室内伪卫星导航星源模拟器设计

发布时间：2018-07-12 18:50

本文选题：伪卫星 + 直接序列扩频　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：全球卫星导航系统的飞速发展使得卫星导航应用越来越广泛。在设计和开发卫星导航终端过程中,测试接收机对卫星信号的捕获跟踪能力是十分重要的环节,而在受遮挡的室内区域可见星数目很少甚至没有可见的卫星,这给产品的设计带来不便。设计一款室内伪卫星导航星源模拟器就可以很好的解决上述问题。本文的目的是设计一款可以模拟卫星信号的硬件系统,在此平台上通过编写软件来模拟产生用户位置处的卫星信号。论文简述了课题的研究背景及现状,阐述了论文的研究意义,分析了伪卫星信号的结构、扩频码的构成、导航电文的规范,研究了直接序列扩频技术。在理论研究与分析的基础之上,设计了室内伪卫星导航星源模拟器。系统的硬件主要由基带部分和射频部分组成。基带部分设计基于FPGA+DSP架构硬件平台,主要完成数字基带信号的生成。射频部分主要完成中频信号的模拟上变频。模拟器的软件部分的设计采用自顶向下,模块化设计的思想,完成了系统接口软件设计、DSP部分的卫星轨道计算模块、卫星可见性判断模块、延迟参数计算模块的设计以及FPGA部分的扩频码生成模块、载波生成模块、扩频调制模块及各个芯片的驱动模块的设计等。系统工作原理为,DSP根据初始参数和算法模型计算并生成导航电文,FPGA接收DSP生成的导航电文,通过直接序列扩频调制完成基带信号的生成,数模转换模块对FPGA输出的中频信号进行数字到模拟的转换,射频部分的上变频模块配合本振模块将中频模拟信号变频到GPS的L1载频上,实现伪卫星信号的模拟。在测试与验证部分,对C/A码的波形、扩频调制的波形进行了实测,分别对导航星源模拟器的中频信号和射频信号进行了频谱分析。借助实验室的GPS接收平台对模拟器射频输出的信号进行了测试,接收机能够完成同步并解算出导航数据。测试结果表明,整个室内伪卫星模拟器系统能够满足设计要求。
[Abstract]:The rapid development of global satellite navigation system makes the application of satellite navigation more and more extensive. In the process of designing and developing satellite navigation terminals, it is very important to test the acquisition and tracking ability of the receiver to satellite signals, and there are few or no visible satellites in the occluded indoor area. This brings inconvenience to the design of the product. Design an indoor pseudosatellite navigation star source simulator can solve the above problems. The purpose of this paper is to design a hardware system which can simulate the satellite signal. On this platform, the software is written to simulate the satellite signal at the user's position. This paper briefly introduces the research background and present situation of the subject, expounds the significance of the research, analyzes the structure of the pseudosatellite signal, the structure of the spread spectrum code, the standard of the navigation message, and studies the direct sequence spread spectrum technology. On the basis of theoretical research and analysis, the indoor pseudosatellite navigation star source simulator is designed. The hardware of the system is mainly composed of baseband part and RF part. The baseband part is based on FPGA DSP architecture hardware platform, mainly completes the digital baseband signal generation. The RF part mainly completes the analog up-conversion of if signal. The software design of the simulator adopts the idea of top-down and modularization design. The system interface software designs the satellite orbit calculation module and the satellite visibility judgment module of DSP part. The design of delay parameter calculation module and FPGA part of the spread spectrum code generation module, carrier generation module, spread spectrum modulation module and each chip driver module design and so on. The working principle of the system is that DSP calculates and generates navigation message based on initial parameters and algorithm model, and FPGA receives the navigation message generated by DSP. The baseband signal is generated by direct sequence spread spectrum modulation. Digital to analog conversion module to FPGA output if signal digital to analog conversion, radio frequency upconversion module with local oscillator module to convert if analog signal to GPS L1 carrier frequency, to achieve pseudosatellite signal simulation. In the part of test and verification, the waveform of C / A code and the waveform of spread spectrum modulation are measured, and the intermediate frequency signal and radio frequency signal of the navigation star source simulator are analyzed respectively. With the help of the GPS receiving platform in the laboratory, the RF output signal of the simulator is tested, and the receiver can complete the synchronization and solve the navigation data. The test results show that the whole indoor pseudosatellite simulator system can meet the design requirements.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN967.1

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