On improvement of the radiation performance of the open-ended circular waveguide

The cross-polar performance is analyzed for radiation of the TE11 mode from the open-ended circular waveguide of typical diameter of around one wavelength. The internal waveguide surface at the end is loaded with a finite longitudinally corrugated section with grooves filled with dielectric. The analysis is based on the mode-matching method combined with the method of factorization taking into account all the effects associated with wave scattering at the open end. It is shown that the width of the frequency band where the cross-polar level is not higher -30 dB can potentially be made a few times wider in comparison with the 27 % bandwidth corresponding to the ordinary circular waveguide. The influence of the higher-order modes excited at the aperture on the radiation performance is also discussed.