Polarization-Selective Fano-Resonance in Cascaded Frequency-Selective Surfaces

In this work we investigate a cascaded system of two symmetric frequency-selective surfaces (FSSs) that supports a Fano resonance (FR) at off-normal incidence in the millimeter-wave range. The first FSS is shaped with the four-arms star, and the second FSS is based on the quasi-square geometry. These two single-layer FSSs present resonant frequencies at 28 GHz (FSS #1) and 36 GHz (FSS #2). Cascading of the two FSSs was realized by using an air gap of 2.5 mm. The FSS prototypes were fabricated and measured in an anechoic chamber. It is demonstrated that a single FR is excited when the symmetry of the overall cascaded element is broken at an incidence of θ ≥ 20°.