30-01-2013, 02:32 PM
PRESENTATION ON TRANSMITTER OF RADAR
[attachment=48903]
INTRODUCTION
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.
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.
Transmitter
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.
ROHINI TRANSMITTER
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.
GENERAL DESCRIPTION
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 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 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.
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.
[attachment=48903]
INTRODUCTION
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.
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.
Transmitter
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.
ROHINI TRANSMITTER
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.
GENERAL DESCRIPTION
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 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 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.
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.