发布时间 : 星期一 文章基于MATLAB的眼图仿真《通信原理》更新完毕开始阅读d4893e66eefdc8d376ee32fa
基于MATLAB的眼图仿真 ——及其与通信实验箱之结果的比较
摘要
通信实验往往可以从硬件和软件两方面着手设计，并加以横向比较，从而达到更深刻地理解和领会通信理论原理的目的。本设计选取眼图为研究对象。可靠性是通信系统的重要指标之一，而眼图是定性衡量传输系统可靠性能——码间串扰大小及受信道噪声的影响等——的方法，简单直观；除了用通信实验箱实现眼图的观察外，软件仿真具有前者所不具备的优点，本设计以MATLAB为主要工具实现了眼图的仿真模拟。
硬件方面使用北京掌宇金仪科教仪器设备有限公司生产的TIMS-301 F系列实验系统，只需较少的模块就能完成眼图的实现，缺点是灵活性不够；MATLAB由初始的矩阵实验室发展成一款具有广泛用途的科学实验软件，在通信系统仿真方面是有效而便捷的。MATLAB本身内置功能强大的函数库和讲解详细的帮助文档，前者使得眼图的仿真更加高效。
眼图仿真考虑了以下几方面因素的影响：调制数字信号的方式、传输系统（滤波）、信道噪声及其大小等等；给出了MATLAB语言编程和Simulink动态建模两种眼图的实现方式，通过仿真有效的验证了眼图判断噪声大小、系统性能的有效性，并尝试了通过眼图调整通信系统的抗干扰能力。
关键字：通信系统，眼图，仿真，MATLAB
I
Simulation of Eye Diagram Based on Matlab ——& Comparison with the rusult of TIMS
Abstract
Experiment in communication system can often be coducted on hardware as well as by sofeware, and by drawing comparison with each other, the principles of the theories in communication system could be understood more deeply and properly . The Eye Diagram was chosed to be studied in this design. The reliability is one of the most important indexes in evaluating the performance of a communication system. Eye Diagram is such a tool to observe the performance of communication systems. By using an Eye Diagram, the magnitude of the noise and the Intersymbole Interference (ISI) could be diagnosed by and large.
Two methods were employed to achieve the Eye Diagram. One was the TIMS-301F teaching & experimental system, which is simple but inflexible; the other was using the language of MATLAB which contains programming by matlab and establishing drammic models of communication system in Simulink. Comparison was drawn between the two.
Many factors were considered in the simulation of Eye Diagram, such as the way which a digital signal was modulated before transmiting, the transmit system, noise of the channel, the filter and so on. Some phenomenons can be observed and some principles be tested, beside, it also tries to improve/adjust the communication system with the help of the Eye Diagram.
Key Words: Communication System, Eye Diagram, Simulation, MATLAB
II
目录
1 绪论 ............................................................................................................................................................ 1 1.1 引言 ...................................................................................................................................................... 1 1.2 通信系统及其性能指标 ...................................................................................................................... 2 1.3 码间干扰及无失真传输 ...................................................................................................................... 4 1.4 眼图及其模型 ...................................................................................................................................... 5 2 眼图的硬件实现 ........................................................................................................................................ 7 2.1 TIMS系统简介 .................................................................................................................................... 7 2.2 眼图的观察及结果 .............................................................................................................................. 8 3 眼图的MATLAB仿真 ........................................................................................................................... 12 3.1 MATLAB简介 ................................................................................................................................. 12 3.2 眼图的仿真及结果 ............................................................................................................................ 14 4 两种结果的比较及结论 .......................................................................................................................... 32 5 附录 .......................................................................................................................................................... 33 致谢 .............................................................................................................................................................. 35 参考文献 ...................................................................................................................................................... 36
III
1 绪论
1.1 引言
21世纪将是一个信息高速膨胀的信息社会，社会生产力水平的大力发展要求社会成员间的合作更加紧密和高效，通信系统的设计与优化因此显得越来越重要；通常，通信系统的性能指标涉及有效性、可靠性、适应性、标准性等等，但从研究消息传输角度考虑，通信的可靠性和有效性是主要的矛盾所在，可靠性主要指消息的“质量“问题???；对于数字通信系统，具体来说，就是传输速率和差错率，差错率就是从可靠性的角度具体化的一个概念。
通信系统的优劣需要一个性能评价机制，眼图就是一个简单有效的定性衡量方法，通过眼图还可以对接收滤波器的特性加以调整，以减小码间串扰和改善系统的传输性能。由于眼图实现所需的设备较少（硬件只需一台示波器），观察容易，因此广泛应用于各种通信系统尤其是数字通信系统的性能的评定。从眼图上还可以大致估计系统的防噪声能力或信道受到噪声污染的情况。
当然，眼图并不是唯一评价方式，甚至也不是最全的评价方式，信号星座图从另一些方面反映了系统[2]。在通信系统仿真中，眼图和信号星座图一起成为模型仿真后处理的一部分[3]。
通信原理往往比较抽象，理论如果能在实验中得到验证，必然可以加深对理论的理解，而本实验从硬件和软件两方面对照，实现眼图的观察，相信会更好的了解眼图，同时综合软硬件的优势，克服各自的缺陷，不失为一种良好的学习方式。
1