Properties of dielectric-rod junctions in circular waveguide

The paper describes the representation of a junction in circular waveguide between a homogeneous region and one containing an axial rod of circular cross-section. The parameters of an approximate equivalent circuit are obtained in terms of the physical properties of the junction. Experiments are described which show that, for dielectric rods of low relative permittivity, it is reasonable to neglect the junction susceptance. If the relative permeability of the rod is unity, the characteristic-admittance ratio assumes a particularly simple form corresponding to the ratio of the dominant-mode phase-change coefficients on either side of the junction. When the relative permeability of the rod differs from unity, as in the ferrite analogue, the expression for the admittance ratio is more complicated. Results obtained using a digital computer are presented.