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

This letter presents a millimeter-wave dual-polarized quasi-3-bit reconfigurable intelligent surface (RIS) for 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 (PIN) diode is loaded on the end of each microstrip line for controlling the reflection phases for realizing 1-bit phase quantization. Furthermore, by adjusting the length of the microstrip lines, four 1-bit reconfigurable units with different initial reflection phases were designed, which achieves a quasi-3-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 to 28.5 GHz.