Measurement of Displacement Motions Based on Unsynchronized Bandpass Sampling with a Low-IF Doppler Radar

In this paper, a displacement motion sensing technique based on unsynchronized bandpass sampling is proposed for Doppler radars with low-intermediate frequency (IF) architecture. The proposed technique leverages unsynchronized bandpass sampling to reduce the sampling rate and realized phase extraction (PE) without the need for synchronization circuitry or algorithms. Moreover, the proposed technique is able to extract the phase evolution of the moving target from the overmodulated IF signals without any distortion, which is superior to the existing state-of-the-arts such as the envelope detection method. Both theoretical analysis and experimental results show that the proposed technique with a low-IF Doppler radar can recover large-scale mechanical motions without distortion and successfully capture physiological signals such as breathing and heartbeat while reducing the sampling rate to 100 Hz for an IF of 1050 Hz.