Measurement of wind velocity at different heights at the launch site is an essential prerequisite for any major satellite launch vehicle program. A wind profiler is a pulsed Doppler radar operating in the VHF band. The wind profiler is designed based on the active aperture design. In the active aperture system each antenna of the array is connected to a Transmit receive module (TRM) located very close to the antenna. The basic building blocks of the TRM are transmitter, duplexer, phase shifter, LNA, timing and signal generator. The entire array consists of as many number of TR modules as antennae. Thus wind profiler uses 576 nos. of Yagi antenna and equal nos. of TR modules. The TR modules are distributed in the antenna array of diameter of app. 120 m and the array starts from approximately 30 m from the control room. One antenna beam is pointed toward zenith and the other two or four beams are pointed about 15-20 degrees off zenith with orthogonal azimuths (three beam systems) or orthogonal and opposite azimuths (five beam systems). The beam steering is done electronically by controlling the phase of each of the TR module such that the phase gradient between successive modules is equal and corresponds to the desired steering angle. The phase data used for beam steering includes the individual phase differences of the channels. The main objective of the Wind Profiler Beam Steering System is to send the command signals from the instrumentation room to each of the TR modules and to receive back the status signals and is implemented using Fiber Optic Network, since Optical fiber is immune to electromagnetic interference, has high reliability, gives increased bandwidth, saves space and reduces weight. The designed network would cater for 24/7 continuous operations that mean high stability and reliability, automation - without manual interruption.
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