数字基带信号传输码型发生器设计

课程设计任务书学生姓名：专业班级：通信1104指导教师：陈适工作单位：信息工程学院题目:数字基带信号传输码型发生器设计初始条件：FPGA芯片（型号不限），仿真工具不限。要求完成的主要任务:（包括课程设计工作量及技术要求，以及说明书撰写等具体要求）要求每位选课同学提交一篇关于FPGA的应用设计报告，选择的FPGA芯片不限，选用的仿真工具不限。格式要求按照课程设计报告的标准格式完成，包括：常见的几种基带码：1.单极性非归零码2.双极性非归零码3.单极性归零码4.双极性归零码5.差分码6.交替极性码7.分相码8.编码信号反转码指导教师签名：年月日系主任（或责任教师）签名：年月日目录摘要·············································································································IAbstract········································································································II1前言···········································································································12数字基带信号······························································································22.1数字基带信号的码型设计原则···························································22.2非归零码(NRZ码)·········································································32.2.1单极性·················································································32.2.2双极性·················································································32.3归零码(RZ码)···············································································32.3.1单极性·················································································32.3.2双极性·················································································42.4差分码·························································································42.5交替极性码(AMI码)·······································································52.6分相码(曼彻斯特码)········································································52.7传号反转码(CMI码)·······································································63EDA概述····································································································73.1VHDL···························································································73.2FPGA···························································································84基带码发生器的设计原理···············································································94.1基带码发生器的原理框图·································································94.2码型转换原理··············································································105软件设计与仿真···························································································115.1VHDL程序设计·············································································115.2软件仿真及结果分析·····································································135.2.1器件仿真结果······································································135.2.2波形仿真结果······································································136总结与体会·······························································································177参考文献··································································································18摘要设计一个基于FPGA的数字基带信号发生器，首先简要介绍了单极性非归零码、双极性非归零码、单极性归零码、双极性归零码、差分码、交替极性码、分相码、传号反转码等基带码的基本特点，然后根据码型转换原理设计发生器模块。由于EDA技术可以简化电路，集成多块芯片，减小电路体积，所以程序采用VHDL进行描述，并用quartusII软件仿真实现所有功能，最后将功能集成到FPGA上，并设计电路，产生的基带码稳定、可靠，可满足不同数字基带系统传输需要。关键词：数字基带码，EDA，VHDL，FPGAAbstractFPGA-baseddesignaletter-numbergeneratorwith,firstofallwebrieflyintroduceunipolarNRZcode,bipolarNRZ,Unipolarzeroyardscode,bipolarzeroyardscode,differentialcode,alternatingpolaritycode,phasecode,code-reversal,andthird-orderhigh-densitybipolarcodesetc.Thenwedesigngeneratormoduleunderthecode-conversiondesignprinciples.AsEDAtechnologycanmakecircuitsimple,integratemultiplechips,reducethesizeofcircuits,sowetakeadvantageofVHDLtodescribeitandusequartusIIsoftwaretosimulate.FinallyweintegrateallthefeturesintotheFPGA,anddesigncircuittogeneratestableandreliablebase-bandcodetomeetthedifferentbase-banddigitaltransmissionsystemneeds.Keywords:digitalbase-bandcode，EDA，VHDL，FPGA1前言近年来，随着大规模集成电路的出现，数字系统的设备复杂程度和技术难度降低，数字通信系统的主要缺点逐渐得到解决，因此数字传输方式日益受到欢迎。数字传输系统中，传输对象通常是二元数字信息，而设计数字传输系统的基本考虑是选择一组有限的离散的波形来表示数字信息。这些取值离散的波形可以是未经调制的电信号，也可以是调制后的信号。未经调制的数字信号所占据的频谱是从零域或很低频率开始，称为数字基带信号。不经载波调制而直接传输数字基带信号的系统，称为数字基带传输系统。数字基带传输系统方框图如图1-1所示。基带脉冲输入输出噪声图1-1数字基带传输系统方框图目前，虽然数字基带传输的应用不是很广泛，但对于基带传输系统的研究仍然十分有意义，主要是因为：1、在利用对称电缆构成的近程数据通信系统中广泛采用了这种传输方式；2、随着数字通信技术的发展，基带传输方式也有迅速发展的趋势；3、基带传输中包含带通传输的许多基本问题；4、任何一个采用线性调制的带通传输系统，可以等效为一个基带传输系统。抽样判决器同步提取信道信号形成器信道接受滤波器2数字基带信号基带传输是最基本的数据传输方式，即按数据波的原样，不包含任何调制，在数字通信的信道上直接传送数据。基带传输不适于传输语言、图像等信息。目前大部分微机局域网，包括控制局域网，都是采用基带传输方式的基带网。基带网的特点是：信号按位流形式传输，整个系统不用调制解调器，降低了价格；传输介质较宽带网便宜；可以达到较高的数据传输速率（目前一般为10～100Mb/s），但其传输距离一般不超过25km，传输距离越长，质量越低；基带网中线路工作方式只能为半双工方式或单工方式。基带系统的工作原理：信源是不经过调制解调的数字基带信号，信源在发送端经过发送滤波器形成适合信道传输的码型，经过含有加性噪声的有线信道后，在接收端通过接收滤波器的滤波去噪，由抽样判决器进一步去噪恢复基带信号，从而完成基带信号的传输。基带传输时，通常对数字信号进行一定的编码，数据编码常用3种方法：非归零码NRZ、曼彻斯特编码和差动曼彻斯特编码。后两种编码不含直流分量，包含时钟脉冲，便于双方自同步，因此，得到了广泛的应用。数字基带信号，是信源发出的、未经调制或频谱变换、直接在有效频带与信号频谱相对应的信道上传输的数字信号，是消息代码的电波形，是用不同的电平或脉冲来表示相应的消息代码。数字基带信号的类型很多，常见的有矩形脉冲，三角波、高斯脉冲和升余弦脉冲等。最常用的是矩形脉冲，因为矩形脉冲易于形成和变换。数字基带信号是数字信息的一种表现形式，被用于数字基带传输系统。可以用不同电压或电流的代码来表示基带码。不同形式的基带码具有不同的频谱结构，合理地设计基带码是基带传输首先要考虑的问题。2.1数字基带信号的码型设计原则（1）对于传输频率很低