A phase center of conical horn antennas

The phase center of a horn is referred to as the center of curvature of an equiphase plane of radiation fields on the central axis of the horn. An equation of the phase center is obtained for the case of axisymmetric and nonaxisymmetric aperture field distributions. Based on this expression, the phase center of TE(11) mode-excited conical horns, corrugated horns, and dual-mode horns is determined. A condition is derived under which the phase centers of the E and H planes coincide, and the validity of the method for determining the phase center is examined numerically. It is shown that in the near-axis region, the center of curvature of the equiphase plane on the central axis of the horn can be used as the phase center with sufficient accuracy.