Low-Pass Frequency-Selective Surface With a Very Wide Stopband

In this letter, a frequency selective surface (FSS) with low-pass characteristics is proposed. A wide stopband above the low-pass band is obtained by cascading bandstop FSS layers with air-spacer layers. It reveals that an additional pole can be generated in the low-pass band, and the low-pass characteristics can be improved by cascading two bandstop FSSs with an air-spacer. Wide stopband can also be achieved by adding a third bandstop FSS layer. The proposed FSS is analyzed and verified by an equivalent circuit model. A prototype is fabricated, assembled, and tested. Simulated results show that our proposed FSS achieves a low-pass band below 2.9 GHz with an insertion loss of 0.41 dB. The bandwidth of the stopband is 123.1%, with a transmission coefficient below –10 dB between 4 GHz and 18 GHz. The full-wave simulation and experimental results show that the structure has an ultrawideband out-of-band suppression while maintaining a good low-pass characteristic.