Multiperson Respiratory Monitoring Using Single-Channel Continuous-Wave Radar With Time Modulated Array

Radio frequency (RF) signals are widely used in respiratory detection due to their non-contact, remote sensing advantages. In order to satisfy multiperson monitoring, the existing RF sensing system greatly increases the complexity of the feeder network, which will affect the stability of the system and have high maintenance costs. In this study, we propose a single-channel, low-complexity multiperson respiratory monitoring system. It uses a time-modulated array (TMA) to detect the position and respiration rate of multiple targets. The TMA is reconstructed into a conventional multichannel array by the harmonic recovery method. Beamforming is used to scan the scene horizontally. At the same time, the beamformed signal is converted to the frequency domain to construct the angle of arrival-frequency map (AFM). By forming a beam pointing to the target, the time domain respiration signal of each target can be acquired. The experimental results show that the maximum respiratory rate (RR) estimation errors of the proposed system in single-person, two-person, and three-person scenarios are 0.77, 0.96, and 1.32 bmp, respectively. In addition, the Bland-Altman analysis shows that our system has good consistency with the reference sensor.