Modeling of Frequency Selective Surfaces Using Impedance Type Boundary Condition

The electromagnetic properties of frequency selective surfaces (FSS) are often calculated using integral equations. The metal strips of an FSS are usually modeled as an infinitesimally thin perfect conductor. This assumption is valid as long as the thickness of the metal strip is significantly smaller than the skin depth. If this condition is not applicable, the discretization of the volume of the metal strip is necessary. In this paper, we propose a method based on the same assumption from which the impedance type boundary condition is also derived to avoid the volumetric discretization when the thickness of the metal strip is comparable to the skin depth. We will show that in this case the accuracy of the modeling is significantly increased, while the number of unknowns remains very low as compared to the full volumetric discretization.