The phase centers of aperture antennas

Two methods are given for the determination of the phase center of aperture antennas. These methods are used to obtain the phase centers of electromagnetic horn antennas treated as aperture antennas. The second-derivative method is more accurate and uses less computer time, while the two-point method is more accurate and uses less computer time, while the two-point method is easier to understand and to derive. Calculated and experimental results are compared.