A Wideband Reconfigurable Bandstop Frequency Selective Surface with Fast Roll-Off Characteristic

We have proposed a wideband tunable second-order bandstop frequency selective surface (FSS) for C-band microwave applications. It consists of three metal layers sandwiched by two dielectric layers, which is commonly regarded as a composite structure. Specifically, the proposed band-stop FSS achieves fast roll-off characteristic with a rectangular coefficient as low as 1.5. The roll-off rate achieves 23 dB/GHz under dual-polarization incidence. The capacitance value of the embedded varactors can be adjusted from 0.3 pF to 3.2 pF by controlling the bias voltage, thus leading to a continuous tunability of the stop-band from 7.81 GHz to 4.82 GHz, with over 90% energy reflection. Furthermore, an equivalent circuit model is established so as to depict the desired frequency response.