Phase-Extraction Method With Multiple Frequencies of FMCW Radar for Human Body Motion Tracking

A phase-extraction technique with multiple frequencies of a frequency-modulated continuous-wave (FMCW) radar is proposed, which allows the detection of target motions exactly. An FMCW chirp signal is decomposed into multiple-frequency continuous-wave (CW) signals to extract modulated phases due to target motions. The demodulated phases at multiple frequencies are summed and averaged. Since the proposed method can extract the phase without performing a fast Fourier transform (FFT), it can overcome the range migration problem, which causes an error in phase extraction using a conventional FFT-based method. Therefore, the proposed method can reduce spurious noises induced by phase errors compared with the conventional method. This was verified experimentally for both human vital sign detection and body motion tracking.