A 140GHz FMCW Radar with 22dB Wideband RF-Domain Multipath Self-Interference Cancellation in 28nm CMOS

This paper presents a D-band CMOS FMCW radar with active self-interference (SI) cancellation in the RF domain. The proposed scheme first uses a transmitter (TX) IQ-mixer to ensure coherent sampling of the SI beat signal and simplify the SI parameter estimation. Then, it replicates the multipath SI using another IQ-mixer and cancels the SI before the LNA. This scheme enhances the radar’s dynamic range and the ability to discern sub-meter short range targets. The chip was fabricated in a 28 nm CMOS process, and the measurements demonstrate 22 dB wideband SI cancellation for a $10-\mathrm{GHz}$ wide FMCW chirp and up to 44.7 dB narrowband SI cancellation.