Hybrid Spoof Surface Plasmon Polariton and Half-Mode Substrate Integrated Waveguide Bandpass Filter

In this study, a simple L-type spoof surface plasmon polariton (SSPP)-based miniaturized half-mode substrate integrated waveguide (HMSIW) bandpass filter (BPF) is proposed. The cut-off frequencies of the passband's left and right edges can easily be changed by modifying the HMSIW and SSPP parameters. Dispersion curves and the distribution of the electric field help to elucidate the physical mechanism of BPF. To improve high frequency performance, the structure is given a quick transverse slit. The simulation results show that the proposed BPF achieves a bandwidth (for S11 < −12 dB and S21 > −0.8 dB) of 80% (7.71 - 15.71 GHz). Comparing this structure to the conventional HMSIW with the same cut-off frequency, this new HMSIW-SSPP design has a 36.2% reduction in lateral dimensions, with a size of only 0.97λ 0 ×0.22λ 0 . The proposed structure can not only realize miniaturization, but also be used in small microwave circuits.