Detection of Human Breathing in Non-Line-of-Sight Region by Using mmWave FMCW Radar

Abstract

Detection of an actionless human hidden in the Non-Line-of-Sight (NLOS) region can be implemented by combining NLOS object detection and vital sign detection. Since the radar waves suffer from severe multipath effects in NLOS environment, a specific detection scheme is required for human position estimation and breathing detection with 77GHz frequency modulated continuous wave (FMCW) radar. After a radar surveying of the NLOS environment, local coordinates and the radar wave reflection and propagation model can be established on-site. An NLOS target positioning algorithm, referred to as the NLOS multipath target searching and position estimating algorithm (NLOS-mTSPE), is proposed to recognize the typical wave propagation paths in the NLOS area for accurate positioning of the human in the NLOS region. According to the recognized signal path, human breathing signals can be correctly extracted and the breathing rate can be acquired with an average error within 1%. The proposed scheme is demonstrated by the detection in a corridor behind an L-shaped corner, in which both the accurate human position and breathing rate can be acquired. The maximum detectable distance and the maximum localizable distance in the NLOS region are analyzed.