A Noise-Immune Motion Sensing Technique with Low-IF CW Radars

The accuracy of motion sensing with a Continuous-Wave (CW) radar is subject to noises. The low intermediate-frequency (IF) CW radar tackles the impact of the flicker noise. However, it still suffers from other noise components which mainly include the Additive White Noise (AWN) in short-range sensing. This paper proposes a novel Noise-Immune Motion Sensing (NIMS) technique for accurate displacement motion sensing against the AWN in low-IF CW radars. It works by dividing the IF signals sequentially into segments, extracting phases from the spectra of the sequential segments, and combing the phases to reconstruct the phase evolution for the target displacement motion. The theory and working principle are presented. Simulation and experimental results show that the Signal-to-Noise Ratio (SNR) is improved for about 20.1 dB with the proposed technique and the mechanical displacement motion is accurately obtained with the root-mean-square-error (RMSE) decreased by 99.2%.