A D-Band 120-GHz 2-D Scalable 4 × 4 Relay Array With Orthogonally Polarized On-Chip Antennas and In-Front-End Fast 2-D Angle-of-Arrival Detection

This work presents a 120-GHz4 × 4active reconfigurable reflective relay array that can enable D-band non-line-of-sight (NLOS) wireless communication links in scenarios with heavily blocked line-of-sight (LOS) paths. The relay array employs orthogonally linear-polarized on-chip4 × 4transmitting/receiving antenna arrays, and is 2-D scalable on aλ/× λ/2 grid. In addition, mixed-signal and low-latency loops are integrated within the front ends of the relay’s channels to detect the angle-of-arrival (AoA) of the external incident beam in both 2-D azimuth/elevation planes. These detection loops operate on the fly, at the carrier frequency, without the need of down-conversion, which avoids lossy mixers, complex local-oscillator (LO) distributions, and additional signal delays, ensuring a low-complexity and a high-scalability relay array design. The relay array operation is analyzed in the presence of non-idealities, including the finite isolation between the transmitting/receiving antennas and the channels’ mismatches. The4 × 4reflective relay array is implemented in GlobalFoundaries 22-nm CMOS fully-depleted silicon-on-insulator (FD-SOI) technology with a total area of5× 5mm. Each channel achieves a measured average gain of 23.6 dB with a 3-dB bandwidth from 110 to 125 GHz, while offering a 360° reconfigurable phase range with a step of 11.25°. Without any prior knowledge of the AoA of the external incident beam, over-the-air (OTA) measurement results demonstrate successful 120-GHz 1.3-m NLOS wireless links through the relay array achieving 64-QAM 2.4, 4.8, and 6 Gb/s with corresponding EVMrmsof 3.4%, 4.6%, and 5%, respectively.