Efficient analysis of two-dimensional reconfigurable intelligent surfaces by characteristic basis functions

The paper presents a Fourier technique suitable for efficiently evaluating the scattered electromagnetic (EM) field due to periodically configured reconfigurable metasurfaces (MTSs), which are the predominant realization approach of reconfigurable intelligent surfaces (RISs). The underlying analysis method, to which the Fourier technique is applied, has been recently developed by the authors for fast calculation of the EM field due to MTSs. It is also demonstrated that the efficiency of the Fourier technique can often be improved significantly when the proximity effect between neighbouring cells can be neglected. The efficacy of the technique for RIS simulation is illustrated by analyzing a reconfigurable line MTS, which is an RIS invariant in one direction.