A novel interferometric millimeter wave Doppler radar architecture

A universal, mixerless millimeter wave (mmW) Doppler radar architecture consisting of simply a Continuous Wave (CW) source and an intensity detector based on optical interferometry technique has been assembled. The phase information is obtained by using an oscillating mirror in the reference arm, similar to that used by the FTIR (Fourier Transform Infrared spectroscopy) technique. The reference mirror oscillates at a frequency that is higher than twice the Doppler frequency of the object. Rigorous mathematical formulas have been derived to solve for both the amplitude and the phase of the Doppler signal, by using the Low-Frequency-Band (LFB) and High-Frequency-Band (HFB) signals. The Doppler frequency signature of a moving object can be obtained from the Fourier transform of the phase. A prototype at 94 GHz was built and tested using a ball pendulum target moving over a full-swing distance much smaller than a wavelength. Both the measured amplitude and phase have been shown to agree well with the experimental parameters. The interferometric Doppler radar architecture is universal and can be extended to THz without significant change of components.