A Compact Filtering Power Divider Based on Spoof Surface Plasmon Polaritons and Substrate Integrated Waveguide

In this letter, a compact bandpass filtering power divider with tunable bandwidth based on spoof surface plasmon polaritons (SSPPs) and substrate integrated waveguide (SIW) is proposed. The hybrid-SIW-SSPP structure shows good potential to expand the scope of bandwidth control of the device. The bandwidth can be designed in a wide range by simply optimizing its dimensions or loading interdigital structures (ISs). Defected ground structure (DGS) is also introduced on the bottom layer to further improve the out-of-band suppression. And good isolation can be obtained via additional resistors welded across the SSPP slot. A prototype loaded with dumbbell-shape DGS and two resistors is fabricated with an overall size of 45 mm <tex-math notation="LaTeX">×18 </tex-math> mm <tex-math notation="LaTeX">×0.5 </tex-math> mm. Both <tex-math notation="LaTeX">S₂₁ </tex-math> and <tex-math notation="LaTeX">S₃₁ </tex-math> are around −3.8 dB within the whole <tex-math notation="LaTeX">X </tex-math> -band. The simulated and measured results agree with each other well.