Research On Evaluation Methods Of GNSS Signal Quality And The Influence Of GNSS Signal On Ranging Performance

Navigation signal is one of the most important factors for a GNSS (Global NavigationSatellite System) to achieve precise navigation, position, velocity and timing. The pros and consof a navigation signal will directly reflect the working conditions and electrical performance ofthe satellite payload. Therefore, evaluating GNSS signal quality is of great importance in thedesign and operation process of a satellite system. It can provide a technical support not onlyfor the design of navigation signal but also for the in-orbit validation of key technologies. Inaddition, monitoring and evaluating signals quality of other navigation satellite systems canprovide a valuable reference for Chinese scientific researches and applications. To provide userswith high-quality services, GPS and Galileo have already built their own signal qualitymonitoring and evaluating systems. They can not only monitor and detect GPS or Galileo signalsbut also signals of other countries, thus to a certain extent improve the accuracy and reliability oftheir navigation satellite systems.The achievements of researches on GNSS signal quality monitoring and evaluating willplay a very significant role in many areas such as signal design, signal validation, performanceassessment, integrity monitoring, and satellite fault fast locating of BeiDou navigation satellitesystem. Those achievements can not only promote the development of signal design andevaluation of Chinese BeiDou navigation satellite system, but also provide the decisionsupporting information for the maintenance and management of BeiDou system. An accurateevaluating result can ensure the high quality of service performance for navigation satellitesystems, which will improve the competitiveness of BeiDou system in the international arena.Therefore, monitoring and evaluating GNSS signal quality is of great economic and strategicsignificance. Meanwhile, the achievements of this thesis will also play an important role in thefield of international cooperation.This thesis conductes researches mainly on the basis of three aspects: evaluation contentsand methods of GNSS signal quality, generation mechanism of GNSS signal distortions and theinfluence of GNSS signal distortions on service performance. Those typical results of GNSSsignal quality evaluating are shown in the end. This thesis could be divided into five parts:(1) GNSS signal systemThe generation mechanism and signal characteristics of GNSS signals are introduced indetail in this thesis, including signals of American GPS, European Galileo, Russian GLONASS and Chinese BeiDou system. In addition, code tracking accuracy and code multipath error ofdifferent signals are analyzed and compared. Consequently, current and future GNSS signals aregiven on this basis, providing a reference for extracting the objects and criteria for evaluatingGNSS signal quality.(2) Objects and criteria for GNSS signal quality evaluatingThose detailed objects and criteria for GNSS downlink signal evaluating are studied anddescribed based on the analysis of GNSS signal system and some other performance indicatorssuch as ICD (Interface Control Documents), technical requirements for payload development,ground test results of payload, ideal values or curves of designed signals. The extractedevaluating objects and criteria could be used as the judging basis and criteria for GNSS signalquality monitoring and evaluating.(3) Methods for evaluating GNSS signal qualityThe processing methods of different data that are needed for GNSS signal qualityevaluating were described in detail. Data used for signal quality evaluating includes the RFsignal monitoring data, offline collected data, outputs of monitoring receivers, interferencemonitoring data, calibrating data, meteorological monitoring data and so on. In addition, theindividual elements and comprehensive contents of GNSS signal quality evaluating are extractedbased on the elements of signal design, evaluating contents of PVT performance and technicalrequirements for payload development. The evaluating methods of all contents are introducedexhaustively, and a suit of methods for GNSS signal quality evaluating is established, which canevaluate GNSS signal quality comprehensively.(4) GNSS signal distortion modelsThe biggest highlight of this thesis is the in-depth analysis of various types of GNSS signaldistortions. The generation mechanisms of GNSS signal distortions, together with the influencesof signal distortions on signal quality evaluation and service performance are analyzed in detail.Mathematical analysis models are constructed for different distortions such as the carrier leakageand asymmetry of PSD, code waveform distortion, inter-symbol interference, multipath,environmental interference, AM-AM Saturation, AM-PM distortion. The qualitative orquantitative analysis of the influence of each distortion on signal quality evaluation and serviceperformance are given in this thesis.(5) Evaluating results of GNSS signal qualitySignals of BeiDou, GPS, Galileo and GLONASS in-orbit satellites are monitored and evaluated comprehensively from such aspects as RF equipments monitoring, offline analysis ofPSD, ranging code waveform, modulation performance, correlation performance, rangingstability, coherency property, and multipath performance. This thesis demonstrates some typicalresults of GNSS signal quality evaluating for the first time in the world. Results show that thoseanalysis methods proposed in this thesis are feasible for GNSS signal quality evaluating withhigh accuracy.