Radar Transmitter

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1 BHARAT ELECTRONICS INDUSTRY
1.1 Introduction
Bharat Electronics Limited (BEL) was established in 1954 as a Public Sector Enterprise
under the administrative control of Ministry of Defence as the fountain head to
manufacture and supply electronics components and equipment. BEL, with a noteworthy
history of pioneering achievements, has met the requirement of state-of-art professional
electronic equipment for Defence, broadcasting, civil Defence and telecommunications as
well as the component requirement of entertainment and medical X-ray industry. Over
the years, BEL has grown to a multi-product, multi-unit, and technology driven company
with track record of a profit earning PSU.
The company has a unique position in India of having dealt with all the generations of
electronic component and equipment. Having started with a HF receiver in collaboration
with T-CSF of France, the company's equipment designs have had a long voyage through
the hybrid, solid state discrete component to the state of art integrated circuit technology.
In the component arena also, the company established its own electron valve
manufacturing facility. It moved on to semiconductors with the manufacture of
germanium and silicon devices and then to the manufacture of Integrated circuits. To
keep in pace with the component and equipment technology, its manufacturing and
product assurance facilities have also undergone sea change. The design groups have
CADDs facility, the manufacturing has CNC machines and a Mass Manufacture Facility,
and Quality Control (QC) checks are preformed with multi-dimensional profile
measurement machines, Automatic testing machines, environmental labs to check
extreme weather and other operational conditions. All these facilities have been
established to meet the stringent requirements of MIL grade systems.Today BEL's
infrastructure is spread over nine locations with 29 production divisions having ISO-
9001/9002 accreditation. Product mix of the company is spread over the entire Electro-
magnetic (EM) spectrum ranging from tiny audio frequency semiconductor to huge radar
systems and X-ray tubes on the upper edge of the spectrum. Its manufacturing units have
special focus towards the product ranges like Defence Communication, Radar's, Optical

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& Opto-electronics, Telecommunications, Sound and Vision Broadcasting, Electronic
Components, etc.
Besides manufacturing and supply of a wide variety of products, BEL offers a variety of
services like Telecom and Radar Systems Consultancy, Contract Manufacturing,
Calibration of Test & Measuring Instruments, etc. At the moment, the company is
installing MSSR radar at important airports under the modernization of airports plan of
National Airport Authority (NAA).
BEL has nurtured and built a strong in-house R&D base by absorbing technologies from
more than 50 leading companies worldwide and DRDO Labs for a wide range of
products. A team of more than 800 engineers is working in R&D. Each unit has its own
R&D Division to bring out new products to the production lines. Central Research
Laboratory (CRL) at Bangalore and Ghaziabad works as independent agency to
undertake contemporary design work on state-of-art and futuristic technologies. About
70% of BEL's products are of in-house design.
BEL was among the first Indian companies to manufacture computer parts and
peripherals under arrangement with International Computers India Limited (ICIL) in
1970s. BEL assembled a limited number of 1901 systems under the arrangement with
ICIL. However, following Government's decision to restrict the computer manufacture to
ECIL, BEL could not progress in its computer manufacturing plans. As many of its
equipment were microprocessor based, the company continued to develop computers
based application, both hardware and software. Most of its software requirements are in
real time. EMCCA, software intensive naval ships control and command system is
probably one of the first projects of its nature in India and Asia.
BEL has won a number of national and international awards for Import Substitution,
Productivity, Quality, Safety Standardization etc. BEL was ranked no.1 in the field of
Electronics and 46th
overall among the top 1000 private and public sector undertakings in
India by the Business Standard in its special supplement "The BS 1000 (1997-98)". BEL
was listed 3rd
among the Mini Ratanas (category II) by the Government of India, 49th
among Asia's top 100 Electronic Companies by the Electronic Business Asia and within
the top 100 worldwide Defence Companies by the Defence News, USA.

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1.2 Manufacturing Units
Bangalore (Karnataka)
BEL started its production activities in Bangalore in 1954 with 400W high
frequency (HF) transmitter and communication receiver for the Army. Since then, the
Bangalore Complex has grown to specialize in communication and Radar/Sonar Systems
for the Army, Navy and Air Force. BEL's in-house R&D and successful tie-ups with
foreign Defence companies and Indian Defence Laboratories has seen the development
and production of over 300 products in Bangalore alone. The Unit has now diversified
into manufacturing of electronic products for the civilian customers such as D.O.T.,
V.S.N.L., A.I.R. and Doordarshan, Meteorological Dept., I.S.R.O., Police, Civil
Aviation, and Railways. As an aid to Electorate, the unit has developed Electronic Voting
Machines that are produced at its Mass Manufacturing Facility (MMF).
Ghaziabad (Uttar Pradesh)
The second largest Unit at Ghaziabad was set up in 1974 to manufacture special
types of radar for the Air Defence Ground Environment Systems (Plan ADGES). The
Unit provides Communication Systems to the Defence Forces and Microwave
Communication Links to the various departments of the State and Central Govt. and other
users. The Unit's product range included Static and Mobile Radar, Tropo scatter
equipment, professional grade Antennae and Microwave components.
Pune (Maharashtra)
This Unit was started in 1979 to manufacture Image Converter Tubes.
Subsequently, Magnesium Manganese-dioxide Batteries, Lithium Sulphur Batteries and
X-ray Tubes/Cables were added to the product range. At the present the Unit
manufactures Laser Sub-unit for tank fire control systems and Laser Range Finders for
the Defence services.
Machilipatnam (Andhra Pradesh)
The Andhra Scientific Co. at Machilipatnam, manufacturing optics/Opto-
electronic equipment was integrated with BEL in 1983. The product line includes Passive
Night Vision Equipment, Binoculars, Binoculars and Goggles, Periscopes, Gun Sights,

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Surgical Microscope and Optical Sights and Mussle Reference Systems for tank fire
control systems. The Unit has successfully diversified to making the Surgical Microscope
with zoom facilities.
Chennai (Tamil Nadu)
In 1985, BEL established another Unit at Chennai to facilitate manufacture of
Gun Control Equipment required for the integration and installation in the Vijayanta
tanks. The Unit is now manufacturing Stabilizer Systems for T-72 tanks, Infantry Combat
Vehicles BMP-II; Commander's Panoramic Sights & Tank Laser Sights are among
others.
Kotdwar (Uttarakhand)
In 1986, BEL started a Unit at Kotdwara to manufacture Telecommunication
Equipment for both Defence and civilian
Customers Focus is being given on the requirement of the Department of
Telecommunications to manufacture Transmission and Switching Equipment.
Taloja (Maharashtra)
For the manufacture of B/W TV Glass bulbs, this plant was established in
collaboration with coming, France in 1986. The Unit is now fully mobilized to
manufacture 20" glass bulbs indigenously.
Hyderabad (Andhra Pradesh)
To coordinate with the major Defence R&D Laboratories located in Hyderabad,
DLRL, DRDL and DMRL, BEL established a unit at Hyderabad in 1986. Force
Multiplier Systems are manufactured here for the Defence services.
1.3 Joint Ventures
BE-Delft Electronics Limited
BE-Delft Electronics Limited, Pune, the first joint venture of the company with
Delft Instruments, Holland and UTI was established in the year 1990 for conducting
research, development and manufacture of Image Intensifier Tubes and associated high

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voltage power supplies for use in military, security and commercial systems. Its products
include night vision goggles and binoculars, night vision weapon sights and low light
level input applications.
GE BE Private Limited
GE BE Private Limited, Bangalore, a JV with General Electric Medical Systems,
USA has been established in 1997-98 for manufacture of High End Rotating Anode
Medical Diagnostic X-ray tube called CT MAX, which is used in CT Scanners. The joint
venture unit will also establish a reloading facility for X-ray tubes and will also market
the conventional X-ray tubes made at Pune Unit of BEL. South East Asia markets are
addressed by this joint venture.
BEL- Multitone Private Limited
A joint venture between Bharat Electronics and Multitone Electronics Plc, UK has
also been established in Bangalore in 1997-98 to manufacture state-of-art Mobile
Communication for the workplace. Multitone invented paging in 1956 when it developed
the world's first system to serve the "life or death" environment of St. Thomas Hospital,
London. With the strength of Bharat Electronics in the Radio Communications field and
the technology of Multitone, in the field of Radio Paging, the joint venture company is in
a position to offer tailor made solution to the Mobile Communication needs at workplace
in various market segments.
1.4 Financial Performance
BEL has a unique history of profit making Public Sector Enterprise right from its
inception. There have been events of decrease in turnover and profit after Tax due to
reasons beyond reasonable control of the company. But the company's strength lies in its
capability to combat the threats, for example US Embargo on exports to BEL.
BEL hopes to generate 25 per cent increase in turnover with a 15 per cent rise in
net profit in the current fiscal year over the previous. Corrective measures against western
sanctions have been undertaken, which are likely to translate into higher turnover and
profitability. The company is putting all efforts to minimize the effect of the restrictions

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by early establishments of alternative arrangements. The Defence Research Laboratories
and Academic Institutions are also being persuaded with for indigenization of certain
special category of devices and components. The company is also opening an office in
Singapore to procure components from Asian markets. Thus in the long run the
restrictions will prove as blessings resulting in self-dependence and better profit margins.
1.5 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.

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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, and 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.
2 RADAR:-
Fig. No.:- 1 Radar

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PROJECT: AN OVERVIEW
2.1 RADAR AND ITS COMPOSITE ENVIRONMENT
2.1.1 INNTTRROODDUUCCTTIIOONN
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 theecho 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.

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Fig.No.:2 Radar and its composit environment
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.
2.1.2 APPLICATION OF RADAR:-
Radar has been employed on the ground, in air, on the sea and in space. Some important
areas of applications are :Air traffic control ( ATC ) A ir craft navigation Ship safety
Space Remote sensing Military WORKING OF A SIMPLE RADAR A simple RADAR
system, as found on many merchant ships, has three main parts.

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These are:-
1. Antenna unit or the scanner.
2. the transmitter/receiver or transceiver and the
3. visual display unit.
The antenna is about 2 or 3 meters wide and focuses pulses of very high frequency radio
energy into a narrow vertical beam. The frequency of the radio waves is usually about
10,000 MHz. the antenna is rotated at the speed of 10 to 25 revolutions per minute so that
the radar beam sweeps through 300 degrees all around the ship out to a range of about 90
kilometers. In all RADARS it is vital that the transmitting and receiving in the transceiver
are in close harmony. Everything depends on accurate measurement of the time which
passes between the transmission of the pulse and the return of the ECHO about 1,000
pulses per second are transmitted. Though it is varied to suit requirements. Short pulses
are best for short-range work, longer pulses are better for long range. An important part
of the transceiver is the modulator circuit. This keys the transmitter so that it can
oscillate, or pulses, for exactly the right length of time. The pulses so generated are video
pulses. These pulses are short range pulses and hence cannot serve out purpose of long-
distance communication. In order to modify these pulses into radio frequency pulses or
RF pulses, we need to generate power. The transmitted power is generated in a device
called ‘magnetron’, which can handle these very short pulses and very high oscillations.
Between each pulse, the transmitter is switched off and isolated. The weak echoes from
the target are picked up by the antenna and fed into the receiver. To avoid overlapping of
these echoes with the next transmitted pulse, another device called duplexer is used.
Thus, by means of a duplexer, undisturbed, two-way communication is established. The
RF echoes emerging from the duplexer are now fed into the mixer where they are mixed
with pulses of RF energy. These pulses are generated by means of a local oscillator. Once
the two are mixed, a signal is produced in the output witch is of intermediate frequency
range or IF range. The IF signals is received by a receiver where it is demodulated to
video frequency range, amplified, and then passed to the display unit. The display unit
usually carried all the controls necessary for the operation of the whole radar. It has a
cathode ray tube, which consist of an electron gun in its neck. The gun shoots a beam of
electron at a phosphorescent screen at the far end. The phosphorescent screen glows

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when hit by the electrons and, the resulting spot of light can be seen through a glass
surface. The screen is circular and is calibrated in degrees around its edge. The electron
beam travels out from the center to the edge. This random motion of the electron beam,
known as the trace, is matched with the rotation of the antenna. So, when the trace is at
zero degrees on the tube calibration, the antenna is pointing dead ahead. The beginning of
each trace corresponds exactly which the moment at which the radar energy is
transmitted. When an echo is received it brightens up the trace for a moment. This is a
blip, and its distance from the center of the tube corresponds exactly with the time taken
for the radar pulse to travel to the target and return. So that blip on the screen gives the
range and bearing of the target. As the trace rotates, a complete picture is built up from
the coating of the tube. This type of display is called a PPI (plane position indicator) and
is the most common form of presenting radar information.
2.1.3 TYPES OF RADAR:-
Based on its functions, RADAR may be classified as:
1. PRIMARY RADAR AND
2. SECONDARY RADAR
A PRIMARY RADAR locates an object by transmitting a signal and detecting the
reflected echo.
A SECONDARY RADAR SYSTEM is similar in operation to primary radar except that
the return signal is radiated from a transmitter on board the target rather than by
reflection. In other words, secondary radar operates with a co-operative ACTIVE
TARGET while the primary radar operates with a PASSIVE TARGET. But in cases such
as controlling of air traffic, the controller must be able to identify the air craft and know
whether it is of a friend or a foe. It is also desired to know the height of the aircraft, so
that on the same source but flying at different levels can be kept apart. To give the
controller this information, a second radar called a ‘secondary surveillance radar’ (SSR)
is used. This works differently and needs the help of the target aircraft. It senses out the

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sequence of pulses to an electronic black box, called an transponder fitted on the aircraft.
The basic operation of a secondary radar is as follows:
SECONDARY RADAR SYSTEM The secondary radar system consists of an
INTERROGATOR and a TRANSPONDER. The interrogator transmitter in the ground
station interrogates transponder equipped aircraft, providing a two way data link to
separate transmit and receive frequencies. The transponder, on board the aircraft, on
receipt of a chain of pulses from the ground interrogator, automatically transmits a reply.
The reply, coded for purposes of Identification is received back at the ground interrogator
where it is decoded and displayed on a radar type presentation. The secondary radar gives
the aircraft identity code and height data derived from a pressure capsule in the aircraft.
In the Secondary Surveillance Radar (SSR), by providing the interrogation pulses above
the minimum triggering level, the transponder makes a powerful reply. This enables the
interrogator transmitters to be of lower power and the ground equipment simpler.
2.2 CENTRAL ACQUISITION RADAR
2.2.1 Introduction
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).

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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.
2.2.2 Salient features of Radar:-
Salient features Radar are:
1. 3D Surveillance Radar
2. S-BAND
3. Capable of Track While Scan (TWS) of airborne Targets upto 150 Kms
4. Coherent TWT based Transmitter

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5. 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.
This designed Radar has the following subsystems:
1. Multi-beam Antenna system
2. Transmitter
3. Receiver
4. Signal Processor
5. Radar Console
6. Data centre
7. Mobile Power Source
8. 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 super heterodyne receiver. The IF Output is given as final
output of the Low Power Microwave Subsystem to be further processed in the signal
processor.

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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 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.
2.2.3 IFF SYSTEM:-
BASIC PRINCIPLE (THE IFF UNIT) GENERAL The identification of Friend and Foe
(IFF) is basically a radar beacon system employed for the purposes of general
identification of military targets. The beacon system when used for the control of civil air
traffic is called as secondary surveillance radar (SSR). Primary IFF ANTENNA RF
SWITCH UNIT TRANSMITTER RECEIVER MK X DECODER MODE S DRAWER
radar locates an object by transmitting a signal and detecting the reflected echo. A
secondary radar system is similar in ration to primary radar except that the return signal is
radiated from a transmitter on board the target rather than by reflection, i.e. it operates
with a co-operative ‘active’ target while the primary radar operates with ‘passive’ target.
Secondary radar system consists of an interrogator and a transponder. The interrogator

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transmitter in the ground station interrogates transponder equipped aircraft, providing a
two way data link on separate transmitting and receiving frequencies. The transponder,
on board the aircraft, on receipt of a chain of pulses from the ground interrogator,
automatically transmits a reply, coded for purposes of identification, is received back at
the ground interrogator where it is decoded and displayed on a radar type presentation.
PURPOSE The IDENTIFICATION FRIEND AND FOE (IFF) is basically a Radar
Beacon System employed for the purpose of general identification of Military targets.
The Beacon System when used for the control of civil air traffic is called as secondary
surveillance Radar (SSR). The Beacon System is designated in general as Secondary
Radar and the normal radar as Primary Radar for distinguishing.
3 TRANSMITTER:-
3.1 INTRODUCTION:-
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.

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Fig. No.:- 3 Input Output diagram of Transmitter
The transmitter is designed to operate in the following modes defined as adequate
controlled states
3.2 MECHANICAL DESCRIPTION
Three rack configuration of Transmitter describes complete functionality of
Transmitter
1. Control Rack
 Monitoring panel
 Control panel
 Synoptic panel
 CPC
 Inverter
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
PRETRG
GRID PULSE
RF out
ROHINI
TRANSMITTER
RF input
System status
RF PULSE

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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
3.3 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.

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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.

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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.
Fig. No. :- 4 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.
RF DRIVER TWT
FIL., GRID, CATHODE,
COLLECTOR SUPPLY
COUPLER
FWD AND
RFLECTED
PWR MONITOR
LIQUID
COOLING
TO
ANTENNA
SSPA
W/G
SWITCH

21. 21
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

22. 22
Fig. No.:- 5 CPC block diagram
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
 COLLECTOR PROTECTION CARD
 COLLECTOR IGBT DRIVER CARD
 SOFT START CARD
TO RADAR
CONTROLLER
C
O
M
P
A
R
A
T
O
R
C
A
R
D
S
EHT VOL
SAMPLES
RF PARAMETERS
OPTICAL
LINKS&
F/V CARD
GRID VOL
SAMPLES
FIL
VOL & I
SAMPLES
O
P
T
O
I
S
O
L
A
T
O
R
C
A
R
D
SSPA
CTRL
CARD
COOLING
CONDITIONS
TIMING
CARD
RADAR
TIMINGS
SWITCH ON
COMMANDS
TO SOLID
STATE RELAYS
FOR HV, MAINS ON
STATUS STATUS
FRONT
PANEL
WITH
SWITCHES,
LED
& LCD
DISPLAY
LCD
INTERFACE
SWITCH ON
COMMANDS
HV POWER
SUPPLIES
EHT PROBES
CROW BAR
TWT
LIQUID
COOLING
UNIT
FLOATING
DECK
MODULATOR
AT - 45KV
POWER
DISTRIBUTION
3Ø 50Hz
400V AC IN
RF DRIVER
&
DIR COUPLERS
EHT CURR
SAMPLES
BEAM CURR,
COLL CURR
CATH CURR
INPUT
POWER
STATUS
CROW BAR SIGNAL
GRID
PULS
E
MICRO
-
CONT
ROLLER
CARD

23. 23
 TEMPERATURE SENSOR CARD
 ZENER CARD (For Cathode and Collector)
 CURRENT SENSOR CARD (For Cathode and Collector)
 CURRENT SENSOR (PEAK) CARD (For Cathode and Coll.)
3.4 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
3.5 FDM (Floating Deck Modulator)
Further in FDM there seven functional cards, which are as follows:
• 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

24. 24
Fig. No.:- 6 FDM
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
3.6 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:
Isol
atio
n
tran
sfor
mer
230V- ph-ph
50Hz
FDM
FIL
GRID
CATHODE
Fil Voltage
Fil Current
Grid Positive
Grid negative
To CPC
Optical links
To TWT
Grid Pulse
From CPC
Optical link

25. 25
(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
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
3.7 Traveling Wave Tube (TWT)
TWT is available in three different constructs, these are listed here:

26. 26
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.

27. 27
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.
Fig. No.:- 7 TWT Power Supply Connection Siagram
-600
+800
RF IN RF OUT
LIQUID COOLING
-45kV,5kW
33kV,18kW
3kV,ION PUMP
-10V,10A
TWT POWER SUPPLIES CONNECTION DIAGRAM

28. 28
3.8 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.
Fig. No. 8:- 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

29. 29
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 10C as compared to the inlet
coolant.
4. CONCLUSION

30. 30
In this training mainly involves industrial and complete knowledge about designing,
assembling and manufacturing process of various equipments manufactured by an
industry
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
IFF SYSTEM BASIC PRINCIPLE (THE IFF UNIT) GENERAL The identification of
Friend and Foe (IFF) is basically a radar beacon system employed for the purposes of
general identification of military targets. The beacon system when used for the control of
civil air traffic is called as secondary surveillance radar (SSR). Primary IFF ANTENNA
RF SWITCH UNIT TRANSMITTER RECEIVER MK X DECODER MODE S
DRAWER radar locates an object by transmitting a signal and detecting the reflected
echo
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.
5. REFERENCE

31. 31
 IEEE Journals & Magazines
 http://en.wikipedia.org/wiki/Radar_Transmitter
 http://www.radarmagazineindia.com