Enhanced Motion Sensing With FMCW Radar Based on a Novel Frequency-Reconfigurable Technique

The motion sensing capability of millimeter-wave radar is significantly contingent upon its operating frequency. However, conventional techniques do not allow frequency modification once the radar hardware is completed. In this article, a novel frequency-reconfigurable technique is proposed to enable the operating frequency reconfiguration without any hardware modifications, enhancing the radar's capability to perceive displacement motions across various scales. This technique splits frequency-modulated continuous-wave (FMCW) beat signals into multiple sub-FMCW signals, yielding pairs of quadrature signals that are similar to those in continuous-wave radars. These quadrature signals are subsequently synthesized to quadrature signals at a new operating frequency. For weak motions of deep subwavelength scale, the proposed technique improves the detection sensitivity by reconstructing equivalent quadrature signals at a higher operating frequency, such as from 60 up to 480 GHz. For large-scale motions, this technique surpasses the radar's velocity limit by reconstructing that at a lower frequency, e.g., 60–1 GHz. Simulation results and theoretical analysis demonstrate the superiority of this technique for motion sensing. Experiments were also carried out to validate this technique in detecting the weak deep subwavelength, large-scale mechanical vibrations, and action gestures. Experimental results indicate that this technique exhibits approximately a three times accuracy improvement in detecting weak motions and about ten times accuracy improvement in detecting large-scale motions compared to the conventional technique.