Efficient current expansions modes for N-arm frequency selective surface elements

An entire domain current expansion set is found for the tripole frequency-selective surface (FSS) using the singularity expansion method (SEM). The SEM analysis is performed on a thin wire model of an isolated FSS element. The SEM natural current modes yield a highly efficient entire domain expansion set for use in a Floquet moment-method analysis of the FSS array. The SEM analysis yields an optimum set of expansions functions without any prior knowledge about the FSS element.<>