Circular waveguide section with dielectric tube - uses rings supported coaxially inside to lower cut-off frequency of unwanted mode

摘要

The circular waveguide section, for the H11-mode, has a tube (2) coaxially inside it to lower the cut-off frequency of the H01-mode in the guide. The tube is constructed of rings of low-loss dielectric material supported to leave a gap between the tube and the guide walls, and located in the region where the H01wave has its greatest electric field strength. The wall thickness of the tube is such that the dielectric material extends (+-) 10% around the diameter traced by maximum electric field strength of the H01 wave. The dielectric tube suppresses unwanted wave modes, especially the E01 wave.