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调制与解调的matlab仿真实现
调制解调的Matlab仿真实现
摘要
在通信过程中，调制与解调占有十分重要的地位。假如没有调制与解调技术，就没有通信，没有广播和电视，也没有今天的 BP 寻呼、手持电话、传真、电脑通信及 Internet 国际互联网。
本设计是基于MATLAB来实现调制与解调的仿真。主要设计思想是利用MATLAB这个强大的数学软件工具方便快捷灵活的功能实现模拟调制解调中的幅度调制和角度调制及数字调制解调中的FSK和DPSK的调制解调设计。首先，先介绍这几种模拟和数字调制解调的产生、频谱、解调等过程及原理，接着就编写相应的m文件先后对模拟调制中的幅度调制和角度调制里面的频率调制的进行仿真，并对仿真得出调试及仿真结果并进行分析。
FM调制的时候是让基带信号去控制振荡电路的频率，AM是用基带信号去控制载波的幅度。无论哪一种调制方式，采用相干解调的性能优于非相干解调的性能。而且DPSK可以消除PSK的“倒?”现象。DPSK的系统性能要优于FSK系统。相干系统要求本地载波与发送信号之间保持同步，否则误码率增加。因此，在高质量的数字通信系统中多采用相干解调，而对抗噪声性能要求不高的就采用较为简单的非相干解调。
关键词：MATLAB；调制解调；AM；FM；FSK；DPSK
调制与解调的matlab仿真实现
SIMULATION OF MODEM IN MATlAB
ABSTRACT
In the communication process, modulation and demodulation is very important position. If there is no modulation and demodulation technology, there is no communication, no radio and television, nor did the BP pager, handheld phone, fax, computer communications and Internet Internet.
The design is based on MATLAB to achieve modulation and demodulation of the simulation. The main design idea is the use of MATLAB software, this powerful mathematical tool for convenient and flexible function for analog modulation and demodulation of amplitude modulation and angle modulation and digital modulation and demodulation of FSK and DPSK modem design. First of all, to introduce these types of analog and digital modulation and demodulation of the resulting spectrum, demodulator,etc. Then the preparation of the corresponding document has m analog modulation of the amplitude modulation and angle modulation frequency modulation inside the simulation, and simulation debugging and simulation results obtained and analyzed.
FM modulation is the time base-band signal to control the frequency of oscillator circuit, AM base-band signals used to control the range of carrier. No matter what kind of modulation, the use of the performance of coherent demodulation is superior to the performance of non-coherent demodulation. DPSK can remove the \π\phenomenon of PSK. DPSK system performance is superior to FSK system. The local carrier coherent system requirements and to maintain synchronization between the transmitted signal, Otherwise, increase the bit error rate. So, In high-quality digital communication systems use coherent demodulation, and noise performance of low-resistance on the use of relatively simple non-coherent demodulation.
Key words: matlab; modem; am; fm; fsk; dpsk
调制与解调的matlab仿真实现
目 录
1 绪论 ........................................................................................................................................ 1
1.1 课题发展的现状 .......................................................................................................... 1 1.2 课题研究的内容和目的 .............................................................................................. 2 1.3 课题研究的步骤 .......................................................................................................... 2 2 调制解调原理 ........................................................................................................................ 3
2.1 实现AM的调制解调的原理 ...................................................................................... 3 2.2 实现FM的调制解调的原理 ...................................................................................... 4 2.3 实现FSK的调制解调的原理 ..................................................................................... 6 2.4 实现DPSK的调制解调的原理 .................................................................................. 8 3 调制与解调的MATLAB仿真实现 .................................................................................... 10
3.1 仿真工具MATLAB的介绍 ...................................................................................... 10
3.1.1 MATLAB软件 ............................................................................................... 10 3.1.2 M文件 ............................................................................................................ 11 3.2 AM的仿真实现 ....................................................................................................... 11
3.2.1 未加噪声时的AM调制解调 .......................................................................... 11 3.2.2 叠加噪声时的AM调制解调 .......................................................................... 13 3.2.3 AM系统的抗噪声性能 ................................................................................. 16 3.3 FM的仿真实现 ....................................................................................................... 17
3.3.1 未加噪声的FM解调实现 .............................................................................. 17 3.3.2 叠加噪声时的 FM解调 ................................................................................. 20 3.4 FSK的调制解调的实现 .......................................................................................... 23
3.4.1 FSK调制实现 ................................................................................................ 23 3.4.2 FSK相干解调实现 ........................................................................................ 25 3.5 DPSK的调制解调的实现 ....................................................................................... 26 4 总结 ..................................................................................................................................... 28 参考文献 .................................................................................................................................. 31 致谢 .......................................................................................................................................... 32