Numerical Green´s function technique for the analysis of screens perforated by multiply connected apertures

A technique for the analysis of perforated screens with multiply connected apertures (frequency selective surfaces) is presented. This type of structure offers higher flexibility with respect to screens perforated with simply connected apertures. In particular, it can be attractive when a response with two reflection bands separated by a transmission band is required. The solution is obtained in two steps. In the first, the Green´s function of a reference structure (a screen with simply connected apertures in a stratified dielectric medium) is determined; in the second, this characterization is exploited to analyze the complete structure. Both steps are carried out by the method of moments in the spectral domain. Screens with tripole patches inside circular apertures are studied. Reflection and transmission characteristics of single and double screen structures are presented. Comparisons with another established method confirm the validity of the new formulation