A wideband frequency selective surface with high roll-off characteristic

Abstract

A hexagonal frequency selective surface (FSS) with wideband and high-selectivity performance is proposed in this article. The structure is characterized by petal-shaped patches on the top and bottom layers, with a hexagonal grid pattern integrated into the middle layer. Vertical vias that connect the upper and lower layers introduce an additional current path along their length, thereby establishing resonance along the via structure. This resonant mechanism gives rise to out-of-band transmission zeros and in-band transmission poles. By strategically engineering the positions of these poles and zeros, the FSS can achieve both a wide passband and a sharp roll-off characteristic. To elaborate on the physical mechanisms underlying broadband and high-selectivity characteristics, an equivalent circuit model (ECM) is established and analyzed using the odd-even mode method. By modifying the element geometry from equilateral triangular patches to petal-shaped ones, the angular stability of the FSS is significantly enhanced. The simulated and measurement results show that the novel design approach results in a bandwidth of 101% with angular stability up to 45°. The transition bandwidths for the upper and lower sidebands with respect to the passband are 1.3% and 4%, respectively.