Vondrak-Cepek组合滤波在北斗共视和卫星双向时间比对融合中的应用

为减小卫星双向时间比对(Two-Way Satellite Time and Frequency Transfer, TWSTFT)中的周日效应,利用北斗共视链路没有周日效应的特点,通过Vondrak-Cepek组合滤波方法对中国科学院国家授时中心(National Time Service Center, NTSC)、德国物理技术研究院(Physikalisch-Technische Bundesanstalt, PTB)以及中国计量科学研究院(National Institute of Metrology, NIM)间的北斗共视时间比对结果分别与硬件卫星时间和距离测量设备(SAtellite Time and Ranging Equipment, SATRE) TWSTFT和软件接收机(Software-Defined Radio, SDR)TWSTFT结果进行了融合处理。采用时间偏差和幅值频谱两个指标以及GPS精密单点定位(Precise Point Positioning, PPP)时间比对分别对融合结果进行内外符合评估。结果表明,经过Vondrak-Cepek滤波的融合结果中周日效应基本消失,其与GPS PPP链路差值结果的绝对值保持在链路校准的不确定度范围内。对于长基线NTSC-PTB链路,融合结果1 d的时间偏差稳定度对SATRE和SDR TWSTFT的增益因子分别为1.85和1.81；对于短基线NTSC-NIM链路,融合结果对SATRE和SDR TWSTFT的增益因子分别为1.69和1.59。融合结果的短期稳定度显著提高。

Application of Vondrak-Cepek combined filtering in the fusion of BeiDou CV and TWSTFT

In order to reduce the diurnal in TWSTFT (two-way satellite time and frequency transfer), based on the fact that there is no diurnal in BeiDou common view link, the Vondrak-Cepek combined filtering was applied to combine BeiDou common view and SATRE (satellite time and ranging equipment) TWSTFT or SDR (software-defined radio) TWSTFT among NTSC (national time service center), Chinese Academy of Sciences, PTB (physikalisch-technische bundesanstalt) and NIM (national institute of metrology). Two indexes, namely time deviation and amplitude spectrum, were used to evaluate the gain factors in reducing the diurnal of the fusion results, and the agreement of the two types of links was revealed by taking GPS PPP (precise point positioning) time comparison as reference. Results show that the diurnal of the fusion results is greatly improved after Vondrak-Cepek combined filtering, and the absolute value of the differences between the fusion solutions and GPS PPP solutions is kept within the calibration uncertainty of time link. For the baseline of NTSC-PTB, the gain factors of 1-day time deviation(TDEV) of fusion results versus SATRE TWSTFT and SDR TWSTFT are 1.85 and 1.81, respectively. For the baseline of NTSC-NIM, the gain factors are 1.69 for SATRE TWSTFT and 1.59 for SDR TWSTFT. The short-term stability of fusion results is significantly improved.