Design of a multi-passband metasurface with ultra-high angular stability based on complementary frequency selective surfaces

This paper proposes a new design of a multi-passband metasurface with ultra-high angular stability based on complementary frequency selective surfaces (FSSs). The proposed design consists of multiple ring slots coupled with a complementary structure on the opposite side of a single substrate layer. This approach effectively enables the design of multiband band-pass FSSs, ranging from dual-passband to penta-passband, using a simplified design process and achieving an ultra-low thickness of 0.004<i>λ</i>. The equivalent circuit model (ECM) is utilized to analyze the proposed structure, revealing the influence of the number of cascaded ring patch layers on the number of passbands. To demonstrate the validity of our method, a penta-band FSS is synthesized to achieve a signal transmission with an insertion loss less than 1.0 dB at the passband frequency existing between two adjacent reflection bands. The penta-band FSS was fabricated and measured to verify our design concept. The experimental results show excellent agreement with the simulation results. The resultant FSS exhibits polarization insensitivity and maintains a highly stable filter response at incidence angles up to 80^∘.