A 29 GHz Dual-Polarized Reconfigurable Intelligent Surface with 2-Dimensional Wide Scanning Range

This paper presents a reconfigurable intelligent surface (RIS) to control the direction of the reflected wave independently in each orthogonally dual-polarized incident wave for deploying millimeter wave RIS-aided wireless communications. A designed 1-bit controlled reflective unit cell is used for both vertical and horizontal polarization by rotating 90 degrees, and the overlapping of these unit cells enables overall size reduction of RIS efficiently. The proposed alignment technique also provides secure 2-dimensional (2-D) operation of each polarization without performance degradation. In addition, dummy patterns are designed and added between each unit cell for a wide scanning range. The 180 degrees phase difference can be maintained for the wider incident and reflected angles by the dummy patterns. Furthermore, a RIS prototype that includes a 40 x 40 array of dual-polarized unit cells, an Arduino microcontroller, and a DCDC converter is designed and fabricated. The measurement is performed using a customized antenna holder that helps to accurately measure the 2-D spherical coordinate while changing the reflected angle from -30 degrees to +30 degrees with a 5 degrees interval. By confirming the measurement and simulation results match well, the validity of the proposed RIS is proven, and it is hoped that it will be widely used in the research on dual-polarized RIS-aided communications in the future.