A Quad-band Highly Selective Frequency Selective Surface With Ultrawideband Rejection

original model of structure In this letter, a highly selective quad-band frequency selective surface (FSS) with ultrawideband rejection is presented. The proposed FSS structure consists of cascading five metallic layers by three thin dielectric substrates. The five metallic layers are composed of two bent slot layers, two metallic square rings and a metal patch. The dimension of the unit cell is 0.13λ0 × 0.13λ0 × 0.18λ0 (λ0 is the free space wavelength at the first operating frequency). The proposed structure achieves four transmission bands, whilst providing two wide stop-bands located at 1 to 5.5 GHz and 14 to 40 GHz with suppressed transmission coefficient below -20 dB. In order to verify the simulation results, a FSS prototype has been fabricated and measured. It can be observed that the measured results are in favorable agreement with the simulation results.