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Wednesday, 25 September 2019

Moving Target Indicator Radar Block Diagram

Moving Target Indicator Radar Block Diagram:

The radars are used to detect targets in the presence of noise. In practical cases, the radars have to deal with more receiver noise when detecting targets since there will be echos receiving from a natural environment. These echoes are known as clutter. Clutter echo’s can be orders of larger magnitude. MTI radar is a type of radar that employs the doppler shift for detecting moving objects in the presence of clutters. These type of radars can detect the location of object more efficiently compared to normal radars.

Moving Target Indicator Radar Block Diagram
The MTI radar uses a single antenna for transmission and reception. This is achieved by using a duplexer. The radar uses high stability local oscillator called stable local oscillator (STALO) generating signals with frequency fe. The other oscillator used by MTI radar is the coherent oscillator (COHO) generating reference signals of frequency fc. The frequencies fe and fc are combined inside a mixer producing the sum of the signals. This signal is amplified by a power amplifier and is transmitted through antenna. The combination of STALO and COHO is called the receiver excited portion of the MTI radar. This combination is used to ensure better stability for the operation of radar. When the amplified signal is transmitted the doppler frequency component fd is added along with the signal. The output of the mixer will be an IF Signal. The IF signal is amplified by an IF amplifier which acts as a matched filter. The phase detector following the IF amplifier is a mixer like device that combines the received signal and reference signal from the COHO so as to produce the difference between the received signal and reference signal frequencies. The output of the phase detector is the doppler frequency.

Non Coherent MTI Radar Block Diagram:

A radar that uses the clutter signals as the reference signal to extract the dopler shifted target is called as Non Coherent MTI radar. It is also known as externally coherent MTI radar.
Non Coherent MTI Radar Block Diagram
The signal to be transmitted is combined inside a mixer with the locally generated carrier signal. The output of the mixer is an IF Signal which is amplified by the IF amplifier. The amplitude detector following the IF amplifier is a non linear device which is used to compare the clutter signal and the doppler shifted signal to produce the doppler frequency as the output. This output signal is then extracted by a doppler filter to indicate the location of the target.

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