Design of 2-Bit Single Linearly Polarized Reconfigurable Intelligent Surface for Single-Beam/Multibeam Scanning

Abstract

Single-/multi-beam scanning is a key technology in modern wireless communications, where extensive works have been devoted to improving the performance of devices, such as the coverage capability. In this letter, a 2-bit single polarization reconfigurable intelligent surface (RIS) for single- and multi-beam radiation in the far field is proposed. Two diodes are loaded onto a trapezoidal patch, utilizing a four-layer PCB structure to construct independent control of 2-bit phase discretization, easy to manufacture. To enlarge the beam scanning range of the RIS, the cell period is designed as 0.41λ. Each PIN diode is independently controlled by the FPGA, enabling real-time two-dimensional beam scanning. For demonstration, the prototype of the RIS is fabricated and measured, which is formed of 16 × 16 units and operates at 3.5 GHz. The far-field radiation patterns corresponding to single- and multi-beam radiation are measured in the microwave chamber and the scanning beams with range of ±60° are also measured. In the direction of θ = 0°, ϕ = 0 °, the RIS has a gain as high as 21.3 dBi, the sidelobe level is less than -11 dB, and the cross-polarization is lower than – 30 dB.