数字调制系统研究与仿真.docx

PAGE 20 数字调制系统研究与仿真 Research and Simulation of digital modulation communication system 作者：良三伯 摘 要 19世纪自从电通信开始发展以来，技术已经得到了飞跃性的发展，特别要注意的是20世纪50年代以后，发展更是日新月异。最早产生和出现的一种数字通讯形式之一就是模拟电报，随后模拟通讯又因为真空管的出现，得到了迅猛的发展。数字通信进入鼎盛时期是由于脉冲编码的基本原理与信息学理论被引入。在模拟和数字通信中，为了将通信信号变换为便于传送的形式，在调制方式的选择上更为多样。 本文首先对数字信号的调制这一课题的研究背景进行了分析，介绍了关于数字信号调制的国内外研究现状，然后对于数字信号的相关理论，各种调制解调的概念与基本原理进行了阐述，以MATLAB 作为辅助工具进行设计，构建GUIDE程序界面，对 2ASK、2FSK、2PSK、2DPSK进行调制与相干解调设计，对各阶段波形图进行了分析比较，最后对不同信噪比下误码率进行比较，明确了各调制系统的优缺点。 总体看来，在这四种二进制调制方式中，当在一样的外部环境条件影响结果下，ASK作为最基础的系统，误码率最高，且传播时受噪声干扰极大，FSK系统受噪声和延迟影响也较大。PSK与前两者相比具有更好的误码率，DPSK系统综合性能优越，但相比PSK容易受噪声影响，因此在不同环境下我们要灵活选用适合的系统，如果对功率利用率和频谱利用率有更高需求，选用2PSK和2DPSK的调制结果相对会更好一些。 关键词：数字信号；调制；MATLAB；仿真 Abstract Since the beginning of the development of electric communication in the 19th century, communication technology has developed rapidly, especially after the 1950s. The earliest form of digital communication is telegraph, and then due to the emergence of vacuum tube, analog communication has been developed rapidly. Then digital communication entered its heyday because of the principle of pulse coding and information theory. In analog and digital communication, in order to transform the communication signal into a form convenient for transmission, a variety of modulation methods are used.[1,2] This paper first analyzes the research background of digital signal modulation, introduces the research status of digital signal modulation at home and abroad, and then expounds the related theories of digital signal, the concepts and basic principles of various modulation and demodulation, designs with MATLAB as an auxiliary tool, constructs guide program interface, and analyzes the simulation results 2ASK, 2FSK, 2PSK and 2DPSK are designed for modulation and coherent demodulation, and the waveforms of each stage are analyzed and compared. Finally, the BER under different SNR is compared, and the advantages and disadvantages of each modulation system are clarified. In general, in the four bin