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Indian MST Radar: | |
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The Indian MST Radar is a highly sensitive VHF phased
array radar operating at 53 MHz with an peak power aperture product
of 3 x 1010
Wm 2
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The
phased array consists of 1024 crossed three-element Yagi antennas occupying
an area of 130m x 130m. It generates a radiation pattern with a main
beam of 3 deg , gain of 36 dB and a side lobe level of -20 dB.The main
beam can, in principle, be positioned at 82 different look angles in
NS and EW plane.
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A total transmiting power of 2.5 MW ( peak ) is provided by 32 transmitters
ranging in power from 20 kW to 120 kW, each feeding a subarray of 32
Yagis. To achieve the desired low side lobe level to the adiation pattern,
the power is tapered across the array according to a modified Taylor
distribution. The required power taper is accomplished in one principal
direction by the differential powers of the transmitters and in the
other direction by the series feed network .
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The transmitters can operate up to a duty cycle of
2.5%, limiting the total average power to about 60 kW. It is possible
to transmit both coded and uncoded pulses with PRF in the range 62.5
Hz-8 kHz.The uncoded / coded pulses can be varied in pulse width from
1 to 64 microsec.
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A phase coherent reciever with quadrature channels
, having an overall gain of 110 dB , a dynamic range of 70 dB , and
a bandwidth matched to the baud length of the coded pulse, detects the
weak back-scattered signal. The switching of the antenna array between
transmitter and receiver is accomplised by T/R switches of hybrid coupler
and PIN diode design. A frequency synthesizer using a master oscillator
with stability better than one part in 1010
( short term ) provides transmitter, carrier and modulation as well
as receiver injection signals, rendering the system phase coherent .
The quadrature outputs of the receiver are given to a pre - processor
unit consisting of two identical channels of A/D convertor ( ADC ),
decoder and coherent integrator. The ADC is of 14-bit resolution to
match the dynamic range ( 70 dB ) of the receiver.The analog signal
in each channel is sampled and converted to digital at the rate of 1
MHz.
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The decoding operation essentially involves correlating
the incoming data from the ADC with the replica of the transmitted code.
It is implemented by means of a 16-bit 64-tap correlator/transversal
filter chip (Two IMS A 100 in cascaded mode). The entire data acqusition
and signal processing is realized with digital signal processing chips.
ADSP21060 DSP processer with 14-bit ADC is used for the data aqusition
and 6 DSP processer base card is used for signal processing purpose.
The entire system works in real time and housed in a window NT based
Work station. The total computational power of DSP system is 800 MFLOPS
in its peak perfomance. The radar operates under instructions from a
PC-AT based radar controller which executes an experiment according
to the program given in the form of an experiment specification file
( ESF ).
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Specifications of Indian MST Radar | |
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Block diagram of Indian MST Radar | |