文档介绍：资料
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。
这篇论文在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
GPS的发展 1
GPS的组成 2
GPS的特点 4
GPS的应用 5
课题介绍 5
2 GPS的基本原理 6
地心地球固连(ECEF)坐标系 6
GPS伪码测距原理 6
伪距计算 7
用户位置计算 8
GPS信号调制格式 8
GPS的传输信号分类 8
GPS卫星信号的组成 9
GPS的导航电文 10
码分多址 12
3 MAX+PLUSⅡ软件开发系统简介 13
设计输入 15
设计项目的编译 19
设计校验 25
4 GPS信号P码的仿真 29
伪随机码的产生及特性分析 29
P码的产生 31
P码发生器仿真结果分析 33
P码发生器