Broadband Low-Pass Frequency Selective Surface with High-Frequency Rejection

This paper proposes a novel low-pass frequency selective surface (FSS) with high-frequency rejection. Through theoretical derivation of the equivalent circuit model (ECM), an additional transmission pole can be generated below the transmission zeros by cascading two band-stop FSSs incorporated with an air spacer, therefore enhancing the low-pass performance. Based on the above findings, a compact and simple FSS is designed, which consists of two dual band-stop FSS with an air spacer. The staggered distribution of the four transmission zeros substantially broadens the stopband. The full-wave simulation result shows that the proposed FSS has an ultra-wide out-of-band rejection with transmission coefficient under −10 dB from 4.42 GHz to 27 GHz (143%), while maintaining a relatively good low-pass characteristic under 4.42 GHz with a maximum insertion loss of 1.36 dB. The full-wave simulation result matches closely with the ECM result.