A Compact Bandpass Filter Using 2.5-D Spoof Surface Plasmon Polaritons with Wide Out-of-band Suppression

Abstract

In this paper, a compact bandpass filter (BPF) is proposed using 2.5-D spoof surface plasmon polaritons (SSPP) structure. The 2.5-D SSPP structure consists of two metal layers, single-side corrugated grooves and metallized via-holes. By etching a gap coupling line (GCL) on the top metal layer and a C-shaped defected ground structure (C-DGS) on the bottom metal layer of the 2.5-D SSPP structure, separately, bandpass filtering features with high selectivity and wide out-of-band suppression are produced. Due to introduction of the 2.5-D SSPP structure in the filter design, the lateral size of the BPF can be reduced by 55.6% compared with that of BPF using the microstrip line in the same frequency band. The simulation results show that the proposed BPF has a 3-dB bandwidth from 7.19 GHz to 12.47 GHz and the upper-stopband suppression is more than 50 dB up to 22 GHz.