Transverse-network representation for inhomogeneously filled circular waveguide

A transverse-network representation for hybrid modes in inhomogeneously filled waveguides is derived using a method employed previously in the representation of slotted waveguides. It is shown that hybrid modes may be represented by a pair of coupled radial-line modes of pure H and E type. General expressions for the input impedances and admittances of the H- and E-type radial lines are developed at the rod boundary, and particular expressions for the unbounded rod and Goubau line are also presented. The influence of the above impedances and admittances upon the propagation characteristics of dielectric-loaded waveguides is considered for circularly symmetric and asymmetric modes. In particular, it is shown that the appearance of a backward-wave region can be interpreted as a frequency-pulling effect of one radial-line resonator upon the other. The extension of the representation to inhomogeneous waveguides with azimuthally nonuniform terminations is also briefly mentioned.