A 2-bit Reconfigurable Intelligent Surface with Wide Beam Steering Angles

Abstract

This paper presents a 2-bit reconfigurable intelligent surface (RIS) with an aperture size of 4.4λ0 × 4.4λ0 aiming for wide angle beam steering applications. The proposed geometry is based on a periodic arrangement of metallic patterns printed on an FR4 substrate, where a varactor diode is mounted between two rectangular patches in each unit cell for regulating the electromagnetic wave. An air spacer terminated with a ground plane is stacked below the dielectric substrate to obtain a high reflection characteristic. By carefully tuning the diode voltage across unit cell, four distinct coding states are generated with different reflection phase values (-165°, -75°, +15°, and +105°). Subsequently, a 2-bit RIS structure is designed from the phase profiles such that a normally incident plane wave can be reflected in specific directions, ranging from -50° to +50° at 4 GHz. The simulation result shows that the structure achieves angular reciprocity for the entire beam steering range and holds great potential for use in various 6G and future wireless communication networks. © 2024 IEEE.