GPS接收机跟踪技术的研究及实现
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。
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.
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。
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.
引文
[1]袁建平,罗建军,越小奎,等.卫星导航原理与应用[M].北京:中国宇航出版社,2003.
[2]中国航空学会.全国第十二届信号与信息处理、第六届DSP应用技术联合学术会议论文集[C].烟台:[出版者不祥],2008.
[3]周祖渊.全球卫星导航系统的构成及其比较[N].重庆交通大学学报,2008,11,27(Suppl).
[4] Elliott D. Kaplan. UNDERSTANDING GPS Principles and Applications[M].邱致和,王万义译.北京:电子工业出版社, 2002.
[5]刘基余.GPS卫星导航定位原理与方法[M].北京:科学出版社, 2005.
[6]张守信,GPS卫星测量定位理论与应用[M],长沙:国防科技大学出版社.1996.
[7]谭述森.北斗卫星导航系统的发展与思考[N].宇航学报,2008,3,29(2):392-396.
[8]张欣.扩频通信数字基带信号处理算法及其VLSI实现[M].北京:科学出版社,2004.
[9]田日才.扩频通信[M].北京:清华大学出版社,2007.
[10]维特比,李世鹤.CDMA扩频通信原理[M].北京:人民邮电出版社,2008.
[11] Altera Corporation. StratixII EP2S180 DSP Development Board Reference Manual. 2005
[12] Altera Corporation.www.altera.com.cn
[13]潘松,黄继业,王国栋.现代DSP技术[M].西安:西安电子科技大学出版社,2004.
[13]王诚,吴继华.Altera FPGA/CPLD设计(基础篇)[M].北京:人民邮电出版社,2005.
[15]沈超,裘正定.基于Matlab/Simulink的GPS系统仿真[J].系统仿真学报,2006 ,
[16]段文娟.GPS接收机基带处理器研究与设计[D].北京:北京交通大学,2008.
[17]姜宇柏,游思晴.软件无线电原理与工程应用[M].北京:机械工业出版社,2007.
[18]孙希延,纪元法,施浒立. GPS基带信号处理与定位实现[N].系统仿真学报,2007,12,19(24):5832-5836.
[19] Lei Dong. IF GPS Signal Simulator Development and Verification[D]. CALGARY, ALBERTA: University of Calgary, 2003.
[20]寇艳红.GNSS软件接收机与信号模拟器系统研究[D].北京:北京航空航天大学,2006.
[21]王伟权,刘昌孝.用FPGA实现GPS的C/A码发生器[N].桂林电子科技大学学报,2006,10,26(5):347-350.
[22]阮芳,潘成胜.基于FPGA的GPS C/A码仿真器的设计与实现[J].沈阳理工大学学报, 2008, 27(2): 1-5.
[23] James Bao-Yen Tsui.Fundamentals of Global Positioning System Receivers: A Software Approach[M]. New York: J.Wiley & Sons,US, 2000
[24] Kai Borre,Dennis M Akos,Nicolaj Bertelsen,etc. A software-defined GPS and GALILEO Receiver.
[25] IS-GPS-200. NAVSTAR GPS Space Segment /Navigation User Interface(Revision D)[S]. U.S.A: ARINC Engineering Services, EI Segundo CA, 2004.
[26]郭呈.卫星定位系统中伪码及载波跟踪技术研究[D].西安:西北工业大学,2007.
[27]孙晓文.基于FPGA的GPS信号捕获与跟踪系统设计研究[D].大连:大连海事大学,2007.
[28]李丹,寇艳红. GPS软件界收集实时化设计与实现[N].无线电工程,2008,38(5):29-31.
[29]王尔中,张淑芳,胡青,等.GPS接收机相关器技术研究及FPGA实现[N].系统仿真学报,2008,7,20(13):3581-3585.
[30]廖炳瑜.星载双频软件GPS接收机研究[D].北京:中国科学院研究生院,2005.
[31]姜毅,张淑芳,张晶泊,等.基于GPGA的GPS接收机跟踪环路的设计与实现[N].大连海事大学学报,2009,8,35(3):16-420.
[32]朱宇虹,张其善,常青. GPS信号模拟器重sine存储表的设计与实现[N].北京航空航天大学学报,2005,12,31(12):1308-1331.
[33]孙进芳,李晓白,金天.量化对GPS接收机性能的影响[N].雷达科学与技术,2007,12,5(6):477-480.
[34]徐业清,朱树明,杨银堂.GPS接收机相关器的电路设计[N].电子器件,2006,9,29(3):722-725.
[35] Michael S.Braasch.GPS Receiver Architectures and Measurements[J].Proceedings of the IEEE,1999,87(1):48-63.
[2]中国航空学会.全国第十二届信号与信息处理、第六届DSP应用技术联合学术会议论文集[C].烟台:[出版者不祥],2008.
[3]周祖渊.全球卫星导航系统的构成及其比较[N].重庆交通大学学报,2008,11,27(Suppl).
[4] Elliott D. Kaplan. UNDERSTANDING GPS Principles and Applications[M].邱致和,王万义译.北京:电子工业出版社, 2002.
[5]刘基余.GPS卫星导航定位原理与方法[M].北京:科学出版社, 2005.
[6]张守信,GPS卫星测量定位理论与应用[M],长沙:国防科技大学出版社.1996.
[7]谭述森.北斗卫星导航系统的发展与思考[N].宇航学报,2008,3,29(2):392-396.
[8]张欣.扩频通信数字基带信号处理算法及其VLSI实现[M].北京:科学出版社,2004.
[9]田日才.扩频通信[M].北京:清华大学出版社,2007.
[10]维特比,李世鹤.CDMA扩频通信原理[M].北京:人民邮电出版社,2008.
[11] Altera Corporation. StratixII EP2S180 DSP Development Board Reference Manual. 2005
[12] Altera Corporation.www.altera.com.cn
[13]潘松,黄继业,王国栋.现代DSP技术[M].西安:西安电子科技大学出版社,2004.
[13]王诚,吴继华.Altera FPGA/CPLD设计(基础篇)[M].北京:人民邮电出版社,2005.
[15]沈超,裘正定.基于Matlab/Simulink的GPS系统仿真[J].系统仿真学报,2006 ,
[16]段文娟.GPS接收机基带处理器研究与设计[D].北京:北京交通大学,2008.
[17]姜宇柏,游思晴.软件无线电原理与工程应用[M].北京:机械工业出版社,2007.
[18]孙希延,纪元法,施浒立. GPS基带信号处理与定位实现[N].系统仿真学报,2007,12,19(24):5832-5836.
[19] Lei Dong. IF GPS Signal Simulator Development and Verification[D]. CALGARY, ALBERTA: University of Calgary, 2003.
[20]寇艳红.GNSS软件接收机与信号模拟器系统研究[D].北京:北京航空航天大学,2006.
[21]王伟权,刘昌孝.用FPGA实现GPS的C/A码发生器[N].桂林电子科技大学学报,2006,10,26(5):347-350.
[22]阮芳,潘成胜.基于FPGA的GPS C/A码仿真器的设计与实现[J].沈阳理工大学学报, 2008, 27(2): 1-5.
[23] James Bao-Yen Tsui.Fundamentals of Global Positioning System Receivers: A Software Approach[M]. New York: J.Wiley & Sons,US, 2000
[24] Kai Borre,Dennis M Akos,Nicolaj Bertelsen,etc. A software-defined GPS and GALILEO Receiver.
[25] IS-GPS-200. NAVSTAR GPS Space Segment /Navigation User Interface(Revision D)[S]. U.S.A: ARINC Engineering Services, EI Segundo CA, 2004.
[26]郭呈.卫星定位系统中伪码及载波跟踪技术研究[D].西安:西北工业大学,2007.
[27]孙晓文.基于FPGA的GPS信号捕获与跟踪系统设计研究[D].大连:大连海事大学,2007.
[28]李丹,寇艳红. GPS软件界收集实时化设计与实现[N].无线电工程,2008,38(5):29-31.
[29]王尔中,张淑芳,胡青,等.GPS接收机相关器技术研究及FPGA实现[N].系统仿真学报,2008,7,20(13):3581-3585.
[30]廖炳瑜.星载双频软件GPS接收机研究[D].北京:中国科学院研究生院,2005.
[31]姜毅,张淑芳,张晶泊,等.基于GPGA的GPS接收机跟踪环路的设计与实现[N].大连海事大学学报,2009,8,35(3):16-420.
[32]朱宇虹,张其善,常青. GPS信号模拟器重sine存储表的设计与实现[N].北京航空航天大学学报,2005,12,31(12):1308-1331.
[33]孙进芳,李晓白,金天.量化对GPS接收机性能的影响[N].雷达科学与技术,2007,12,5(6):477-480.
[34]徐业清,朱树明,杨银堂.GPS接收机相关器的电路设计[N].电子器件,2006,9,29(3):722-725.
[35] Michael S.Braasch.GPS Receiver Architectures and Measurements[J].Proceedings of the IEEE,1999,87(1):48-63.
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