INTRODUCTION TO Central Acquisition

Radar (3D-CAR) – ROHINI / REVATHI

CAR would be a stand-alone all weather 3D surveillance radar. This CAR is

known as ROHINI in army and REVATHI in navy. The radar operates in S-band

( 2 – 4 GHz) 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 30 and a height ceiling of 15 Kms. The antenna is mechanically

rotated in azimuth to provide a 360 coverage. To get an optimum detection

performance against various classes of targets, different Antenna Rotation

Rate [ARR] of 7.5 & 15 RPM modes are planned to be implemented and these

are 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. It is

also supported by a tracker ball/mouse. Rohini is an offshoot of the fully and

successfully developed and demonstrated radar called as 3D Central

Acquisition Radar (3D-CAR).

Rohini is designed to play the role of medium range surveillance radar

mounted on a mobile platform. The radar carries out detection, tracking and

interception of targets with an RCS of 2m2 upto 130 Kms in range. The

antenna is rotated mechanically in azimuth to provide for coverage of 3600.

To achieve a higher range, the radar is capable of being operated at a lower

ARR of 7.5 RPM against the normal ARR of 15 RPM.

Rohini is provided with all terrain mobility and various modes of

transportation. To achieve this goal a versatile mobile platform is developed.

This product is fitted on a TATRA class of vehicle.

CAR has the following subsystems

a) Multi-beam Antenna system

b) Transmitter

c) Receiver

d) Signal Processor

e) Radar Data Extractor

f) Radar Data Processor

g) Radar Controller

h) Radar Console

i) Electronic Equipment Cabin

j) Data centre

k) Mobile Power Source

l) IFF System

The Multibeam antenna system for Rohini is planned to be realized to have

360 Coverage in Azimuth and 30 Coverage in elevation. The antenna will

have a wide beam in transmit mode and eight simultaneous narrow beams in

receive mode to give 30 Coverage in elevation.

The requirement of Transmitter is to amplify the pulsed RF signal from 1W to

140kW while maintaining the phase noise (additive noise) to –60dBc/Hz at

100Hz away as demanded by the system.

The antenna can be manually positioned at different look angles in steps of

0.50,

covering – 2 degrees to +1 degree from normal position. In the receive mode

the eight beams cater for a height coverage of greater than 15 Kms. The IFF

antenna is placed atop the main antenna

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.

The Radar Console is a local display. 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.

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.

Data Centre also referred to as Operator’s workstation, is one of the three

vehicles forming the Rohini configuration. Data centre has to meet the

functional, operational, electrical and environmental requirements set by the

user. The high power RF, low power RF, antenna, signal and data processor

and a monitor console are all integrated into the sensor vehicle.

This can, if needed, provide autonomous radar functionality. Data Centre will

be separated from the sensor by maximum of 100 mts. The two are

connected for exchange of data and control messages.

Mobile power source is required to provide the main supply to Radar Sensor

and Data Centre for electronic and mechanical units of Radar including air

conditioning units. The total power requirement for both vehicles is approx.

60KVA.

The radar normally operates at 15 RPM to get the optimum detection

performance up to 150 Km against fighter class of aircraft. 7.5 RPM mode will

be selected for getting higher detection ranges against larger cross-section

targets [up to 200 Km]. 15 RPM mode is specifically provided, where faster

update is needed.

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

Sl.No

ITEM REVATHI ROHINI

1.Antenna Elevation coverage

Up to 50° Up to 30°

2.Antenna Weight

< 2400 kg. -

3. No. of 8+1 7+1

Beams

4.Transmitter

TWT based3.3% Duty

TWT based3.3% Duty

5.Receiver / Exciter

Digital IF/DDSDigital IF / DDS

6.Signal Processor

Software Changes are incorporated.Indigenous SHARC boards

Software Changes are incorporated.

ARRAY ANTENNA

(4x8 HORIZONTAL ARRAY SEGMENT)

SLC ANTENNA

IFF ANTENNA

LIMITER +LNA

TRANSMIT BEAMFORMER(TBF)

LIMITER(32 Nos)+ LNA(32 Nos.)

RECEIVE BEAM FORMER(RBF)

RF, IF VIDEO, ROTARY JOINT (8 Rx Channel)

LOAD(32Nos.)

7 NARROW BEAMS

CIRCULATOR(32 Nos)

COLLECTING ANDDISTRIBUTION SYSTEM(CDS)

RECEIVER UNITS(RCV)

8 BEAMS(BEAM 6 OR 7 SELECTABLE)

8 IF BEAMS(7 FOR EL, 1 FOR SLC)

1 SLC BEAM

BLOCK SCHEMATIC

TRANSMITTER OF ”3D-CAR – REVATHI/ ROHINI”

SCOPE: The transmitter of CAR is capable of delivering RF peak power of greater

than 140 KW and RF average peak power greater than 4 KW. The transmitter

uses fully indigenous technology established by LRDE for 3D CAR

programme. The transmitter is planned to be realized as production version

M/S BEL Bangalore based on transfer of technology (TOT) from LRDE.

SALIENT FEATURES OF THE REVATHI / ROHINI RADAR

MANUAL / REMOTE OPERATION SECTOR BLANKING FACILITY FOR FULL 360 DEG AZIMUTHS USE OF 1.5KW SSPA FOR FAIL SAFE MODE OF OPERATION MODULAR DESIGN APPROCH FOR EASE OF MAINTAINABILITY HVPS: IGBT BASED FULL BRIDGE RESONANT CONVERTER USING PHASE

MODULATION TECHNIQUE FDM: SOLID STATE SWITCHING CPC: MICROCONTROLLER BASED PROTECTION

CONFIGURATION OF TRANSMITTER:

CONTROL RACK– MONITORING PANEL– CONTROL PANEL– SYNOPTIC PANEL– CPC– INVERTER

• HIGH VOLTAGE RACK– FDM– COLLECTOR ASSEMBLY– CATHODE ASSEMBLY– BLOWER UNIT– HEATER UNIT

• MICROWAVE RACK-TWT-RF PLUMBING-RF DRIVE UNIT-SSPA-ION PUMP CONTROLLER

REQUIREMENTS:

The requirement is to amplify the pulsed RF signal from 1W to 140 KW while

maintaining the phase noise (additive noise) to 60 dBz/Hz at 100 Hz away as

demanded by the system. In addition, a failsafe mode of delivering 2 KW of

peak power to antennae, in case of liquid coolant as redundant measure. RTS

-400 is the TWT based transmitter capable of delivering 140 KW of peak and

4 KW of average.

-600+800RF IN

RF OUTLIQUID COOLING

-45kV,5kW33kV,18kW

3kV,ION PUMP-10V,10A

TWT POWER SUPPLIES CONNECTION DIAGRAM

TECHNICAL SPECIFICATIONS:

The Transmitter for 3D Surveillance radar “REVATHI” is a Coherent Master

Oscillator Power Amplifier (MOPA) type employing Traveling Wave Tube (TWT)

Type VTS – 5754 D2 of M/s CPI, USA as final power amplifier. The transmitter

is capable of delivering RF power of more than 140 kW (peak) and 4.0KW

(average) in t he frequency band of 3.1 to 3.5 GHz, while maintaining phase

noise performance of –60dBc/Hz at 100Hz away from carrier. M/s. BEL

Bangalore is realizing the transmitter, based on TOT from LRDE.

The input output diagram of the transmitter is shown in fig 2.2.1. The

electrical specifications of the transmitter are:

8. Duty: T on / T on + T off = 3.2 % (max).

9. RF drive power level: (It has to be passed through this power level , before

passing through TWT ) : - 5 DBM to 13 DBM.

10. Blanking (screening of particular area from where a lot of energy is

coming): Sector blanking facility for full 360 degree azimuth.

11. Protection: crow bar protection technique is used. This method involves

grounding the power by using and gate and a triode.

ENVIRONMENTALSPECIFICATIONS:

S.NO QUANTITY OPERATING NON - OPERATING

1. TEMPERATURE( centigrade)

- 20 to 55 - 30 to 70

2. HUMIDITY 95% RH at 40 degrees

95% RH at 40 degrees

3. ALTITUDE( in meters) 4160 9100

MODES OF OPERATION AND CONTROL: The transmitter is designed to operate in the following modes defined as

adequate controlled states.

OFF: all subsystems switched off.

COLD STAND BY: only LVPSU, TWT heater and grid bias are switched on. No

high voltage applied.

HOT STAND BY: high voltage applied, no RF and no grid pulsing required.

TRANSMISSION: RF power delivered to antennae / matched load.

Full power mode: full RF power delivered to antennae (120 KW peak)

Reduced power mode: The transmitter is operated at 1/ 10 of its full power

based on selection of the user.

Fail safe mode: A power of 1 KW peak at required duty is delivered to

antennae through Solid State Power Amplifier when liquid cooling fails.

TRANSMITTER CONTROL:-

Local: To control through control panel on the transmitter.

Remote Control: to control from the operator console through control

interface RS 422.

DIMENSION AND WEIGHT:

Over all size of the transmitter (excluding liquid cooling unit)

HEIGHT: 1800 mm.

WIDTH: 1800 mm

DEPTH: 800 mm.

Weight of the transmitter (including liquid cooling unit) should not exceed

1200 kg.

GENERAL COOLING REQUIREMENT:

The system is a forced liquid-to-air type, used for cooling systems of the S-

Band Transmitter. The primary coolant used for circulation through this

transmitter heat loads is Dematerialized water / Glycol to catch for operation

from -20C to 55C. The transmitter employs liquid cooling for TWT, high

power circulator RF dummy load and high voltage power supplies and forced

air-cooling for all other sub-assemblies. Independent of air-cooling, a dry air

with low dew point and dust particles should be applied for wave-guide

pressurizing and for TWT.

General design of the cooling is worked out in such a way that the

temperature rise for outlet coolant is around 10C than the inlet. The total

heat load on liquid to air cooling unit is 25kW and for forced air cooling 3 kW.

The TWT, High Power Ferrite Isolator and high voltage power supplies are

cooled with de – ionized water and ethylene glycol mixture (50: 50). Liquid

cooling distribution is realized in such a way that the liquid cooling unit will

have a minimal pressure on the connections.

Forced air – cooling is employed to other components using the ambient air

properly filtered to ensure dust – free air. A dry air with low dew point and

dust particles is applied for wave guide channel.

FUNCTION

1. The Transmitter amplifies the pulsed RF signal from 1W to 120 kW while

maintaining the phase noise (additive noise) to -60 dBc/Hz at 100 Hz away 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 of delivering 1.5 kW

of peak power to antenna, in case of failure of liquid coolant.

2 It employs a Traveling Wave Tube (TWT) Type VTS - 5754 D2 of M/s CPI, USA

as final power amplifier. Low power amplifier stage (RF Driver) amplifies

pulsed RF signal from 1 mW (0 dBm) to 3 - 4 W which is necessary to drive

the TWT amplifier.

3. The RF Driver stage uses a Pin attenuator transistor followed by power

amplifiers to amplify RF signal from 0 dBm to 37 dBm. 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.

4. The RF Driver output (approx. 3 to 4 W) is given to the input of TWT, which

amplifies the pulsed RF signal from 3 Watts to a level of 120 to 185 kW at the

TWT output. High power RF plumbing components are connected at the

output of TWT.

Collector Supply

5. 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 2:1 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. Three Phase power supply is passed through an

EMI/EMC Filter unit to reduce EMI/EMC interference. The output of filter unit is

given to Power Distribution unit to distribute power to various units of the

transmitter.

6. 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.

7. 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.

8. 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.

9. High Voltage Power Supply unit (HVPSU) is used to supply high voltage to

collector and cathode of the TWT.

10. 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 11.Power Ferrite Isolator, high Voltage Power supplies and RF

dummy load are cooled with de-ionized water and ethylene glycol mixture

(50:50). Forced air-cooling is employed to cool other components using

ambient air which is filtered to ensure dust free air.

12. The Dry Air unit ensures that the wave guide is at all times pressurized

and dry.

General Mechanical Design

The transmitter consists of three metal racks containing respectively three

functional units: Microwave Unit (MU), Power Supply Unit (PSU), and Control

Unit (CU). All racks have front doors properly gasket for protection against

EMI.

At the upper part of each unit, above the door, slip panels containing RF

input, Transmitter pulse input, control and measurement connectors, control

lamps, hour meters, CBs and high voltage meters are placed. The Transmitter

is housed in 3 separate racks.

1. Microwave Rack consists of TWT, microwave plumbing components, SSPA

and RF driver.

2. High voltage rack Consists of all high voltage components and FDM

capacitor.

3. Control Rack Consisting of Monitoring and Diagnostics circuits, Control

Circuits, Power distribution along with line filter unit and high voltage inverter

unit.

BLOCK DIAGRAM OF HIGH VOLTAGE RACK

The transmitter consists of the following racks:

HIGH VOLTAGE RACK: It consists of FDM, cathode and

collector assembly, heater and blower unit. The main function of the high

voltage rack is to provide high voltage power supply to cathode and collector

of the TWT. FDM is the most important component and it provides the

filament supply, grid bias and grid positive and negative supply to the TWT. It

also communicates with the CPC via optical links.

Cathode assembly provides the cathode supply and collector assembly

provides the collector supply to TWT. Heater unit is used for removing the

moisture within the rack. Blower unit provides cooling for cathode and

cathode assemblies.AC components probes in cathode and collector are used

to get the sample of output voltage and same is used to control the pulse

width of the inverter to achieve a regulation of .2%.

CONTROL RACK: The rack houses the inverter, control and protection

circuit, synoptic panel, control panel and monitoring panel.

MICROWAVE RACK: it consists of the low power amplifier, high power

TWT amplifier, ion pump supply, ferrite isolator, and high power dual direction

coupler and wave guide channel.. The microwave unit consists of the

following functional assemblies:

(a) Low power amplifier [RF drive unit]

(b) High power TWT amplifier

(c) RF Plumbing, Wave-guide switch & dummy load

(d) Solid state power amplifier (2 kW) for low power transmission

mode

(e) Protection, monitoring and diagnostic circuits

(f) Low voltage supply

(g) TWT ion pump supply

(h) Resistive TWT anode divider

(i) Microwave power measurement circuits

(j) Air cooling components

CONSRUCTION OF FDM (Floating Deck Modulator) ASSEMBLY:

The FDM assembly is on a space of 420 mm square with a depth of 700 mm.

the Floating Deck Modulator assembly houses FDM, carbon resistor block and

isolation transformer . the FDM assembly is covered on all sides by FRP

sheets and also floats on FRP mounts machined suitably for the purpose . The

FDM sub rack is at a distance of 390 mm from the front. The carbon resistors

are mounted on the front of the FDM rack. The isolation transformer is also

mounted in front of the carbon resistors. The voltmeters, hour meters are

fixed on to the front panel of FDM assembly.

The FDM assembly is being locally cooled by fans housed inside. The cooling

of entire sub assembly is taken care by mounting blowers at the rear end of

the compartment.

FDM consists of the following:

1. Filament supply and the timer card to generate filament supply for TWT

using fly – back converter.

2. Grid positive and grid negative supply card to generate grid bias and grid

positive supply.

3. Switch card to switch TWT between + 870 V and – 600 V.

4. LVPSU to generate all low voltage power supplies like + 15 V, + 5 V and +

24 V.

5. FDM transformer.

FUNCTIONS OF FDM:

1. Generates filament supply for TWT with surge current protection.

2. Generates grid bias and the grid positive supplies.

3. Provides switching function. (Switching of TWT grid as per pulse width and

the PRF requirement.)

4. Communication to CPC on optical link.

All the circuitry necessary to achieve the following functions is floating at the

cathode potential of – 45 V DC and needs special consideration in

engineering. All circuits are housed inside an equipotential surface.

SPECIFICATIONS OF FDM:

VOLTAGE SPECIFICATIONS:

Voltage generation:

1. Filament voltage: 8V to 11V (adjustable.)

2. Filament current: 10 A with surge current limited to 15 A.

3. Voltage regulation: 0.01%

4. Grid positive voltage: 800 to 1100(adjustable.)

5. Grid current: 20 mA (adjustable)

6. Voltage regulation: 0.01%

7. Grid negative voltage: - 600 to 1100(adjustable.)

8. Grid current: 10 mA (adjustable)

9. Voltage regulation: 0.1%

Switch specifications:1) Switch output: - 800 to 1100 pulse.

2) Pulse width: 50, 25, 4 microseconds.

3) PRF: .5, 1, 4 (KHz)

4) Pulse rise time: < 0.5 microsecs. (The time taken by pulse to rise)

5) Pulse fall time : < 0.5 microsecs. (The time taken by pulse to fall.)

6) Pulse jitter: < 10 nsec.

7) Drop on the top of pulse :< 1V for 25 microsecs.

PROTECTIONS OF FDM:

1. Pulse width / PRF PROTECTION.

2. Short circuit protection.

3. Overload protection

4. Voltage too high and too low (window) protection

5. Thermal protection.

DESCRIPTION OF VARIOUS CARDS USED IN FDM:

1) V TO F CARD: This card contains six V to F converter (AD 650), four of which are used to

convert the grid positive, grid negative, filament voltage and filament current

samples to corresponding frequencies. This consists of four optical

transmitters for converting electrical pulses into light signals, which are

transmitted to CPC (cathode protection card) by optical links and optical

receivers to convert light signals to electrical pulses.

2) FILAMENT SUPPLY AND TIMER CARD – 1

The filament supply is a - 10 V/ 10 A supply for TWT filament. It is a switched

mode power supply and topology followed is fly – back converter. The supply

operates at a frequency of 25 KHz and PWM scheme is followed for

regulation. The switching device is protected against over currents by pulse

to pulse current limiting using a current transformer and current limit

comparator of UC 1526.

The supply has electronic current limiting which limits the initial current the

TWT initial surge current to 15 A and operates in current control mode until

the filament warms up. It is also provided with hard current limiting by means

of a series limiting resistor which is bypassed by operating a relay after 5 min

from initial power on. The current control feature is available only when this

card is operated along with filament supply and timer card – 2 . the card also

generates 115 V DC / 2 A supply , which is used as input for filament and grid

fly back converter.

3) FILAMENT SUPPLY AND TIMER CARD – 2

This is responsible for the hard current limiting feature which is achieved by

inserted 1 ohm, 100W resistor in series with the filament at power on and

passing it by operating a relay after 5 minutes. The time delay of relay

operation is controlled by 555 timer circuit. The PCB also generates the

filament current samples for current control and for transmission to CPC on

optical link through V/F Card.

4) LVPSU CARD

It generates all low voltages power supplies like the + 24, + 15, - 15, + 5

V.three of these supplies (+ 15, - 15, + 5) are generated using the DC – DC

converter.

5) NEGATIVE GRID SUPPLY CARD

The grid supply is a switched mode power supply and the topology followed is

a fly - back converter. The supply operates at a frequency of 25 KHz and PWM

scheme is followed for regulation. the switching device is protected against

over currents by pulse to pulse current limiting using a current transformer

and current limiting comparator card IC 1526.The card is capable of

generating output voltage of - 550 to - 650 V DC , 10 mA.

6) POSITIVE GRID SUPPLY CARD

The grid supply is a switched mode power supply and the topology followed is

a fly - back converter. The supply operates at a frequency of 25 KHz and PWM

scheme is followed for regulation. the switching device is protected against

over currents by pulse to pulse current limiting using a current transformer

and current limiting comparator card IC 1526.The card is capable of

generating output voltage of +700 to +1000 V DC , 25 mA.

7) SWITCH CARD

It uses a fast high voltage switch of BHELKE make to switch the grid between

+ 870 V and – 600 V at required pulse width and PRF, based on input

command. The circuit configuration enables availability of continuous grid

– ve at TWT grid even if the bottom switch becomes faulty.

COLLECTOR ASSEMBLY

The collector assembly provides 33 KV dc supply required for TWT amplifier. It

consists of a collector transformer, high voltage capacitors, a high voltage

moulded diode resistor block, a two terminal spark gap, two high voltage DC

probes, a high voltage AC compensated probe and a collector EHT meter

card. Some high voltage distribution blocks are also used.

The collector transformer takes 550 volts 20 KHZ inputs from the inverter

assembly and gives the required 33 KV DC output. The high voltage

compensated probe CP1 is used to get the sample output voltage and the

same is used to control the pulse width of the inverted to achieve the

required regulation of 0.002% on pulse to pulse basis.

High voltage probe CP2 provides interlock to inverter and to CPC for proper

collector. High voltage CP3 probe gives a sample to collector EH meter card

which also takes a sample of cathode voltage to give the metering output for

cathode and collector voltage. The two terminal spark gap is for protection of

transmitter.

COLLECTOR EHT METER CARD

Collector EHT meter card is used to give the sample input to EHT meter and

display the differential voltage (collector w.r.t cathode) as EHT meter.

When +5 volts is applied at TP1, TP3 and TP4 (GND), output received at TP6

and TP7 (GND) is approximately 0 volts which is difference of TP1 and TP3

input voltage.

CATHODE ASSEMBLYThe cathode assembly provides - 45 KV DC supply required for the TWT

amplifier. It consists of a cathode transformer, a high wattage capacitor, a

high voltage diode block, resistor plate assembly, a three terminal spark gap,

two high voltage DC probes; a high voltage AC compensated probe, a

crowbar trigger unit and a droop circuit. Some high voltage distribution blocks

are also used.

The cathode transformer takes 550 volts; 20 KHz input from the inverter

assembly and give the required 45 KV DC output. The high voltage

compensated probe CP1 is used to get the sample output voltage and the

same is used to control the pulse width of the inverted to achieve the

required regulation of 0.002% on pulse to pulse basis.

High voltage probe CP2 provides interlock to inverter and to CPC for proper

collector. High voltage CP3 probe gives a sample to collector EHT meter card.

In case of fault CPC gives a control signal to the crowbar trigger unit, which

gives a 25 KHz pulse to the three terminal spark gap to switch off the high

voltage supply. The droop circuit is used for monitoring the droop voltage on the

monitoring panel, housed in control rack.

HEATER UNIT

The heater unit contains four heaters, each of 250 rating. The heater unit

gets 230 V AC supply as soon as the transmitter is switched on and this

supply is cut off automatically after ten minute. With the help of this unit,

moisture is removed before high voltage is applied.

BLOWER UNIT

The blower unit contains twelve blowers, each operating at 230 volts AC. The

unit is used for cooling of the transmitter.

MICROWAVE RACK:

It consists of low power Low Power Driver for TWT, traveling Wave Tube

(TWT), Ferrite Isolator, Dual Directional Coupler and Wave guide Channel. Low

Power amplifier stage (RF Driver) amplifies pulsed RF signal from 1mW

(0dBm) to 3-4 W, necessary to drive the TWT amplifier. Twt is the main power

amplifier used in transmitter. It amplifies the pulse RF signal from 2W to a

level of 125 to 185 KW at TWT output. Ferrite Isolator is used to protect the

microwave tube against failure / damage due to reflected power in case of

excess VSWR at Antenna input port. High Power Dual Directional Coupler

(DDC) is used for measuring the transmit power and reflected power. To

connect all components in the required form, flexible sections, E-bends, H-

bends and straight sections are used.

DESCRIPTION OF VARIOUS COMPONENTS

OF MICRO – WAVE RACK:

a) Low Power Driver for TWT (RF Driver)

Low Power amplifier stage (RF Driver) amplifies pulsed RF signal from 1mW

(0dBm) to 2 – 4 W, necessary to drive the TWT amplifier

b) High Power Microwave Stage

High Power RF stage consists of:

(a) Traveling Wave Tube (TWT)

(b) Ferrite Circulator

(c) Dual Directional Coupler (DDC)

(d) High Power dummy load

(e) Wave guide channel

(f) Wave guide switch

Traveling Wave Tube (TWT)TWT is the main power amplifier used in the transmitter. A coupled cavity

TWT type VTS – 5754 D2 is selected for this transmitter.

Diagram of TWT

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 SC3-19 is used as an isolator.

Dual Directional Coupler

High Power Dual Directional Coupler (DDC) is used for measuring the Transmit

Power and reflected power. If reflected power exceeds the specified limit of

2:1 VSWR, video signal is generated to cut-off the RF drive through control

and protection unit.

High power dummy load

High power dummy load is used to test the transmitter with out connecting

the antenna during standalone testing.

Wave-guide Channel

To connect all the components in the required form, flexible sections, E-

bends, H-bends and straight sections are used. Standard W/G sections are

being used for this purpose.

PEAK DETECTOR CARD

The function of this card is to detect the peak amplitude of the input signal

after amplifying it. The signal from crystal detector is given to the input of

this card, which is of the order of mill volts. This signal is amplified to about 7

times of the input. The peak is detected and its output is DC signal in the

order of volts.

The card has two peak detector channels.

When pulsed signal corresponding to the duty of transmitter is detected at

TP1 and TP2, AD847 OPAMP amplifies it to about 7 times. IC 139 is used as a

comparator.

Transistor Q1 is ON when output at U 2 - 1 is high. The DC output

corresponding to the peak amplitude of the input signal is measured at J 1 – 9

and GND.

The output RC time constant is adjusted such a way that the DC value holds

till the next pulse arrives. the time constant derived by R5 and C1 should

neither be too large, because in case of fault, where in the input will absent,

the output should die down within minimum time and nor should be too

small, that the output DC value droops down from the peak value at a much

higher rate, before the next pulse comes.

SIGNAL COMPILER CARD

Signal compiler card consist of two 25- pin Female Connector, six 9- Pin Male

Connector to provide one to one connection between Microwave Rack and

CPC.

Electronic Equipment Cabin (EEC)

Electronic Equipment Cabin (EEC) has the following subsystems

• Transmitter• Solid State Power Amplifier (SSPA)• Signal Data Processor (SDP)• Display Console• IFF• Master Control Unit (MCU)• Deployment Console Unit (DCU)• Dehydrator• Advance Land Navigation System (ALNS)• PC• Power Distribution Panel (PDP)• EMI Filter

Do’s & Don’ts

Radar positioning

1. Ground should be hard enough to sustain the pressure of elephant legs.

2. Ground slop should not be more than 4 degree for leveling.

3. Ideally terrain should be with zero obstruction upto 500 mtr radius. If this condition does not meet, at least area of interest should meet the requirement

4. Obstruction diagram for short range with the help of Theodolite and visibility diagram for long range to be done with the help of

map of concern location.

5. Radar should be 500 mtr away from high tension line.

PROJECTCENTRAL ACQUISITION RADAR

(CAR)

UNDER THE GUIDANCE OF: SUBMITTED BY:

TUSHAR AGARWAL

UPT NO. 634 ECE (070271111)

BEL, GHAZIABAD AKGEC, GHAZIABAD

PREFACE

This six week training program is a part of 4-year B.Tech. course. Practical industrial training mainly aims at making one aware of industrial environment, which means that one get to know the limitation, constraints and freedom under which an engineer works. One also gets an opportunity to see from close quarter that indicates management relation. This training mainly involves industrial and complete knowledge about designing, assembling and manufacturing of equipment.

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.

ACKNOWLEGEMENT

First of all I would like to express my gratitude to Mr._________________ , HR Department for arranging my training for the duration of six weeks. The training schedule prepared by them gave me an opportunity to have an insight of working methodology and procedures of BEL. I would like to thank department of HRD for the cooperation.

I offer my sincere gratitude to my guide ________________ for his continuous guidance and support. I would like to thank Mr .________________ and all the members of C.A.R radar assembly for helping me throughout my training.

My special thanks to whole staff of BEL for accepting me as a

trainee & helping me in Radar assembly. they proved themselves inspiring, helpful, productive and fruitful to me.

It will be in debt on my part if I forgot to give my thanks to all those visible and invisible hands that helped me throughout my training period.

TUSHAR AGARWAL

CERTIFICATE

This is to certify that Mr. TUSHAR AGARWAL, student of B.Tech (Electronics and Communication), AJAY KUMAR GARG ENGINEERING COLLEGE, GHAZIABAD successfully completed his six weeks training in BHARAT ELECTRONICS LIMITED, GHAZIABAD.

A project on “Central Acquisition Radar (3D-CAR)

Transmitter” was assigned to him. In this period he

worked hard and made valuable contribution in

developing the project. All his work is genuine and

original and was timely completed.