A Polarization Insensitive and Angularly Stable Reconfigurable Unit Cell for Reconfigurable Intelligent Surfaces

A tunable unit cell is the building block of Reconfigurable Intelligent Surfaces (RIS). By controlling the reflection properties of individual unit cells, the propagation of the reflected electromagnetic (EM) wave can be manipulated in a programmable way. In this paper a new reconfigurable unit cell for RIS applications is proposed. The unit cell uses PIN diodes to switch between two reflection states which has a phase difference close to 180° over the frequency range of 7.25 to 8.5 GHz. The design is polarization insensitive, and the reflection responses are stable for oblique incidence of angle up to 45° for both TE and TM modes.