Offset Gregorian antenna

The paper considers the theoretical and experimental characteristics of the offset Gregorian antenna. The configuration conditions, the method of computation of the radiation characteristics, and a design example for a test antenna are given, and the computed and experimental radiation characteristics are compared when a conventional conical horn and a dielectric loaded horn are used as the primary radiator. Data are also given for the case where absorbers suppress the sidelobes in the wide-angle directions. Although no surface correction is done, the test antenna has an aperture efficiency of about 66% and the maximum value of its cross-polarized lobe near the main beam is about 30 dB below the main beam. The envelope is almost at the isotropic level at an angle from the axis eight times greater than that of the 3-dB down point on the main beam, and in the wide-angle direction the envelope is about 30 dB below the isotropic level.