Multi-Target Vital Sign Monitoring in the Same Beam Using A FMCW Radar Based on Tags

A respiration monitoring technique of multiple subjects by frequency-modulated continuous-wave(FMCW) radar based on tags is proposed, which achieve the detection of multi-target vital sign and location even when targets are very close to each other. The system uses tags to reflect signals of different frequency bands to distinguish different targets, which is equivalent to decomposing the received FMCW signal into multiple small segments of chirp signals. Then extracting the beat frequency signal corresponding to the time period of each cycle to separate signals from multiple targets. The tags in this paper are the planar passive retro-reflective arrays with polarization rotation property, which suppresses clutter and makes it possible to detect vital signs in highly cluttered environments.