A Novel Frequency Selective Surface With UltraWideband and Broad Stopband For High Selectivity

A novel frequency selective surface (FSS) structure with ultra-wide passband and high selectivity is proposed in this paper. The model widens the passband by adding rectangular polygonal lines and symmetrical helical structures in the middle layer, producing wide suppression bands. When a vertically incident wave is considered, the -3 dB ultra-wide bandwidth of FSS is achieved from 3.5 to 20.4 GHz, and the relative bandwidth reaches $141.4 \%$, which represents a significant improvement compared to previous works. At the same time, a steep wide suppression band of $20.6-26.7 \mathrm{GHz}$ is formed through the addition of the helical structure, and the suppression level exceeds -20 dB in the frequency range of $20.6-25.9 \mathrm{GHz}$. In addition, the wide passband of the FSS maintains excellent operational performance in the 0-35 degree angle of incident range.