GPS信号P码发生器设计

GPS信号P码发生器设计

文档编号:TX418 文档字数:23721,页数:57

摘要

GPS系统采用伪码测距的原理，其采用的伪随机序列之一的P码具有很强的抗干扰和保密性能，一直以来为军方所用。GPS系统中P码的捕获通常是先捕获到C/A码，然后利用C/A码调制的导航电文中的HOW所提供的P码信息对P码进行捕获。然而，C/A码的码长短，码速率低易受干扰，因此很难通过C/A码来捕获到P码，直接捕获P码一直以来备受关注，产生P码并对其特性进行分析对进一步研究码的捕获有重要意义。
这篇文档在MAX+PLUSⅡ环境下，根据ICD-200设计了P码发生器，并进行了仿真，对GPS星期的开始和结束进行了仿真验证。设计的P码发生器在开始和结束产生的码序列是正确的。用P码对的导航电文进行了直接序列扩频。最后利用MATLAB对部分P码进行了相关性验证。

关键词：GPS信号；P码；MAX+PLUSⅡ；仿真；相关

Abstract

The GPS system uses the pseudo-code to obtain the range. One of the pseudorandom noise codes used is p-code, which has very strong anti-jamming and secrecy. It has been widely used in the military. Traditionally, the GPS receiver locks onto the C/A code to extract the navigation data message. Then, starting from the HOW of the navigation data, acquisition is transferred to the P-code acquisition. However, because of short period and low chip rate, C/A code is easily disturbed. As a result it is very hard to use the C/A code to implement the p-code acquisition. The direct acquisition of p-code has been paid attention to generate p-code and analysis its characteristic. This will have an important significance for the deep research of p-code acquisition.
The overall objective of this dissertation is to implement the design of p-code generator and simulator using the MAX+PLUS. As the result shows, the GPS week starting and ending codes generated by the designed generator are right. Then using the p-code implement the direct sequence spread spectrum to the navigation data. Finally, using the matlab verifies the correlation of part p-code.

Key words: GPS signal; P code; MAX+PLUSⅡ; simulate; correlation

目录

1 绪论 1
1.1 GPS的发展 1
1.2 GPS的组成 2
1.3 GPS的特点 4
1.4 GPS的应用 5
1.5 课题介绍 5
2 GPS的基本原理 6
2.1 地心地球固连(ECEF)坐标系 6
2.2 GPS伪码测距原理 6
2.2.1 伪距计算 7
2.2.2 用户位置计算 8
2.3 GPS信号调制格式 8
2.3.1 GPS的传输信号分类 8
2.3.2 GPS卫星信号的组成 9
2.3.3 GPS的导航电文 10
2.4 码分多址 12
3 MAX+PLUSⅡ软件开发系统简介 13
3.1 设计输入 15
3.2 设计项目的编译 19
3.3 设计校验 25
4 GPS信号P码的仿真 29
4.1 伪随机码的产生及特性分析 29
4.2 P码的产生 31
4.3 P码发生器仿真结果分析 33
4.3.1 P码发生器初始状态的确定 33
4.3.2 P码发生器的仿真 34
4.4 利用P码进行扩频 42
4.5 P码的相关性验证 43
致谢 45
参考文献 46
附录A 英文原文 47
附录B 英文翻译 52

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