Dielectrically sheathed posts in waveguides

Abstract

In this thesis the problem of coaxial-line cylindrical probe transitions to a variety of different waveguide environments is examined for the case where the probe is located between two parallel metal plates. A general model is developed for a dielectrically sheathed, coaxially driven probe to general radial-line type waveguide region which is characterised by an environment factor. The general model is then used to examine coaxial-line to radial-line, cylindrical cavity, and rectangular waveguide junctions. Three probe configurations are considered, firstly where the probe extends the full height of the waveguide, secondly where the probe extends part of the way into the waveguide, and thirdly where the probe spans the full height of the waveguide and has a gap of arbitrary size and position. The Iast two cases make use of the full height model as a kernel and so the generality of the full height solution is retained in the partial height solutions. Theoretical investigations of the influence of dielectric sheathing on the current distribution on the probe and input admittance to the junctions, including an examination of the bandwidth performance of coaxial-line to rectangular waveguide, are presented. Comparisons of theoretical predictions with experimental measurements for a range of different dielectric sheath parameters shows the theoretical model to be very accurate.