Multilayer Fourth Order Single Band Aperture Coupled Bandpass Frequency Selective Surface

Abstract

In this paper, a Band Pass Frequency Selective Surface (FSS) is presented with an aperture-coupled single band fourth order. Firstly, a pair of square and triangular truncations are introduced in a square patch along the rightside diagonal and left-side diagonal, respectively, forming a structure that appears as two tilted hexagons cascaded together. With simultaneous excitation, the symmetry of this structure introduces two orthogonal degenerative modes. However, perturbations in the form of square and triangular truncations split the orthogonal modes into two different frequencies. This approach can be used to implement a compact bandpass FSS. Subsequently, a composite resonator is employed by strategically rotating the patches by 90 degrees between adjacent patches, designed to remove the crosspolarization reflection produced by the two orthogonal modes. Building upon this groundwork, a three-layered structure is designed, with the top and bottom conducting layers serving as composite resonators and the middle conducting layer coupled through a circular aperture. Finally, using the proposed FSS element, a fourth-order single band bandpass FSS is designed.