Highly Selective Antenna-Filter-Antenna Based Frequency Selective Surface Loaded With Absorptive Branch

A kind of antenna-filter-antenna based frequency selective surface (FSS) with high selectivity is proposed by using the absorptive branch. The proposed FSS unit consists of a pair of patches connected with each other via a metal pin passing through the common ground, and a pair of absorptive bandstop branches loading to each patch respectively. On one hand, the antenna-filter-antenna architecture supports the frequency selective characteristic. On the other hand, the absorptive bandstop branch possessing the opposite frequency response of the patch could consume the out-of-band power to improve the frequency selectivity. Simulated results show that the proposed FSS has a 3.4% 10-dB fractional bandwidth covering from 9.84 to 10.18 GHz and the roll-off rates of $\left|\mathrm{S}_{21}\right|$ are 24.26 and 28.46 $\mathrm{dB} / \mathrm{GHz}$ at both band edges respectively.