Millimeter-Wave Large-Angle Dual-Polarization Reconfigurable Intelligent Surface for 6G Communication Relay

This letter presents a millimeter-wave dual-polarized quasi-three-bit reconfigurable intelligent surface (RIS) for a 6G wireless communication relay with a large beam-scanning angle range. The RIS unit consists of two stacked patches and a pair of orthogonal aperture-coupled microstrip lines. A positive-intrinsic-negative diode is loaded on the end of each microstrip line for controlling the reflection phases for realizing one-bit phase quantization. Furthermore, by adjusting the length of the microstrip lines, four one-bit reconfigurable units with different initial reflection phases were designed, which achieves a quasi-three-bit phase quantization for the RIS aperture with the phase step of 45°. The genetic algorithm is used to optimize the placement of the four units in the array to improve the beam-scanning performance. To validate the proposed RIS, a 10 × 10 array is designed, fabricated, and measured. The measured results show that the developed RIS has a beam scanning range of ±60° from 26.5 GHz to 28.5 GHz.