基于multisim的锁相环解调系统仿真.doc

基于Multisim的锁相环解调系统仿真
PLL Demodulation System Simulation Based on Multisim

摘要
实现调频波解调的方法有很多，而锁相环鉴频是利用现代锁相环技术来实现鉴频，具有工作稳定，失真小，信噪比高等优点，所以被广泛用在通信电路系统中。锁相环其原理是通过鉴相检测输入信号和输出信号的相位差，并将检测出的相位差信号转换成电压信号输出，该信号经低通滤波器滤波后形成压控振荡器的控制电压，对振荡器输出信号的频率实施控制。
该文首先介绍了锁相环技术发展的现状、方向以及背景，并对PLL的原理进行了阐述。在以上的基础上，分别设计了2ASK、2PSK、2FSK的调制解调电路，其功能为数字基带信号经过调制输出一个模拟信号，然后用锁相环进行解调，最后采用Multisim软件进行仿真。在对2ASK、2FSK、2PSK解调时，低通滤波器输出的波形失真比较大，不过最后经过抽样判决电路整形后可以再生数字基带脉冲。在整个电路设计中，力求要做到电路简单，并完成任务书提到的要求。
关键词：调制；解调； Multisim；锁相环

Abstrack
There are many ways to realize frequency wave demodulation, and PLL frequency which has the advantages of stable operation, small distortion, high signal-to-noise ratio and so on is achieved by using modern PLL frequency technology, so it is widely used in communication circuit system. Phase-locked loop through the difference   of the phase detection of input signal and the output signal phase, and the detected phase difference signal into output voltage signal, the signal through a low pass filter. After the formation of the voltage control oscillator , the output signal of the oscillator frequency control.
This paper first introduces the present situation, development direction, phase-locked loop technology as well as the background, and the principle of PLL is discussed. On the basis of the above, the modulation and demodulation circuit of 2ASK, 2PSK, 2FSK which function is a digital baseband signal is modulated by an analog signal and output were designed, and then useing the PLL demodulation, finally using Multisim software simulation. In the 2ASK, 2FSK, 2PSK demodulation, the output of the low pass filter waveform distortion is relatively large, but finally it can regenerate digital baseband pulse sampling decision circuit after shaping. In the circuit design, and strive to do a simple circuit, and complete the task book mentioned requirements.
Keywords： modulate ；modulation ；PLL；Multisim

目 录
第1章  绪论 1
1.1 研究背景 1
1.2 研究现状 1
1.3 研究内容介绍 2
第2章  基本原理 3
2.1  Multisim介绍 3
2.2  锁相环基本原理 5
2.2.1锁相环的基本组成 5
2.2.2 锁相环的工作原理 5
第3章  调制解调电路设计 8
3.1  2FSK调制解调电路设计 8
3.1.1  2FSK调制电路设计原理 8
3.1.2  2FSK调制单元电路的设计 9
3.1.3  2FSK解调单元电路的设计 13
3.1.4  2FSK解调电路的整体设计 15
3.2  2PSK调制解调电路设计 17
3.2.1  2PSK调制解调电路设计原理 17
3.2.2  2PSK调制与解调电路的设计与仿真 18
3.3  2ASK调制解调电路设计 19
3.3.1  2ASK调制解调电路设计原理 19
3.3.2  2ASK调制与解调电路的设计与仿真 20
3.4  解调结果分析 22
总结 24
参考文献 25
附录：(外文翻译) 26
致谢 50