Microwave Integrated Circuit used extensively in production of subsystems for Radar and Communication equipment constitutes a very important part of technology for these systems are generally imported. Owing to the crucial and building block nature of the technology involved, BEL is currently setting up a modern MIC manufacturing facility at a planned expenditure of Rs. 2 crore. When in full operation this facility will be the main center for the MIC requirements of all the units of the company.

The manufacturing facility of hybrid microwave components available at BEL Ghaziabad includes facility for preparation of substrates, assembly of miniaturized components on substrates, bonding and testing. Testing of these microwave components viz. Directional couplers, Waveguides, low noise amplifiers, phase shifters, synthesis etc. involve scalar as well as vector measurements. For this state of the network, analyses are used. Various losses such as return loss, bending loss, insertion loss are measured and testing is done in a way to minimize these losses.

MICROWAVE LAB

This section undertakes:

1. Manufacturing of films and microwave components to meet internal requirements.

2. Testing of low power antenna for which test-site is about 100 Km from the factory at sohna.

The main component testing in this department is:

Oscillators

Amplifiers

Mixers

Radiation elements (e.g. Feeders)

Microwave components (e.g. Isolators, circulators, waveguides etc.)

Filters (e.g. LPF, BPF, Uniplexers, and Multiplexers etc.)

Functioning of component is listed below:

Frequency response

Noise figure

VSWR

Directivity and coupling

Power measurements

Various instruments in the lab are:

Adaptor

Attenuator

Coupler

Mixer

Detector

ENVIRONMENTAL LAB

Various tests 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 conditions. In a given system reliability is given as

R = R1 * R2 * R3 ……

The standards available here are:

JSS 55555 - Joint Services Specifications (Military Standard of India)

Mil Standards - U.S. Military standards

QM333 - Civil Aviation and Police

TYPES OF TESTS

1. FIRST ARTICLE TEST (FAT)These tests are performed on the prototype. If these tests are successful then the mass

production is taken up.

The tests are:

1. Vibration Test System2. High Temperature Operate and Storage3. Low Temperature Operate and Storage4. Damp Heat Operate and Storage5. Altitude Chamber6. Bump Test Machine7. Salt Fog Chamber8. Tropical Storage9. Mould Growth Chamber

VARIOUS TESTS IN DETAIL:

1. Vibration Test System The item is vibrated when kept over the plate of the machine. The frequency Range is 1 to 2,000 Hz. Radar PCB’s are vibrated at 10 to 50 Hz at 2g (g=9.8m/s2) for 15’.

2. Humidity chamber Used to test the product under varying humidity conditions. For Navy instruments conditions for humidity are 95% at +45C for 16 hours.

3. Cold Heat This chamber has a temperature of –90 to +180. This chamber program is controlled and has an accuracy of +0.5 and has a graph plotting system.

4. Mould GrowthThis chamber is used to test how immune the product is against mould growth.

5. Salt Spray It is used to check the resistivity of the item produced against salty water.

6. Climatic ChamberTemperature range of – 65C to +200C and relative humidity is from 20%

To 98%RH.

7. Walk – In Chamber

This is a big chamber of size 2.6m, 2.4m, 3m Temp. range of – 60C to

+100C and the humidity is from 20% to 90% RH.

8. Bump Machine Item is dropped from a certain height every time it receives bump from Machine. Maximum capacity of the machine is 11.35 Kg. Drop height is Around 1 inch.

9. Altitude Chamber

Used to test the item under different temperature and humidity conditions.The temperature range for this chamber is from -40C to +150C and can create environmental conditions as per a height of 50,000 feet’s.

For airforce equipment the instrument is kept at a temperature of +40C for 30,000 ft and at 0C for 13,500 ft.

2. ACCEPTANCE TEST PROCEDURE

This sets on the extent to which a test is to be conducted and also decides what tests should be conducted.

There are three types of tests:

a) Class A test: This test includes visual and dimensional checks. All equipments of regular production go through these checks. These include quality control and electrical tests.

b) Class B test: These are quality assurance and reliability tests. Only 10% of equipments go through these tests. They include quality control, electrical tests and some environmental tests.

c) Class C test: These are carried out on 1% of the components. All the environmental tests are performed. If any failure is seen, the component must be redesigned. Also the customer must be supplied with modified goods. This test comes in picture for bulk production only.

FAILURE RATE GRAPH

Failure rate graph- It is the failure versus time graph.The infant morality is the critical period. It is due to:

Weak componentManufacturing defect

This is the area where the producer tries to cover in the warranty period.The repeated failures are detrimental to a company’s reputation as these are eliminated by screening while in manufacturing stage. The other screening is the stress screening method. This consists of:

a) HUMIDITY TEST: Humidity is created with the help of boilers and fans in the chamber. Required temperature and duration of the tests are selected as per the specified BEL standards.

b) ALTITUDE TEST: The conditions such as very low temperature (created with the help of cooling systems) and very low temperature and pressure (created with the help of a vacuum pump) are maintained in a chamber. These conditions are comparable to those at high altitudes where the products have to work.

c) AGEING AND THERMAL SHOCKS: One cycle of ageing is of 7 hours. Ageing is done to relieve the stresses developed in the PCB due to blazing, welding, riveting etc. The sample is first kept at ambient temperature (250 degree Celsius) and then cooled to -400 degree Celsius.

d) BUMP TEST: The sample is given bumps in one direction only, with the help of machine. The number of bumps to be given is set with the help of proper switches. The sample is operated after giving bumps. If it works properly, it is passed.

e) VIBRATION TEST:The sample is subjected to vibrations. Required frequency and amplitude for vibrations is selected accordingly.

f) SALT SPRAY TEST: Salt solution is sprayed in a chamber. The specimens are hanged in the chamber. The test helps to decide any corrosion that takes place due to spraying of solution.

g) RAIN TEST: In this test, conditions are created such that the sample is made to bath in heavy rain, so that if any problem arises in the sample due to rain that can be sorted accordingly.

h) DROP TEST : The sample is made to survive in such a environment where there is possibility of snow fall. Such conditions are created in a chamber, to sort out any problem arises due to this.

i) ROADABILITY TEST: While doing bump test, bumps are given to the sample in unidirectional only. But in the roadability test, bumps are given to the sample in all the directions. It means that the test is being carried, considering the device to be moving in a zigzag manner on an uneven road. For e.g. in sand or in water etc. This test helps to make out any fault or loosening of components while moving the specimen from one place to another.

j) BOMB TEST: This is a test conducted for special types of samples. In this the samples are exposed to a situation like a bomb blast and it is checked whether the sample is able to bear the bomb explosion.

WALK IN CHAMBER

A very huge used for conducting humidity and temperature tests. The size of the chamber is such that a person can easily walk into it. It is for large sized specimens.

PCB FABRICATION

PCB is abbreviated form of printed circuit board. As the name suggests, in a PCB the electrical circuit is printed on a glass epoxy board. This reduces the complex writing network whose trouble shooting in case of shorting or misconnection is not easy.PCB fabrication is mostly done for house requirements. It also takes some external jobs.

Types of PCB’s

Single Sided: Having circuit pattern only on one side of the board.Double Sided: Having circuit pattern on both sides of the board.Multilayered: Having many layers of circuit.

BEL – Ghaziabad produces only single-sided and double-sided PCB’s.

FABRICATION OF SINGLE SIDED PCB’s:

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 now 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 (stripping). 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.

P C B MANUFACTURING PROCESS:

1. Copper clad2. Drill location holes3. Drill holes for T.H.P. (Through Hole Plating)4. Clean scrub and laminate5. Photo print6. Develop7. Copper electroplate8. Tin electroplate9. Strip film10. Etch and clean11. Strip tin12. L.P.I.S.M. (Liquid Photo Imageable Solder Mask)13. Photo print14. Develop15. Thermal baking16. Hot air level17. Legend marking/Reverse marking18. Route and clean

But these PCB’s 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 the components on opposite side.

Moisture or dust between the gaps may disrupt smooth soldering.

These disadvantages are overcome by soldered mask PCB’s. in the later one an additional film is put on the earlier fabricated PCB, leaving points where components are to be soldered.

TEST EQUIPMENT & AUTOMATION

TEST EQUIPMENT SUPPORT (TES) Main functions are:

Develops technical support to other departments.Repair of equipment in case of failure.Maintenance of equipments.Periodic calibration of equipments.Provide technical support to other departments. This includes:

1. Handling requests from the other department for equipments.2. Storage of rejected equipments.3. Approval of equipments to be purchased.

This section deals with testing and the calibration of electronic equipments only the standards of this department are calibrated by National Physics Laboratory (NPL).

AUTOMATION TEST EQUIPMENT (ATE)

1. Component testing gives faults of various discrete components of a PCB.2. Integrated circuits tester tests various IC’s. 3. Functional testing compares output to decide whether the function is being

performed to the desired level of accuracy.

WORKS ASSEMBLY

This department plays an important role in the production. Its main function is to assemble various components, equipment’s and instruments in a particular procedure. It has two sections, namely:

1. PCB assembly2. Electronic assembly

In PCB assembly, the different types of PCB are assembled as per BEL standards. PCB is received from the PCB department on which soldering of component is done either by hand soldering or wave soldering.

HAND SOLDERING: In case of hand soldering, soldering is done manually.WAVE SOLDERING: Wave soldering is a procedure in which PCB’s are fed to

the wave soldering machine from the opening on one side and the soldering is done by machine and after the soldering is done PCB’s are collected from the another opening of the machine and after that cleaning is done.

The PCB’s are than send to testing department for testing according to the product Test procedure issued by the D&E department. After testing PCB’s are lacquered and Send to the planning store for storage.

In electronic assembly, the cable assemblies, cable forms modules, drawers, racks and shelters are assembled. Every shelter (e.g. - DMT) is made of racks, racks are made up of drawers, drawers are made up of modules and modules are made up of PCB’s, cable assembly and cable forms.

Every module or drawer before using in next assembly is send for testing according to their PTP. Shop planning collects the purchase from the IG store, takes fabricated parts, PCB’s etc. from planning stores and issued to the assembly department as per the part list of the assembly to be made.

The documents issued to the assembly are:

KS : Key SheetPL : Parts ListCL : Connection List for cable formWL : Wiring List for modulesWD : Wiring DiagramGA : General Assembly diagram

This department has been broadly classified as:

1. WORK ASSEMBLY RADAR e.g. : INDRA-2 , REPORTER ,CAR2. WORK ASSEMBLY COMMUNICATION e.g. : EMC CA , MSSR , MFC

EMCCA: EQUIPMENT MODULAR FOR COMMAND CONTROL APPLICATION

MSSR: MONOPULSE SECONDARY SURVEILLANCE RADAR

MFC: MULTI FUNCTIONAL CONSOLE

The stepwise process 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 connection to be made and brief idea about all

components.4) Writing list of all components.

METHOD OF P C B PROCESSING

1. Tinning2. Preparation3. Mounting4. Wave soldering5. Touch up6. Quality control7. Ageing8. Testing9. lacquering (AV)10. Storing

SURFACE MOUNTING TECHNOLOGY

The works assembly has a totally computerized section of PCB assembling of SMD (Surface Mounting Device). In this section the operation of PCB assembling is totally controlled by computers. The various steps taken in computer PCB assembling of SMD’s are as follows:

1. Application of solder paste: Solder paste is applied onto the places on PCB where the SMD’s are to be soldered. This is done by computer controlled machine. The program is loaded in the machine; it reads the program and applies the solder paste at the required place.

2. Fixture of SMD’s:a) The SMD’s are fixed at the right place on PCB by another computer

controlled machine. b) The components (SMD) are first fed to various feeder lines that are

attached to the machine and the related software and program is loaded in computer.

c) There is a provision for a camera also so that we can monitor the entire operation.

d) The PCB is then fed to the machine. e) When the appropriate command is given to the computer, it initiates

the machine attached to itf) The machine picks the correct SMD from the feeder line and fix it at

the right place on the PCB and within seconds all SMD’s are fixed on the PCB.

3. Thermal Baking: After the fixture of SMD’s, thermal baking is done. In this the PCB is fed to the oven and after 10 to 20 minutes PCB is taken out.

NOTE: Surface Mounting Device (SMD) does not require any hole on PCB as they are mounted directly on the PCB. The pins of SMD components are called ’legs’ as they have leg like structure unlike simple components that have straight pins that are soldered in the holes on the PCB manually.

SHOP ORDER

Process Sheet (assembly)All operations fill the work order and shop order in operator’s time card

(OTC). They punch the time of starting the job and its finishing time. By this productivity services calculates the time taken to complete the job.

Efficiency = time allotted in shop order X 100

Actual time takenTime allotted is so called standard hours.

This deals with the assembly of common projects e.g. DMT, 2 GHz radio relay, Mobile tropo, Static RRD etc.

MAGNETICS

This department manufactures all types of transformers and coils that are used in various equipments manufactured by BEL. This department basically consists of four sections:

1. Planning section2. Mechanical section3. Moulding section4. Inspection section

The D&E department gives the following descriptions to the magnetics department. They are as follows:

Number of layersNumber of turnsType of windingGap in coreInsulation between layersAc/dc impedanceDielectric strengthElectrical parameters andEarthing

The various transformers being made are:

Open type transformerOil cooling type transformerMoulding type transformerPCB moulding type transformer

The transformer is mechanically assembled, leads are taken out and checking of specification is done.

Winding machines are of three types:

Heavier ones- DNR for 0.1 to 0.4 mm diameterLC controlled machinesTorroidal machines having 32 operations from winding to mechanical assembly.

The various types of windings used are:

Hand windingTorroidal windingSector windingPitch windingVariable pitch windingWave winding

Two main types of core used are:

E-type for 3-phaseC-type for single phase

Following procedure involved in the manufacture of the transformer is as follows:

1. Formers of glass epoxy2. Winding3. Core winding4. Varnishing5. Impregnation – In this process various varnished coils are heated, then

cooled, reheated and put into vacuum. Then air is blown to remove the humidity.

6. Moulding – Araldite (a certain type of strong glue) mixed with black dye is used to increase mechanical as well as electrical strength. Moulding is done at 120 degree Celsius for 12 hours.A RDB compound is used for leakage protection. Oil is then boiled at 70 to 80 degree Celsius under vacuum condition to remove air bubbles trapped

inside during manufacturing process. After this the coils are dipped in varnish and core is attached.

7. Painting8. Mechanical assembly9. Termination10. Stenciling11. Testing – Dielectric testing (both ac/dc) is done at 50 KV voltage

is applied for a minimum of one minute. During inspection, the following characteristics are checked:

a. Turns ratiob. DC resistance for each coilc. Inductanced. No load voltagee. Leakage

This section the material used for making transformer is Bakelite comprising a male and female plates which are joined alternately to form a hollow rectangular box on which winding is done. Winding is done with different material and thickness of wire. The winding has specified number of layers with each layer 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.

Types of Windings:1) Layer Winding2) Wave Winding3) Bank Winding

Different types of windings are done to control some parameters such as inductance and capacitance. Varying the spacing between the two turns can vary these parameters. Two consecutive turns act as capacitor. As gap between the turns increases the capacitance decreases and inductance increases. Since capacitance is inversely proportional to the gap between the plates of capacitor and inductance is directly proportional. After winding the core is inserted between the primary and secondary. Contact leads are taken out and molding is done for maximum heat dissipation. Rubber solution is used to give strength to the wires, so that they cannot break. This is done before molding. Varnishing is done as anti fungus prevention for against environmental hazard. After compilation of manufacturing process it is sent for testing. Different parameters such as inductance, capacitance efficiency, turns ration, continuity are tested.

QUALITY CONTROL WORKS

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

The raw materials and components etc. purchased are inspected according to the specifications by the IG department. Similarly QC works department inspects all the items manufactured in the factory.

The fabrication inspection checks all the fabricated parts and ensures that these are made as per the part drawing. Plating, Painting and stenciling etc are done and checked as per the BEL standards.

The assembly inspection department 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 mistakeShop mistakeInspection mistake

A process card is attached to each PCB under inspection. Any error in the PCB is entered into the process card by certain codes specified for each error or defect.

After mistake is detected, following actions are taken:

Observation is made.Object code is given.Division code is given.Change code is prepared.Recommended action is taken.

RADAR ASSEMBLY

This deals with the assembly of RADARS, e.g. INDRA-I, INDRA-II, FLY CATCHER, EMMCA, IRMA, REPORTER, CAR etc.

The main projects under construction are:

CAR

In RADAR section RADAR being tested is REPORTER, FLY CATCHER, EMCCA, etc.

PROJECT

PROJECT : STUDY OF CAR TRANSMITTER

PROJECT: AN OVERVIEW

RADAR AND ITS COMPOSITE ENVIRONMENT

INTRODUCTIONNTRODUCTION

The two most basic functions of radar are inherent in the word, whose letters stand for RAdio Detection And Ranging. Measurement of target angles has been included as a basic function of most radar, and Doppler velocity is often measured directly as a fourth basic quantity. Discrimination of the desired target from background noise and clutter is a prerequisite to detection and measurement, and resolution of surface features is essential to mapping or imaging radar. The block diagram of typical pulsed radar is shown in Figure. The equipment has been divided arbitrarily into seven subsystems, corresponding to the usual design specialties within the radar engineering field. The radar operation in more complex systems is controlled by a computer with specific actions initiated by a synchronizer, which in turn controls the time sequence of transmissions, receiver gates and gain settings, signal processing, and display. When called for by the synchronizer, the modulator applies a pulse of high voltage to the radio frequency (RF) amplifier, simultaneously with an RF drive signal from the exciter. The resulting high-power RF pulse is passed through transmission line or waveguide to the duplexer, which connects it to the antenna for radiation into space. The antenna shown is of the reflector type, steered mechanically by a servo-driven pedestal. A stationary array may also be used, with electrical steering of the radiated beam. After reflection from a target, the echo signal reenters the antenna, which is connected to the receiver preamplifier or mixer by the duplexer.

A local oscillator signal furnished by the exciter translates the echo frequency to one or more intermediate frequencies (IFs), which can be amplified, filtered, envelope or quadrature detected, and subjected to more refined signal processing. Data to control the antenna steering and to provide outputs to an associated computer are extracted from the time delay and modulation on the signal. There are many variations from the diagram of Figure that can be made in radars for specific applications, but the operating sequence described in the foregoing forms the basis of most common radar systems. This project provides the basics of radar and many of the relationships that are common to most forms of target-detection radar. The emphasis is on the goals established for the radar or the system that contains the radar.

Evolution of Radar Signal Processing

The term radar signal processing encompasses the choice of transmit waveforms for various radars, detection theory, performance evaluation, and the circuitry between the antenna and the displays or data processing computers. The relationship of signal processing to radar design is analogous to modulation theory in communication systems. Both fields continually emphasize communicating a maximum of information in a specified bandwidth and minimizing the effects of interference. The somewhat slow evolution of signal processing as a subject can be related to the time lags between the telegraph, voice communication, and color television. Although Theory with Applications to Radar in 1953 laid the basic ground rules; the term radar signal processing was not used until the late 1950s. During World War I1 there were numerous studies on how to design radar receivers in order to optimize the signal-to-noise ratio for pulse and continuous wave (CW) transmissions. These transmitted signals were basically simple, and most of the effort was to relate performance to the limitations of the components available at the time. For about 10 years after 1945, most of the effort was on larger-power transmitters and antennas and receiver-mixers with lower noise figures. When the practical peak transmitted power was well into the megawatts, the merit of further increases became questionable, from the financial aspect if not from technical limitations. The pulse length of these high powered radars was being constantly increased because of the ever present desire for longer detection and tracking ranges. The coarseness of the resulting range measurement led to the requirement for what is now commonly referred to as pulse compression. The development of the power amplifier chain (klystron amplifiers, etc.) gave the radar designer the opportunity to transmit complex waveforms at microwave frequencies. This led to the development of the “chirp” system and to some similar efforts in coding of the transmissions by phase reversal, whereby better resolution and measurements of range could be obtained without significant change in the detection range of the radar.

At about the same time, diode mixers gave way to the parametric amplifier and in some cases the traveling wave tube. The promise of vastly increased sensitivity seemed to open the way for truly long range systems. Unfortunately, the displays of these sensitive, high powered radars became cluttered by rain, land objects, sea reflections, clouds, birds, etc. The increased sensitivity also made it possible for an enemy to jam the radars with low-power wideband noise or pulses at approximately the transmit frequency. These problems

led to experiments and theoretical studies on radar reflections from various environmental reflectors. It was soon realized that the reflectivity of natural objects varied by a factor of over 10 to power 8 with frequency, incidence angle, polarization, etc. This made any single set of measurements of little general value. At the same time that moving target indicator (MTI) systems were being expanded to include multiple cancellation techniques, pulse Doppler systems appeared to take advantage of the resolution of pulse radars, chirp systems were designed using various forms of linear and nonlinear frequency modulation, and frequency coding was added to numerous forms of phase coding. As the range of the radars increased and their resolution became finer, the operator viewing the conventional radar scope was faced with too much information to handle, especially in air defense radar networks. The rapid reaction time required by military applications led to attempts to implement automatic detection in surface radars for detecting both aircraft and missiles.In the 1950s, proliferation of signal-processing techniques and the resulting hardware too often preceded the analysis of their overall effectiveness. To a great extent, this was caused by an insufficient understanding of the statistics of the radar environment and an absence of standard terminology (e.g., sub clutter visibility or interference rejection). By 1962, with the help of such radar texts as M. I. Skolnik’s Introduction to Radar Systems [the target-detection range of completely designed radar could be predicted to within about 50 percent when limited by receiver noise, and to perhaps within a factor of 2 when limited by simple countermeasures. As late as 1975, however, the estimated range performance of a known technique in an environment of rain, chaff, sea, or land clutter often varied by a factor of 2, and the performance of untried “improvements” even exceeded this factor. While the calculations of radar performance may never achieve the accuracy expected in other fields of engineering, it has become necessary for the radar engineer to be able to predict performance in the total radar environment and to present both the system designer and the customer with the means for comparing the multitude of radar waveforms and receiver configurations.

Radar and the Radar Equation

In this section the basic radar relations are reviewed in order to establish the terminology to be used throughout the report. The emphasis in this project is on radars radiating a pulsed sinusoid of duration r. This duration is related to distance units by cΓ/2, where c is the velocity of propagation of electromagnetic waves. The factor of 2 accounts for the two-way path and appears throughout the radar equations. If the pulse is a sample of a sine wave without modulation, r is often called the range resolution in time units and cΓ/2 the range resolution in distance units. This is illustrated in Figure

To a first approximation, the echo power from all targets within the radar beam over a distance cΓ/2 is added. In as much as the target phases are random, the average power returned is the sum of the power reflected by the individual targets. The precise total power reflected is a function of the power backscattered from each target and the relative phases of each reflected signal of amplitude ak. More specifically, the voltage return from a collection of N targets in a single resolution cell from a single transmitted pulse may be written

Where, is the phase angle of the return signal from the Kth target.

The instantaneous power return can be written

Since the instantaneous power at the radar varies in a statistical manner, the tools of probability theory are required for its study. Doppler shiftOne of the principal techniques used to separate real targets from background clutter (clutter is the undesired echo signal from precipitation, chaff, sea, or ground) is the use of the Doppler shift phenomenon. It relies on the fact that, although most targets of interest have a radial range rate with respect to the radar, most clutter has near-zero range rate for ground-based radars. (Airborne and shipboard radars present more difficult problems.) If target and clutter radial velocities do not at least partially differ, Doppler discrimination does not work.

The Doppler shift for a CW signal is given by

where c = propagation velocity (3 x 10' d s ) .vr or R = range rate.

For f = 10 raise to the power 9 Hz, and R = 300 m/s, the Doppler shift fd= 2 kHz. It is apparent that either a continuous signal or more than one pulse must be used in radar to take advantage of Doppler shift. (A single pulse usually has a bandwidth measured in hundreds of kilohertz or megahertz). It should be noted that relativistic effects have been neglected. For typical mono static radar (transmitter and receiver co-located) applications, no problem arises. For radars used to track space craft, the error made by neglecting relativistic effects might become important. It is thus possible to discriminate between targets in the same range resolution cell if the targets possess different range rates. A quantitative assessment of the discrimination depends on both the vagaries of nature (how stationary is a tree with its leaves moving in the wind?) and equipment limitations (what spurious signals are generated in the radar?)

Antenna-gain beam width relations

If power PT were to be radiated from an omni-directional antenna, the power density (power per unit area) at a range R would be given by PT/4πR2 since 4πR2 is the surface area of a sphere with radius R. Such an omni-directional antenna is physically unrealizable, but it does serve as a reference to which real antennas may be compared. For example, the gain GT of a transmitting antenna is the ratio of its maximum radiation intensity to the intensity that would be realized with a lossless omni-directional antenna if both were driven at equal power levels. To obtain some appreciation for the relationships between antenna gain, antenna size, and directivity, consider a linear array of 2N + 1Omni-directional radiators separated by one-half wavelength with each element radiating the same in-phase signal

At a great distance from the antenna, the resultant radiation pattern is

where A = a constant depending on rangec = the propagation velocityθ = the angle measured from broadsideX = the wavelengthThis particular sum may be evaluated to yield

It can be seen that for an antenna array many wavelengths long, the radiated energy is concentrated in a narrow beam. For small θ, sin θ can be approximated by θ, and the half-power beam width (3-dB one way beam width) is approximately

In addition, it can be determined from Equation that the first side lobes are down 13.2 dB from the main lobe. The narrower the antenna beam becomes, the greater the gain GT becomes. For a lossless antenna, the gain may be computed once the antenna pattern is known.

A concept of special interest is that of effective antenna aperture. If an antenna intercepts a portion of a wave with a given power density (namely, P(w)/m2), the power available at the antenna terminals is the power intercepted by the effective area of the antenna. The relationship between effective area Ae and gain is

Transmitted and received power

If a pulse of peak power PT is radiated, the peak power density at a target at range R is obtained from the inverse square law

If it is assumed that the target reradiates the intercepted power, the peak power density at the radar receive aperture is

Where σt is the radar cross-sectional area. The peak power received by the radar is then

Where Ae, is the effective receiving area of the antenna. If the relationship between effective area and receive antenna gain GR = 4πAe/λ2 is used

It is known that the ability to detect the pulse reflected by the target depends on the pulse energy rather than its peak power. Thus, including system noise power density, the range of the pulseRadar may be described by

Where τ = the pulse duration(S/N) = required signal-to-noiseK = Boltzmann’s constantTs = the system noise temperature

It is also shown that for surveillance radars the receive aperture area, Ae, is primary rather than GT or GR.

The preceding simplified relationships neglected such things as atmospheric attenuation, solar and galactic noise, clutter, jamming, and system losses.

Functions of Various Types of Radar

The rather simple algebraic equation that is given for radar detection range is often misleading in that it does not emphasize either the multiplicity of functions that are expected from the modern radar or the performance of the radar in adverse environments. Before any treatise on signal processing can begin, it is necessary to discuss some criteria for measuring the quality of performance of a radar system. The relative importance of these criteria depends on the particular radar problem.

1. Reliability of detection includes not only the maximum detection range, but also the probability or percentage of the time that the desired targets will be detected at any range. Since detection is inherently a statistical problem, this measure of performance must also include the probability of mistaking unwanted targets or noise for the true target.

2. Accuracy is measured with respect to target parameter estimates. These parameters include target range; angular coordinates; range and angular rates; and, in more recent radars, range and angular accelerations.

3. A third quality criterion is the extent to which the accuracy parameters can be measured without ambiguity or, alternately, the difficulty encountered in resolving any ambiguities that may be present.

4. Resolution is the degree to which two or more targets may be separated in one or more spatial coordinates, in radial velocity or in acceleration. In the simplest sense, resolution measures the ability to distinguish between the radar echoes from similar aircraft in a formation or to distinguish a missile from possible decoys. In the more sophisticated sense, resolution in ground-mapping radars includes the separation of a multitude of targets with widely divergent radar-echoing areas without self-clutter or cross-talk between the various reflectors.

5. To these four quality factors a fifth must be added: discrimination capability of the radar. Discrimination is the ability to detect or to track a target echo in the presence of environmental echoes (clutter). It can be thought of as the resolution of echoes from different classes of targets. It is convenient to include here the discrimination of a missile or an aircraft from man-made dipoles (chaff) or decoys or deceptive jamming signals, target identification from radar signatures, and the ability to separate the echoes of missiles from their launch platforms.

6. In a military radar system, another measure of performance must be defined: the Relative Electronic Countermeasure Or Jamming Immunity.

(a) “Selection of a transmitted signal to give the enemy the least possible information from reconnaissance (Elint”) compatible with the requirements of receiver signal processing.”

(b) “Selection of those processing techniques to make the best use of the identifying characteristics of the desired signal, while making as much use as possible of the known characteristics of the interfering noise or signals.”

(c) “In some cases, the information received by two or more receivers, or derived by two or more complete systems at different locations or utilizing different principles, parameters, or operation may be compared (correlated) to provide useful discrimination between desired and undesired signals.”

7. Finally, a term must be added to describe radar’s performance in the presence of friendly interference or radio frequency interference (RFI). The increasing importance of this item results from the proliferation of both military and civil radar systems. Immunity to radio frequency interference measures the ability of a radar system to perform its mission in close proximity to other radar systems. It includes both the ability to inhibit detection or display of the transmitted signals (direct or reflected) from other radar and the ability to detect the desired targets in the presence of other radar's signals. RFI immunity is often called electromagnetic compatibility.

Target-Detection Radars for Aircraft, Missiles and Satellites

The radar-processing techniques described in this report emphasize the detection, discrimination, and resolution of man-made targets rather than of those targets important to mapping and meteorological radars. This emphasis is consistent with the general trend of radar research, which in recent years has concentrated on improving the capability of radars searching for usually distant targets of small radar cross section.

The problem of detection of small airborne or space targets is generally characterized by the large volume of space that is to be searched and by the multitude of competing environmental reflectors, both natural and man-made. The advent of satellites and small missiles would have made the military radar problem almost impossible if it were not for velocity-discrimination techniques. It is perhaps this combination of small radar cross section and a complex environment that justifies he heavy emphasis placed here on this type of radar. In most of this report, the discussion of radar processing applies to radar located on the surface of the earth. These discussions may be applied to satellite, missile, or airplane radars without much difficulty except for the effect of the radar backscatter from the surface of the earth.

The detection and tracking of low-altitude aircraft or missiles require a specialized analysis. There are several unique problems that are discussed in later sections.

1. The vertical lobbing effect of low-frequency radars due to forward scatter causes nulls in the antenna patterns due to reflections from the earth (discussed in this chapter in the sections on surface targets and forward scatter).2. The target echoes must compete with the backscatter or clutter from surface features of the earth.3. The tracking radar may attempt to track the target’s reflected signals or to track the clutter itself 4. Propagation conditions can significantly affect the target echo power and the competing clutter.

Several other factors must be considered before a discussion of the numerous signal-processing techniques for surface radars can begin.In order to determine the applicability of the various processing techniques discussed in the text, it is useful to make a checklist to determine whether the system specifications constrain the receiver design or some parts of the radar design have been “frozen” and limit the choice. As an example, a checklist for an air surveillance radar might include the following:

1. Can the transmitter support complex waveforms?

2. Is the transmitter suitable for pulsed or continuous wave transmissions?Is there a minimum duty factor as solid-state transmitters imply?

3. Is there an unavoidable bandwidth limitation in the transmitter, receiver, or antenna?

4. Has the transmitter carrier frequency been chosen? Is frequency shifting from pulse to pulse practical?

5. How much time is allotted to scan the volume of interest? How much time per beam position?

6. Is there a requirement to detect crossing targets (zero radial velocity) or stationary targets?

7. Is there an all-weather requirement? How much rain, etc. should be used for the design case?

8. Will the radar be subject to jamming or chaff?

9. Is the radar likely to detect undesired targets, birds, insects, and enemy decoys, etc., and interpret them as true targets?

10. Is automatic detection of the target a requirement, or does an operator make the decisions? Is the radar to be unattended?

11. Will nearby radars cause interference (RFI)?

12. Are transmitting and receiving antennas polarizations fixed? Can the transmitted and received polarizations be switched from pulse to pulse? Can dual polarization be used?

13. What is the accuracy that is needed in range, velocity, and angle?How much smoothing time can be allowed?

14. Is there more than one target to be expected within the beam width of the antenna?

15. Does the target need to be identified using the surveillance or other waveforms?

Ideally, the choice of signal-processing technique should be established at the earliest possible time in the design of the radar system so that arbitrary decisions on transmitters, antennas, carrier frequencies, etc. do not lead to unnecessarily complex processing.

As an example, a change in one frequency band (typically a factor of 1.5 or 2 to 1) may have little effect on the detection range of radar on a clear day, but the higher-frequency radar may require an additional factor of 10 in rejection of unwanted weather echoes, since weather backscatter generally varies as the fourth power of the carrier frequency.In order to avoid continual repetition throughout the report, several general assumptions are made for subsequent discussions of radar signal-processing techniques and surveillance radars.

1. The bandwidth of the radar transmission is assumed to be small compared with the carrier frequency.

2. The target is assumed to be physically small compared with the volume defined by the pulse length and the antenna beam widths at the target range.

3. The targets are assumed to have either a zero or constant radial velocity, allowing target acceleration effects to be neglected. This radial velocity is small enough compared

with the speed of light to neglect relativity effects, and the Doppler frequency shift is small compared with the carrier frequency.

4. The compression of the envelope of the target echoes due to the radial velocity of high-speed targets is neglected.

5. Positive Doppler frequencies correspond to inbound targets; negative Doppler frequencies, to outbound targets.

6. The receiver implementations that are shown fall into the general class of real-time processors, meaning that the radar output, whether it is detection or an estimate of a particular parameter, occurs within a fraction of a second after reception of the target echoes. This does not preclude the increasingly prevalent practice of storing the input data in digital memory or with digital logic, which in general means the insertion of the storage elements into the appropriate block diagrams.

7. The variations in electronic gain required for different processors are neglected since the cost of amplification is negligible compared with other parts of the processors unless the signal bandwidth is in excess of 100 MHz.

The environment for the surveillance radar is emphasized in much of the discussion of signal-processing techniques. Some of the reasons for this emphasis are:

1. While many radar engineers can design radars and predict their performance to an acceptable degree in the absence of weather, sea, or land clutter, radar design and analysis in adverse environments leave much to be desired.

2. It requires relatively little chaff, interference, or jamming power to confuse many large and powerful surveillance radars.

3. Both natural and man-made environments create tremendous demands on the dynamic range of the receiver of the surveillance radar to avoid undesired nonlinearities.

4. In the missile era, the demand for rapid identification of potential enemy targets has led to increasing requirements for automatic or semiautomatic detection plus some form of identification. Inadequate dynamic range is often the problem in many current radars, rather than inadequate signal-to-noise or signal-to-clutter ratios.

5. As the radar cross sections of missile targets are decreased by using favorable geometric designs or by using radar-absorbing materials (RAM), the target echoes are reduced to those of small natural scatterers. For example, the theoretical radar cross section of an object shaped like a cone-sphere may be less than that of a single, metallic, half-wave dipole at microwave frequencies. The use of high-resolution radar for detecting these targets is a subject in itself, often calling for combinations of several of the techniques discussed in later chapters.

6. Finally, in this era of intense competition for large radar contracts, the proposals for new radars are required to be quite explicit for all environments. Both the system engineer and the potential customer need to know how to make performance computations and apply figures of merit under all environments.

Figure illustrates in a simplified way the magnitude of the problem for a typical, but fictitious, narrow-beam width, pulsed air surveillance radar with a C-band (5600 MHz) carrier frequency. The presentation is somewhat unusual in that most of the radar’s parameters have been held constant. The echoes from the environmental factors are plotted versus radar range; the left ordinate shows the equivalent radar cross section. The slopes of the various lines illustrate the different range dependencies of the different

kinds of environmental factors discussed in later chapters. The rapid drop of the sea and land clutter curves illustrates the rapid reduction of backscatter echoes at the radar horizon in a rather arbitrary way. Also shown on the graph is the equivalent receiver noise power in the bandwidth of the transmitted pulse. This is the amount of receiver noise power that is equal to the target power into the radar that is returned from a particular range.* The right-hand ordinate is the typical target cross section ut that can be detected at the various ranges, assuming that the signal-to-mean clutter power ratio is typically 20 to 1 (13 dB). The other major assumption is that the clutter does not appear at ambiguous ranges (second-time-around echoes, etc.). The effects of forward scatter of the radar waves have been neglected in figures. In normalizing these graphs to radar cross section, backscatter following an R -4 law, such as targets or land or sea clutter echoes at low grazing angles (small angles from the horizon), appears as a constant cross section, and echo power from uniform rain and chaff appears to increase as the square of range.

There are two significant features of this graph.

1. The surface radar, especially in a military environment, is rarely receiver noise limited except at high elevation angles on a clear day (at frequencies of 3000 MHz and above).

2. Even the relatively short 1-ks pulse (150 m in radar range) in the example needs further processing for the echoes from small targets to be sufficiently above the mean backscatter from the clutter.In summary, some form of clutter, and perhaps electronic-countermeasure rejection, is required for detection of small (- 1 m2) radar cross-section targets to ranges of 100 nmi (185 km).

The reduction of the clutter echoes from a single uncoded transmitted pulse as compared to those of the target is called the improvement factor I. Since the clutter shown in the figure generally has considerable extent, it is generally desirable to minimize the antenna beam widths and usually the pulse length. Another appropriate generalization is that the clutter signals, as well as the target echoes, increase with increasing transmitted power. In designing a noise-limited surface radar system, the system engineer can increase the transmit energy, reduce the receiver noise density, or increase the antenna size. In the cluttered environment, increased antenna size is usually most desirable.

Radar Frequency Bands and Carrier Selection

While radar techniques can be used at any frequency, from a few megahertz up into the optical and ultraviolet ( f > 3 x 1015 Hz, A < 1O-7 m), most equipment has been built for microwave bands between 0.4 and 40 GHz. The IEEE has adopted as a standard the letter band system, which has been used in engineering literature since World War II. The 1984 revision is shown in Table 1.1. Note that only a small portion of each band is allocated for radar usage.

One reason for identifying these separate radar bands, rather than using the coarser International Telecommunications Union (ITU) designation of UHF, SHF, and EHF, is

that the propagation characteristics and applications of radar tend to change quite rapidly in the microwave region. Attenuation in rain (measured in decibels) varies about f2, and backscatter from rain and other small particles vary as f4, over most of the microwave region. Ionospheric effects vary inversely with frequency, and can be important at frequencies below about 3 GHz. Backscatter from the aurora is significant near the polar regions at frequencies below about 2 GHz.The dimensions of the radar resolution cell tend to vary inversely with frequency, unless antenna size and percentage bandwidth of the signal are changed. These factors lead to the following general preferences in use of the different bands as illustrated in Table. After a several-year period of using the Electronic Warfare Bands, the U.S. Department of Defense readopted those in Table for radar systems. The IEEE updates the radar bands on a 7- to 10-year cycle. It is believed that there will be no changes in the next revision. Note the designation of V- and W-bands for the 40- to 100-GHz region. A comparison with the ITU and Electronic Warfare nomenclature is shown in Table.

NOTES: (1) These frequency assignments are based on the results of the World Administrative Radio Conference of 1979. The ITU defines no specific service for radar,

and the assignments are derived from those radio services which use radar: radiolocation, radio navigation, meteorological aids, earth exploration satellite, and space research.(2) There are no official ITU radiolocation bands at HF. So-called HF radars might operate anywhere from just above the broadcast band (1.605 MHz) to 40 MHz or higher.(3) The official ITU designation for the ultra-high-frequency band extends to 3000 MHz. In radar practice, however, the upper limit is usually taken as 1000 MHz, L- and S-bands being used to describe the higher UHF region.(4)Sometimes called P-band, but use is rare.(5) Sometimes included in L-band.(6) The designation mm is derived from millimeter wave radar, and is also used to refer to V- and W-bands when general information relating to the region above 40 GHz is to be conveyed.(7) The region from 300 GHz-3000 GHz is called the submillimeter band.

The common usage of the radar bands can be summarized:

HF Over-the-horizon radar, combining very long range with lower resolution and accuracy. It’s more useful over oceans.

VHF and UHF Long-range, line-of-sight surveillance with low to medium resolution and accuracy and freedom from weather effects.

L-band Long-range surveillance with medium resolution and slight weather effects (200 nmi).

S-band Short-range surveillance (60 nmi), long-range tracking with medium accuracy. Subject to moderate weather effects in heavy rain or snow.

C-band Short-range surveillance, long-range tracking with high accuracy. Subject to increased weather effects in light to medium rain.

X-band Short-range surveillance in clear weather or light rain; long-range tracking with high accuracy in clear weather, reduced to short range in rain.

Ku and Ka-band Short-range tracking, real and synthetic aperture imaging, especially when antenna size is very limited and when all-weather operation is not required or ranges are short.

V-, W- and mm-band Limited to short ranges in a relatively clear atmosphere, very short ranges in rain. Generally for tracking and missile homing and “smart seekers” with very small antennas. Remote sensing of clouds.

Note that the words long range appears in the lower band usage, and resolution and accuracy appear at the higher bands. There are good reasons for these preferences. It is known that long range detection requires large antenna apertures. At lower carrier frequencies (longer wavelengths) these are easier to construct since tolerances are based on fractions of a wavelength. Also, at lower frequencies antenna reflectors need not be solid, and mesh or grid types are utilized. At the higher bands, the radar antennas are often constrained in size to fit aircraft, spacecraft, or missiles; and the shorter wavelengths are needed for the desired resolutions or accuracies. It is shown in later sections that clutter problems may dominate radar carrier-frequency selection.There are, of course, many cases in which band usage is stretched, for example, to provide accurate tracking at L-band with very large antennas and compensation for ionospheric refraction, or to search a C- or X-band with special Doppler processing can reject rain clutter and with high power to overcome attenuation and limited aperture size. However, once a radar band and overall size and power are established, its potential for search and tracking functions is fairly well constrained.

Criteria for Choice of Signal-Processing Techniques

The desire for ever greater detection and tracking ranges for weapon system radars forced the peak power of the radars of the post-World War II era well into the megawatt region. Even then, the detection ranges were not considered adequate for short-pulse radar transmissions.When longer pulses were transmitted, target resolution and accuracy became unacceptable. Despite efforts to increase detection range with low-noise receivers, it became apparent that external noise and clutter in the military all-weather environments would negate the improvements in noise figure. Siebert and others pointed out that the detection range for given radar and target was dependent only on the ratio of the received signal energy to noise power spectral density and was independent of the waveform. The efforts at most radar laboratories then switched from attempts to construct higher-power transmitters to attempts to use pulses that were of longer duration than the range-resolution and accuracy requirements would allow. These pulses were then internally coded in some way to regain the resolution.There is a conflict in obtaining range resolution and accuracy and simultaneously obtaining velocity resolution and accuracy with simple waveforms. Range resolution is defined here as the ability to separate two targets of similar reflectivity. For a pulsed sinusoid, resolution can be approximated by ΔR = (l/B), where ΔR is the range resolution in time units and B is the transmission 3-dB bandwidth of a pulsed sinusoidal signal.For a single-pulse transmission when the target velocity is known and acceleration is neglected,

Where σT = the standard deviation of range error in time units.

2E/No = the signal energy to noise power per hertz of the double sided spectrum assuming white Gaussian noise. For near optimum receivers, and considering only the real part of the noise, this is numerically equal to S/N, the peak signal to- noise power at the output of the receiver matched filter.

β= root-mean-square (angular) bandwidth of the signal envelope about the mean frequency. β2 is the normalized second moment of the spectrum about the mean (taken here to be zero frequency)

Thus, both range-resolution and accuracy requirements generally are in direct opposition to detectability requirements, which vary as Ptτ (peak power times pulse length) for simple pulses.

In its simplest form, velocity resolution, i.e., the ability to separate two targets separated in Doppler, can be expressed by ΔV = 1/T, where ΔV is Doppler resolution in frequency units and T is time duration of the waveform. As one would expect, the longer the duration of the signal, the easier it is to measure accurately the Doppler shift. It has been

shown that the accuracy with which Doppler frequency can be determined (when range is known) is given by

Where σd = the standard deviation of the Doppler frequency measurement

te, = the effective time duration of the waveform

The measurement of radial velocity is often made by successive measurements of range; or, preferably, by the rate of change of phase with time.

Antenna and Array Considerations

In military radar systems prior to the mid-l960s, the conflicting requirements for detection, resolution, and accuracy were often resolved by having two or more different radars, each of which was most suited to a particular function. These would include search radars, height finders, track radars, and sometimes gunfire control and missile guidance radars. In civil radars for airports there is often a functional division into general air-surveillance radars, and meteorological radars.To circumvent this need for separate radars, many programs combine the goals into single multifunction radar. It is worthwhile to point out some of the compromises that are necessary in the design of multifunction radars.It can be seen from Equation that long-range target detection requires having a large effective receiving aperture area; however, large aperture areas imply narrow beam widths as can be seen from the following relationships for a rectangular aperture.

Where G = the antenna gainAe = the effective antenna apertureλ = the transmit wavelengthθ1Ф1 = one-way 3-dB beam widths in radians

The angular cross section of the radar beam is

Thus, beam width decreases as (Ae) ½ increases. If good angular resolution is also desired, the wavelength is usually kept small. When the radar requirement includes surveillance of the entire hemisphere, the number of beam positions to be searched, NB, with some overlap of the beam, is

For example if Ae = 10 m2, the number of beams in the hemisphere is about6000 at a wavelength A = 10 cm (S-band). If the desired scan time is10 s, there are about 600 beam positions to be observed per second or 1.6 ms per beam position. The significance for signal processing is that pulse-compression techniques, MTI, or short bursts of coherent pulses can often yield adequate performance in detecting aircraft in a 1.6-ms period and that CW or pulse Doppler techniques are generally more time consuming. However, with stealth aircraft or small missiles a good bit more time is required per beam for clutter rejection.

A related problem with narrow-beam surveillance radars is the difficulty of achieving reliable detection of complex targets with only one or two pulses per beam width.

The desire to place radar energy where it is most needed and to change the mode or waveform rapidly has led to greater use of the electronically steered array. With a planar aperture, steering can be in either one or two dimensions. Additional functions such as tracking, mapping, and missile guidance are incorporated into military radars.While arrays were slowly introduced into production in the 1970s, the ultra low side lobes of the AWACS array proved to be a great advantage in military jamming environments, and in the 1980s other planar arrays were being updated with lower side lobe designs.

For frequency or phase-scanned array antennas, the usable spectrum of the transmitted waveform is limited because of the beam dispersion as bandwidth is increased. This is generally not a significant problem with conventional dish antennas. With a frequency-scanned antenna, the transmission bandwidth limit is obvious since a change in carrier frequency is deliberately used to steer the beam in elevation or azimuth. However, with a phase-scanned antenna the limitations are somewhat more subtle. These limitations can be separated into at least two classes: the phase approximation to time delay and transient effects. The phase approximation results from the widespread use of array phase shifters rather than time delays that are limited to a maximum of about 360 degrees variation (modulo 2π). When arrays whose linear dimensions are many wavelengths are steered more than a few beam widths from the bore sight position, the modulo 2π phase approximation to the desired wave front is accurate only over a narrow band of carrier frequencies. The reduction in antenna gain (one way) for a parallel-fed antenna as a function of scan (steering) angle from bore sight, for short-pulse or compressed-pulse systems, can be approximated by

Where U = sine of the steering angle from bore sight at which L is measured

τ = -3-dB pulse duration at the matched-filter output, in seconds

α = sine of the one-way beam width at bore sight and the center frequency, measured in the plane through bore sight and the steering angle

f0 = center frequency of the transmission in Hz

It can also be shown that at 60 degrees scan angle a reasonable maximum transmission bandwidth occurs where

At lesser scan angles the antenna gain is reduced by less than 1 dB (two way) from the gain at the single frequency for which the phase approximation was made if this criterion is satisfied. The highest antenna side lobe remains 10 dB below the main beam.

The second transient-like effect introduces an antenna bandwidth limitation when a linear array is excited from its center or from one end. If a rectangular pulse of RF energy is fed to one end of an antenna array, the signal will immediately begin propagating into space. Until the array becomes fully energized, the radiated energy originates from only a portion of the full aperture and has a much broader beam width than the normal antenna pattern, which is based on the continuous wave excitation. During the transient period, considerable portion of the energy is radiated into what would be normally be considered the side lobes of the antenna. If the pulse duration τ is long compared with the propagation time across the array tf , most of the total energy is radiated into the normal or steady-state pattern and there is little increase in the antenna side lobes. There is a similar transient period in the trailing edge of the pulse. The length of the steady-pattern is tss = τ - tf.

Transmitters

This section briefly describes the primary devices for radar transmitters and how they affect the overall systems design. Transmitters are often developed for continuous radiation in communication, electronic warfare system, or continuous wave (CW) radars, but the emphasis here is on pulsed transmitters that are developed for the majority of radar uses. There are five primary types of devices: the magnetron, the crossed-field amplifier (CFA), the klystron, the traveling wave tube (TWT), and the solid-state amplifier. The selection depends on the required power levels, the carrier frequencyband, the desired efficiency, coherence or stability requirements, noise radiation, and size cost.

The magnetron is a crossed-field device that was developed during World War I1 and was widely used in the earlier days of radar. It is still quite common in low-cost radars that do not require much clutter rejection. The magnetron is basically an oscillator that is turned on by a modulator. Unfortunately, when the oscillation is initiated, the initial phase is random and “coherency” from pulse to pulse is not easily achieved. With

random phase there is a noise-like modulation to the transmitted waveform. That is, with multipulse waveforms such as in moving target indicator (MTI) or pulse Doppler (PD) systems, it is difficult to separate targets and clutter by the differences in their radial velocities (Doppler effect) without the coherence from pulse to pulse.Numerous attempts have been made to lock the phase of a magnetron by injecting signals from a stable source. Some success has been achieved that allows clutter rejection of 30 to 35 dB. In a few cases there have been reports of 40- to 45-dB clutter rejection. While this is adequate in some designs, modern systems generally require considerably more.

A second limitation is that there is a broadband noise component radiated with the desired waveform. In these days of increasing crowding in the allocated radar spectrum, this noise tends to interfere with other systems in the radar band. As a result, frequency allocations are often withheld from systems with high-power magnetrons.

The remaining devices are primarily used as amplifiers in a master oscillator power- amplifier (MOPA) chain. Signals from stable oscillators are mixed or multiplied to the desired carrier frequency, then amplified to the required levels. Thus, the desired stability depends on both the process to get the signal to the desired frequency and the properties of the amplifier devices themselves.The crossed-field amplifier (CFA) is used in many higher-power ground-based systems due to its high efficiency (25 to 65 percent) and low operating voltages. It is linear and relatively easy to modulate. It has relatively low gain (7 to 16 dB), and must be driven by other CFAs, TWTs or klystrons. The noise output is much better than a magnetron, but it is still higher than other devices. Some operational systems have achieved clutter rejections of 60 dB, but 40 to 45 dB is more common. The CFA appears to be chosen more often when transmit pulse widths are 2 ps or greater. The average power output of a CFA can be quite high, especially at C-band or lower carrier frequencies. The RF bandwidth can be up to about 10 to 15 percent of the carrier frequency.There are several efforts to improve the gain and lower the noise output of the CFA family of transmitters.

The klystron amplifier is characterized by high-gain and high-power capabilities. Devices with high power (megawatts) and excellent reliability are used in air traffic control and long-range weather radars at 3 GHz with multi kilowatt klystrons available well into the millimeter wave bands. The noise output is quite low, making them suitable for coherent multipulse waveforms.The limitations of the klystron include relatively narrow bandwidths and the high voltages required for high power and efficiency. The bandwidth can be increased with some sacrifice in other properties.Like the klystron, the traveling wave tube (TWT) amplifier can deliver high power with low noise up to the millimeter wave bands. The additional benefit is that it can be used over an extremely high-percentage bandwidth. The gain of a TWT often exceeds 45 dB and it can be easily modulated. Unfortunately, the operating voltages are high and the phase sensitivity to changes in these voltages is much higher than with CFAs. Thus, much of the stability problem is transferred to the power supply design.

The newest and most rapidly evolving transmitters are those based on solid-state devices. The reason for their rapid development and use in current operating systems is the promise of dramatically increased reliability. The other primary advantages include low power supply voltage requirements and good stability.

There are two primary limitations to solid-state power amplifiers.The first is that high-power modules are efficient only at the lower microwave frequencies (currently about 3 GHz). This figure increases in frequency as development continues. The second limitation is that the solid-state devices are peak-power limited, and overall energy efficiency is best obtained with duty factors of well over 10 percent. It is shown in later chapters that this creates some waveform design problems for pulse-train waveform systems.Ultimately the solid-state power amplifiers will dominate most radar transmitter design tradeoffs if the cost savings in mass production and the millions of hours of reliability per device are realized.All the transmit devices summarized here operate more efficiently at the lower microwave frequencies and require higher operating voltages at the higher frequencies.

Radar Target and Study of General Scattering Properties of Simple Shapes

The radar range equation expresses the range at which a target may be detected with a given probability by radar having a given set of parameters. This equation includes the target's radar cross section (RCS), which is a measure of the proportion of the incident energy reflected back to the radar." This returned energy varies with a multitude of parameters such as transmitted wavelength, target geometry, orientation, and reflectivity.

The radar cross section of an object is proportional to the far-field ratio of reflected to incident power density, that is

Using this definition, consider the RCS of a perfectly conducting isotropic scatterer. The power intercepted by the radiator is the product of the incident power density PI and its geometric projected area AI.

The power of an isotropic scatterer is uniformly distributed over 4π steradians, in which case

Thus, the RCS of such an isotropic reflector is its geometric projected area. The RCS of any reflector may be thought of as the projected area of an equivalent isotropic reflector which would return the same power per unit solid angle. A reflector that concentrates its

reflected energy over a limited angular direction may have an RCS for that direction that exceeds its projected area. This indicates that, when specifying cross sections, one must also specify the aspect of the target. The RCS is also dependent on other parameters besides aspect angle.

SYSTEM DEFINITION

CENTRAL ACQUISITION RADARINTRODUCTION

The designed Radar would be a stand-alone all weather 3D surveillance radar. The radar operates in S-band and is capable of Track-While-Scan [TWS] of airborne targets up to 130 Kms, subject to line-of-sight clearance and radar horizon. The radar employs Multibeam coverage in the receive mode to provide for necessary discrimination in elevation data. It employs 8 beams to achieve elevation coverage of prescribed margin and a height ceiling of prescribed margin. The antenna is mechanically rotated in azimuth to provide 360 coverage. To get an optimum detection performance against various class of targets, different Antenna Rotation Rate [ARR] RPM modes are implemented and these can be selected by the operator.

The unique feature of the radar is, its operation is fully automated and controlled from a Radar Console with sufficient menus, keys and Hot keys. The designed Radar is an offshoot of the fully and successfully developed and demonstrated radar called as 3D Central Acquisition Radar (3D-CAR).

3D-CAR is designed to play the role of medium range surveillance radar mounted on a mobile platform. The radar carries out detection, tracking and interception of targets with an RCS of 2m2 upto 130 Kms in range. The antenna can be manually positioned at different look angles in steps. In the receive mode the eight beams cater for a height coverage of required margin. The IFF antenna is placed atop the main antenna and it integrates the IFF for including of IFF data with the Primary Radar Data.

The RDP (Radar Data Processor) is implemented on a SBC and is fully software-based system with adequate memory and external interfaces to handle upto 150 target tracks. Robust algorithms for filtering are used to lock on to maneuvering target upto 6g without loss of tracking.

LAN interfaces are used to communicate with external systems. High-speed data transfer of target parameters can be done. This helps in data remoting upto a distance of 500 mtrs that can be extended with suitable repeaters. Facility for manual track indication for low speed targets and targets in heavy clutter zones are available to the console operator.

The color display has features for monitoring of radar performance, the radar output selection for radar modes of operation. Interfaces to radar control signals are built-in. The Radar generates different videos viz., Analog and Digital videos at the Receiver and Signal Processor. These are interfaced to the display over dedicated lines and displayed In addition to providing real time data on screen for viewing, the consoles will provide

facility for training controllers/operators/ technical crew. The system is capable of creating targets and assigns values for range, azimuth, height and speed as defined by operator. It will enable the operator to control the motion of these targets for gaining/ loosing height, turning left/right, cruising, and rolling out. The software running on console will provide an online handy aid, for target interception. The training part of the software will be active as an offline facility or with tracked targets in real time. The offline mode will be capable of using recorded data.

Salient features Radar are:

1. 3D Surveillance Radar2. S-BAND 3. Capable of Track While Scan (TWS) of airborne Targets upto 150 Kms4. Coherent TWT based Transmitter5. Planar Array Antenna with low side lobes 6. Multiple beams in the receive mode. 7. ECCM (Side lobe blanking, Frequency Agility, Jammer analysis)8. Integrated IFF 9. System operation is controlled from Radar Console in Data centre.10. Redundant Power supply unit with UPS backup.

I have been working in Transmitter section of CAR developed by BEL, Ghaziabad. Before explaining the technical details of Transmitter of Radar, it is necessity to understand the general working of Radar.

This designed Radar has the following subsystems:

1. Multi-beam Antenna system2. Transmitter3. Receiver 4. Signal Processor 5. Radar Console6. Data centre7. Mobile Power Source8. IFF System

The Multi beam antenna system for Radar is planned to be realized to have 360 Coverage in Azimuth and prescribed coverage in elevation. The antenna will have a wide beam in transmit mode and eight simultaneous narrow beams in receive mode to give prescribed coverage in elevation.

The requirement of Transmitter is to amplify the pulsed RF signal from few watts to high power RF signal while maintaining the phase noise (additive noise) to its minimal as demanded by the system.

The Low Power Microwave Subsystem includes the major portion of Receiver RF System of the 3D-Radar. The Multibeam Antenna receives the reflected signals from the target. These signals are amplified by the Low Noise Amplifier, down converted to IF Frequency using two-stage superheterodyne receiver. The IF Output is given as final output of the Low Power Microwave Subsystem to be further processed in the signal processor.Customization of the console for user application will be carried out in the software and hardware. The Display Console is the operator's center to initialize, remotely setup, operate, observe, and diagnose the radar, both online and offline. The Primary and secondary radar video, target tracks, plots, geographical map along with other diagnostic and configuration messages are presented in 2D.The Signal Processor for Radar is realized as 8 parallel and identical channels. Each Signal Processor accepts IF videos from the corresponding RF Receiver channel (8 beams + 1 Omni) and provides detection reports to the Radar Data Extractor (RDE) independently for these 8 channels. The detection reports for each channel must have range and strength information in addition to the associated flags. Jammer data is also to be reported. Configuration and mode control, diagnostics and status reporting are done through a Radar Controller (RC).The electronic equipment cabin is provided for installation of transmitter, signal processor, receiver, display console, IFF equipment and a working place for maintenance.The Data centre is required to provide basic functions like viewing of the air picture, remote operation of radar, and radio communication. At the same time the cabin provides shelter for the operators, with reasonable level of comfort and, protected against heat, rain and dust.Mobile power source is required to provide the main supply to Radar and Data Centre for electronic and mechanical units of Radar including air conditioning units. The Identification Friend or Foe (IFF) system is a good example of a secondary radar system that is in wide use in the military environment. A great deal of valuable information can be provided to the secondary radar by the target’s transponder. The transponder provides an identifying code to the secondary radar that then uses the code and an associated data base system to look up aircraft origin and destination, flight number, aircraft type and even the numbers of personnel onboard. This type of information is clearly not available from a primary radar system.

TRANSMITTER

TransmitterINTRODUCTION

The transmitter for Radar is Coherent MOPA type that operates in S Band using TWT as the final amplifier. The transmitter is used to amplify the pulsed RF signal from low power RF signal to High power RF signal as demanded by the system. TWT dissipates large amount of energy, therefore it is subjected to both air and liquid cooling.

The input to the transmitter is 3 phase, 415V, 50 Hz, which is later amplified to the optimal value for driving the TWT amplifier.A generalized diagram here briefly explains the inputs and outputs of the transmitter.

Input output diagram of Transmitter

3-phase,400V,50Hz

3-channel liq cooling in

3-channel liq cooling out

Air cooling in

SP signals

Air cooling out

Dry air

BIT0

BIT1

PRETRGGRID PULSE

RF outROHINI

TRANSMITTER

RF input

System status

RF PULSE

The transmitter is designed to operate in the following modes defined as adequate controlled states

Transmitter modes

a) OFF : All subsystems switched OFF

b) Cold Standby : Only LVPSU’s , TWT heater and Grid biases are switched ON. No High Voltage applied.

c) Hot Stand By : High Voltages applied, No RF and No grid Pulsing.

d) Transmission : RF power delivered to Antenna / Matched load.

i) Full Power mode : Full RF Power delivered to the Antenna

ii) Reduced Power mode : The transmitter is operated at 1/10 of

its full power based on the selection by the user.

iii) Fail safe mode : A low power at required dutydelivered to antenna through Solid State Power Amplifier when liquid cooling fails.

Modes are selected by the operator.

Transmitter control

a) Local : To control through control panel on the transmitter.

b) Remote control : To control from the operator console through control interface RS422.

MECHANICAL DESCRIPTION

Three rack configuration of Transmitter describes complete functionality of Transmitter

1. Control Rack Monitoring panel Control panel Synoptic panel CPC Inverter

2. High Voltage Rack FDM (Solid state Switching) Cathode Assembly Collector Assembly Blower Unit Heater Unit

3. Microwave Rack TWT RF Plumbing RF Drive Unit SSPA ION Pump Controller

GENERAL DESCRIPTION

The Transmitter amplifies the pulsed RF signal from few Watts to many KW while maintaining the phase noise (additive noise) to prescribed margin as demanded by the system. In addition, a Solid State Power Amplifier (SSPA) is provided, as a stand by option, to ensure fail-safe mode, in case of failure of liquid coolant.

It employs a Traveling Wave Tube as final power amplifier. Low power amplifier stage (RF Driver) amplifies pulsed RF signal from 1mW (0 dBm) to few W which is necessary to drive the TWT amplifier.

The RF Driver stage uses a PIN attenuator transistor followed by power amplifiers to amplify RF signal. This is followed by an isolator. The isolator protects the transistor power amplifiers against excessive reflections from TWT. The signal is thereafter passed through a DC, a RF switch and an attenuator to cater for the three transmission modes. The sampled output of the DC is used for monitoring the input RF signal to the TWT.

The RF Driver output is given to the input of TWT, which amplifies the pulsed RF signal from few Watts to a level of many kW at the TWT output. High power RF plumbing components are connected at the output of TWT.

The TWT output is given to an arc detector followed by a ferrite circulator. The Ferrite circulator is used to protect the microwave tube against failure /damage due to reflected power in case of excessive VSWR at Antenna input port. The output of

Ferrite Circulator is given to High Power Dual Directional Coupler (DDC), which is used for measuring the transmitted and reflected power. If reflected power exceeds the specified limit of VSWR, a video signal is generated to cut off the RF drive through control and protection circuit. The output of the DDC is given to Antenna. To connect all the components in the required form, flexible sections, E-bends, H-bends and straight sections are used.

Control and Protection Circuit ensures the sequential switching ON of the transmitter, continuous monitoring and interlocking of various parameters, detection and indication of errors. All these are achieved by dedicated hardware and software.Synoptic Panel consists of LEDs, switches and LCD display. LEDs are used to show the status of the transmitter. They also show the fault, if any, in the transmitter. The LCD display, mounted on Synoptic panel, is used to show the value of cathode voltage & current, collector voltage and current. It also displays the Filament voltage and current, Grid + ve and -ve voltages and RF forward power.

The Inverter unit converts the incoming ac supply to DC and then converts the DC to high frequency AC (Pulse width controlled square wave) operating at 20 kHz. The output

of the Inverter unit is given to HV rack for generation of Cathode and Collector voltages of the TWT amplifier.

High Voltage Power Supply unit (HVPSU) is used to supply high voltage to collector and cathode of the TWT.

The Floating Deck Modulator (FDM) unit generates filament voltage with surge current protection and also generates grid +ve and grid -ve voltages. Switching of grid voltage as per pulse width and PRF requirements are also provided by FDM.

Cooling Unit is used to cool the various components of the transmitter. The TWT, High Power Ferrite Isolator, high Voltage Power supplies and RF dummy load are cooled with de-ionized water and ethylene glycol mixture.

Forced air-cooling is employed to cool other components using ambient air which is filtered to ensure dust free air. The Dry Air unit ensures that the wave guide is at all times pressurized and dry.

RF DRIVER TWT

FIL., GRID, CATHODE, COLLECTOR SUPPLY

COUPLER

FWD AND RFLECTED PWR MONITOR

LIQUID COOLING

TOANTENNA

SSPA

W/GSWITCH

DETAILED DESCRIPTION

Control Rack

Control Rack provides the protection controls and indications. As mentioned before, this rack is divided in five sections according to their functions.

1. Monitoring Panel

The Monitoring Panel provides monitoring ports for measuring of trigger signals to the transmitter, liquid cooling status, collector and cathode Inverter currents and bridge voltages. It provides an emergency switch OFF button and digital displays for collector and cathode voltages.

2. Control Panel

The control panel controls the power supplies of various units such as the fans, heater, LVPSU, Inverter, Modulator, RF Drive Unit and SSPA. The hour meters for filament, EHT and RF are also placed on the control panel.

3. Synoptic Panel

Synoptic Panel is located above the Control and Protection Circuit (CPC). It indicates the faults and status signals generated by CPC. Green LEDs represent status signals while Red LEDs represent faults. Audio alarms are also provided to indicate faults.

4. Control and Protection Circuits

The CPC ensures the sequential switching ON/OFF of the transmitter, continuous monitoring and interlocking of various parameters, detection and indication of errors.

CPC card Configuration comprises of ten different cards.

COMPARATOR CARD-I COMPARATOR CARD-II COMPARATOR CARD-III TIMING CARD SSPA CTRL CARD F TO V CARD OPTPISOLATOR CARD MC-I CARD MC-II CARD OPTO TRANSCEIVER CARD

5. Inverter

The Inverter is the main functional block of the (cathode/collector) HV Power supplies. A number of indicators are placed on the front panel of the Inverter unit.

AC-DC CARD CATHODE PROTECTION CARD CATHODE IGBT DRIVER CARD

TO RADARCONTROLLER

CPC BLOCK DIAGRAM

CO

MPA

RA

TO

R C

AR

DS

EHT VOLSAMPLES

RF PARAMETERS

OPTICAL LINKS&

F/V CARD

GRID VOL SAMPLES

FILVOL & I

SAMPLES

OP

TO

IS

OL

AT

OR

CA

RD

SSPACTRL CARD

COOLING CONDITIONS

TIMING CARD

RADARTIMINGS

SWITCH ON COMMANDS

TO SOLIDSTATE RELAYS

FOR HV, MAINS ON

STATUS STATUS

FRONT PANELWITH

SWITCHES, LED

& LCD DISPLAY

LCD INTERFACE

SWITCH ON COMMANDS

HV POWER SUPPLIES

EHT PROBESCROW BAR

TWT

LIQUIDCOOLING

UNIT

FLOATINGDECK

MODULATORAT - 45KV

POWERDISTRIBUTION

3Ø 50Hz400V AC IN

RF DRIVER&

DIR COUPLERS

EHT CURR SAMPLES

BEAM CURR, COLL CURRCATH CURR

INPUTPOWERSTATUS

CROW BAR SIGNAL

GRID

PULSE

MICRO-

CONTROLLER

CARD

COLLECTOR PROTECTION CARD COLLECTOR IGBT DRIVER CARD SOFT START CARD TEMPERATURE SENSOR CARD ZENER CARD (For Cathode and Collector) CURRENT SENSOR CARD (For Cathode and Collector) CURRENT SENSOR (PEAK) CARD (For Cathode and Coll.)

High Voltage Rack

This is central block of the transmitter, where cabins for HV Cathode and Collector are assembled. Above this is a FDM block where all the cards are installed and insulated from the transmitter that works on HV.As mentioned earlier, High Voltage Rack is divided in five more units. Each unit has its defined working.

1. FDM (Floating Deck Modulator)

Further in FDM there seven functional cards, which are as follows:

Isolation

transformer

230V- ph-ph50Hz FDM

FIL

GRID

CATHODE

Fil VoltageFil CurrentGrid PositiveGrid negative

To CPCOptical links

To TWT

Grid PulseFrom CPCOptical link

• LVPS Card• Grid Bias Card• Positive Grid Supply Card • Switch Card• Filament Supply & Timer Card-1• Filament Supply & Timer Card-2• V to F Card

Microwave Rack

The functional block diagram of microwave unit is shown in the figure. The microwave unit consists of the following functional assemblies:

Low power amplifier [RF drive unit] High power TWT amplifier RF Plumbing, Wave-guide switch & dummy load Solid state power amplifier (2 kW) for low power transmission mode TWT ion pump supply Resistive TWT anode divider Microwave power measurement circuits Air cooling components

Low Power Driver for TWT (RF Driver)

Low Power amplifier stage (RF Driver) amplifies pulsed RF signal from 1mW (0dBm) to few Watts power, necessary to drive the TWT amplifier. This low power RF Driver consists of following stages:

(a) Transistor Power amplifier : Amplifies the Pulsed signal from 0dBm to 37dBm

(b) Separating isolator : Used to protect the transistor power amplifier against excessive reflections

from TWT.

(c) Directional Coupler : To monitor the power available at the input TWT.

Figure given below shows the Input and output diagram of RF Driver

RF DRIVER

To SSPA i/p

To TWT i/p

To CPC for RF drive fail protection

TWT drive MONITOR

RF IN

Control i/p from CPC

High Power Microwave Stage

High Power Microwave consists of mainly TWT, which amplifies the pulsed RF signal received from the RF Driver of few watt power to a level of 120 -185 KW at the TWT output followed by High Power RF plumbing components. Figure given below shows the block diagram of high power chain.

High Power RF stage consists of:

Traveling Wave Tube (TWT) Ferrite Circulator Dual Directional Coupler (DDC) High Power dummy load Wave guide channel Wave guide switch

Traveling Wave Tube (TWT)

TWT is available in three different constructs, these are listed here:

1. Helix TWTs

These amplify relatively to low power levels, but it provides a very wide bandwidth, both in octave and multioctave.

2. Ring Loop / Ring Bar TWTs

These amplify at relatively high power levels, and provide a wideband, that is of 25 % of bandwidth.

3. Coupled Cavity TWTs

This TWT in family of TWTs provides highest amplified power levels. It has relatively narrower bandwidth that is 10% to 15 % of bandwidth.

TWT is the main power amplifier used in the transmitter. A coupled cavity TWT type is selected for this transmitter.

The collector in the TWT is further divided as:

1. Ground collector

2. Depressed collector

Single stage depressed collector Double depressed collector Multi stage depressed collector

Ferrite circulator

Ferrite circulator is used to protect the microwave tube against failure / damage due to reflected power in case of excess VSWR at Antenna input port. The Four port Ferrite circulator type is used as an isolator.

Dual Directional Coupler

High Power Dual Directional Coupler (DDC) is used for measuring the Transmit Power and reflected power. If reflected power exceeds the specified limit of 2:1 VSWR, video signal is generated to cut-off the RF drive through control and protection unit.

High power dummy load

High power dummy load is used to test the transmitter with out connecting the antenna during standalone testing.

Wave-guide Channel

To connect all the components in the required form, flexible sections, E-bends, H-bends and straight sections are used. Standard W/G sections are being used for this purpose.

-600

+800

RF IN RF OUT

LIQUID COOLING

-45kV,5kW

33kV,18kW

3kV,ION PUMP

-10V,10A

TWT POWER SUPPLIES CONNECTION DIAGRAM

Microwave Channel (High Power)

Figure below shows the schematic diagram of the microwave channel. The microwave channel consists of high power amplifier using TWT amplifier and high power RF plumbing components.

Schematic Diagram of microwave channel

Antenna channel matching requirements

Mismatch in the antenna channel, being the load of the transmitter, significantly decides of VSWR as seen from the TWT output. According to the Antenna System requirements, matching of the antenna channel at the transmitter output should be equivalent to VSWR prescribed margin in frequency range of S band in which the radar operates. It seems to be difficult to satisfy, because the TWT should operate at VSWR <1, the isolator of proper directivity has to be applied in the wave-guide channel.

Power Variation along RF line

Max. RF power losses along the output wave-guide channel altogether with VSWR losses taken into consideration, were calculated for operation on the antenna. Assuming that RF pulse power at the TWT output is equal 120 kW (min), RF pulse power at the transmitter output should be contained within in the range of 90 kW in the case of operation on the antenna. Figure given above shows the power variation along the RF line.

Solid State Power amplifier

This Solid-state power amplifier is used during the fail-safe mode. A power of 1.5 KW peak at required duty is delivered to antenna through Solid State Power Amplifier when liquid cooling fails. This Mode is selected by the operator.

Ion Pump Supply

Ion pump supply is a source of positive voltage about 3.3kV, intended to supply TWT ion pump, which is integral part of the TWT to maintain the vacuum level inside TWT.

Transmitter Cooling

This system is a forced liquid-to-air type, used for cooling sub systems of the F-Band Transmitter. The primary coolant used for circulation through this transmitter heat loads is Dematerialized water / Glycol for operation from required range of temperature. The transmitter employs liquid cooling for TWT, high power circulator, RF dummy load and high voltage inverter and forced air-cooling for all other sub-assemblies. Independent of air-cooling, a dry air with low dew point and dust particles should be applied for wave-guide pressurizing and for TWT. General design of the cooling is worked out in such a way that the temperature rise for outlet coolant is around 10C as compared to the inlet coolant.

CONCLUSION

I have successfully completed our 6-week industrial training in BEL, Ghaziabad.We have done our project on the Study of CAR Radar (Transmitter) & learned various aspects of Radar manufacturing such as Assembling & Testing of Radar to our utmost satisfaction.