Highly Selective Frequency Selective Surface With Ultrawideband Rejection

Frequency selective surface (FSS) with ultrawide out-of-band rejection is proposed in this article. For achieving an ultrawide and high-intensity stopband, a common second-order bandpass FSS is designed and then improved by an equivalent circuit model (ECM) design. The hybrid resonator pole separation (HRPS) decoupling method is proposed and applied during the design process. The modified ECM could realize the suppress effect on the unexcepted out-of-band transmission pole caused by coupling between layers and achieve the desired ultrawideband rejection. Furthermore, the corresponding FSS structure is established from the modified ECM through the mapping method. In addition, we conducted a detailed analysis of equivalent circuit design and the required frequency response achieve method. The measured results show that a second-order passband from 3.12 to 4.64 GHz with 0.3 dB insertion loss (IL) in the band is obtained by the proposed FSS. Meanwhile, transition bands from the passband to the stopband are narrow, and the transmission coefficients out of the passband could be suppressed under -20 dB from 5.5 to over 40 GHz. All the results demonstrate that the proposed FSS can realize an excellent out-of-band rejection while maintaining a well passband.