Surface Plasmon Transmission Line Based on Folded Stepped Grooves and Spiral-Shaped Structures

In this paper, a novel coplanar waveguide (CPW) spoof surface plasmon polariton (SSPP) transmission line (TL) is firstly proposed. The equivalent circuit model is established to analyze the effects of the folded stepped groove and spiral-shaped structure. The investigation based on the equivalent circuit model indicates that the dispersion curves can be easily controlled by changing the inductance brought by the etched grooves and spiral structure. The proposed SSPP has a lower cutoff frequency, stronger field confinement, and smaller system size. The proposed SSPP TL is designed, fabricated, and tested, providing experimental demonstration for the design and analysis. The measured S-parameters and electric field distributions indicate that the designed SSPP structure enhances the electric field confinement ability, while achieving miniaturization of SSPP TL.