New direction-of-motion Doppler detector

A new phenomenon has been observed with self-oscillating mixers which permits discrimination between approaching and receding homodyne radar targets. The detected Doppler low frequency signal shows nonsinusoidal asymmetry which allows signal processing circuitry to give gated display outputs for positive or negative Doppler shift of the microwaves. The phenomenon has been observed with GaAs and InP Gunn devices, and with silicon Impatt devices, thus demonstrating its general nature. The effect has been shown with both c.w.1.2 and pulsed3 self-oscillating mixers, and confirmed at 15, 33, 66 and 75 GHz.