0000000000085082
AUTHOR
M.v. Andres
Technical memorandum: Mode classification in cylindrical surface waveguides
A new method to analyse the TM-TE field structure of hybrid modes in cylindrical surface waveguides is proposed. This method, as well as others previously suggested, is applied to a dielectric-coated wire with an intervening airgap. Our results reveal that they cannot be classified into quasi-TM and quasi-TE modes. However, a scheme of mode designation is proposed, based more on mathematical properties than on the field structure.
Cylindrical surface waveguide modes using a surface impedance dyadic method
The fields and characteristic parameters of nonradiating modes of a dielectric-coated wire with an intervening airgap are derived using a surface impedance dyadic method. This method shows several advantages and provides a straightforward method for working out the characteristic equation, cutoff conditions, far-from-cutoff conditions and field coefficients. Important results about the hybrid nature of these modes are shown, and some of them are common to any cylindrical surface waveguide.
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.