Corrugated Horn of HE11 and HE21 Mode

A corrugated conical horn for monopulse feed, which uses the HE11 mode as sum. one and the HE21 as difference one, is described in this paper. When the ratio for the radius of the hor aperture and the free space wavelength is very large, the balanced hybrid condition can be met for both HE11 and RE21 modes. Therefore, the horn has rotational symmetry beams and low side-lobe levels for both sum. and difference modes. The method of design on selecting modes by utilizing special point on trace charts and that of using ringloaded corrugated taper section as the transformation section from the smooth wall waveguide to corrugated horn will be discussed. The input VSWR measured in the sum. channel is less than 1.05 in 20% bandwidth.