polarization insensitive

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.