直接扩频通信系统抗干扰分析与仿真

目录

摘要 .................................................................................................... 1 第一章 绪论 .................................................................................. 1 第二章 扩展频谱基本原理 .............................................................. 2 第三章 直接序列扩频基本模型 ...................................................... 5 第四章 MATLAB对直接扩频系统的仿真 ............................... 10

4.1.PN码产生模块 ................................................................... 10 4.2.数据产生模块 .................................................................... 11 4.3．扩频解扩模块 .................................................................. 12 4.4．调制与解调模块 ............................................................... 14 4.5．相关模块 .......................................................................... 15 4.6. 计算误码率模块 .............................................................. 16 第五章 扩频系统抗干扰的研究 .................................................... 17

5.1白噪声干扰及其理论说明 .................................................. 17 5.2．扫频干扰的仿真 ............................................................... 24 5.3．多频干扰 ........................................................................... 35 5.4．单频干扰 ........................................................................... 40

摘要 1

摘要

本文首先从香农定理分析，得到了无误差传输系统中信噪比和带宽是可以互换的。接着介绍了扩频通信的几种方式，并把讨论的重点放在了直接序列扩频系统，还介绍了用QPSK调制方式对扩频信号进行调制。本文用MATLAB对直接序列扩频系统进行了仿真，文中对所仿真的各个模块进行了叙述。在对直接序列扩频系统进行分析时，用了不同形式的干扰测试了系统性能，这些方式中重点分析了白噪声干扰和扫频干扰。并从仿真数据和理论上证实，直扩系统不能对白噪声干扰进行有效的抵抗。在扫频干扰时，分别从连续扫频干扰方式和间断扫频干扰方式两个方面进行了分析仿真，并得出，对于一些扩频码，扫频干扰强于白噪声干扰，提出了以基带为干扰带宽的间断干扰方式的一种干扰形式，这种干扰形式的干扰效果强于其它干扰。最后还做了多频干扰，单频干扰。 本文的关键词：

直接序列扩频 白噪声干扰 扫频干扰 多频干扰

Abstract 2

Abstract

According to Shanon Theory, we got the inclusion that SNR and bandwidth can be offset mutually in the inerrant channel. signal should be widen. Then the conception of spread spectrum was produced. Some spread spectrum modes were introduced and the key point was put on the direct spread spectrum system. Modulating the spread spectrum signal using QPSK mode. Simulating the direct spread spectrum system using MATLAB. The paper depicted the modules need to be simulated in detail. Different noises were used to test the performance of the system, such as white noise and chirp. We can got the inclusion that the direct spread spectrum system can not resist the white noise efficiently. When using chirp, two modes were introduced: continuous mode and discontinuous mode. In some spread spectrum codes, chirp was more fierce than white noise. Multiple-Tone and Single-tone were included also. .

Keyword: direct spread spectrum system, white noise interfere, chirp, Multiple-Tone.