PSO-Algorithm-Assisted Design of Compact SSPP Transmission Line

Abstract

This letter proposes a compact spoof surface plasmon polariton (SSPP) transmission line (TL) structure. The particle swarm optimization (PSO) algorithm is utilized to numerically optimize the traditional rectangular groove SSPP structure. The SSPP unit cell is pixelated into 23 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 9 pixels with a resolution of 0.2 mm, and the asymptotic frequency is reduced to 5.4 GHz through optimization. The developed SSPP TL exhibits a compact structure, and its electrical dimension is only about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.842\lambda _{g} \times 0.28\lambda _{g}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{g}$ </tex-math></inline-formula> is the wavelength of the cutoff frequency. A prototype of the developed SSPP TL is fabricated and tested, and the experimental result agrees well with the simulated one. The proposed optimization approach is applicable to both single- and dual-conductor SSPP structures. The results are of great significance to the miniaturization of components and circuits based on SSPP.