Design of Multi-Passband Frequency Selective Surfaces with Ultra-high Angular Stability Based on Complementary Structure

This image proposes a new class of multi-frequency band-pass frequency selective surfaces (FSSs) with ultra-high angular stability and polarization insensitivity. 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 0.004λ. 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°, which is among the best of existing designs.  The view of the dual-layer complementary structure. (a) Dual-passband. (b) Triple-passband. (c) Quad-passband. (d) Penta-passband.Optimized geometric parameters are: R2 = 1.0 mm, W2 = 0.5 mm, M2 = 0.5 mm, G2 = 0.05 mm, subH = 0.2 mm, D2 = 4.1 mm, D3 =6.1 mm, D4 = 8.1 mm, and D5 = 10.1 mm.