Compact wideband FSS bandstop filter for S, C, and X band applications

This paper presents a novel triple-band frequency selective surface (FSS) designed as a bandstop filter operating at 3.24, 6.08, and 10.88 GHz, corresponding to the S, C, and X bands, respectively. The design is notable for its polarization insensitivity, exhibiting a consistent frequency response for both TE and TM modes. A key feature of the proposed design is its stability at oblique incidence angles up to 45° for both polarizations. The proposed model is validated using an equivalent circuit model. A detailed examination of the electric field and surface current distribution is conducted to explain the resonance behavior. The fabricated triple bandstop FSS prototype shows good agreement between simulation results and experimental measurements. The structure is highly compact, with each unit cell area of 0.25λg×0.25λg, where λg represents the guided wavelength.