基于复子载波信号无模糊跟踪的组合环路设计
Design of Unambiguous Combined Tracking Loop for GNSS Complex Subcarrier Signal

复子载波信号是指采用方波复指数函数作为子载波调制的BOC信号，目前已经被广泛应用于全球卫星导航系统。复子载波信号的自相关函数存在多个相关值，在信号同步时会产生信号误捕和跟踪到旁峰的问题。为此，提出了一种适用于复子载波信号的组合跟踪环结构，其中主环采用常规的BPSK-like算法实现信号的初始同步，辅助环分别采用双重估计跟踪算法和旁峰消除算法，与主环共同完成高精度跟踪。首先给出双重估计跟踪算法和旁峰消除算法在此组合环结构下的实现。然后利用仿真数据从跟踪精度和抗多径能力两方面对辅助跟踪环的性能进行分析，并利用实测数据对此环路结构的实用性进行检验。仿真和实测数据跟踪结果表明，提出的辅助组合跟踪结构切实可行并具有较好的抗噪声和抗多径性能。
Complex subcarrier modulation signal, is a kind of BOC signal which is used complex exponential function as subcarrier, has been widely applied in GNSS(Global Navigation satellite system). The existence of multiple correlation peaks of the autocorrelation function of the complex subcarrier signal, will cause the acquisition error and tracking to the side peak when the signal is synchronized. To solve this problem, an unambiguous combined tracking loop for complex subcarrier signals is proposed. In this loop architecture, the main loop completes the coarse synchronization with BPSK-like algorithm, and the assisted loop realizes the accurate tracking together main loop. In this paper, the dual estimate tracking algorithm and the side-peak cancellation scheme are employed respectively in the assisted loop. The performance of tracking accuracy and anti-multipath capability of the proposed architecture is analyzed, and the practicability is verified by using the actual collected data. Simulation and experimental results show that the tracking structure proposed in this paper is practical and has good performance of anti-noise and anti-multipath