Real-time Detection of Two Subjects' Respiratory Rates Using Wavelet-Transform-Based 5.8 GHz CW Doppler Radar

Using the continuous-wave (CW) Doppler radar to identify and extract the respiratory rates of two subjects is challenging, especially when the subjects have time-varying respiratory rates. In this work, a novel wavelet-transform-based algorithm is proposed to obtain the respiratory rates for the scenario when two subjects are presenting in the CW Doppler radar detection field. A two-point time-frequency spectrum was obtained from the continuous wavelet transform spectrogram, then a peak power density was calculated based on the two-point time-frequency spectrum, with which the respiratory rates can be eventually extracted. The algorithm was evaluated with numerical simulation and tested with human subjects using a 5.8-GHz continuous-wave Doppler radar platform.