Doppler Radar Physiological Assessments

The Doppler radar detects all motion in the radar field of view, through detection of phase variations in the received signal. The challenge in physiological monitoring via Doppler radar is to effectively isolate the subject's random fidgeting physiological motion. The percentage of measurement interval containing significant motion may be used as a measure of subject rest/activity cycle, determining the degree of restlessness, for example, actigraphy. Phase demodulation provides the output proportional to chest displacement, and this information can be further analyzed to extract respiratory and heart rates, analyze the shape of respiratory signals, assess heart rate variability (HRV) parameters, and estimate displacement amplitude and related respiratory volume. The magnitude of received RF power can be analyzed to determine cardiopulmonary radar cross section (RCS) and further determine subject orientation. The variation of RCS with size and curvature of the target surface is the basis for detecting orientation of a human subject.