Surveying Antenna For Satellite Navigation System

Antenna phase center variations and multipath effect are two major error sources of Satellite Navigation receiver surveying accuracy, which can not be ignored in high precision surveying applications. Based on the above application background, this thesis focuses on surveying antenna to analyze antenna phase center characteristics and multipath rejection, including studying the effect of antenna performance on carrier signal accuracy, design of antenna with high phase center stability, design of choke ring, and studying on anechoic chamber antenna phase center calibration method. It contains four sections:In section I, the effect of antenna performance on positioning accuracy is described. Antenna phase center is described and its influence on positioning accuracy is analyzed. Methods to mitigate antenna phase center variations are listed: stable phase center antenna design and phase center calibration. The antenna performance characteristics in presence of multipath are analyzed in terms of axial ratio based on the model of multipath signals. The relationship between antenna performance and carrier amplitude/phase measurement accuracy is presented, providing the base for Satellite Navigation receiver antenna design.In section II, an Archimedean spiral slot antenna is studied. Parameters of the antenna are analyzed in order to find out how they affect antenna performance. The optimum parameters of the antenna are listed and measured results show that zenith gain, low elevation angle gain, axial ratio, 3dB bandwidth and phase center stability of the optimum antenna are significantly improved compared to the initial design. Compared to Novatel's GPS-702 antenna, zenith gain, low elevation angle gain, axial ratio and 3dB bandwidth of the optimum antenna are improved while phase center stability keeping the same. A novel dual-band 8-arm spiral slot antenna with inner/outer feed is designed. The novel antenna has two output ports with each resonating at one band. Each band of the antenna can be left circular polarization or right circular polarization.Anechoic chamber antenna phase center calibration method is analyzed in section III. Mean phase center offset and phase center variations are estimated by means of least-squares estimation based on measured antenna phase pattern. The error sources of the calibration method are analyzed through theory analysis and numerical simulations in order to provide methods to reduce calibration errors. The antenna phase center calibration examples show that the difference of calibration results between anechoic chamber and NGS's field calibration is less than 2mm and the repeatability of the calibration method is less than 1mm. So the creditability of the calibration method is verified. Choke ring which is an effective method to mitigate multipath effect is analyzed in section IV. Surface impedance model is used to analyze boundary conditions of choke ring to find out basic rules of deciding choke ring parameters. Performance of choke ring can be improved in terms of low elevation gain and multipath rejection ability by optimizing its various parameters. A 3D choke ring is designed according to the above parameters analysis results. Several different types of antennas mounted on the 3D choke ring are measured. Results show that the 3D choke ring has no effect on phase center stability of the antennas. Low elevation angle gain and multipath rejection can not be satisfied simultaneously. Improving multipath rejection will decrease low elevation angle gain.This thesis provides guidance for high precision satellite navigation surveying antenna design, and provides the methods for antenna mulitpath mitigation and anechoic chamber antenna phase center calibration.