基于卫星授时的高精度时间同步方法研究

发布时间：2018-03-02 16:28

本文选题：卫星授时　切入点：时间同步　出处：《西安工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：时间的重要意义不言而喻。随着科技的快速进步,在通信、军事和空间探索等领域对时间同步的精度要求越来越高,如何能够实现高精度的时间同步也成为了学者研究的热点和重点。本文研究了基于卫星授时的高精度时间同步方法,该方法综合考虑了卫星授时信号具有的全球性、全天时、全天候覆盖的特点,卫星接收机输出的1PPS信号具有较高的长期平均准确度和稳定度的特点,并且恒温晶振的输出频率具有较高的短期稳定性的特点。使用卫星授时信号对恒温晶振进行驯服,驯服后的恒温晶振作为频率源能够输出高精度的频率信号,从而可以构成基于卫星授时的高精度时间同步系统。在基于卫星授时的高精度时间同步方法研究中,利用卫星接收机锁定卫星后输出1PPS信号,将该信号作为参考频率信号;在FPGA中实现倍频,分频和时间间隔测量功能,FPGA中对恒温晶振进行倍频和分频处理,时间间隔测量方法使用脉冲计数法,测量恒温晶振分频1Hz信号和1PPS信号之间的时间间隔差值,测量完成后产生中断;数据处理模块从FPGA中读取时间间隔差值,通过滑动中位数算法剔除数据序列中的异常值,然后采用无偏FIR滤波算法对时间间隔差值进行处理,消除毛刺和减弱随机抖动,得到相对真实的时间差值,最后使用数字PID控制算法计算出控制量;通过高性能的DA转换模块将控制量转换成模拟电压输入到恒温晶振的压控输入端,调节恒温晶振输出稳定,最终实现1PPS信号与恒温晶振的分频信号保持高度同步,误差在30ns以内。最后,考虑到卫星信号容易受到干扰或丢失,无法作为参考频率信号使用,本文论述了利用预测控制算法依靠历史数据对晶振进行调节,使其输出频率在一段时间保持较高的精度。综合上述的技术,本文在基本原理的基础上设计了一个基于卫星授时的时间同步系统的样机,介绍了系统的相关硬件设计和软件设计流程,以及滤波和控制算法的实现等。设计了上位机软件对系统进行了测试,通过分析实验的数据,利用该方法可以在一定程度上改善恒温晶振的长期平均准确度和长期稳定度,作为高精度时间同步系统的频率源。
[Abstract]:The importance of time is self-evident. With the rapid development of science and technology, the accuracy of time synchronization is becoming more and more demanding in the fields of communication, military and space exploration. How to achieve high precision time synchronization has also become a hot topic and focus of scholars. In this paper, a high precision time synchronization method based on satellite timing is studied. This method takes into account the global and all-day time of satellite timing signals. With all-weather coverage, the 1PPS signal output from the satellite receiver has the characteristics of high long-term average accuracy and stability. And the output frequency of the thermostatic crystal oscillator has the characteristics of high short-term stability. Using the satellite timing signal to tame the constant temperature crystal oscillator, the tamed constant temperature crystal oscillator can output high precision frequency signal as the frequency source. Therefore, a high precision time synchronization system based on satellite timing can be constructed. In the research of high precision time synchronization method based on satellite timing service, the 1PPS signal is output by using satellite receiver after locking the satellite, and the signal is taken as the reference frequency signal. The function of frequency doubling, frequency division and time interval measurement is realized in FPGA. The frequency doubling and frequency division processing of constant temperature crystal oscillator is carried out in FPGA. The time interval measurement method uses pulse counting method to measure the time interval difference between 1Hz signal and 1PPS signal. The data processing module reads the time interval difference from the FPGA, removes the outlier value from the data sequence by sliding median algorithm, and then processes the time interval difference by using the unbiased FIR filter algorithm. Eliminating burr and weakening random jitter, the relative real time difference is obtained. Finally, the control quantity is calculated by using digital PID control algorithm. Through the high performance DA conversion module, the control quantity is converted into analog voltage input to the voltage control input of the constant temperature crystal oscillator, and the output of the constant temperature crystal oscillator is adjusted stably. Finally, the 1PPS signal and the frequency division signal of the constant temperature crystal oscillator are kept in high synchronization. The error is within 30 ns. Finally, considering that the satellite signal is easily disturbed or lost and can not be used as a reference frequency signal, this paper discusses how to adjust the crystal oscillator by using predictive control algorithm based on historical data. In this paper, a prototype of time synchronization system based on satellite timing is designed on the basis of the basic principle. This paper introduces the related hardware design and software design flow of the system, as well as the realization of filtering and control algorithm, etc. The software of upper computer is designed to test the system, and the data of the experiment are analyzed. The method can improve the long-term average accuracy and long-term stability of the thermostatic crystal oscillator to a certain extent and can be used as the frequency source of the high-precision time synchronization system.
【学位授予单位】：西安工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP273;TN752;P127.1

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