Rotated Feed-Combined Reconfigurable Transmit RIS With Disparate Deployment of 1-bit Hybrid Units for B5G/6G

This communication presents an initial disparate deployment of 1-bit hybrid units using p-i-n diodes in transmit reconfigurable intelligent surface (TRIS) combined with a rotated feed source to address the gain limitation of the existing 1-bit TRIS. Two types of hybrid units, with a radiation phase difference of 90° by the delay line, are proposed in this study. The TRIS aperture is divided into two sections based on two different radiation centers by rotated feed, and the hybrid units in each Section are initially configured to implement optimized quasi 2-bit beam collimation in the 0° and 40° for enhanced quantization loss. It is found that the array envelope is higher even in radiation directions other than the optimized directions, despite the initial disparate deployment of each section. Beamforming for –theta direction in the H-plane is only considered for the proof of concept with the smallest size of TRIS aperture. A $16\times16$ ( $7.6\times 7.6\,\,\lambda_{0}$ at 28 GHz) 1-bit hybrid TRIS offers gain enhancement of 0–5.6 dB in −70 ° to −0 ° directions of the array envelope compared with the conventional 1-bit TRIS. The proposed 1-bit hybrid TRIS yields an improved aperture efficiency of 24.4%.