Properties of oversized corrugated waveguides at moderate diameter-wavelength ratio

The corrugated oversized waveguides are especially attractive for application in antenna feeds because the lowest hybrid eigenmode HE/sub 11/ in corrugated waveguide produces a radiation pattern with very low sidelobes and cross-poIarization. Besides, under a certain set of parameters (the electrical depth of corrugation about a quarter of wavelength and period less than half-wavelength) this wave in rather wide operating band has much lower attenuation than for any other linearly polarized wave in smooth waveguide. This very interesting effect of ohmic losses decreasing for certain waves in oversized waveguides is mainly considered for travelling HE/sub 11/ wave which has the simplest structure and has frequency far above the cutoff.