Analytical Framework to Model Reconfigurable Metasurfaces including Lumped Elements

This paper presents an analytical framework, based on Floquet modal expansions of the electromagnetic fields and equivalent circuits, to model reconfigurable metasurfaces loaded with generic lumped elements (resistors, capacitors, inductors, varactors, etc.). The analytical approach is computationally efficient compared to full-wave solvers. Additionally, it works under oblique-incidence conditions in a wideband range of frequencies, even far beyond the onset of the first grating lobe (diffraction regime). The analytical framework is validated with some numerical examples in the commercial software CST Studio Suite, demonstrating its potential for analyzing and designing RF and microwave devices, including lumped elements, such as absorbers, polarizers, and reflectarray/transmitarray cells.