Design of A Dual-band High Selective FSS

In this paper, we propose a new frequency selective surface (FSS) with dual-band and good filtering response. The unit cell of the developed FSS employs multi-layer triangle metal patch resonators which are coupled through the coupling aperture etched in the middle ground layer. Attributing to the electromagnetic hybrid coupling introduced by the coupling aperture, a four-order dual-band response with three transmission zeros are generated. The two passbands are centered at 4.63 GHz and 7.50 GHz, with $3-\text{dB}$ fractional bandwidths of $\mathbf{2 4 . 5 \%}$ and $\mathbf{2 2 . 6} \%$, respectively. Meanwhile, three transmission zeros locating at $5.40 \text{GHz}, 5.85 \text{GHz}$, and 8.93 GHz are achieved, which exhibits high selectivity. Besides, the filtering response maintains stability up to a 30° oblique incidence under TE polarization.