Design of Single and Dual-Channel Filters Based on Spoof Surface Plasmon Polaritons

A novel single-channel lowpass filter and a dual-channel filter based on spoof surface plasmon polaritons (SSPPs) with great out-of-band suppression are proposed in this paper. The novel H-shaped SSPPs unit structure has a circular slot, unlike the conventional H-shaped SSPPs unit. On the basis of the novel H-shaped SSPPs unit, the folded resonator with a short circuit at one end is added to form a new SSPPs structure that can realize the stopband, named the novel H-shaped unit with the folded resonator. To achieve outstanding performance, the filters need to adjust the lengths of the grooves in the transition regions. The bottom of the filters is metallic ground plane. The cutoff frequency of the single-channel lowpass filter is 10.33 GHz, the rejection is 50.45 dB at 11.27 GHz and the insertion loss is better than 1.48 dB. The dual-channel filter comprises a lowpass frequency response in the passband 1 and a bandpass frequency response in the passband 2, respectively. The rejection of the dual-channel filter is better than 50 dB. The filters exhibit good out-of-band suppression and low insertion loss.