Tushar Bel Report 2

8/7/2019 Tushar Bel Report 2

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STUDY OF

TRANSMITTER OFRADARREPORT

The radar transmitter produces the shortduration high-power of pulses of energy thatare radiated into space by the antenna.

TUSHAR

UPT\982\B.TECH.\2010


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CERTIFICATE

2 VIVEKANAND INSTITUTE OF TECH. AND SCIENCE,GHAZIABAD


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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-------------(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 ------------- Deputy General 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 ---------(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.

TUSHAR

PLACE: GHAZIABAD



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PREFACE

With the ongoing revolution in electronics and communication where innovations are taking

place at the blink of eye, it is impossible to keep pace with the emerging trends.

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 collating 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.



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CONTENTS

S.No. Topics Page Nos.

1 BEL

Introduction 5-8

2 Manufacturing Units 9-11

3 BEL (Ghaziabad Unit) 12

4 Product Ranges 13

5 Services of BEL 14

6 Rotation Programme 15-26

Test Equipment and Automations

PCB Fabrication

Quality Control Works-Radar

Work Assembly-Communication

Magnetics

Microwave Lab

7 Radar 27-35

8 Different Types of Radar 36-38

9 Radar Application 39

10 Radar Transmitter 40-45

11 Signal Processing Unit 46-65

12 Fully Coharent Radar 66-68

13 Magnetron 69-77

14 Pulse Compression 78-93

15 Bibliography 94



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BHARAT ELECTRONICS LIMITED

INTRODUCTION

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

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

in the year 1876, which was invented in 1852. First wireless communication equipment were

introduced in Indian Army in the year 1909 with the discovery of Radio waves in 1887 by

Hertz and demonstration of first wireless link in the year 1905 by Marconi . Setting up of

radio station for broadcast and other telecom facilities almost immediately after their

commercial introduction abroad followed this. After independence of India in 1947 and

adoption of its constitution in 1950, the government was seized with the plans to lay the

foundations of a strong, self-sufficient modern India. On the industrial front, Industrial Policy

Resolution (IPR) was announced in the year 1952. It was recognized that in certain core

sectors infrastructure facilities require huge investments, which cannot be met by private

sector. With telecom and electronics recognized among the core sectors, Indian Telephone

Industry, now renamed as ITI Limited, was formed in 1953 to undertake local manufacture of

telephone equipment, which were of electro-mechanical nature at that stage. Hindustan Cable

Limited was also started to take care of telecom cables.



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MSSR radar at important airports under the modernization of airports plan of National

Airport Authority (NAA).

BEL has nurtured and built a strong in-house R&D base by absorbing technologies

from more than 50 leading companies worldwide and DRDO Labs for a wide range of

products. A team of more than 800 engineers is working in R&D. Each unit has its own R&D

Division to bring out new products to the production lines. Central Research Laboratory

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

design work on state-of-art and futuristic technologies. About 70% of BELs products are of

in-house design.

BEL was among the first Indian companies to manufacture computer parts and

peripherals under arrangement with International Computers India Limited (ICIL) in

1970s. BEL assembled a limited number of 1901 systems under the arrangement with ICIL.

However, following Governments decision to restrict the computer manufacture to ECIL,

BEL could not progress in its computer manufacturing plans. As many of its equipment were

microprocessor based, the company, Continued to develop computers based application, both

hardware and software. Most of its software requirements are in real time. EMCCA, software

intensive navel ships control and command system is probably one of the first projects of its

nature in India and Asia.

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

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

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

India by the Business Standard in its special supplement The BS 1000 (1997-98). BEL waslisted 3rd among the Mini Rattans (Category II) by the Government of India, 49th among

Asias top 100 worldwide Defence Companies by the Defence News, USA. During 2008-

09, BEL recorded a turnover of Rs.4624 crores.



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CORPORATE MOTTO , MISSION AND OBJECTIVES:

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

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

CORPORATE MOTTO

Quality, Technology and Innovation.

CORPORATE MISSION

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

CORPORATE OBJECTIVES

To become a customer-driven company supplying quality products at competitive prices

at the expected time and providing excellent customer support.

To achieve growth in the operations commensurate with the growth of professional

electronic industry in the country.

To generate internal resources for financing the investments required for modernization,

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

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

materials and components.

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

of electronics through in-house research and development as well as through

Collaboration/Co-operation with Defence/National Research Laboratories, International

Companies, Universities and Academic Institutions.

To progressively increase overseas sales of its products and services.

To create an organizational culture which encourages members of the organization to real

and through continuous learning on the job



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MANUFACTURING UNITS

BANGALORE (KANARATAKA)

BEL started its production activities in Bangalore on 1954 with 400W high frequency

(HF) transmitter and communication receiver for the Army. Since then, the Bangalore

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

Navy and Air-force.

BELs in-house R&D and successful tie-ups with foreign Defence companies and

Indian Defence Laboratories has seen the development and production of over 300 products

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

for the civilian customers such as DoT, VSNL, AIR and Doordarshan, Meteorological Dept.,

ISRO, Police, Civil Aviation and Railways. As an aid to Electorate, the unit has developed

Electronic Voting Machines that are produced at its Mass Manufacturing Facility (MMF).

GHAZIABAD (UTTER PRADESH)

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

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

provides Communication Systems to the Defence Forces and Microwave Communication

Links to the various departments of the State and Central Govt. and other users. The Units

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

Antennae and Microwave components.

PUNE (MAHARASHTRA)

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

Magnesium Manganese-dioxide Batteries, Lithium Sulphur Batteries and X-ray Tubes/Cables

were added to the product range. At the present the Laser Range Finders for the Defence

services.

MACHILIPATNAM (ANDHRA PRADESH)

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



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equipment was integrated with BEL in 1983. the product line includes passive Night Vision

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

Optical Sights and Mussel Reference Systems for tank fire control systems. The Unit has

successfully diversified to making the Surgical Microscope with zoom facilities.

PANCHKULA (HARYANA)

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

1985. Professional grade Radio-communication Equipment in VHF and UHF ranges entirely

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

CHENNAI (TAMIL NADU)

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

Control Equipment required for the integration and installation and the Vijay anta tanks. The

Unit is now manufacturing Stabilizer Systems for T-72 tanks, Infantry Combat Vehicles

BMP-II; Commanders Panoramic Sights & Tank Laser Sights are among others.

KOTDWARA (UTTER PRADESH)

In 1986, BEL STARTED A unit at Kotdwara to manufacture Telecommunication

Equipment for both Defence and civilian customers. Focus is being given on therequirement of the Switching Equipment.

TALOJA (MAHARASHTRA)

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

collaboration with coming, France in 1986. The Unit is now fully mobilized to manufacture

HYDERABAD (ANDHRA PRADESH)

To coordinate with the major Defence R&D Laboratories located in Hyderabad,

DLRL, DRDL and DMRL, BEL established a Unit at Hyderabad in 1986. Force Multiplier

Systems are manufactured here for the Defence services 20 glass bulbs indigenously.



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BEL GHAZIABAD UNIT

Formation

In the mid 60s, while reviewing the Defence requirement of the country, the

government focused its attention to strengthen the Air Defence system, in particular the

ground electronics system support, for the air Defence network. This led to the formulation of

a very major plan for an integrated Air Defence Ground Environment System known as the

plan ADGES with Prime Minister as the presiding officer of the apex review committee .At

about the same time, Public attention was focused on the report of the Bhabha committee on

the development and production of electronic equipment. The ministry of Defence

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

equipment requirements for its plan ADGES.

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

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

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

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

industrial license for manufacture of radar and microwave equipment was obtained, 1972 saw

the commencement of construction activities and production was launched in 1974.

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

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

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

needed to match a variety of primary raiders. More than 30 versions of IFFs have already

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

Component based system.



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PRODUCT RANGES

The product ranges today of the company are:

RADAR SYSTEMS

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

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

Tactical Control Radar System for the Army.

Battlefield Surveillance Rader for the Army.

IFF Mk-X Radar systems for the Defence and export.

ASR/MSSR systems for Civil Aviation.

Radar & allied systems Data Processing Systems.

COMMUNICATIONS

Digital Static Tropo scatters Communication Systems for the Air Force.

Digital Mobile Tropo scatters communication System for the Air Force and Army.

VHF, UHF & Microwave Communication Equipment.

Bulk Encryption Equipment.

Turnkey communication Systems Projects for Defence & civil users.

Static and Mobile Satellite Communication Systems for Defence.

Telemetry /Tele-control Systems.

ANTENNA

Antennae for Radar, Terrestrial & Satellite Communication Systems.

Antennae for TV Satellite Receive and Broadcast applications.

Antennae for Line-of-sight Microwave Communication Systems.

MICROWAVE COMPONENT

Active Microwave components like LNAs, Synthesizer, and Receivers etc.

Passive Microwave components like Double Balanced Mixers, etc.



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SERVICES OF BHARAT ELECTRONICS LIMITED (BEL):-

DEFENCE PRODUCTS:-

Naval System

Military Communication Equipment

Radars

Tele Communication & Broadcasting Services

Opto Electronics

Electronic Warfare

Tank Electronics

NON-DEFENCE PRODUCTS:-

Electronic Voting Machine

Solar Products

Simputer

DTH



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ROTATION PROGRAM

Under this students are introduced to the company by putting them under a

rotation program to various departments. The several departments where I had goneunder my rotational program are:

1. Test Equipment and Automation

2. P.C.B. Fabrication

3. Quality Control Works-Radar

4. Work Assembly- Communication

5. Magnetics

6. Microwave lab

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

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

departments was given. The cooperative staff at the various departments made the

learning process very interesting , which allowed me to know about the company in a

very short time.

TEST EQUIPMENT AND AUTOMATION

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

equipments and they are of 16 types.

Examples of some test equipments are:

Oscilloscope(CRO)

Multimeter

Signal Analyzer

Logical Pulsar

Counter

Function Generator etc.

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

standard of National Physical Laboratory (NPL). So, it is said to be one set down to NPL. As

every instrument has a calibration period after which the accuracy of the instrument falls

from the required standards. So if any of the instruments is not working properly, it is being



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sent here for its correct calibration. To calibrate instruments software techniques are used

which includes the program written in any suitable programming language. So it is not the

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

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

unit if it can afford it.

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

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

mainly used for Defence purpose.

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

with the help of standard equipment should be of some make, model and type.

The national physical laboratory (NPL), New Delhi provides the standard values

yearly. BEL follows International Standard Organization (ISO) standard. The test equipments

are calibrated either half yearly or yearly.

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

1. Green O.K , Perfect

2. Yellow Satisfactory but some trouble is present.

3. Red Cant be used, should be disposed off.

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

1. WS 102

2. WS 104

3. PS 520

4. PS 809

5. PS 811

6. PS 369

Where, WS = Workmanship & PS = Process Standard

After the inspection of cables, PCBs and other things the defect found are given in following

codes.



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Operation in process

Following steps are there for PCB manufacturing:-

CNC Drilling

Drill Location

Through Hole Plating

Clean Scrub and Laminate

Photo Print

Develop

Cu electroplate

Tin electroplate

Strip

Etching and cleaning

Tin Stripping

Gold plating

Liquid Photo Imageable Solder Masking (LPISM)

Photo print

Develop

Thermal Baking

Hot Air leaving

Non Plated Hole Drilling

Reverse Marking

Sharing & Routing

Debarring & Packing

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

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

Procedure for through hole metallization

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

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



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Rinse- Electrolyses Copper-Plating-Plating- Spray water-Rinse-Anti Tarnish Dip-Hot Air

Drying- Unloading.

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

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

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

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

positive otherwise negative.

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

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

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

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

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

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

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

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

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

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

circuit functionally done.

There are three types of solder marking done in BEL:

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

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

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

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

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

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



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The next is ink preparation:

Ink + Hardener

71 %: 29 %

(150 gms.) : (300gms.)

+

Butyrate solo solve 50gms/kg.

Ink preparation-

It uses:-

Ink-----100gm

Catalyst----10% of total weight

Reducer-----10% of total weight

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

The three things are then fully mixed.

For wash out, following procedure takes place.

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

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

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



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QUALITY CONTROL

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

quality of the product. The raw materials and components etc. purchased and inspected

according to the specifications by IG department. Similarly QC work department inspects all

the items manufactured in the factory. The fabrication department checks all the fabricated

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

stenciling etc are done as per BEL standards.

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

cable assembly ,cable form , modules , racks and shelters as per latest documents and BEL

standards .

The mistakes in the PCB can be categorized as:

D & E mistakes

Shop mistakes

Inspection mistakes

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

entered in the process card by certain code specified for each error or defect.

After a mistake is detected following actions are taken:

1. Observation is made.

2. Object code is given.

3. Division code is given.

4. Change code is prepared.

5. Recommendation action is taken



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WORK ASSEMBLY

This department plays an important role in the production. Its main function is to

assemble various components, equipments and instruments in a particular procedure.

It has been broadly classified as:

WORK ASSEMBLY RADARe.g. INDRA II, REPORTER.

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

EMCCA: EQUIPMENT MODULAR FOR COMMAND CONTROL APPLICATION.

MSSR: MONOPULSE SECONDARY SURVEILLANCE RADAR.

MFC: MULTI FUNCTIONAL CONSOLE.

The stepwise procedure followed by work assembly department is:

o Preparation of part list that is to be assembled.

o Preparation of general assembly.

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

o Writing lists of all components.

In work assembly following things are done :

M aterial Receive :

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

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

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

by applying flux on it so that it does not tarnished and soldering becomes easy.

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

all the components before doing the work.



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

tools. The soldering irons are generally of 25 W and are of variable temperature, one of the

wires of the component is soldered so that they dont move from their respective places on

the PCB plate. On the other hand of the component is also adjusted so that the PCB does not

burn.

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

tinned.

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

Cleaning:

Inspection- This comes under quality work.

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

three cycles.

Testing:

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

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

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



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MAGNETICS

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

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

equipments.

This department basically consists of three sections :

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

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

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

(a) Planning and (b) Planning store .

2.) WORKS (PRODUCTION) :- Production of transformers and coils are being

carried out by the works departments.

3.) QUALITY CONTROL :- After manufacturing the transformer/coils the item is

offered to the inspection department to check the electrical parameters(DCR , No load

current , full load current , dielectric strength , inductance , insulation resistance and

mechanical dimension as mentioned in the GA drawing of the product.

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

transformer.

The various types of transformers are as follows :

1. Air cored transformers

2. Oil filled transformers

3. Moulding type transformers

4. P.C.B Mounting transformers :-

(a) Impedance matching transformers

(b) RF transformers

(c) IF transformers



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MICROWAVE LABORATORY

Microwave lab deals with very high frequency measurements or very short

wavelength measurements. The testing of microwave components is done with the help of

various radio and communication devices. Phase and magnitude measurements are done in

this section. Power measurements are done for microwave components because current and

voltage are very high at such frequencies.

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

circular waveguides. These waveguides can be used to transmit TE mode or TM mode. This

depends on the users requirements. A good waveguide should have fewer loses and its walls

should be perfect conductors.

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

the antenna is rotating. The power measurements being done in microwave lab are in terms of

S- parameters. Mainly the testing is done on coupler and isolators and parameters are testedhere.

There are two methods of testing:

a.) Acceptance Test Procedure(ATP)

b.) Production Test Procedure(PTP)

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

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

parameters such as gain ,bandwidth ,VSWR , phase ,return loss, reflection etc. are checked.

The instruments used for this purpose are as follow:

i) Filters

ii) Isolators

iii) Reflectors

iv) Network Analyzers

v) Spectrum Analyzers



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vi) Amplifiers and Accessories



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RADAR

History of RADAR

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

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

the technology of the time. It wasn't until the early 20th century that a radar system was first

built. One of the biggest advocators of radar technology was Robert Watson-Watt, a British

scientist.

Great Britain made a big effort to develop radar in the years leading up to World WarTwo. Some people credit them with being pioneers in the field. As it was, the early warning

radar system (called "Chain Home") that they built around the British Isles warned them of

all aerial invasions. This gave the outnumbered Royal Air Force the edge they needed to

defeat the German Luftwaffe during the Battle of Britain.

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

came about as an anti-collision system. After the Titanic ran into an iceberg and sank in 1912,people were interested in ways to make such happenings avoidable

Introduction

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

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

RDF(Radio Direction Finding).

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

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

of Doppler Effect frequency shift of the reflected signal. A transmitter emits radio waves,

which are reflected by the target, and detected by a receiver, typically in the same location as

the transmitter. Although the radio signal returned is usually very small, radio signals can

easily be amplified, so radar can detect objects at ranges where other emission, such as sound

or visible light, would be too weak to detect. Radar is used in many contexts, including

http://www.windows.ucar.edu/tour/link=/earth/Atmosphere/tornado/radar.htmlhttp://en.wikipedia.org/wiki/Acronym_and_initialismhttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Aircrafthttp://en.wikipedia.org/wiki/Shiphttp://en.wikipedia.org/wiki/Rainhttp://en.wikipedia.org/wiki/Doppler_Effecthttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Visible_lighthttp://www.windows.ucar.edu/tour/link=/earth/Atmosphere/tornado/radar.htmlhttp://en.wikipedia.org/wiki/Acronym_and_initialismhttp://en.wikipedia.org/wiki/Radiohttp://en.wikipedia.org/wiki/Aircrafthttp://en.wikipedia.org/wiki/Shiphttp://en.wikipedia.org/wiki/Rainhttp://en.wikipedia.org/wiki/Doppler_Effecthttp://en.wikipedia.org/wiki/Soundhttp://en.wikipedia.org/wiki/Visible_light


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meteorological detection ofprecipitation, air traffic control, police detection of speeding

traffic, and by the military.

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

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

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

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

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

1936 at the Tungsram laboratory

BASIC PRINCIPLE

Echo and Doppler Shift

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

the echo comes back a moment later. The echo occurs because some of the sound waves in

your shout reflect off of a surface (either the water at the bottom of the well or the canyon

wall on the far side) and travel back to your ears. The length of time between the moments

you shout and the distance between you and the surface that creates the echo determines the

moment that you hear the echo.

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

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

object. Doppler shift in the extreme creates sonic booms (see below). Here's how to

understand Doppler shift (you may also want to try this experiment in an empty parking lot).

Let's say there is a car coming toward you at 60 miles per hour (mph) and its horn is blaring.

You will hear the horn playing one "note" as the car approaches, but when the car passes you

the sound of the horn will suddenly shift to a lower note. It's the same horn making the same

sound the whole time. The change you hear is caused by Doppler shift.

http://en.wikipedia.org/wiki/Meteorologyhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)http://en.wikipedia.org/wiki/Air_traffic_controlhttp://en.wikipedia.org/wiki/Policehttp://en.wikipedia.org/wiki/Speedinghttp://en.wikipedia.org/wiki/Traffichttp://en.wikipedia.org/wiki/Inventorhttp://en.wikipedia.org/wiki/Scientisthttp://en.wikipedia.org/wiki/Engineerhttp://en.wikipedia.org/wiki/History_of_radarhttp://en.wikipedia.org/w/index.php?title=Christian_H%C3%BClsmeyer&action=edithttp://en.wikipedia.org/wiki/Zolt%C3%A1n_Bayhttp://en.wikipedia.org/wiki/Tungsramhttp://en.wikipedia.org/wiki/Meteorologyhttp://en.wikipedia.org/wiki/Precipitation_(meteorology)http://en.wikipedia.org/wiki/Air_traffic_controlhttp://en.wikipedia.org/wiki/Policehttp://en.wikipedia.org/wiki/Speedinghttp://en.wikipedia.org/wiki/Traffichttp://en.wikipedia.org/wiki/Inventorhttp://en.wikipedia.org/wiki/Scientisthttp://en.wikipedia.org/wiki/Engineerhttp://en.wikipedia.org/wiki/History_of_radarhttp://en.wikipedia.org/w/index.php?title=Christian_H%C3%BClsmeyer&action=edithttp://en.wikipedia.org/wiki/Zolt%C3%A1n_Bayhttp://en.wikipedia.org/wiki/Tungsram


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HOW RADAR WORKS

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

1. The antenna unit or the scanner

2. The transmitter receiver or transceiver and

3. the visual display unit

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

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

10,000 Mhz. The antenna is rotated at the rate of 10 to 25 rpm so that radar beam swaps

through 300degree Celsius all around the shiout to a range of about 90 kms.

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

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

between the transmission of pulse and the return of the echo. About 1000, pulses per second

are transmitted. Though it is varied to suit the requirements. Short pulses are best for short-

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

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

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

are video pulses. These pulses are short range pulses hence cant serve out the purpose of

long range work .In order to modify these pulses to long range pulses or the RF pulses, we

need to generate the power. The transmitted power is generated in a device called the

magnetron which can handle all these short pulses and very high oscillations.

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

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

shouts electron to the phosphorescent screen at the far end. Phosphorescent screen glows

when hit by an electron and the resulting spot can be seen through the glass face.

The basic idea behind radar is very simple: a signal is transmitted, it bounces off an

object and some type of receiver later receives it. They use certain kinds of electromagnetic

waves called radio waves and microwaves. This is where the name RADAR comes from

(Radio Detection And Ranging). Sound is used as a signal to detect objects in devices called



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SONAR (Sound Navigation Ranging). Another type of signal used that is relatively new is

laser light that is used in devices called LIDAR (Light Detection And Ranging).

Once the radar receives the returned signal, it calculates useful information from it

such as the time taken for it to be received, the strength of the returned signal, or the change

in frequency of the signal.

Basic Radar System:

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

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

it transmits a high power pulse to a switch, which then directs the pulse to be transmitted out

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

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

and the receiver as much as 1000 times per second.

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

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

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

Some radar transmitters do not transmit constant, uninterrupted electromagnetic

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

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

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

pulse is called the pulse repetition time (PRT) and the number of pulses transmitted in one



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second is called the pulse repetition frequency (PRF). The time taken for each pulse to be

transmitted is called the pulse width (PW) orpulse duration. Typically they can be around

0.1 microseconds long for penetrating radars or 10-50 microseconds long for imaging radars

(a display. microsecond is a millionth of a second).

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

PRT = 1 / PRF

or

PRF = 1 / PRT

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

RT means repetition time .

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

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

frequency of the waves are not the same and they change as time goes on. This is called

frequency modulation, which means the frequency changes or modulates.

It looks something like this...



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

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

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

bandwidth. Radars use bandwidth for several reasons regarding the resolution of a data

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

can yield a finer resolution but take up more memory. When an EM wave hits a surface, it

gets partly reflected away from the surface and refracted into the surface. The amount of

reflection and refraction depends on the properties of the surface and the properties of the

matter, which the wave was originally traveling through. This is what happens to radar

signals when they hit objects. If a radar signal hits a surface that is perfectly flat then the

signal gets reflected in a single direction (the same is true for refraction). If the signal hits asurface that is not perfectly flat (like all surfaces on Earth) then it gets reflected in all

directions. Only a very small fraction of the original signal is transmitted back in the

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

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

can be around 10 watts.

TYPES OF RADAR

Based on function radar can be divided into two types:

1. PRIMARY RADAR

2. SECONDRY RADAR

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

But in cases as controlling of air traffic, the controller must be able to identify the aircraft and

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

To give controller this information second radar called the secondary surveillance

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

out a sequence of pulses to an electronic BLACK BOX called the TRANSPONDER, fitted

on the aircraft. The transponder is connected to the aircrafts altimeter (the device which

measures the planes altitude) to transmit back the coded message to the radar about its status

and altitude. Military aircrafts uses a similar kind of radar system with secrete code to make



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sure that it is friend or foe, a hostile aircraft does not know what code to transmit back to the

ground station for the corresponding receiver code.

IFF UNIT

IFF is basically a radar bacon system employed for the purpose of general

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

traffic is called as SECONDARY SURVEILLANCE RADAR (SSR).

Primary radar locates an object by transmitting signal and detecting the

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

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

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

the primary radar operates with passive target.

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

interrogator transmitter in the ground station interrogates transponder equipped aircraft,

providing two way data communication on different transmitter and receiver frequency .The

transponder on board the aircraft on receipt of a chain of pulses from ground interrogator,

automatically transmit the reply, coded for the purpose of identification, is received back to

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

RADAR EQUATION

The amount of powerPrreturning to the receiving antenna is given by the radar equation:

where

Pt = transmitter power

Gt = gain of the transmitting antenna

Ar= effective aperture (area) of the receiving antenna

= radar cross section, or scattering coefficient, of the target F= pattern propagation factor

http://en.wikipedia.org/wiki/Radar_cross_sectionhttp://en.wikipedia.org/wiki/Radar_cross_section


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Rt = distance from the transmitter to the target

Rr= distance from the target to the receiver.

In the common case where the transmitter and the receiver are at the same location, Rt

=Rrand the termRt2Rr

2 can be replaced byR4, whereR is the range. This yields:

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

means that the reflected power from distant targets is very, very small.

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

The propagation factor accounts for the effects ofmultipath and shadowing and depends on

the details of the environment. In a real-world situation, pathloss effects should also be

considered.

RADAR SIGNAL PROCESSING

Distance measurement

Transit time

Principle of radar distance measurement using pulse round trip time.

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

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

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

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receiver) and the speed of the signal.2

cRange = where c is the speed of light in a vacuum,

and is the round trip time. For radar, the speed of signal is the speed of light, making the

round trip times very short for terrestrial ranging. Accurate distance measurement requires

high-performance electronics.

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

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

distinct minimum range, which is the length of the pulse multiplied by the speed of light,

divided by two. In order to detect closer targets one must use a shorterpulse length.

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

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

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

inter-pulse time.

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

both good short range and good long range in a single radar. This is because the short pulses

needed for a good minimum range broadcast have less total energy, making the returns much

smaller and the target harder to detect. This could be offset by using more pulses, but this

would shorten the maximum range again. So each radar uses a particular type of signal. Long

range radars tend to use long pulses with long delays between them, and short range radars

use smaller pulses with less time between them. This pattern of pulses and pauses is known

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

radar. As electronics have improved many radars now can change their PRF.

http://en.wikipedia.org/wiki/Speed_of_lighthttp://en.wikipedia.org/wiki/Speed_of_lighthttp://en.wikipedia.org/wiki/Distancehttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Signal_(information_theory)http://en.wikipedia.org/wiki/Pulse_Repetition_Frequencyhttp://en.wikipedia.org/wiki/Pulse_Repetition_Frequencyhttp://en.wikipedia.org/wiki/PRFhttp://en.wikipedia.org/wiki/Speed_of_lighthttp://en.wikipedia.org/wiki/Speed_of_lighthttp://en.wikipedia.org/wiki/Distancehttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Signal_(information_theory)http://en.wikipedia.org/wiki/Pulse_Repetition_Frequencyhttp://en.wikipedia.org/wiki/PRF


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DIFFERENT TYPES OF RADARS

1. 3D Mobile Radar (PSM 33 Mk II)

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

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

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

defence radar network. The Radar is configured in three transport vehicles, viz., Antenna,

Transmitter cabin, Receiver and Processor Cabin. The radar has an autonomous display for

stand-alone operation.

FEATURES

Frequency agility

Monopulse processing for height estimation

Adaptive sensitivity time control

Jamming analysis indication, pulse compression, plot filtering / tracking data

remoting

Comprehensive BITE facility

2. Low Flying Detection Radar (INDRA II)

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

transportable and self-contained system with easy mobility and deployment features. The

system consists mainly of an Antenna, Transmitter cabin and Display cabin mounted on three

separate vehicles.



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SYSTEM CHARACTERISTICS

Range up to 90 km (for fighter aircraft)

Height coverage 35m to 3000m subject to Radar horizon

Probability of detection: 90% (Single scan)

Probability of false alarm: 10E-6

Track While Scan (TWS) for 2D tracking

Capability to handle 200 tracks

Association of primary and secondary targets

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

Deployment time of about 60 minutes

FEATURESFully coherent system

Frequency agility

Pulse compression

Advanced signal processing using MTD and CFAR Techniques

Track while scan for 2-D tracking

Full tracking capabilities for maneuverings targets

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

Integral IFF

3. Tactical Control Radar

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

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



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as on the ground. This radar minimizes mutual interference of tasks of both air defenders and

friendly air space users. This will result in an increased effectiveness of the combined combat

operations. The command and control capabilities of the RADAR in combination with an

effective ground based air Defence provide maximum operational effectiveness with a safe,

efficient and flexible use of the airspace.

FEATURESAll weather day and night capability

40 km ranges, giving a large coverage

Multiple target handling and engagement capability

Local threat evaluation and engagement calculations assist the commander's

decision making process, and give effective local fire distribution

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

times (deployment/redeployment)

Clutter suppression



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RADAR APPLICATION

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

also to guide planes in for smooth landings.

Police use radar to detect the speed of passing motorists.

NASA uses radar to map the Earth and other planets, to tracksatellites and space

debris and to help with things like docking and maneuvering.

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

http://electronics.howstuffworks.com/air-traffic-control.htmhttp://electronics.howstuffworks.com/airplane.htmhttp://electronics.howstuffworks.com/satellite.htmhttp://electronics.howstuffworks.com/air-traffic-control.htmhttp://electronics.howstuffworks.com/airplane.htmhttp://electronics.howstuffworks.com/satellite.htm


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RADAR TRANSMITTER

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

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

technical and operating characteristics:

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

required peak power

The transmitter must have a suitable RF bandwidth.

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

The transmitter must be easily modulated to meet waveform design requirements.

The transmitter must be efficient, reliable and easy to maintain and the life expectancyand cost of the output device must be acceptable.

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

transmitter chapter is devoted to describing output devices therefore:

Picture: transmitter of P-37



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One main type of transmitters is the keyed-oscillator type. In this transmitter one

stage or tube, usually a magnetron, produces the rf pulse. The oscillator tube is keyed

by a high-power dc pulse of energy generated by a separate unit called the modulator.

This transmitting system is called POT (PowerOscillatorTransmitter). Radar units

fitted with an POT are eithernon-coherent orpseudo-coherent.

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

In this system the transmitting pulse is caused with a small performance in a

waveform generator. It is taken to the necessary power with an amplifier flowingly

(Amplitron, klystron or Solid-State-Amplifier). Radar units fitted with an PAT are

fully coherent in the majority of cases.

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

Even every antenna element

or every antenna-group is equipped with an own amplifier here.

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

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

a magnetron oscillator and a waveguide transmission line. The magnetron at the middle of the

figure is connected to the waveguide by a coaxial connector. High-power magnetrons,

however, are usually coupled directly to the waveguide. Beside the magnetron with its

magnetes you can see the modulator with its thyratron. The impulse-transformer and the

pulse-forming network with the charging diode and the high-voltage transformer are in the

lower bay of this rack.

http://www.radartutorial.eu/08.transmitters/tx08.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx06.en.htmlhttp://www.radartutorial.eu/01.basics/rb05.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx05.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx16.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx11.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx12.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx14.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx10.en.htmlhttp://www.radartutorial.eu/06.antennas/an15.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx08.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx07.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx08.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx06.en.htmlhttp://www.radartutorial.eu/01.basics/rb05.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx05.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx16.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx11.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx12.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx14.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx10.en.htmlhttp://www.radartutorial.eu/06.antennas/an15.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx08.en.htmlhttp://www.radartutorial.eu/08.transmitters/tx07.en.html


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BRIEF DESCRIPTION OF THE RADAR SUBSYSTEM

Main Circuit of Radar Subsystem

High Tension Unit

Transmitter Unit

Lo+Afc Unit

Receiver Unit

Antenna

Video Processor

High Tension Unit-

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

supply voltage of about 4.2kv for the transmitter unit.

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

Prevent the dissipation of the magnetron from becoming too high PRF the lower the supplied

high voltage

Transmitter Unit

The transmitter unit Comprises

Submodulator

Modulator

Magnetron

Afc control Unit

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

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

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

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

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



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

to trigger the thyraton in the modulator. Which is supplied by the high tension unit, Produces

high voltage Pulses of about 20kvDC.As a magnetron is self- oscillating some kind of

frequency control is required. The magnetron is provided with a tunning mechanism to adjust

the oscillating frequency b/w certain limits. This tunning mechanism is operated by an

electric motor being part of the Afc control circuit. Together with circuits in the Lo+Afc

units, a frequency control loop is created thus maintaining a frequency of the SSLO and the

magnetron output frequency.

LO+AFC Unit

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

Lock Pulses mixer

Afc discriminator

Solid state local oscillator(SSLO)

Coherent oscillator(COHO)

The Afc lock Pulses are Pulses are also applied to the COHO. The COHO outputssignals with a freq. of 30Hz, and it is synchronized with the pulse of each transmitter Pulse.

In this way a phase reference signal is obtained, required by the Phase sensitive detector in

the receiver unit.

Receiver unit

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

in two different ways, two receiver channel are obtained, called MTI channel and linearchannel.

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

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

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

linear channel.via directional coupler, a fraction of the low noise amplifier output is branch

offer and applied to the broadband jamming detector. The BJD is a wideband device, which

amplifies and detects the signal applied. The resulting signal is passed on the SJI-STC circuit

(Search jamming indication sensitivity time control) in the video Processor , if jamming



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

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

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

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

extra PRF. The 64 point stagger for extra PRF is actually is compound of a 32 point staggered

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

Canceller

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

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

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

the phase is constant (i.e. the PSD output is constant). The suppression by the canceller is

limited. The higher the PRF of the radar pulses, the better the suppression factor; a further

cancellation improvement can be obtained by using a triple canceller instead of a double

canceller; here a compromise is to found.

The operation of the canceller depends on the selected PRF :

Low and high PRF ;

The canceller is swithched as double canceller.

Extra PRF :

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

The canceller switched to double is a digital three pulse comparison canceller.

Videos are :

Undelayed video (V0)

Video delayed by one PRT (V1)

Video delayed by two PRTs (V2)

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

canceller output according to the following formula.

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

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

This circuit the following videos are obtained :

Undelayed Video (V0)



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Video delayed by one PRT (V1)

Video delayed by two PRT (V2)

Video delayed by three PRTs (V3)

Canceller output according to the following formula :

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

SIGNAL PROCESSING UNIT

INTRODUCTION

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

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

operating conditions are initially processed by the analogue processing stages (such as LNA,

IF, VIDEO DETECTOR etc.) and then processed by signal processor.

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

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

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

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

chain.

PRINCIPLE OF OPERATION

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

prewhitening clutter cancellation filter in the form of three pulses in MTI. The MTI output is

then processed by a sixteen point FFT processor with frequency domain windowing feature.

Final stage of data processing is detection. In detection block Cell Averaging (CACFAR)

with programmable threshold setting features in range/Doppler domain is used.

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

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

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



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

scan-to-scan and CPI-to-CPI basis is employed to ensure better performance against blind

speed conditions.

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

offset corrected (if AUTO OFFSET is ON SP control panel) and passed on to Digital Pulse

Compression (DPC) block.

The Digital Pulse Compression block carries out the matched filtering and correlation

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

signals under noise and clutter backgrounds, and extraction of signal parameters such as

Doppler content, strength, range and azimuthal positions etc. further processing needs to becarried out using clutter cancellation, filtering and integrations, and detection techniques.

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

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

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

for the given specifications, the MTD technique naturally turns out to be the ideal choice of

its implementation.

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

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

design feature. To facilitate the validation and testing of the signal processor, a swept

Doppler BITE is also provided. Similarly, to monitor on Oscilloscope outputs of MTI, FFT

and ZVF blocks, the necessary circuits in the form of D/A converters are also provided.

Interface circuits for MTD processed video on PPI as well for MTD data transfer tocentroid/RDP processor also form part of the design features.

HARDWARE ORGANISATION

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

into functions are packed into a single card cage. Each card cage is capable of housing up to

15 PCBs, along with a power supply module. The power supply takes ac input and caters for

the +5V, +15V and -15V supply needs of that card cage.



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

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

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

purpose.

FUNCTIONAL ORGANISATION

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

groups:

SIGNAL PROCESSING FUNCTIONS:

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

functional chain.

DIGITAL PULSE COMPRESSION

AUTO OFFSET CORRECTION

MATCHED FILTER

MOVING TARGET INDICATOR

FFT PROCESSING

ZERO VELCITY FILTER (ZVF)

ADAPTIVE THRESHOLDING (CFAR)

INTERFACE FUNCTIONS:

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

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

interfaces are part of their respective hardware.

DISPLAY INTERFACE

CENTROIDER INTERFACE

SYSTEM FUNCTIONS:



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

performed by other units of radar.

SYSTEM TIMING (also contain circuits for internal timing requirements of SP).

SYSTEM BITE Generates control for simulated target generation by Receiver.

ADAPTIVE MSC (AMSC) Adaptive map generation and transfer to receiver for

Adaptive Microwave Sensitive Control.

ECCM Analyze and generate control for optimum frequency selection and jammer

indication on PPI.

MONITORING FUNCTIONS:

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

functions are performed:

RPM monitoring.

SP output monitoring.

Control Panel Function.

FUNCTIONAL DESCRIPTION

The following are detailed description of each functional block.

DIGITAL PULSE COMPRESSION (DPC) BLOCK

DPC card module performs the following functions:

I/Q channel Digital Matched Filtering.

Automatic DC offset correction for I/Q ADC data.

Adaptive Microwave Sensitivity Control.

Online JAM sensing with real time ECCM controls.

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

levels.

PD /Pfa / Antenna RPM monitoring & Indication.

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

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



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This card module receives theINPHASEand QUADRATURE channel ADC data

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

data and inputted to the digital matched filter. The I & Q channel pulse compressed signal is

then fed to the corner turning memory of the MTD processor in the next card module. The

received ADC data also goes after buffering to the Adaptive Microwave Sensitivity Control

(AMSC) card and ECCM control card.



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

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

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

analysis.

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

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

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

CARD # 1 & # 2.

AUTO OFFSET CORRECTION FUNCTION

Auto offset correction block comprises

Auto offset correction hardware card, and

AMSC- Master Card.

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

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

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

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

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

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

channels. These I/Q offset values are passed on to the Auto Offset Correction Card, where the

hardware corrects the offset in the two channels on-line in the following scan.

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

corrects the offset in the two channels and passes on to DPC CONTROL CARD # 1. It also

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

BULK MEMORY FUNCTION BLOCK

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

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



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circuit consists of two PCBs. The first PCB is the Bulk Memory Control Card. In this PCB,

the address generations for both read and write operations; control generation and BITE

generation are implemented. In the second card mainly the memory and the corresponding

switching buffer is available. The memory in the second board is organized in such a way

that while DPC output data is written in one of the memories called bank A, the other

memory called bank B, outputs the previous CPI data for processing block. The clock used

for the read operation is gated Rck, generated in system timing card. The bank switching is

done after every CPI.

MOVING TARGET DETECTOR PROCESSOR BLOCK

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

various capabilities offered by digital techniques to produce improved detection of moving

targets.

Infact,

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

MOVING TARGET INDICATOR FUNCTION BLOCK

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

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

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

applications. One of the methods of eliminating clutter is the use of MTI, which employs the

DOPPLER EFFECT in its operation.

DOPPLER EFFECT

The apparent frequency of electromagnetic sound waves depends on the relative

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

each other, the apparent frequency will decrease, while if they are moving towards each

other, the apparent frequency will increase.

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

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



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

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

FUNDAMENTALS OF MTI

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

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

are then cancelled out. This applies to echoes due to stationary objects, but those due to

moving targets do show a phase change; they are thus not cancelled-nor is noise, for obvious

reasons.

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

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

display.

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

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

completely masked.

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

fixed targets, whereas it will vary for moving target.

The advantage offered by digital MTI processing:

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

between the echo signal and the MTI reference signal. This is achieved by use of I & Q

processing, something that was always known to be of value for MTI processing, but

which was not convenient to implement with analog methods.

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

Digital processor can be made reprogrammable.

Digital MTI is more stable and reliable than analog MTI, and requires less adjustments

during operation in the field.



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FFT PROCESSOR FUNCTION BLOCK

FAST FOURIER TRANSFORM (FFT)

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

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

however compared to. The number of samples has to be expressed as 2n if a filter bank is

being generated, all filters have identical responses, they will be uniformly spaced

frequencies, and the weighting coefficients are not optimum since they cannot be chosen

independently for each filter. The filters possible with a non-FFT filter bank also can achieve

greater attenuation of moving clutter (such as rain or chaff) because of the greater flexibility

available in their design. There are times, therefore, when the classical Fourier transform may

be more advantageous than the FFT even though the FFT might be quicker and require less

complexity.

HARDWARE

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

FFT Timing and Control

Cascade Buffer for FFT

Processor 1 ALE

Processor 1 Feedback

Processor 1 Feed forward

Complex multiplier

Processor 2 ALE (Architecture same as Processor 1 ALE)

Processor 2 Feedback (Architecture same as Processor 1 Feedback)

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

Frequency Domain Window (Real)

Frequency Domain Window (Imag.)

Magnituder



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ZERO VELOCITY FILTER FUNCTION

The MTD also uses a new concept of Zero Velocity filter (ZVF) to overcome the

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

will be the case of targets which are flying tangential radar and low velocity radial targets,

whos Doppler is such hat they fall in zeroeth filter. Also since the response of the DMTI is

rather poor for low Doppler targets, there is every chance that these targets may go under.

ZVF performs its function by forming a clutter map.

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

eliminates aircraft moving on a crossing trajectory (one perpendicular to the radar line of

sight) which causes the aircrafts radial velocity to be zero. This is unfortunate since the radar

cross-section of an aircraft is relatively large when viewed at the broadside aspect presented

by a crossing trajectory. The MTD took advantage of this large cross-section to detect the

targets that normally would be lost to a simple MTI radar. It did this with the aid of a clutter

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

established the thresholds used for detecting those aircraft targets which produce zero radial

velocity.

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

but due to the poor response of MTI. These may be the implementation of the ZVF will allow

the detection of targets whose return exceeds that of the clutter in that particular range

azimuth cell. The ZVF is implemented by integrating all the 18 returns of a CPI, and whose

response extends to the frequency band covered by the zeroeth filter.

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

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

fine grain resolution cells and the returns are stored in the form of a map. To build up the map

accurately, each antenna resolution is broken into 256 CPIs and there are 2560 range cells.

The ZVF is made up of magnitude of 18 samples, which are formed by first adding 9 samples

and then adding the next 9 samples coherently and non-coherently adding up the sums.



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CFAR PROCESSOR BLOCK

CFARis used in radars to maintain effectiveness when there are too many extraneous

crossings of a fixed threshold caused by clutter or noise. Automatic tracking of targets can be

seriously degraded if excessive false alarms occur.

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

functional blocks of digital signal processor. The output of the FFT filtering block is further

processed to facilitate the following

Generation of adaptive threshold levels using Moving Window concept.

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

the detected signals.

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

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

Mode Selection Multiplier and threshold detection constitute the hardware blocks of the

CFAR processor. In the CFAR processor block, the threshold levels are so found, so as to

enable the detection of the signals with the constant false alarm rate under conditions of

mainly thermal noise and also under jamming and interference backgrounds. In order to

achieve this Newman Person detection criterion, with adaptive thresholding in all the Doppler

channels using moving window concepts is implemented.

In case of Non-Gaussian clutter dominated Doppler channels designed features have

been provided to selectively apply higher threshold levels, so as to restrict the false alarm to

the acceptable level.

The CFAR Processor block functions with its own timing and control signals. The

master source for these timings however is from the system timing circuit. CFAR BITE

facility has also been provided to test and validate the CFAR processor block in stand-alone

mode.



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DISPLAY VIDEO INTERFACE FUNCTION

This function is to generate trigger and videos for two Display consoles.

The raw video from IF processor is mixed with Jammer video and is then buffered to

generate RAW video for Display Consoles.

Mixing CFAR output with Jammer video and AMSC video generates the MTD video

for Display Consoles.

The triggers are suitably delayed Radar Trigger (RT), they are also buffered before

sending to Display Consoles.

CENTROID INTERFACE FUNCTION

The data packet to be sent to the centroider from CFAR Processor, basically, contains

the information such as signal strength, Doppler bin number (velocity bin), Range cell

number, CPI number, PRF code and data pertaining Jam to strobe, Tx blanking flag, carrier

frequency code, etc.

This data packet needs to be tagged to the threshold crossing pulse to facilitate

centroiding and subsequent data processing. The Threshold Crossing decision on sample-to-

sample basis is carried out at real time processing rate of 250ns per report. However the

centroider accepts the information asynchronously. This necessitates the use of hardware

buffering devices such as FIFOs. The information needs to be passed to a 16-bit data bus.

Hence various sets of information indicated above need to be generated, edited, formatted

and sequenced before data-transfer.

The required hardware design was carried out in two PCBs. The first PCB consists of

timing and control circuits and a part of data editing. The next PCB consists of sequencing,

FIFO store and data interface.

SYSTEM TIMING FUNCTION



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This is the function that generates all the basic timing signals required for use within the

Signal Processor as well as other units of the radar. It generates necessary synchronization

signals for Transmitter and Sampling clock for IF Processor. The signals thus generated are

described below.

20 MHz GENERATOR

20 KHz GENERATOR

PRF GENERATOR

CPI PAIR GATE

NM AND ACP GENERATION

BITE FUNCTION BL

Tushar Bel Report 2

Documents

Transcript of Tushar Bel Report 2