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Deep Sub-Wavelength Millimeter-Wave Radar Interferometry with a Novel Ego-Motion based Calibration Technique

Owing to the short wavelength, the millimeter-wave interferometric radar is superior in detecting the subtle vibration motions. Signal calibration is the precondition for accurate linear phase demodulation. The conventional signal calibration in a quadrature radar relies on the I/Q trajectory. However, for the small displacement motions of deep sub-wavelength, the I/Q trajectory is so short that it cannot provide sufficient information for accurate signal calibration, which leads to false phase demodulation i.e. inaccurate motion reconstruction. This paper proposes a novel calibration technique by leveraging the radar sensor's ego-motion to extract the calibration parameters that are necessary for accurate calibration. The working principle of the proposed technique is discussed in details. Both simulations and experiments are carried out for a 120 GHz interferometric radar to detect the subtle displacement motions as small as 1/312 wavelength. The experimental results show that the proposed calibration technique makes it possible for a millimeter-wave radar to precisely detect deep sub-wavelength displacement motions with a root mean square error (RMSE) of < 3%.