DS18B20温度报警器设计毕业论文.doc

摘 要 第三代移动通信系统是建立在ITU-2000建议基础上的工作在2GHz频段、最高速率可达2Mbit/s的宽带移动通信系统。第三代移动通信的主流是采用了码分多址（CDMA）的通信方式。CDMA系统中的初始同步技术作为第三代移动系统的关键技术，是其他关键技术得以实现的必要基础。CDMA通信系统接收机的初始同步包括PN码同步、符号同步、帧同步和扰码同步等。由于DS-SS技术在CDMA系统中的广泛应用最为广泛，因此基于DS-SS方面的PN码捕获方法研究很多。伪随机码的同步一般分两步进行。第一步是搜索和捕获伪随机码的初始相位，使与发送端的码相位误差小于1bit，即序列捕获；第二步是在初始同步的基础上，使码相位误差进一步减小，使所建立的同步保持下去，通常称这一步未跟踪。如何判断PN码是否捕获是码同步问题中的重要内容。传统的PN码捕获的判定是通过能量检测的办法进行的。 关键词：小波变换； 码分多址； 扩频序列； 捕获检测 Abstract The third mobile communication system is built on the basis of ITU-2000 suggestion, and it can work on 2GHz. Meanwhile, the wideband system’s rate can get 2Mbit/s and this system use communication pattern of CDMA. As a key technique of key technologies. Initial synchronisms of CDMA communication system receiver include PN code sync, symbol sync, frame sync, sync of scramble code, and so on. Because that DS-SS technology is used most widely in the system of CDMA, a great deal of research on method for acquisition of PN code is based on DS-SS. The sync of code is divided into two steps generally: The first step is the searching and acquiring of PN code phase (namely, acquisition of sequences) so that the phase error between sending code and receiving code is within 1 bit. The second step is tracking which is on the base of the initial acquisition, so the error of phase is decreased more and sync is keeping. The judgments of PN code acquisition is an important problem of the code sync and the traditional of it is power detection. Keywords: Wavelet Transform; Code Division Multiple Access; Spectrum spread Sequence; Detection of Acquisition 目 录 摘要…………………………………………………………………VI ABSTRACT……………………………………………………………VII 第一章 绪论…………………………………………………………1 1.1 扩频通信的背景和意义…………………………………1 1.2 论文的主要内容…………………………………………2 1.3 论文的结构安排…………………………………………2 第二章 扩频通信……………………………………………………3 2.1 扩频通信的基本概念……………………………………3 2.2 扩频通信系统的分类……………………………………4 2.3 扩频通信的主要特点……………………………………4 2.4 扩频系统中的伪随机序列………………………………5 2.5 直接序列扩频通信系统…………………………………12 第三章 直接序列扩频通信及其伪随机码同步技术………………16 3.1 直接序列扩频原理……………