Range-forming for FMCW Radar Vital Sign Monitoring

In the radar vital sign monitoring, compared with continuous wave radar (CW), frequency modulated radar (such as FMCW and UWB) can effectively distinguish the target from the clutter in terms of distance. Through the range Fourier transform, the heartbeat and breathing signals of the target can be extracted from different distance intervals,thereby improving the monitoring accuracy. The range FFT widely used in the literature has some defects: first, the breathing amplitude of the subject may cross the boundary of the range bin and affect the integrity of the signal. Secondly, the breathing movement of the subject will cause amplitude modulation of the physiological signal, which is not conducive to the waveform recovery of the vital sign signal. Third, in muti-subject scenario, the sidelobe leakage of the energy of the close targets will affect the extraction of the signal of the farther target. Based on the above reasons, we proposed an algorithm architecture based on range-forming. For the above three situations, the algorithm performance was evaluated in simulation and experiment. Simulation and experimental show that when the target across the range bin, the proposed method can effectively suppress amplitude modulation, thereby accurately restoring phase information and accurately tracking heart beat intervals. And in the dual-target scenario, the proposed method is also better than the traditional range FFT method.