Network Based Hybrid Spatial-Spectral RIS Synthesis Method

A network-based technique is presented that incorporates the full-wave scattering from reconfigurable intelligent surfaces (RISs) with global periodicity. The RIS is treated as a multi-port network that connects loaded RIS ports to propagating plane waves. The scattering matrix is collected using a commercial solver in the spectral domain to alleviate the computational cost of computing the hybrid spatial-spectral scattering matrix of the RIS. Using the Neumann method, sparsity within the scattering matrix is leveraged to compute the scattered field rapidly. Further, the Gerchberg-Saxton algorithm is modified to directly synthesize load impedances distributed throughout the RIS. Beam splitting is demonstrated for an active RIS containing 9,801 unit cells where a plane wave illuminates the surface and redirects the radiation in two directions- a retroreflected component back towards the illumination, and a desired auxiliary scanned direction.