Modal decomposition equivalent circuit method application for multilayer FSS

In the previous works a detailed review of existing equivalent circuit methods for the analysis and design of frequency selective surfaces (FSS) has been presented. It has been already shown that the proposed modal decomposition equivalent circuit method (MDECM) offers a higher accuracy and a better physical understanding of an FSS compared with other equivalent circuit methods. The method is based on determining the admittances that relate the voltage and current intensity amplitudes for any incident Floquet mode and is achieved by studying the interaction of plane waves of arbitrary angles of incidence with the structure. An important feature of the technique is that the resulting formulation can be expressed as a multi-tapped ideal transformer connected to a set of mode admittances and approximations can be made to give a very elegant solution, so long as the FSS element aperture field can be well approximated by a simple mode combination. The method has been recently extended to deal with complicated FSS geometry such as multi-frequency and multi-layer structures. It has been found that the method offers even more advantages in simulation time for those structures in comparison with full-wave solutions and computational electromagnetic (CEM) software results. The solution obtained for multilayer structures, has been successfully applied for two layers FSSs of different geometry. Good agreement with other methods results has been obtained. Method advantages and limitations will be discussed in the conclusions.