Effects of an intervening airgap on the two fundamental modes of a surface waveguide

The introduction of an intervening airgap in a circular surface waveguide is investigated. The radial field structure and the propagation characteristics of the two fundamental modes are shown, as well as their dependence on the airgap and the frequency. The thickness of the airgap is a new parameter that might be used to improve the propagation characteristics of the surface waveguide as a low-loss transmission line, or to control the penetration of the fields in the surrounding medium, allowing a design of the waveguide as a leaky transmission line.