Higher Order Bandpass Single and Dual Band Frequency Selective Surfaces With Aperture Coupled Patch Resonators

In this article, a low profile aperture coupled single and dual band higher order bandpass frequency selective surface (FSS) is proposed. Initially, a basic patch resonator with L-shape truncated corner is investigated theoretically so that two orthogonal modes can be excited simultaneously. Next, to avoid the cross-polarized reflection produced by two orthogonal modes, a combination of four such L-shape truncated patch resonators with 90° between two adjoining patches are implemented and analyzed.Further, by arranging two of such combination resonators placed back-to-back manner through aperture coupling metallic layer in middle, a three layer single mode fourth order and a dual band second order bandpass FSS is designed. The proposed bandpass FSS enables higher order bandpass FSSs where the order of the modes is twice than traditional aperture coupled patch resonators (AC-PRs). It provides more flexibility at higher order filtering responses. To endorse the design concept, a single and dual bandpass FSS is simulated to initiate magnetic and electric coupling through the aperture metallic layer. Moreover, an equivalent circuit model for the even and odd mode analysis method is examined the principle of operation. Finally, the proposed bandpass FSS is fabricated and tested in a vector network analyzer (VNA) setup. The measured and simulated results are compared and validated.