Vital Signal Radar With Adaptive Compensation Circuits to Effectively Eliminate DC Offsets

A new type of vital signal radar with adaptive dc compensation circuits that can automatically eliminate the dc offsets caused by clutter signals without software controlled units is presented. The theoretical analysis of the dc compensation circuits, which are connected to the outputs of a direct conversion mixer will be described. A 2.5-GHz experimental prototype was fabricated on a printed circuit board substrate to verify the proposed adaptively compensated radar. All circuits are realized by commercially available devices. Measurements show very good agreement with theoretical prediction. The radar can be used with only a single antenna connected to the proposed module and have successfully detected clearly heartbeat and respiration signals at any distance within the detectable range by incorporating phase-shifting technique.