Phase- and Self-Injection-Locked Radar for Detecting Vital Signs with Efficient Elimination of DC Offsets and Null Points

A phase- and self-injection-locked radar is presented for robust vital-sign detection. The dc offset from the clutter is eliminated by using a dual-tuning voltage-controlled oscillator without complex clutter cancellation techniques. Phase noise analysis shows that the proposed radar has the advantages of both phase-locked oscillators and self-injection-locked oscillators to achieve high power spectral signal-to-noise ratio. Path-diversity transmission is employed to eliminate null points and reduce average transmitted power. Experiments demonstrate successful detection of breathing and heartbeat from a distance of 4 m with -22 dBm (6 μW ) average transmitted power.