Design of a Multi-layer Dual-band Frequency Selective Surface Bandpass Filter

A multi-layer cascaded passive bandpass frequency selective surface is presented in this paper. It provides a narrow and wideband passband in the frequency range of 2 to 8 GHz. It is based on a square patch and aperture with a double split ring-shaped slot in the middle layers. The FSS demonstrates bandpass response of higher order with three transmission poles at 4.5-6 GHz band and one pole at 4.2 GHz. The passbands are significantly distanced by two transmission zeros at 4.4 GHz and 4.6 GHz, resulting in substantial out-of-band rejection. It is illustrated that changing the split ring slot’s gap can control thepoles, then one design is selected as optimum.