基于两级互模糊函数的脉冲星导航系统累积脉冲轮廓时间延迟测量算法

Pulsar Integrated Pulse Profile Time Delay Measurement Based on Two-level Cross Ambiguity Function

在X射线脉冲星导航系统中,X射线脉冲星信号累积脉冲轮廓的时间延迟测量精度受到时间尺度伸缩的影响严重。为解决该问题,提高累积脉冲轮廓时间延迟的测量精度,降低运算量,首先分析了X射线脉冲星累积脉冲轮廓特征,建立了一种新的累积脉冲轮廓数学模型。在此基础上,提出了一种基于两级互模糊函数的时间延迟测量算法。该算法可精确表征脉冲星标准轮廓和累积脉冲轮廓之间的尺度差异,可精确估计累积脉冲轮廓和标准轮廓之间的相位差,推导了时间延迟估计的克拉美罗下界。最后,采用美国罗西卫星X射线时变探测器的观测数据进行试验。结果表明,提出的算法不受时间尺度的影响,当信噪比高于26 d B时,时间延迟测量精度逼近克拉美罗下界。与现有的Taylor FFT算法相比,本文提出的算法具有更高的测量精度和更强的适应性,适用于X射线脉冲星导航的工程应用。

In X-ray pulsar based navigation（XNAV） system,the time delay measurement accuracy of pulsar integrated pulse profile（IPP） is seriously affected by the time scaling of IPP.To improve the time delay measurement accuracy,this paper analyses the features of IPP in XNAV system,and builds a new mathematical model to characterize the time scaling of IPP.Then,a time delay measurement algorithm based on two-level cross ambiguity function（TLCAF） is proposed.The TLCAF can represent the commonality between IPP and pulsar standard profile through the Gaussian common function,and thus the time delay and time scaling can be jointly estimated by the maximum of TLCAF. The Cramer-Rao lower bound（CRLB） for the estimation of time delay is also presented.The experiments are conducted using the data observed by Rossi X-ray timing explorer.The results show that this algorithm can eliminate the time scaling affect,and reaches the CRLB when the SNR of IPP is higher than 26 d B.This algorithm has higher measurement accuracy than the existing algorithms and is more suitable for XNAV system.