MODE SPECTRUM OF THE MODIFIED GOUBAU LINE.

The problem of surface-wave propagation over the modified Goubau line, which consists of a Goubau line with an airgap between the conductor and dielectric, is formulated by the boundary-value method. The various modes which exist on the line as well as their cutoff conditions and the specific effects of the airgap are obtained from a solution of the characteristic equation. The mode spectrum for the symmetric and hybrid modes as well as the transverse field distributions for the E//0//0 and H//0//1 modes are presented. The axial power flow and the attenuation constant are calculated for the dominant mode. The salient low-loss feature may be explained in terms of total internal reflection or duct propagation phenomena. 24 refs.