Microprocessor-controlled automatic clutter-cancellation circuits for microwave systems to sense physiological movements remotely through the rubble

A novel microprocessor-controlled automatic clutter-cancellation subsystem, consisting of a programmable microwave attenuator and a programmable microwave phase shifter controlled by a microprocessor-based control unit, has been developed for a microwave life-detection system (L-band 2 GHz or X-band 10 GHz) which can remotely sense breathing and heartbeat movements of living subjects. This automatic clutter-cancellation subsystem is a drastic improvement over the very slow process of adjusting clutter-cancellation manually in the old microwave system; this is very important for some potential applications, which include locating earthquake- or avalanche-trapped victims through rubble. A series of experiments have been conducted to demonstrate the applicability of this microwave life-detection system. The 2-GHz system performs well for remotely detecting human breathing and heartbeat signals through a pile of rubble of up to about 3 ft thick. The automatic clutter canceler may also have a potential application in some CW (continuous wave) radars.