Characterizations of GPS User Antennas: Reanalysis and New Results

For several years we have been measuring the RF characteristics of a variety of GPS user antennas at both L1 and L2 using the Goddard Space Flight Center anechoic chamber. The properties that we have measured have included the location of the antenna phase center, and the amplitude, phase, and axial ratio response of the antenna as a function of zenith distance and azimuth. The use of our phase patterns and associated phase centers in the processing of GPS data has proven to be useful. However, a close examination of the phase patterns that we have measured has shown that the locations of the phase centers that we have published may not be optimal.