Tunable SIW-SSPP Hybrid Filter with Monolayer Graphene

In this paper, a graphene-based tunable filter with adjustable bandwidth and amplitude is proposed. The structure of filter consists of substrate integrated waveguide (SIW) and spoof surface plasmon polariton (SSPP), controlling the lower and upper cut-off frequencies of the filter, respectively. By integrating monolayer graphene on the surface of SSPP and sweeping the graphene conductivity, the structure of the hybrid filter can be reconfigured, which correspondingly changes the SSPP upper cut-off frequency for bandwidth control. The measurement results of the prototype show that the filter bandwidth changes from 18% to 30%, and the amplitude modulation is larger than 10 dB under a bias voltage from 0 V to 1 V, which has a good agreement with the simulation. The proposed device paves a way to develop graphene-integrated tunable devices at microwave frequencies.