Radar target discriminator using target velocity - uses low-pass Doppler filter followed by band-pass filter

摘要

This technique in coherent pulse radar achieves the sepn. of approaching targets from those which are receding, through a single signal-handling channel. The echo signal at frequency Fi beats with a reference wave at a shifted frequency Fi-Fc so that the power spectrum of the resulting signal detected is non-symmetrical around the zero frequency. The shift frequency Fc is equal to -FR/4+nFR if approaching targets are selected, and to FR/4+nFR for receding targets, n being an arbitrary integer and FR the pulse rate. The high frequencies are eliminated by low-pass Doppler filter in the band (0, FR/4 - Fmin), followed by a pass band filter (Fr - Fmin, FR+ F min) centered on FR/4. Fmin is a suitably low frequency to eliminate stationary or low speed obstacles.