双TWSTFT链路北斗站间时间频率传递：钟差阿伦方差的置信区间计算  

2-GEO TWSTFT for BDS ground stations: Confidence interval of clock difference Allan variance

作　　者：杨文可 龚航[2] 胡小工[3] 韦素媛 郭文普[1] 

机构地区：[1]第二炮兵工程大学信息工程系,西安710025 [2]国防科学技术大学,电子科学与工程学院,长沙410073 [3]中国科学院上海天文台,上海200030

出　　处：《中国科学：物理学、力学、天文学》2015年第7期8-15,共8页Scientia Sinica Physica,Mechanica & Astronomica

摘　　要：卫星双向时间频率传递(TWSTFT)是我国北斗卫星导航系统(BDS)中实现地面站之间时间频率传递的重要方法.不同于通常的站间时频传递系统,BDS的一些地面站之间通过两颗地球静止轨道卫星实现了双TWSTFT独立比对链路.基于此双链路特征,我们之前的研究表明,通过有效分离钟差阿伦方差与测量噪声阿伦方差,可降低测量噪声对站间钟差频率稳定度评估(阿伦方差表示)的影响.本文在假设测量噪声为相位白噪声,钟差噪声为频率白噪声的情况下,推导给出了BDS双TWSTFT链路分离测量噪声阿伦方差获得的站间钟差阿伦方差置信区间的计算方法.对BDS实测数据分析表明,平滑时间=1 s时,通过双TWSTFT链路可获得的站间钟差的阿伦偏差(阿伦方差的平方根)的置信区间上限为3.2481012(置信度0.95).相比之下,通过单TWSTFT链路直接获得的站间钟差的阿伦偏差仅为(8.59–8.91)×1011(=1 s).本文结果进一步表明,利用两条独立比对链路,可以将测量噪声阿伦方差与钟差阿伦方差进行有效分离,从而减少测量噪声对钟差频率稳定度评估结果的影响.Two-way satellite time and frequency transfer （TWSTFT） is important for time and frequency transfer between ground stations in Chinese BeiDou Navigation Satellite System （BDS）. Different from ordinary TWSTFT links with single geostationary （GEO） satellite between each pair of ground stations, there are 2-GEO TWSTFT links between ground stations in BDS. Based on the 2-GEO TWSTFT links, we have proposed a separation method of estimating Allan variance of clock difference apart from the influence of Allan variance of noise measurement. This paper analyzes the confidence interval of the clock difference Allan variance obtained by this method with the condition that the noise measurement is white phase noise and the clock difference is affected by white frequency noise. The results applied to the BDS measurement data show that the obtained confidence interval upper bound of clock difference Allan deviation （the square root of Allan variance） is 3.248×10-12 with 0.95 confidence. Compared with the single link TWSTFT with Allan deviation of （8.59-8.91）×10-11（r=-i s）, it proves further that the separation method has ability to weaken the influence of noise measurement on the evaluation of Allan deviation of clock difference measured by two independent TWSTFT links.

关 键 词：北斗卫星导航系统 卫星双向时间频率传递 频率稳定度 阿伦方差 置信区间 

分 类 号：TN96.1[电子电信—信号与信息处理]