Yu. N. Kalinin - Ph.D. (Eng.), Leading Research Scientist, «Scientific and Production Enterprise «TRIM» Co., Ltd. (St. Petersburg). E-mail: kalinin_yuri@mail.ru

The subject of measuring the antenna phase center coordinates is one of the most important and actual tasks of antenna measurements. However, this topic is not covered in detail both in national and foreign literature. Recently this task has gained special relevancy in connection with the rapid development and enhanced accuracy of global navigation systems. At present time the method of selecting the positions of an antenna on the positioner is most commonly used to determine the phase center coordinates. In this case, only separate cuts of phase pattern in azimuth plane are measured as a rule and the change of positions occurs in one longitudinal coordinate, which, as a result, determines the PhC position. This article describes the computation algorithm for phase pattern three-dimensional spatial coordinates using a singly measured tridimensional phase pattern. This algorithm can be used during measurements in various spherical coordinate systems corresponding to various types of two-coordinate positioners. It can be used to calculate the phase center coordinates by a random phase pattern section. However, the processing algorithm is greatly simplified during measurements on symmetrical angular intervals relative to zero direction. The special case of this algorithm is used to calculate the phase center two-dimensional coordinates by phase pattern separate cross-sections. The relationships for compensating the phase center displacement during measurements of tridimensional phase patterns and their cuts are provided. The measurement features of antenna tridimensional phase patterns with linear and circular polarization and necessary transformations of these diagrams to eliminate uncertainties and discontinuities in the spherical coordinate system nodes are considered. The peculiarities of phase center application for antennas with circular polarization are considered. The experimental measurement results of spatial phase center coordinates of a satellite navigation system antenna are provided. The computation features of phase center coordinates in measuring the antenna characteristics by the planar scanning method in the near field are considered as well. The software and antenna phase center measurement method have been developed on the basis of materials stated in this articles. They have been implemented in automated antenna measuring systems (AAMS) produced by research and production enterprise TRIM (Saint Petersburg) and successfully applied at many enterprises. This software and measurement method are tailored to user's certain tasks and AAMS application conditions (positioner type, auxiliary antenna polarization type, polarization type of antenna under test, required coordinate system, tuning and monitoring methods for antenna parameters applied by the user etc.).