Circuit Modelling of Reflecting Intelligent Surfaces

We present an accurate and simple analytical model for the computation of the reflection coefficient amplitude and phase of Reflecting Intelligent Surfaces (RIS). The proposed approach takes into account mutual coupling among cells, the effect of incidence angle and polarization of impinging electro-magnetic waves. The model is based on a transmission-line circuit representation of the RIS unit cells, and it is a physics-based approach which includes the effect of all relevant geometrical and electrical properties of the designed surface. The proposed approach is useful for a quick but physically aware design of RIS-based communications links.