极弱信号环境下GPS位同步和载波跟踪技术  

Bit Synchronization and Carrier Tracking for Very Weak GPS Signals

作　　者：赵琳[1] 丁继成[1] 孙明[1] 舒宇[1] 

机构地区：[1]哈尔滨工程大学自动化学院,黑龙江哈尔滨150001

出　　处：《航空学报》2010年第6期1204-1212,共9页Acta Aeronautica et Astronautica Sinica

基　　金：国家自然科学基金(60474046)

摘　　要：为解决环路未锁定、无法找出正确的导航数据位跳变点时极弱全球定位系统(GPS)信号跟踪问题,通过分析信号跟踪模型和相关器1 ms采样数据特性,将最优路径动态规划算法应用于GPS位同步,并提出基于平方根无迹卡尔曼滤波(SRUKF)和位同步结合的载波联合跟踪算法。建立了适合位同步的SRUKF载波环参数估计模型,针对位同步的实现条件和无相位频率先验信息的情况,将位同步模块提前,研究设计了环路未锁定时串行和并行两种弱信号跟踪方案。位同步跟踪完成后环路采用单独的SRUKF工作方式。实验结果证实该文提出的算法具有较高的数据位边缘检测概率(EDR)和参数估计性能,而无须关心环路是否处于锁定状态,能够对载噪比低至22 dB/Hz的弱信号实现跟踪。To implement very weak global positioning system（GPS） signal tracking when the tracking loop is unlocked and data bit edge is unknown,this article analyzes GPS signal tracking models and output characterization of correlators in 1 ms intervals.Dynamic programming algorithm is applied for GPS bit synchronization.In addition,two combination carrier tracking schemes are proposed based on square root unscented Kalman filtering（SRUKF） and designed bit synchronization module,both of which are designed for very low carrier to noise ratio（CNR） signals.To satisfy the bit synchronization operability and realize weak signal tracking,a special SRUKF error tracking model is established and bit synchronization module is performed in advance.The SRUKF works alone after bit synchronization.The testing results indicate that the methods can successfully detect bit edge position with high parametric estimation whether or not the tracking loop is locked.When CNR decreases to 22 dB/Hz,the co-operational tracking scheme is still able to perform.

关 键 词：全球定位系统 位同步 最优路径动态规划 平方根无迹卡尔曼滤波 弱信号 载波跟踪 

分 类 号：V249.3[航空宇航科学与技术—飞行器设计] TP391.9[自动化与计算机技术—计算机应用技术]