Efficient living subject localization and weak vital-sign signal enhancement using impulse radio based UWB radar

In recent years, with the help of Ultra-wideband (UWB) radar, contactless measurement of vital signs become possible. This type of radar has sufficient range accuracy for micro-motion such as chest displacement or belly displacement. However, ambient clutter is strong in some scenarios such as a vehicle cabin so that a vital sign of living subject could be obscured and hard to extract. In addition, for multi-person vital signs detection, the sign of people sitting further away from the radar could become weaker due to the strong signal reflected by people in front. This paper describes an efficient way of a vital sign signal localization and a cross-correlation based method to enhance vital signs. The localization method proposed a threshold-based searching method to reduce searching range and save computational power for localization computation. The purpose of vital signs enhancement is 1) to make the weak vital sign signal observable and 2) to increase the signal-to-noise ratio (SNR) of a living subject sitting in at some distance for better localization and vital sign signal extraction accuracy. The enhancement algorithm is to cross-correlate the adjacent bins of the original signal for vital sign signal amplification. Tests are made with multiple people sitting in indoor space with strong reflected material around to simulate vehicle cabin environment. This method has been proved effective for vital sign enhancement in which the SNR increased by more than 40%. In addition, the speed of localization has increased by more than 20% for the two executed test scenarios.