Detecting and monitoring the micro-motions of trapped people hidden by obstacles based on wavelet entropy with low centre-frequency UWB radar

Abstract

Efficient detection and monitoring of physiological conditions and activity hidden by walls or rubble are considered challenging in rescue, surveillance, and security operations. In this paper, a new method based on wavelet analysis called wavelet entropy (WE) is proposed to not only detect vital signs but also to monitor the target’s physiological conditions through ultra-wideband (UWB) radar with a centre frequency of 400 MHz. Results of the experiments show that this new method can accurately locate a human target in free space, through a brick wall at a certain distance, and in cases of simulated rubble. Furthermore, a human target’s micro-motion responses due to different physiological conditions with a stationary body in the case of simulated rubble, and that are unrecognizable using common methods, were also quantitatively detected. The WE method not only locates the target’s position but also monitors changes in his/her physiological conditions. This method may also be a useful tool in the practical application of UWB radar.