Antenna Phase Center Determination Using a Six-Port-Based Direction-of-Arrival Detector

This article presents a novel technique to determine the antenna phase center. It relies on measuring the direction of arrival (DOA) of the radiated field. Therefore, no access of the measurement equipment to the antenna under test (AUT) is required. A direction-of-arrival detector is implemented that performs phase difference measurements in two orthogonal planes. Six-port interferometers are used for this purpose. By considering phase differences, the proposed method is robust against phase disturbances, which may occur at the feed of the AUT, e.g., due to flexible cables or rotary joints. Besides, impairments stemming from reflections in the measurement environment are addressed. Measurements of a K-band horn and a patch antenna in an anechoic chamber validate the approach. A single phase center is determined for each principle plane as well as for the 3-D main beam. In addition, the phase center locus is retrieved.