Rectangular dielectric waveguide and its optimal transition to a metal waveguide

摘要

The purpose of this work was to study the rectangular dielectric waveguide and its transitions to metal waveguide at millimeter wavelengths. The thesis reviews different dielectric waveguiding structures, their analysis methods and their transitions to the metal waveguide. In this thesis work the analysis methods and transitions are further developed. The main results of this work are: It was shown that, after modifications, the Marcatili and Goell methods can be applied for calculating propagation constants of rectangular dielectric waveguide made of uniaxial anisotropic material with the optical axis oriented along the dielectric waveguide. Several tapering shapes were studied. It was shown that symmetrical E-tapering gives lower insertion losses and smaller reflections compared with the H-tapering. Different cross-sections and geometry of tapering were studied using Agilent HFSS program. The most appropriate dimensions were found. In the case of unsymmetrical tapering it was shown that better results are achieved when the axes of metal and dielectric waveguides do not coincide but differ by half of the tapering angle. Low insertion loss and small reflections were obtained with sapphire waveguide section. For a 100 mm sapphire waveguide section lower losses were obtained than for a 100 mm standard metal waveguide section. Characteristics of a dielectric rod antenna were measured.