Heart and respiration rate measurement using Doppler radar is a non-contact and non-obstructive way for remote thorough-clothing monitoring of vital signs. First, the Doppler radar signal, which is phase modulated by physiological motion, is captured and downconverted, and then the heartbeat and respiration rates are obtained by processing the baseband signal. The modulated back-scattered radar signal in the presence of high noise and interference is non-stationary with hidden periodicities, which cannot be detected by ordinary Fourier analysis. In this paper, we propose a cyclostationary approach for such signals and show that by using non-linear transformation and Fourier analysis of the radar signal, the hidden periodicities of heart and respiration information can be accurately obtained. Numerical and experimental results show that the vital signs can be extracted as cyclic frequencies, independent of SNR and without any filtering or phase unwrapping.
- Doppler radar
- Hidden periodicity
- Non-Stationary signal
- Phase modulation
- Time varying statistical parameter