Design of a Multilayer Frequency Selective Surface Structure with Air Gaps

This work presents a novel frequency selective surface structure that integrates edge slots, complementary square units, and air gaps. The double- and triple-layer configurations achieve an optimal balance between passband width and flatness by adjusting the air gap thickness. Increasing the number of layers introduces additional poles within the passband and enhances the roll-off characteristics. The proposed structure demonstrates a passband ranging from 8.19 to 10.96 GHz with robust performance under oblique incidence. A 20×20-unit prototypes were fabricated to validate the proposed design, and experimental results closely align with simulations, confirming the design’s effectiveness.