Noncontact Multi-Target Vital Sign Detection using Self-Injection-Locked Radar Sensor based on Metamaterial Leaky Wave Antenna

This paper presents a new kind of noncontact vital sign detection architecture using self-injection locked (SIL) radar sensor integrated with a metamaterial (MTM) leaky wave antenna (LWA), which can detect vital sign signals of multiple people at different positions simultaneously. A one-dimensional (1-D) MTM LWA is designed to scan from - 50 degrees to +30 degrees as the frequency increases from 1.85-2.75 GHz. For the proof of concept, two frequencies, 2.24 GHz and 2.48 GHz are chosen for vital sign detection with two targets at two different positions. A microwave differentiator is then designed to perform frequency demodulation of the proposed MTM SIL radar. By using the differentiator, the output signal of SIL radar is converted from 2.24-2.48 GHz to radio-frequency (RF) signal with amplitude variance. Experimental verification for sensing both heartbeat and respiration rates from two people at different positions was carried out to demonstrate the validity of the proposed MTM SIL radar sensing architecture.