Vital-sign detection Doppler radar based on phase locked self- injection oscillator

A Doppler radar based on a phase locked self-injection oscillator is presented for vital-sign detection. The phase-locked loop (PLL) stabilizes the output frequency and serves as the demodulator. The architecture has a well defined operating frequency compared to a free-running self-injection oscillator. A frequency domain model is developed to calculate the circuit parameters for desired sensitivity requirements. Experiments demonstrate successful detections of the vital signs up to 3 m.