A Second-Order Dual X-/Ka-Band Frequency Selective Surface

In this letter, a new technique for designing dual-band frequency selective surfaces with arbitrary bands of operation, with second-order band-pass responses at each band of operation, is presented and experimentally verified. The technique is based on utilizing a particular topology of a second-order band-pass microwave filter and synthesizing its constituting elements using periodic structures with inductive, capacitive, or resonant type surface impedances. The result is a low-profile planar structure composed of three metal and two dielectric layers that acts as a spatial version of the dual-band microwave filter.