Vital sign detection using 60-GHz Doppler radar system

Non-contact vital sign detection using 60-GHz radar offers various advantages such as higher sensitivity and smaller antennas compared to lower-frequency systems, however, the respiration amplitude comparable to wavelength causes strong non-linear phase modulation, and relatively small heartbeat amplitude results in detection difficulty. In this paper, theoretical analysis and simulation of 60-GHz detection are provided to address these issues. Both shallow and deep breathings are tested in the experiments, and the detection technique monitoring both the fundamental and second harmonic of respiration is proposed. The phenomena explained in the work can be applied to many millimeter-wave Doppler radar applications where target displacement is comparable to or larger than the wavelength to ensure robust detection.