A W-band quasi-optical homodyne Doppler radar for detection of very slow-moving targets

A simple homodyne, quasi-optical W-band (99 GHz) Doppler radar utilizing free-space optics to reduce the number of expensive mm-wave components was designed, assembled, and characterized. The system exploited the low 1/f noise and high responsivity of a zero-bias Schottky diode detector. Target velocity as slow as 1.3 mm/sec was measured with a resolution of 94 mum/sec and an detection time of 16 seconds. A SNR greater than 20 dB was measured, off a target with a radar cross section of 11.3 cm² at a 1 m range and a total source power of -10 dBm, and was also detected with a target power as low as -26 dBm. From our measurements, a 1/f noise-limited maximum range was found to be 3.6 m at a total power of -10 dBm.