Corrugated horn of HE/11/ and HE/21/ mode

A corrugated, monopulse feed conical horn is described which uses HE(11) as the sum mode and HE(21) as the difference mode. It is shown that when the horn aperture radius-to-free space wavelength ratio is large, the balanced hybrid condition can be met for both modes in order to yield rotational symmetry beams and low sidelobe levels. A discussion is given of the mode selection method which uses special points on trace charts, and that which uses a ringloaded, corrugated taper section as the transformation section from the smooth-wall waveguide to the corrugated horn. The input voltage standing wave ratio measured in the sum channel is less than 1.05 in 20% bandwidth.