【作者】 金璐；

【导师】 王忠勇；

【作者基本信息】 郑州大学 ， 通信与信息系统， 2013， 硕士

【摘要】 卫星导航系统对一个国家的政治、经济、军事、文化等领域都发挥着非常重要的作用,对维护国家利益具有重大意义。建设具有全球导航定位能力的北斗卫星导航系统,对我国经济建设和国防建设产生着深远的影响。北斗二代卫星系统是我国独立自主研制的新一代卫星导航系统。北斗卫星系统的发展越来越完善,作为其重要组成部分的北斗用户机的广泛应用已经迈入了新的台阶。基带信号处理模块是北斗用户机的核心模块之一,它实现的功能主要是完成模数转换、数字下变频、载波提取、载波锁定指示、扩频码同步、解扩以及信号判决等。可见,同步技术是北斗用户机的关键技术。本文主要探讨了北斗用户机的同步技术。首先介绍了本课题研究的背景与意义,然后结合扩频通信的理论描述了北斗用户机的工作原理及北斗卫星信号的结构及其调制方法,详细阐述了伪码捕获技术,并提出两种改进的捕获算法,在捕获速度捕获效率以及硬件复杂度等方面基于Tong检测算法做了详细分析和仿真。最后讨论了载波跟踪算法。采用锁相环(PLL)和锁频环(FLL)相结合并加以载波辅助的载波跟踪算法,通过对跟踪后的载波多普勒频移与预设的门限相比较,实现在PLL与FLL之间自动切换。经过验证表明本文设计的跟踪环路能够稳定的实现对载波和码相位的跟踪。理论分析及仿真表明,本文所提方案具有可行性,达到了预期设计的目标。更多还原

【Abstract】 On a country’s political, economic, military, cultural and other fields of satellite navigation system plays a very important role, is of great significance to safeguard the interests of the state. The construction of Compass with global navigation and positioning capabilities, has a profound impact on China’s economic construction and national defense construction.The two generation Compass is a new generation of satellite navigation system which is developed by China stand on its’own. With the gradual improvement of the Compass, large-scale application of Compass user machine has entered a substantive stage. The baseband signal processing module is the core module of the Compass user machine, the function of it is mainly to complete the analog-to-digital conversion, digital down conversion,carrier extracted, carrier locked indication,PN code synchronization, signal de-spreading and judgments and so on.This paper mainly discusses the baseband signal processing algorithm based on Compass.First of all.this paper introduces the researched background and significance of the topic.Then combining the concept of the spread spectrum communication, the article introduces the working principle of Compass user machine.meanwhile introducing its signal structure and modulation methods. And then putting forward two new acquisition schemes in the several common acquisition algorithm of PN code.which can improve SNR well.and weak the carrier Doppler frequency shift. In addition,based on the Tong detection algorithm for the acquisition performance of the system are analyzed in detail. Finally discussing the carrier tracking algorithm.Using phase-locked loop (FLL)and frequency locked loop(FLL)combined with some auxiliary carrier tracking algorithm, Based on the carrier Doppler frequency shift track after comparing with a preset threshold, to realize the automatic switching between PLL and FLL. After verification it shows that the pseudo-code frequency fluctuation of carrier Doppler frequency shift is to be greatly offset.The theory analysis and simulation indicates that the proposed method is feasible, and it can achieve the expected design goals.更多还原