A numerical model for analyzing electromagnetic scattering from a planar Frequency Selective Surface (FSS) is developed. The model can represent an FSS with multiple arrays of arbitrary piecewise linear scatterers in a stratified dielectric medium. The FSS\u27s arrays are finite by infinite, accounting for edge effects, where a periodic array element is formed from the piecewise linear connection of thin slots in a groundplane. The stratified dielectric medium is defined as an arbitrary stack of lossless dielectric slabs that sandwich the user defined arrays, simulating an FSS. The Surface Equivalence theorem is used to construct an equivalent problem based on groundplanes and magnetic current sources. Integral equations based on the equivalent magnetic scattering currents are solved via the moment method. These unknown currents are expanded such that independent modes are defined for each infinite column of an array, where the current fluctuations along each column are defined in terms of a reference element and Floquet\u27s theorem. Individual column contributions are determined using the Array Scanning Method, preserving the plane wave form of the solution. The model has been implemented in a user-friendly computer program, and admittance calculations and scattering predictions have been validated against measured data and appropriately similar FSS codes
