An Automatic Test System for Axial Ratio of GPS Microstrip Antenna

During the design of GPS microtrip antenna, the axial ratio of antenna is a vital parameter, so it should be measured and assure it less than 2dB. In order to promoting the efficiency of testing, it´s necessary to design an automatic test system for axial ratio. In this paper, an automatic test system based on GPIB and NI Labwindows/CVI for GPS microtrip antennas is discussed. With the automatic test system, we can measure the axial ratios automatically in the microwave anechoic chamber, which can reduce the electromagnetic interface outdoor. The tested axial ratio varied with measuring frequencies is displayed with the diagram of curve and tables. By the diagram we can judge intuitively if the frequency of the best axial ratio is on the GPS working frequency or not. If there is frequency shift, the shift direction can be a guidance to modify the GPS patch. The automatic test system has been used in our research center and works well.