高灵敏度GPS接收机捕获算法研究及实现

发布时间：2018-01-29 18:36

本文关键词： GPS 弱信号捕获单元概率系统概率混合峰均比 FPGA　出处：《电子科技大学》2013年硕士论文　论文类型：学位论文

【摘要】：作为为近年来全球发展最快的信息产业之一，以GPS为代表的卫星导航产业在我们的日常生活中发挥着越来越重要的作用。但是在城市，森林，，山区等环境下，遮挡、多径和干扰等现象较严重，这会造成信号的衰弱和退化，现有的普通捕获技术就不能够满足捕获低信噪比条件下GPS卫星信号的需要。因此如何在微弱信号条件下实现信号的捕获成为人们研究的一个热点，本文就是主要针对这个问题进行的。论文首先介绍了GPS信号的基本结构，讨论了信号的功率和多普勒频移特性，构建了GPS中频信号模型。接着讨论了GPS信号捕获的基本原理和两种常规的捕获算法：串行捕获算法和并行捕获算法，并对这两种算法进行了计算机仿真。其次，论文研究了三种适用于弱信号条件下的捕获算法：相干积累、非相干积累和差分相干积累。并对相干积累和非相干积累算法捕获检测量的统计特性、门限设置以及算法的性能进行了分析，得到了适用于单个搜索单元格的单元概率，并进行了MATLAB仿真。在单元概率的基础上，论文重点研究了一种具有恒虚警特性的检测算法：混合峰均比算法，主要从单元概率和系统概率两个方面进行了对这种算法进行了讨论。详细的理论分析和蒙特卡洛仿真表明，相较于传统的最大峰均比算法，混合峰均比算法在相近的系统概率条件下能够节省大约一半的捕获搜索运算量。最后，文章选取了基于FFT的并行捕获算法进行了FPGA实现，并行捕获算法能够通过一次计算得到一个多普勒频率上所有码相位的相关值，大大提升了捕获速度。论文从工程实现角度详细的给出了并行捕获算法中各个模块的实现原理和实现流程图，在ISE软件开发环境下，利用Verilog HDL硬件描述语对算法进行了实现。首先仿真数据和开发板采集数据对程序进行了功能测试，随后进行了程序的外场实验测试，实验结果表明该程序能够很好的捕获到GPS卫星。
[Abstract]:As one of the fastest growing information industries in the world in recent years, the satellite navigation industry represented by GPS plays a more and more important role in our daily life. But in cities, forests. In mountainous environment, occlusion, multipath and interference are more serious, which will lead to signal debilitating and degradation. The existing common acquisition technology can not meet the need of capturing GPS satellite signals under low SNR. Therefore, how to achieve signal acquisition under weak signal conditions has become a hot topic. This article is mainly aimed at this problem. Firstly, the basic structure of GPS signal is introduced, and the power and Doppler frequency shift characteristics of the signal are discussed. Then the basic principle of GPS signal acquisition and two conventional acquisition algorithms: serial acquisition algorithm and parallel acquisition algorithm are discussed. The two algorithms are simulated by computer. Secondly, we study three acquisition algorithms for weak signal: coherent integration, incoherent integration and differential coherent integration, and measure the statistical characteristics of coherent and incoherent integration algorithms. The threshold setting and the performance of the algorithm are analyzed, the cell probability suitable for a single search cell is obtained, and the MATLAB simulation is carried out. On the basis of the unit probability, this paper focuses on a CFAR detection algorithm: hybrid peak-to-average ratio (PAPR) algorithm. This algorithm is mainly discussed from the aspects of unit probability and system probability. The detailed theoretical analysis and Monte Carlo simulation show that compared with the traditional maximum peak-to-average ratio algorithm. The hybrid peak-to-average ratio algorithm can save about half of the acquisition search operation under the condition of similar system probability. Finally, the parallel acquisition algorithm based on FFT is implemented by FPGA. The parallel acquisition algorithm can get the correlation value of all the code phases in a Doppler frequency. From the point of view of engineering implementation, the paper gives the realization principle and flow chart of each module in parallel acquisition algorithm, under the environment of ISE software development. The algorithm is implemented by using Verilog HDL hardware description language. Firstly, the simulation data and the data collected by the development board are used to test the function of the program, and then the external field test of the program is carried out. Experimental results show that the program can capture GPS satellite well.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：P228.4

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