Square loop frequency selective surface with wide-passband properties using multi-period structures

The frequency selective surface (FSS) with ultra-wide passband performance and a sharp rejection near the side of the passband is investigated in this paper. The proposed cascaded FSS consists of a 2-D periodic array of square loop aperture (SLA) and an array of bandstop square loop (SL) with different period. Under different incident waves, the proposed second-order FSS and third-order FSS provide 3 dB relative bandwidth 114% and 125%, which achieve wider bandwidth in comparison with the previously proposed structures.