文档介绍：目录
摘要 I
Abstract II
1. FM调制系统的介绍及设计 1
通信系统的简介 1
FM调制模型的建立 2
FM调制仿真结果 4
2. FM解调系统的介绍及设计 7
FM解调模型的建立 7
解调过程分析 7
FM解调的部分程序及波形 8
3. 高斯白噪声信道特性 11
4. 调频系统的抗噪声性能分析 14
5. MATLAB源代码 19
21
22
摘要
调制在通信系统中有十分重要的作用。通过调制,不仅可以进行频谱搬移,把调制信号的频谱搬移到所希望的位置上,从而将调制信号转换成适合于传播的已调信号,而且它对系统的传输有效性和传输的可靠性有着很大的影响,调制方式往往决定了一个通信系统的性能。FM信号的调制属于频谱的非线性搬移,它的解调也有相干和非相干解调两种方式。
本课程设计使用的仿真软件为MATLAB ,利用MATLAB集成环境下的M文件,编写程序来实现FM信号的仿真分析,并分别绘制出基带信号、载波信号、已调信号的时域波形和频域波形;再进一步分别绘制出对已调信号叠加噪声后信号、同步解调前信号和解调后基带信号的时域波形;最后绘出FM基带信号调制和解调系统后的输入输出信噪比的关系,并通过与理论结果波形对比来分析该仿真调制与解调过程的正确性及噪声对FM信号解调的影响。在课程设计中,系统开发平台为Windows Xp,在该平台运行MATLAB程序完成了对FM调制和解调以及对叠加噪声后解调结果的观察和分析。
关键词 FM;调制;解调;MATLAB ;噪声
Abstract
Modulation in munication system has extremely important role. Through the modulation, not only can frequency shift, the modulation signal spectrum is moved to want, thus will position modulation signal is converted into suitable for transmission of the signal, and it has attune to the transmission effectiveness and reliability of transferring having very big effect, modulation method often determines munication system performance. FM signals modulation of nonlinear shift, belong to the spectrum of its demodulation also have coherent and incoherent demodulation in two ways.
The course is designed to use simulation software for MATLAB , use of MATLAB integration environment of M files, write a program to realize FM signals of the simulation analysis, and draw the baseband signal respectively, carrier signal, already adjustable signal and the time domain waveform frequency domain waveform; Further respectively to map out already adjustable signal after adding noise signal, synchronous demodulation signal demodulation before and after baseband signal temporal profile, Finally draw FM baseband signal modulation and demodulation system after the input/output SNR, and the relationship with the theoretical results wave contrast to analyze the simulation modulation and d