A Full-wave Simulation Technique for Reconfigurable Intelligent Surfaces

This paper presents a full-wave simulation technique based on the Finite Element-Boundary Element-Domain Decomposition Method (FEM-BEM-DDM) for the analysis of Reconfigurable Intelligent Surfaces (RISs) loaded with lumped-element loads. The RISs considered in this study consist of electrically controlled elements loaded on quasi-periodic geometries. The method separates the geometric model of the lumped-element loads on each unit of the quasi-periodic array into a geometric structure without the lumped-element loads and an additional term representing the lumped-element loads, with the geometric structure partitioned and meshed according to the array units. The additional term treats the mesh at the location of the lumped-element loads separately, considering it as an additional current boundary condition, and utilizes zeroth-order Whitney basis functions for computation. The accuracy of the proposed technique are demonstrated through a numerical examples.