A Novel Millimeter Wave and Terahertz Wave Interferometric Radar Architecture
Doppler radars have broad applications like velocity monitoring of cars, human tracking, building vibration monitoring, and even human heart rate non-contact sensing.
Conventional Doppler radars at microwave and millimeter wave usually employ expensive mixers. Even worse, such mixers are still not available at the THz regime. To overcome these shortcomings, we invent our patent-pending low-cost, mixerless Doppler radar based on interferometry technique.
A universal, mixerless millimeter wave (mmW) and THz wave 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. Two prototypes at 94 GHz and 150 GHz were 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.