Design of a single-slab low-profile frequency selective surface

This paper presents an extremely thin bandpass frequency selective surface (FSS) operating in X-band. The center frequency of the FSS is 11GHz and its 3-dB fractional bandwidth is 19%. The FSS is composed of conductive circular patches on one side and inductive square rings on the other side of a thin substrate. The diameter of the circular patches, the width of the square rings and the thickness of the substrate are determined using an iterative optimization technique to make the structure resonate at the required frequency. A multi-objective fitness function is used to monitor the scattering parameters to achieve the minimum insertion loss at the center frequency and a good out-of-band rejection.