BDS-3时间频率传递方法及其性能分析

我国独立自主建设的全球卫星导航系统——北斗三号（BDS-3），在2018年底已完成基本系统建设，计划2020年底全面建成并正式为全球用户提供定位、导航和授时服务。考虑到BDS-3系统与BDS-2区域系统在覆盖范围、卫星载荷、信号设计等方面的差异，其远程时间传递的性能有待进一步分析研究。利用GNSS时间传递中的共视法和载波相位时间传递方法，基于国际时间实验室BDS-2和BDS-3的短基线、长基线时间传递链路，对其时间传递链路的噪声水平和频率稳定度进行定量分析。实验结果表明，对于共视法，在时间传递的噪声水平和频率稳定度方面，BDS-3都明显优于BDS-2；长基线链路的精度为1.48ns（BDS-3）和3.13ns（BDS-2），短基线链路的精度为0.65ns（BDS-3）和1.02ns（BDS-2）。对于载波相位方法，BDS-3和BDS-2时间传递的噪声水平相当，长基线链路的精度为0.20ns，短基线链路的精度为0.02ns；但在频率稳定度方面，BDS-3优于BDS-2。

BDS-3 Time Frequency Transfer Method and Performance Analysis

As a global satellite navigation system independently built by China, BDS-3, has completed the basic system construction by the end of 2018. It is scheduled to be fully completed by the end of 2020 and officially provide positioning, navigation and timing services for global users. Considering the difference between BDS-3 system and BDS-2 regional system in coverage, satellite load, signal design and so on, the performance of remote time and frequency transfer needs further analysis and research. In this paper, the short and long baseline time links of BDS-2 and BDS-3 in international time laboratories are formed, and the noise level and frequency stability of time transfer links are quantitatively analyzed by using common view (CV) and carrier phase (CP) approaches in GNSS time transfer. The results show that BDS-3 is superior to BDS-2 in terms of noise level and frequency stability of time transfer in the CV approach, the accuracies are 1.48ns (BDS-3) and 3.13ns (BDS-2) for long baseline time link, and 0.65ns (BDS-3) and 1.02ns (BDS-2) for the short baseline time link. For the CP approach, BDS-3 and BDS-2 have the identical noise level in time transmission, the accuracies are 0.20ns and 0.02ns for the long baseline and short baseline time links respectively, but BDS-3 is better than BDS-2 in frequency stability.