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.