Interaction between Surface Waves on Wire Lines

This paper investigates the coupling properties between surface waves on parallel wires. Finite Element Method (FEM) based and analytical models are developed for both single wire Sommerfeld and Goubau lines. Starting with the Sommerfeld type wave, we derive the analytical expression based on the assumption that the two-wire surface wave is a superposition of the two surface waves on the individual wires. Models are validated via measurements and a comparison study conducted between the analytic and the FEM-based computations for coupled Sommerfeld type lines. We then investigate the coupling between two Goubau lines with the FEM model. The measurement and calculations show remarkable agreement. The FEM-based and the analytical models match remarkably well too. The results exhibit new properties of favourable effects on surface waves propagation over multiple conductors. The short range behaviour of the coupled wires and consequently the existence of an optimum separation of coupled wires, is one of the most significant findings of this paper. We comment on the relevance of our results especially in relation to applications of high bandwidth demands and immanent cross-coupling effects.