A 265-GHz CMOS Reflectarray With 98×98 Elements for 1°-Wide Beam Forming and High-Angular-Resolution Radar Imaging

Abstract

The high-angular-resolution imaging capability of future automotive and security sensing systems is in favor of compact, fully integrated, and reconfigurable antenna arrays. The adoption of sub-terahertz (sub-THz) frequencies for such systems relieves the hardware requirements for the physical size and fractional bandwidth (BW). Phased/MIMO arrays, when a large 2-D aperture size is required, are facing great challenges related to high circuit complexities, electronic density, and computation power. This article presents a digitally controlled 265-GHz reflectarray that decouples the designs of active circuits and large passive antenna array. The array is constructed using stitched CMOS chips, fabricated on Intel 16 process, and each unit adopts 1-bit phase quantization and cross-polarization backscatter approaches. With a credit-card size ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5.6\ttimes5.6$</tex-math> </inline-formula> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^2$</tex-math> </inline-formula> ), the reflectarray performs 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^\circ$</tex-math> </inline-formula> -wide pencil beamforming ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 42-dBi directivity) and electric steering within <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 60 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^\circ$</tex-math> </inline-formula> range in both azimuth and elevation directions. The reflectarray is also equipped with 780-Mb integrated under-antenna memory, which not only eliminates high-speed data communication during raster scan but also enables techniques such as time-dithering sidelobe reduction, and beam squint corrections. Pairing with a commercial sub-THz transceiver (TRX), this work also, for the first time, demonstrates high-angular-resolution, mechanical-movement-free terahertz (THz) imaging.