Modes of Propagation in a Coaxial Shielded Surface Wave Guide

Abstract

The characteristic equations giving the allowed modes of propagation of electromagnetic waves in a coaxial cable are obtained, assuming a lossless structure with the bounding sur-faces offering a reactive impedance. Only the axially symme-tric mode is considered and the possible surface wave modes between general reactive boundaries are obtained by a graphical solution, of the eigen value equation, In general, two surface wave modes and infinitely many waveguide modes are obtained. One of the surface waves is found to exhibit a threshold pheno-menon when the parameters of the system are varied and is found to go into the lowest order conventional waveguide mode when the threshold point is crossed, while the other surface wave exists for all values of the parameters. The latter is iden-tified as the dual coaxial surface wave mentioned by Barlow. Also the electric field patterns of the surface wave modes are obtained, wherein the surface wave exhibiting thre-shold phenomenon is found to have a pattern quite resembling th-1t cf the lowest order waveguide mode. Extensive use of IBM 1620 computer has been made during the course of the investigation.