Dual bandpass filter based on spoof surface plasmon polaritons and half-mode substrate integrated waveguide

In this work, a dual-bandpass filter based on spoof surface plasmon polaritons (SSPPs) and half-mode substrate integrated waveguide (HMSIW) is designed. This filter uses etched metal layers with periodic rectangular groove unit to support SSPPs. Meanwhile, the substrate integrated waveguide (SIW) unit is combined to produce a strong coupling along the propagation direction of the waveguide. The transition section of the gradient of the rectangular groove is supplemented with double rows of metal through holes to limit the propagation of the signal, thus achieving the effect of the dual-bandpass filter. This filter is fabricated and measured. The results verify the excellent ability of the filter and the great band selection ability of the stopband. The measured results show that the insertion loss of the dual-bandpass filter is less than 3 dB in the frequency from 8.7 to 16.4 GHz and 28.3 to 34.6 GHz, and the stopband rejection level is lower than - 20 dB from 17.2 to 26.6 GHz. Compared with the traditional dual-bandpass filter, the proposed filter has lower loss in the passband and stronger rejection ability of the stopband between two passbands.