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Wednesday, 25 September 2019

Pulsed Radar and its Comparison with CW Radar

Pulsed Radar:

It is a high power, high frequency radar which transmits pulses towards the target object. The range and resolution of radar depends on pulse repetition frequency. The radio frequency transmitted by the pulsed radar consists of series of equally spaced pulses having duration about 1μsec separated by very short intervals.

Pulsed Radar Block Diagram
The transmitter is possibly an oscillator for instance a magnetism that is pulsed by the modulator to generate repetitive train of pulses. The wave form generated by the transmitter travels through the transmission line through the antenna where it is radiated into the space. The trigger source or synchronizer coordinates the timing for range detection. It provides high power to the transmitter to transmit during the transmission period. The output tube may be an oscillator such as a magnetron or amplifier such as klystron amplifier. The pulse modulated wave travels through the duplexer where it is radiated into space. A single parabolic antenna is used for both transmission and reception. The duplexer consist of Transmitter Receiver tube (TR switch) and anti transmitter receiver tube (ATR Switch). The TR switch protects the receiver during the transmission and ATR switch helps in directing the received eco signals to the receiver. The receiver is usually superheterodyne type. The first stage of the receiver is a low noise amplifier. The mixer and LO convert the RF output from the amplifier to comparatively lower frequency level called intermediate frequency state. Thus in a mixer, the carrier frequency is reduced. The detector used is a schottky barrier diode which extracts the modulated pulse waveform from the IF amplifier output. The detector output is then amplified by an amplifier to a stage where it can be correctly displayed on an indicator directly.

Comparison between Pulsed Radar and CW Radar

Pulsed Radar
CW Radar
In this system, pulse modulated signal is used for transmission.
This system uses continuous wave modulated signals for transmission.
Duplexer is used to use common antenna for transmission and reception.
Circulator is used to separate antenna for transmission and reception.
It indicates the range of the radar
It indicates the velocity of the moving target
Higher Transmission Power
Lower Transmission Power
Complicated and Complex
Does not use Doppler shift
Uses Doppler Shift for working

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