Combined-element frequency selective surfaces with multiple transmission poles and zeros

A novel combined-element frequency selective surface (FSS) is proposed for multi-band applications. In this design, complementary square loops and meandering slots are combined to construct the composite FSS. The proposed FSS provides three transmission poles and two transmission zeros, transmitting the desired signals at 8.5, 11 and 16 GHz while reflecting the unnecessary signals at 9.6 and 13.1 GHz. This FSS has the advantages of flexible and simple structure, easy processing and low profile compared with traditional multi-pole FSSs. The design strategy of the proposed FSS and the associated equivalent circuit model are provided to analyse the frequency characteristics. A prototype is fabricated and measured, showing a superior and stable frequency response in case of oblique incidence for both the transverse-electric (TE) and transverse-magnetic (TM) polarisations. Good agreement between the simulated and measured results is observed. Finally, the higher-order FSS with good frequency selectivity is investigated.