基于GPS的LXI主时钟模块研制

发布时间：2018-06-08 04:27

本文选题：LXI + GPS　；参考：《哈尔滨工业大学》2012年硕士论文

【摘要】：网络技术和总线技术的进步极大的推动了自动化测试系统的发展。基于网络的LXI总线技术自2005年发布第一个版本的规范后一直成为众多企业和研究机构的研究热门。目前，市场上已经有了各种功能的LXI仪器，随着技术的发展，LXI仪器的应用范围必将越来越广泛。在LXI仪器的三个功能类中，A类和B类仪器需要IEEE1588精密时钟同步协议的支持。出于降低成本考虑， LXI系统的主时钟一般由普通的晶体振荡器来驱动，由于普通晶振的输出频率精度不高，且易受环境温度影响、长期稳定性差，因此导致主时钟与物理时间有较大偏差。这个偏差的存在导致主时钟与从时钟之间有较大误差，为了提高IEEE1588同步精度必须研制精度高稳定性好的主时钟模块。本文研究和设计了基于GPS的LXI主时钟模块，利用GPS发布的高精度和高稳定度时间信息来修正LXI仪器上的实时时钟模块，提高了精密时钟同步协议的同步精度。为了获取GPS面向全球发布的时间信息，，本文设计了一款低成本的GPS接收机。GPS接收机是一种典型的嵌入式系统，在硬件上主要包括微处理器、相关通道、射频前端和存储器，在软件上包括嵌入式操作系统、设备驱动程序和实现时间解算的应用程序。GPS接收机的核心是伪码跟踪环和载波跟踪环，本文设计了一阶锁频环辅助的二阶锁相环来实现载波和伪码的捕获与跟踪。在跟踪锁定载波和伪码后，GPS接收机提取导航电文，算出UTC时间，并输出与UTC高度同步的秒脉冲。LXI仪器接收GPS输出的UTC时间信息和秒脉冲，以秒脉冲为触发信号对LXI仪器上的实时时钟模块进行修正，使被修正的LXI仪器成为LXI系统的主时钟。本文最后对GPS接收机的高频通道进行了测试，并使用本文设计的主时钟模块进行了同步实验，实验结果表明使用本模块可以达到较高的同步精度。
[Abstract]:The progress of network technology and bus technology has greatly promoted the development of automated test system. Network-based LXI bus technology has been a hot topic in many enterprises and research institutions since the first version of the specification was released in 2005. At present, there are various kinds of LXI instruments in the market. With the development of technology, the application of LXI instruments will be more and more extensive. Among the three functional classes of LXI instruments, class A and class B require the support of IEEE1588 precision clock synchronization protocol. In order to reduce the cost, the main clock of the LXI system is generally driven by the ordinary crystal oscillator. Because the output frequency accuracy of the ordinary crystal oscillator is not high, and is easy to be affected by the environment temperature, the long-term stability is poor. As a result, the main clock has a large deviation from the physical time. In order to improve the synchronization accuracy of IEEE1588, the master clock module with high precision and stability must be developed. In this paper, the LXI master clock module based on GPS is studied and designed. The high precision and high stability time information issued by GPS is used to correct the real time clock module in the LXI instrument, and the synchronization accuracy of the precision clock synchronization protocol is improved. This paper designs a low cost GPS receiver. GPS receiver is a typical embedded system. In hardware, it mainly includes microprocessor, correlation channel, RF front-end and memory, and includes embedded operating system in software. The core of GPS receiver is pseudo-code tracking loop and carrier tracking loop. In this paper, a first-order frequency-locked loop assisted second-order phase-locked loop is designed to realize carrier and pseudo-code acquisition and tracking. After tracking and locking the carrier and pseudo-code, the GPS receiver extracts the navigation message, calculates the UTC time, and outputs the UTC time information and the second pulse from the GPS output by the second pulse .LXI instrument, which is in high synchronization with the UTC. The real time clock module on LXI instrument is modified by using second pulse as trigger signal, which makes the modified LXI instrument become the main clock of LXI system. In the end, the high frequency channel of GPS receiver is tested. The synchronization experiment is carried out with the main clock module designed in this paper. The experimental results show that the synchronization precision can be achieved by using this module.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TP336

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