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.

In this letter, a miniaturized and dual-stopband frequency selective surface(FSS) with a large band ratio(BR) is presented. This structure is composed of one metal layer and two dielectric layers and has excellent miniaturization characteristics. In particular, the unit size is only 0.054λ0 and the thickness is only 0.014λ0, where λ0 is the wavelength corresponding to the first resonant frequency. And there is only one layer of metal layer, which greatly reduces the processing complexity and cost.