毕业论文设计基于matlab和simulink的系统仿真.docx

基于matlab/simulink的QPSK通信系统仿真
课程设计目的: 本课程设计主要是学会运用MATLAB中的Simulink来实现数字基带信号的模拟传输。在知道其传输原理的情况下，将仿真电路到Simulink之中。并且对正交振幅调制、解调过程的频谱和波形的分析，同时在无噪声和有噪声的进行分析，加入高斯白噪声，瑞利噪声，莱斯噪声分析调制解调后的频谱、波形，观察其误码率。
（1） 巩固和加深学生对QPSK调制解调技术的基本知识的理解和掌握；
（2）掌握编程和程序调试的基本技能；
（3）利用MATLAB进行基本的软件设计，掌握软件设计一般方法，了解软件设计的思路；
（4）掌握书写程序设计报告的能力；
（5）提高运用MATLAB解决实际问题的能力；
课程设计仪器:(1) MATLAB7.0 （2）simulink
MATLAB是由美国mathworks公司发布的主要面对科学计算、可视化以及交互式程序设计的高科技计算环境。它将数值分析、矩阵计算、科学数据可视化以及非线性动态系统的建模和仿真等诸多强大功能集成在一个易于使用的视窗环境中，为科学研究、工程设计以及必须进行有效数值计算的众多科学领域提供了一种全面的解决方案。
相关原理：4PSK常称为正交相移键控(QPSK)。4PSK信号每个码元含有2 比特的信息，现用ab代表这两个比特。两个比特有4种组合，即00、01、10和11。它们和相位qk之间的关系通常都按格雷码的规律安排，如下表所示。
QPSK信号的编码
QPSK信号矢量图
格雷码的好处在于相邻相位所代表的两个比特只有一位不同。由于因相位误差造成错判至相邻相位上的概率最大，故这样编码使之仅造成一个比特误码的概率最大
2、QPSK调制
两种产生方法:相乘电路法
二进制信号码元“0”和“1在相乘电路中与不归零双极性矩形脉冲振幅的关系如下：二进制码元“1” ® 双极性脉冲“+1”；二进制码元“0” ® 双极性脉冲“-1”。符合上述关系才能得到第6章中的B方式编码规则。

3、QPSK解调
原理方框图

仿真结果：
QPSK原理框图

调制端的眼图

解调端眼图

星座图
基带信号与调制信号的波形比较

无噪声的误码率
设计体会:这次的课程设计是在MATLAB的SIMULINK环境下仿真实现QPSK的调试与解调，刚开始是没有完全理解QPSK的的原理，以至于多走了很多的弯路，后来又因为没能正确的使用示波器而导致出现了很多的错误，后来加如噪声后，更是有很多的错误出现了，误码率也很大，星座图也跳跃不停。通过出现的问题，我看到了自己的不足，也学会了SIMULINK模块的运用，更重要的是了解了多进制的调制与解调原理，通过课程设计来巩固本学期的通信原理与数字信号的专业知识内容，同时也运用理论知识与实际电路的设计相结合了起来，通过综合分析，找出了自己学习过程中的不足，为今后的学习提供实践依据，打下了基础。
这次实习是运用MATLAB中的SIMULINK仿真出8PSK的调制与解调，这是多进制的调制与解调，我开始没能完全理解多进制的调制与解调，错误的使用了二进制的方式去调制与解调，输入了二进制的正弦波，也使用了只能显示二进制的示波器，导致实验过程中一直都有错，没能正确的运行，再一次次的失败后，仍然找不到出错点在哪。后来老师来给我讲解了多进制的原理后，我明白了原来自己的
专业知识不够扎实，原理没有理解透
再接下来就是如何正确的调制了，由于没有波形，我一直没能正确的算出延时，导致误码率的居高不下，后来经老师提点，知道了，其实可以将多进制进行转换，转换为二进制的方式在示波器上显示，于是，我使用了一个转换器，成功的显示了多进制的波形。
在此次课程设计中，我掌握了SIMULINK软件的使用，虽然不是很熟悉，但是，以后我将会更加努力的学习，还有专业知识的加强，在这次课程设计中，问题出现的如此多，主要在于专业知识的不够完善，幸亏老师一次次的细心指导，才能完成此次设计，今后一定加强学习。
参考文献
【1】 张 琨，高思超，毕靖，《MATLAB 2010 从入门到精通》，电子工业出版社，2011
【2】 赵景波，逢锦梅，《MATLAB控制系统仿真与设计》，机械工业出版社，2010
【3】 孙屹,《Simulink通信仿真开发手册》,国防工业出版社,2004
【4】 樊昌信，曹丽娜，《通信原理》，国防工业出版社，2006
【5】 钟麟,《MATLAB仿真技术与应用教程》,国防工业出版社,2003
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