Research Of Coherent-on-Receive Method For Non-Coherent Radar

Pulsed Doppler Radar (PD Radar) is the most common Moving Target Indication (MTI) Radar, its local oscillator is strictly coherent with the transmitted signal. Because of the Doppler Effect, amplitudes of a moving target’s echo pulses are modulated by the Doppler-shift frequency, and echo pulses of fixed targets just have equal amplitudes. Based on this phenomenon, PD Radar could distinguish moving targets from fixed targets, and calculate their Doppler-shift frequencies and radial velocities.Pulsed magnetron Radar is non-coherent Radar. Signals transmitted from pulsed magnetrons have random initial phases and frequency deviation, so they could not be coherent with the local oscillator. Therefore, pulsed magnetron Radar is usually used for distance measurement only; it can’t complete velocity measurement or moving target detection. A new Coherent-on-Receive Processing (CORP) method designed for pulsed magnetron Radar is proposed in this paper, which aims at eliminating the effects of random initial phases and frequency deviation by digital signal processing. The method is separated into three steps. First, mix the transmitted signal with local oscillator, and do the intermediate frequency sampling, and then estimate the value of transmitted pulse’s initial phase and frequency deviation. Second, when the according echo pulse returns, it is sampled at intermediate frequency as well after it passes the mixing filter. Then phase and frequency compensation will be done using digital signal processing algorithm. Finally, Use the digital quadrature coherent detection to obtain I/Q quadrature signals, which can be used for moving target indication and velocity measurement.Coherent Radar with Solid-state transmitter is very expensive. Pulsed magnetron Radar using this coherent-on-receive processing arithmetic is able to be applied to velocity measuring occasions where don’t require much accuracy, which is very useful for cost reduction.