EM-Based Design of All Metal Frequency Selective Surfaces with Finite Transmission Zeros

An electromagnetic (EM) design methodology for all metal frequency selective surfaces (FSS) with finite transmission zeros is proposed in this work. Single polarization is considered in the design, which is based on an evanescent field mechanism. An infinite 2D-periodic square-shaped metallic lattice performs the stopband behavior of the FSS, whereas H-shaped slot resonators on the sidewalls of the metallic lattice allow for the evanescent field in the desired polarization to be pushed forward in the FSS at some target passband. Finite transmission zeros next to the passband are introduced to increase the FSS selectivity using concepts from filter theory.The EM design is carried out by means of a recently proposed approach based on the electromagnetics coupling matrix. In this new methodology, not only the S parameter response is obtained out of one single full-wave simulation with the finite element method (FEM), but also the EM couplings among the EM circuit resonators. We use this electromagnetics coupling matrix to carry out an ad hoc synthesis of the FSS response directly in electromagnetics. As a result, we get a target electromagnetics coupling matrix that is used for CAD purposes. The EM-based optimization loop is guided by this target electromagnetics coupling matrix, which allows to achieve our target electrical response in very few iterations, resulting in very few FEM simulations to achieve the goal.Several design examples will illustrate the capabilities and possibilities of the proposed approach.