【作者】 张望全；

【导师】 黄勇；

【作者基本信息】 西华大学 ， 信号与信息处理， 2010， 硕士

【摘要】 近年来,卫星导航定位产品在航空、航海、测绘领域以及人们的日常生活中都已起到明显作用,其影响在未来还将有空前增长。GPS(Global Positioning System,全球定位系统)接收机的研发成为了世界各国研究的热门课题,我国也迫切需要研制具有自主知识产权的GPS接收机。GPS接收机的研究都是从数字化的中频信号这一基础开始的,GPS数字中频信号是开展GPS接收机研究工作的前提。GPS信号仿真器价格昂贵,并且大都不具备新的信号格式(L5 signals),不利于深入研究。GPS接收机工作时,信号同步要完成复杂的处理过程。有效跟踪GPS信号是实现精确定位的前提;如何捕获卫星信号并保持对信号的跟踪是重要的核心技术。本文首先介绍了卫星定位系统的相关理论,之后阐述了GPS接收机的基本工作原理以及信号跟踪方面的理论知识,最后提出系统的实现方案进行研究。本论文所实现的系统主要包括两大部分:GPS信号源部分和信号跟踪部分。GPS信号源为后续的处理提供合适的中频信号,本论文设计的GPS信号源能够根据用户设定的初始时刻等条件产生L1频点上的中频信号,文中详细说明了C/A码、P码产生以及初始时刻设定的方法。跟踪部分主要针对L1频点C/A码进行了设计实现,采用载波跟踪环与码跟踪环耦合的方法实现,其中载波跟踪环采用二阶科斯塔斯(COSTAS)锁相环实现,码跟踪环采用延迟锁定环(Delay-locked Loop,DLL)实现。在提出系统实现方案之后,首先利用Matlab/Simulink搭建模型进行了系统级设计仿真,测试验证了方案的可行性;然后运用verilog硬件描述语言编写各功能模块并用modelsim进行仿真验证,主要功能模块包括C/A码模块、P码模块、导航电文生成模块、载波生成模块以及BPSK模块、载波混频器、码产生器、载波产生器、积分清零单元、码相关器、码NCO、鉴相器、环路滤波器;利用Synplify Pro对设计进行逻辑综合;最后用Altera Quartus II将整个设计编译映射到Altera公司Stratix II系列的EP2S180 FPGA芯片。更多还原

【Abstract】 In recent years, satellite navigation and positioning products have played a great role in the fields of aviation, voyage, surveying and mapping, and people’s daily life.The impact will unprecedentedly increase in the future. The Research and Development of GPS receiver has become a hot topic around the world, China has an urgent need to develop our own proprietary GPS receiver.All the study of GPS receiver begins with digitized Intermediate Frequency(IF) signal.Digitized IF GPS signal is the premise to carry out the research work of GPS receiver . GPS signal simulators are very expensive,and most of them do not have the new signal format(L5 signals), which is not conducive to in-depth study.When GPS receiver works, signal synchronization needs complex process.Effectively tracking the GPS signal is a prerequisite to achieve precise positioning.How to capture the satellite signal and maintain signal tracking are important core technology.This paper firstly introduces some related theory of satellite positioning system, then expounds the basic principle of GPS receiver and the theory of signal track,finally the implementation method is provided.The system implemented in this paper includes two main section:GPS signal source and signal tracking subsystem. GPS signal source provide appropriate IF signal for the next processing.The GPS signal source realized in this paper is able to generate IF signal on L1frequency based on the initial stated set by user.The generation of C/A code and P code,and the way to set initial time are in detail described.The design and implementation of C/A code tracking on L1 frequency is done in this paper. The tracking section is achieved by carrier tracking loop and code tracking loop coupling coupling,the carrier tracking loop is a second-order costas PLL ,the code tracking loop is DLL.After the system implementation method is provided,firstly the system level model is built up and the simulation is done in Matlab/Simulink to verify the feasibility;secondly write each fuctional module using verilog hardware description language and simulate in modelsim,the main fuctional modules include C/A code,P code,navigation data ,carrier generator,BPSK,carrier mixer,code generator,integrate & dump unit,code correlator,code NCO,phase detector,and loop filter; then synthesize the design in Synplify Pro;finally compile and map the whole design to Altera Stratix II EP2S180 using Altera Quartus II.更多还原