A novel low-profile tri-band frequency selective surface

Based on a proposed approach, a novel low-profile tri-band frequency selective surface (FSS) is presented. The FSS consists of a two-dimensional periodic array of metallic square loops and complementary apertures arranged periodically, centered within a wire grid and an aperture grid respectively. A very thin substrate, with the overall thickness of 0.007 λ₁, 0.013 λ₂ or 0.0195 λ₃, where λ₁, λ₂ and λ₃ are the free space wavelengths of the three bands respectively, supports this whole structure. The proposed FSS provides: 1) three passbands separated by transmission zeros, 2) advantage of low profile, and 3) insensitivity to incident angles and polarizations. An equivalent circuit model is given for predicting and analyzing the frequency characteristics of this structure. Furthermore, a tri-band FSS with uniform band spacing is fabricated and measured. Good agreement between the simulated and measured results is obtained.