Beyond Imaging: A 256 GHz Superheterodyne FMCW Radar System for 3-D Imaging and Micro-Doppler Based Sound Reconstruction

This paper presents a state-of-the-art FMCW imaging radar system capable of both high resolution diffraction-limited 3-D imaging and micro-Doppler based speech reconstruction. The system consists of a Phase Locked Loop based heterodyne chirp generation unit and transmitter-receiver chips fabricated in 65-nm CMOS. Operating with a 24-GHz bandwidth centered at 256 GHz, the radar achieves a 6.25-mm range resolution and forms 3-D images with sub-millimeter cross-range resolution. The system’s phase stability and long-term phase coherence are verified through inverse synthetic aperture radar measurements using multiple targets, where the resulting images show a cross-range resolution near the theoretical diffraction limit. To demonstrate its 4-D capability, we perform over-the-air audio and speech reconstruction by capturing the micro-Doppler signature of a speaker on an aluminum membrane. To the best of our knowledge, this is the first integrated CMOS demonstration of a 4-D imaging radar achieving coherent superheterodyne FMCW operation above 200 GHz.