Experimental 2.4 GHz CMOS RF front-ends for non-contact vital-sign sensing

A 2.4 GHz CMOS front-ends for non-contact vital-sign sensing including respiration and heartbeat is presented. The sensor using one circulator and one differential oscillator not only achieves the injection-locked function but also reduces the system complexity. Moreover, the injection-locked signals are then down-converted by a phase demodulator constituted by a lumped power divider and a mixer. Finally, the signals are bandpass filtered and amplified for subsequently performing the vital signals. Under total power consumption of 32 mW, the respiration and heartbeat information can be recognised correctly up to 1.2 m away from the subject.