Research of Modulation and Demodulation in Digital Communication System Based on the
Matlab
Abstract
Nowadays,
with
the
rapid
development
of
communication technology, especially the rapid spread of the digital communication, makes communication technology is developing requirements
rapidly.
Modern
communication distance,
system
communication
communication
capacity, transmission quality is good, because this communication system all kinds of communication system design r&d link, the software indispensable part of. Application of computer simulation, Simulink Matlab tool box and signal processing toolbox module, especially Matlab language dynamic system simulation software package of simulink on digital demodulation system, and simulation results of simulation and error analysis, and the modern digital communication and intuitive understanding. Emphasis on 2 ASK, 2 PSK, 2 FSK performance comparison, in actual communication system, according to the specific circumstances to select the most appropriate modulation
mode, and further promote the development of digital communication.
This paper firstly introduces the background of the subject research and the meaning of digital communication simulation, and then introduced to digital communication system simulation of Matlab Simulink used by the software used in the software and the matters needing attention and some methods used, then introduces digital modulation system and based on the principle of digital demodulation system simulation, finally the results for error was analyzed, the design was summarized, summed up in the digital demodulation of the simulation to the matters of attention when, to the aspects of learning and provide some reference for researchers and their own experience.
Key words：Digital communication system；Demodulation；Matlab；Simulink；Simulation
目 录
第一章 绪论 ........................................................................................................................ 1
1.1 研究的目的和意义 .................................................................................................... 1
1.1.1 研究目的 ............................................................................................................. 1
1.1.2 研究意义 ............................................................................................................. 2
1.2 国内外研究现状 ........................................................................................................ 2
第二章 仿真的意义和仿真软件 ........................................................................................ 4
2.1仿真的意义 ................................................................................................................ 4
2.2仿真软件Matlab简介 ............................................................................................................... 4
2.3 Simulink简介 ................................................................................................................................ 6
2.4 Matlab与Simulink的联系 ..................................................................................................... 6
第三章 数字通信系统 ........................................................................................................ 7
3.1 数字通信系统的概念 ................................................................................................................ 7
3.2 数字通信系统的组成 ............................................................................................................... 7
3.3 通信系统的分类与通信方式 .................................................................................... 8
第四章 信号的调制与解调 .............................................................................................. 10
4.1调制的意义和类别 .................................................................................................. 10
4.2 模拟信号的调制与解调 .......................................................................................... 11
4.2.1幅度调制 ............................................................................................................ 11
4.2.2角度调制 ............................................................................................................ 13
4.3 数字信号的调制与解调 .......................................................................................... 14
4.3.1数字频率调制 .................................................................................................... 14
4.3.2数字相位调制 .................................................................................................... 15
4.3.3正交振幅调制 .................................................................................................... 17
第五章 系统设计与仿真 .................................................................................................. 19
5.1 2ASK信号的调制与解调 ......................................................................................... 19
5.1.1 2ASK信号调制仿真........................................................................................ 19
5.1.2 2ASK信号解调仿真........................................................................................ 21
5.2 2FSK信号的调制与解调 ......................................................................................... 23
5.2.1 2FSK信号调制仿真 ........................................................................................ 23
5.2.2 2FSK信号解调仿真 ........................................................................................ 26
5.3 2PSK信号的调制与解调 ......................................................................................... 28
5.3.1 2PSK信号调制仿真 ........................................................................................ 28
5.3.2 2PSK信号解调仿真 ........................................................................................ 30
结论 .................................................................................................................................... 33
参考文献 ............................................................................................................................ 34
谢辞 .................................................................................................................................... 35
第一章 绪论
1.1 研究的目的和意义
信息是一种资源，通过广泛的传播与交流，能促进社会成员之间的合作，推动生产力的发展和社会的进步。在当今高度信息化的社会，信息和通信已成为现代社会的“命脉”，因此人们对信息传递的速度、质量等要求也越来越高。现代通信可以分为模拟通信和数字通信两类，与模拟通信相比，数字通信具有抗干扰能力强、噪声不积累、传输差错可控、易于集成和加密、便于用现代数字信号处理技术对数字信息进行处理、变换和储存等优点，而其缺点相比其优点来说则不重要，因此数字通信的应用必将越来越广泛。作为现代通信系统的关键技术之一的调制解调技术是人们重点研究的方向。在各种通信系统的设计研发环节中，软件仿真已成为必不可少的部分。应用Matlab＼Simulink的计算机仿真具有经济、安全、可靠、编程简易以及实验周期短等特点，因此基于Matlab的数字通信系通调制解调研究具有重要意义。 1.1.1 研究目的
二进制数字信号调制最基础的三个方面是二进制振幅键控2ASK、二进制频移键控2FSK和二进制相移键控2PSK，由于2PSK体制中存在相位不确定性，又发展出差分相移键控2DPSK。ASK是一种应用最早的基本调制方式，优点是设备简单，频谱利用率较高，但它也是受噪声影响最大的调制技术，抗噪声性能差。2FSK在数字通信中应用较为广泛，优点是抗干扰能力强，不受信道参数变化的影响，但其占用频带较宽，频带利用率较低。PSK和DPSK是高传输效率的调制方式，其