How do I design a vital signs detection radar for non-contact monitoring of breathing and heart rate?

Designing a vital signs detection radar for non-contact monitoring of breathing and heart rate uses a CW or FMCW radar to detect the tiny chest wall displacements caused by respiration (chest displacement approximately 4-12 mm) and heartbeat (chest displacement approximately 0.1-0.5 mm). The radar detects these motions through the phase modulation of the reflected signal: as the chest wall moves toward and away from the radar, the round-trip path length changes, causing a phase shift in the reflected signal: delta_phi = 4 × pi × delta_d / lambda, where delta_d is the chest displacement and lambda is the radar wavelength. For respiration (delta_d = 5 mm) at 24 GHz (lambda = 12.5 mm): delta_phi = 4 × pi × 5/12.5 = 5.03 radians (easily detectable). For heartbeat (delta_d = 0.2 mm) at 24 GHz: delta_phi = 0.2 radians (much smaller but still detectable with advanced processing). The radar operates as follows: the CW or FMCW signal is transmitted and reflected from the subject's chest. The reflected signal is demodulated using I/Q (quadrature) detection to extract the phase variation over time. The phase signal contains: a slow component (0.15-0.5 Hz) from respiration, and a faster component (0.8-2 Hz) from the heartbeat. Bandpass filtering separates the breathing signal from the heartbeat signal. The breathing rate and heart rate are extracted from the filtered signals using peak counting, FFT, or autocorrelation.