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 degrees. 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 x 10 array is designed, fabricated, and measured. The measured results show that the developed RIS has a beam scanning range of +/- 60 degrees from 26.5 GHz to 28.5 GHz.