SIX-WEEKS INDUSTRIAL TRAINING (JUNE-JULY2012) AT BHARAT ELECTRONICS LIMITED (BEL) GHAZIABAD ON “RADAR TRANSMITTER” SUBMITTED BY H I T E S H M I T TA L 101005021
CONTENTS Bharat Electronics Limited –An Overview Rotation Introduction to RADAR Its block diagram Transmitter Its mechanical description Its general description
BEL -An Overview It was founded in 1954. Founded as a public Sector Enterprise under the administrative control of Ministry of Defence as the fountainhead to supply and manufacture electronics components and equipments. Today BEL’s infrastructure is spread over nine locations with 29 production divisions having ISO 9001/9002 accredition.
BEL -An Overview CORPORATE MOTTO-“Quality,Technology and Innovation.”• CORPORATE MISSION-• To be the market leader in Defence electronics and in other chosen fields and products.
BEL -An Overview CORPORATE OBJECTIVES- To become a customer driven company. To achieve growth in operation commensurate with the growth of professional electronic industry in the country. To generate internal resources for financing the investments. In order to meet the nation’s strategic needs,to strive for self reliance by indigenization of materials and components.
BEL-Ghaziabad Plant Over the years the unit has successfully manufactured a wide variety of equipment needed for defence and civil use. It enjoys a unique status as manufacture of IFF systems needed to match a variety of primary radars. The operations at BEL Ghaziabad are headed by General manager with Additional/Deputy General Manager heading various divisions.
PROJECT1)ROTATION(brief sight to various departments)2)RADAR TRANSMITTER
ROTATIONTEST EQUIPMENT SUPPORT (TES)• Develops technical supports to other departments. This includes :- Handling requests for equipments from other departments. Storage of rejected equipments. Approval of equipments to be purchased.• Repair of equipment in case of failure.• Maintenance of equipments.
ROTATIONAUTOMATION TEST EQUIPMENT (ATP)1) Component testing-gives faults of various discrete components of a PCB.2) Integrated Circuit-tester tests various IC’s.3) Functional testing-compares output to decide whether the function is being performed to the desired accuracy level.
ROTATIONPCB FABRICATION• It is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non conductive substrate.
ROTATIONWORKS ASSEMBLY• Its main function to assemble various products ,components and instruments in particular procedure.
ROTATIONQUALITY CONTROL WORKS• Its main function to ensure the quality of the product.• It inspects all items manufactured in the factory After mistake is detected –i. Observation is made.ii. Object code is given.iii. Division code is giveniv. Change code is preparedv. Recommended action is taken
RADAR RADAR-Radio detection and Ranging.FUNCTIONS Measurement of target angles as its primary function. Measurement of Doppler velocity and discrimination of a desired target from background noise and clutter is a prerequisite to detection and measurement.
Sign conventions The Doppler frequency is negative (lower frequency, red shift) for objects receding from the radar The Doppler frequency is positive (higher frequency, blue shift) for objects approaching the radarThese “color” shift conventions are typically alsoused on radar displays of Doppler velocity Red: Receding from radar Blue: Toward radar
RADAR Operates in S –band. Capable of track while scan (TWS) mode of airborne targets upto 130 km. It employs multibeam coverage to in the receiving mode to provide for necessary discrimination. The antenna is mechanically rotated in azimuth to provide 360 degree coverage. It is designed to play the role of medium range surveillance.
TRANSMITERSALIENT FEATURES- It is of coherent MOPA type. It operates in S –band using TWT as a final amplifier. It is used to amplify low RF power 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.
3-phase,400V,50Hz 3-channel liq cooling in 3-channel liq cooling out ROHINI RF out Air cooling in Air cooling out TRANSMITTER SP signals System status BIT0 BIT1 RF PULSE Dry air PRETRGGRID PULSE RF input Input output diagram of Transmitter
OPERATION MODES OF TRANSMITTERa) OFF : All subsystems switched OFFb) Cold Standby : Only LVPSU’s, TWT heater and Grid biases are switched ON. No High Voltage applied.c) Hot Stand By : High Voltages applied, No RF and No grid Pulsing.d) Transmission : RF power delivered to Antenna / matched Load.i) Full Power mode : Full RF Power delivered to the Antennaii) Reduced Power mode : The transmitter is operated at 1/10 of its full power based on the selection by the user.iii) Fail safe mode : A low power at required duty delivered to antenna through solid state Power amplifier when liquid cooling fails.Modes are selected by the operator.
CONTROL RACK Control Rack provides the protection controls and indications. As mentioned before, this rack is divided in five sections according to their functions. 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. 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.
CONTROL RACK 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. 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. 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.
2.)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.
MICROWAVE RACK The microwave unit consists of the following functional assemblies:1. Low power amplifier [RF drive unit]2. High power TWT amplifier3. RF Plumbing, Wave-guide switch & dummy load4. Solid state power amplifier (2 kW) for low power transmission mode5. TWT ion pump supply6. Resistive TWT anode divider7. Microwave power measurement circuits8. Air cooling components
MICROWAVE RACKLow 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.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.
MICROWAVE RACK 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
MICROWAVE RACK A traveling-wave tube (TWT) is a specialised vacuum tube that is used in electronics to amplify radio frequency (RF) signals to high power, usually as part of an electronic assembly known as a traveling-wave tube amplifier (TWTA). The bandwidth of a broadband TWT can be as high as one octave, although tuned (narrowband) versions exist, and operating frequencies range from 300 MHz to 50 GHz. The voltage gain of the tube is on the order of 70 decibels.
MICROWAVE RACK Ferrite circulator Ferrite circulator is used to protect the microwave tube against failure / damage due to reflected power in case of excess VSWR at Antenna input port. The Four port Ferrite circulator type is used as an isolator. Dual Directional Coupler High Power Dual Directional Coupler (DDC) is used for measuring the Transmit Power and reflected power. If reflected power exceeds the specified limit of 2:1 VSWR, video signal is generated to cut-off the RF drive through control and protection unit. High power dummy load• High power dummy load is used to test the transmitter with out connecting the antenna during stand alone 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.
GENERAL DESCRIPTION SSPA W/G RF DRIVER TWT COUPLER SWITCH TO ANTENNA FWD AND RFLECTED PWR MONITOR LIQUID COOLING FIL., GRID, CATHODE, COLLECTOR SUPPLY
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 to few W which is necessary to drive the TWT amplifier. 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.
GENERAL DESCRIPTION The RF Driver output is given to the input of TWT, which amplifies the pulsed RF signal from few Watts to a level of many kW at the TWT output. High power RF plumbing components are connected at the output of TWT. The TWT output is given to an arc detector followed by a ferrite circulator. The Ferrite circulator is used to protect the microwave tube against failure /damage due to reflected power in case of excessive VSWR at Antenna input port. The output of Ferrite Circulator is given to High Power Dual Directional Coupler (DDC), which is used for measuring the transmitted and reflected power. If reflected power exceeds the specified limit of VSWR, a video signal is generated to cut off the RF drive through control and protection circuit.
GENERAL DESCRIPTION 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.
GENERAL DESCRIPTION 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.
GENERAL DESCRIPTION Cooling Unit is used to cool the various components of the transmitter. The TWT, High Power Ferrite Isolator, high Voltage Power supplies and RF dummy load are cooled with de-ionized water and ethylene glycol mixture. Forced air-cooling is employed to cool other components using ambient air which is filtered to ensure dust free air. The Dry Air unit ensures that the wave guide is at all times pressurized and dry.