An 8 TX–16 RX W-Band 2-D Distributed Active Array TD-MIMO FMCW Radar in 28-nm CMOS

This article presents a 94-GHz time-domain multiple-input–multiple-output (TD-MIMO) frequency- modulated continuous-wave (FMCW) radar system with 8 transmitters (TXs) and 16 receivers (RXs). The system incorporates a single-channel TX chip and a four-channel RX chip, which are separately designed to enable flexible antenna array optimization. Both chips are implemented in 28-nm bulk CMOS technology and feature a$\times 24$frequency multiplication scheme, along with a direct backside antenna-feeding architecture through the silicon substrate. This approach effectively reduces the complexity and cost of large-scale W-band array implementation by eliminating the need for low-yield, expensive millimeter-wave (mm-wave) packaging. A compact, center-fed antenna is directly integrated into the package, removing the external antenna feedlines and enabling efficient arrangement of a 2-D thinned active array, which is optimized using a genetic algorithm (GA) for enhanced angular resolution. Furthermore, a time-interleaved intermediate-frequency (IF) sampling architecture is adopted to realize 128 virtual channels with reduced back-end hardware and processing burden. The fabricated antenna-integrated TX and RX module achieve an equivalent isotropic radiated power (EIRP) of 27 dBm and a conversion gain of 34 dB, respectively. The radar system demonstrates high angular resolutions of 0.81° in azimuth and 1.5° in elevation direction.