A New Unit-Cell Design for a 2-Bit Reflective Metasurface for RIS Applications

Abstract

In this research, a novel unit-cell design for a 2-bit reflective metasurface using the theory of characteristic modes is presented. The initial unit-cell consists of three sub-patches with 2-PIN diodes integrated within the gaps between sub-patches. The initial structure provides limited tuning of the phase curves with the change in switching states of PIN diodes. To provide the phase deviation required for the 2-bit operation, the symmetry of the modal currents is used to propose multiple slots in the sub-patches. Slots are introduced to lower the resonant frequencies, as well as provide tuning of the resonance of modes and consequently phase change between different switching states. For further resonance tuning and phase optimization, two vias are loaded in the middle patch to provide a 90° phase difference between each switching state. Simulated results show that the proposed unit-cell design with the aid of characteristic modes has a smaller size and provides 2-bit operation in the frequency range of 3.9–4.04 GHz.