Towards High-Angular-Resolution Radar Imaging at Sub-THz
Ultra-sharp beam forming in high angular resolution imaging poses overwhelming challenges to conventional radar hardware schemes. To achieve 1-degree response in both azimuth and elevation directions, the aperture size required at 77GHz is as large as hundreds of cm². Data conversion and processing also need to apply to over 100 signal channels in commonly adopted MIMO operations. The formed angular response also often has high sidelobe floors, making the radar susceptible to false detection. In this talk, we discuss a technology path utilizing sub-THz carrier frequencies. Through tiled 22nm CMOS reflectarray chips at 265GHz, 98×98 electrically-controlled antennas are densely implemented within ~5×5cm² area. Through under-antenna memory, the hardware enables 2D steering of a 1-degree-wide beam with <-30dB sidelobe floor (or <-60dB if used for both TX and RX). A high-angular-resolution imaging demo based on the reflectarray will be given, too. Lastly, we will discuss the challenges and solutions of the sub-THz transceiver that drives the above reflectarray, especially regarding the TX-RX antenna co-location requirement to avoid TX and RX beam misalignment. To that end, a monostatic transceiver prototype that is free of the normal 6dB directional coupler loss is presented at 140GHz.