Binary Phase Modulation FMCW Radar for High-Performance Multiperson Cardiac-Induced Thoracic Micro-Motion Sensing

Abstract

This article focuses on the exploitation of binary phase modulation (BPM) radar architecture for multiperson fine-grained cardiac-induced thoracic micro-motion monitoring. The BPM scheme is developed based on a conventional frequency-modulated continuous-wave (FMCW) radar framework. By introducing a phase shifter at each transmit (TX) channel, all TX channels can operate simultaneously while preserving temporal resolution. Compared with conventional radar architectures, such as phased-array and time-division multiplexing (TDM) MIMO radar, the proposed scheme provides improved signal-to-noise ratio ( $SNR$ ), making it suitable for noncontact biomedical sensing applications. A rigorous mathematical analysis of the BPM operating principle is presented in the context of vital sign extraction, with particular emphasis on the impact of practical imperfections, such as phase errors and amplitude mismatches, on displacement demodulation. A phase-based displacement reconstruction framework is proposed to recover thoracic motion and associated fine physiological information. Finally, a prototype BPM radar system is implemented, and experiments are conducted to validate its capability in target separation and high-fidelity reconstruction of micro-motion vital sign waveforms.