电离层闪烁对卫星导航信号及性能的影响机理研究

Currently the Beidou Satellite Navigation System (Beidou) has stepped into initial navigation service operation for the Asia-Pacific Region. Beidou navigation signal testing and performance evaluation are the main focus during the later stage Beidou system construction. Almost one third of China's airspace is located in low attitude, where most severe ionosphere activity exists. Ionospheric scintillation, one of such activity, has great influence on navigation signals and performance. Based on the current Beidou system technology and foundation, our project will deeply investigate the influence mechanism of ionospheric scintillation on navigation signals. The research is conducted from the aspects of ionospheric scintillation influences on navigation signal propagation, receiving and performance evaluation. Adaptive supportive vector machine (SVM) is adopted to classify navigation signals effected by ionospheric scintillation with different degrees, so as to build a high precision navigation signal model under scintillation; Interactive multiple model (IMM) is adopted to maintain continuous navigation signals tracking under scintillation; a joint code-carrier navigation observation architecture is designed to achieve robust navigation integrity evaluation under scintillation. Our goal is to break through the key technology of Beidou signal receiving and performance evaluation under ionospheric scintillation, and further broaden Beidou's application fields. Our research also provides theoretical foundation and technical support for high safety operation of aircraft and land vehicles.

目前, 我国具有独立自主知识产权的北斗二代导航系统已具备亚太地区的导航服务能力，北斗二代导航信号接收的测试和性能评估成为二代导航系统后期建设的主要攻关方向。我国空域约有三分之一处于电离层活动频繁的低纬度地区，该区域的电离层闪烁对卫星导航信号及性能具有较大影响。本课题将结合我国北斗二代卫星导航系统技术现状基础，从导航信号传播、接收和性能评估三个层面，深入研究我国空域范围内电离层闪烁对导航信号性能的影响机理，通过自适应支持向量机对不同程度闪烁信号进行分类，实现电离层闪烁下高准确度导航信号建模；通过交互式多模型导航信号跟踪构架实现电离层闪烁下导航信号高连续性跟踪；通过联合观测量的自主完好性监测实现电离层闪烁下导航完好性高可靠性评估。从而突破电离层闪烁下北斗二代导航信号接收和导航性能提升的关键技术，以扩展其导航应用领域，为复杂条件下飞机、车辆等机动载体的高安全性运行提供理论储备和技术支撑。

电离层闪烁对卫星导航信号产生影响主要表现在幅度的衰减和相位的震荡，进而影响导航信号的接收和使用。本项目研究了电离层闪烁对卫星导航信号及性能的影响机理，通过对地基卫星导航电离层闪烁监测数据进行时空统计分析和特征关联挖掘，验证了电离层闪烁下导航信号幅度的逼近统计模型符合a-u分布；在此基础上，考虑电离层闪烁下部分导航信号受到的衰减影响，形成强、弱导航信号共同存在的接收场景，设计双门限导航信号检测方法以降低强、弱导航信号互相关干扰对弱信号接收的影响；考虑电离层闪烁下导航跟踪观测量的不稳定性，设计了非线性滤波导航信号跟踪方法和残差卡方失锁检测机制，以提高电离层闪烁下导航信号跟踪鲁棒性；考虑到电离层闪烁下部分导航观测量质量下降甚至失效，建立了面向航空运行的导航性能评估体制，并从理论上分析了电离层闪烁引起失锁对导航精度、完好性等的影响；采用空地联合电离层闪烁观测数据，分析了南半球电离层闪烁的时空相关性、季节相关性，验证了电离层闪烁与太阳活动、地磁活动之间的强耦合关系，并发现了一些电离层闪烁反映的异常空间天气事件。本项目的研究为全面认知电离层闪烁与导航信号、性能之间的耦合机理奠定良好基础，可应用于空间天气监测、卫星导航、空天通信等领域。