Cross-polarization characteristics of a dielectric-loaded horn antenna

It is found with a square horn antenna that the three conditions of low sidelobe level, axially symmetric beam and low cross-polarization level are satisfied when the principal mode, the TE12 mode and the TM12 mode are mixed at the ratio of 82%, 4% and 14%, respectively. With a conical horn the cross-polarization level is less than -28 dB over 13% relative bandwidth and -40 dB over 3% relative bandwidth within a -3-dB beam. When this type of horn is used as a primary radiator an offset paraboloid provides low cross-polarization in circular polarization. It is concluded that a dielectric-loaded horn antenna is suitable for frequency re-use in cross polarization.