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兰州理工大学毕业设计I摘要虚拟仪器是仪器发展的最新方向之一，已成为信息技术的一个重要领域。本文基于“虚拟仪器”的思想提出了虚拟频率特性测试仪的设计方法，其主要目标是利用美国国家仪器公司提供的虚拟仪器开发平台——LabVIEW并结合相应的硬件环境实现频率特性测试，该系统主要包括扫频信号产生、数据采集和频率特性分析三个模块。本文首先论述了基于虚拟仪器频率特性测试仪开发的目的和意义，介绍了虚拟仪器的特点、结构和发展。通过LabVIEW编程，控制函数信号源产生测试所需的扫频信号，并使用数据采集卡NIUSB-6251采集扫频信号和测试网络的响应信号。最后经计算机分析计算和显示，较好地实现了频率特性测量。本设计是充分利用正在蓬勃发展的虚拟仪器技术，即利用微型计算机强大的软件功能和图形环境，研制了一种新型频率特性测试仪。这种新型的测试仪将以其新颖、清晰的图形曲线显示更好地满足科研和工程设计的需要。关键词：虚拟仪器；LabVIEW；幅频特性；相频特性；扫频信号兰州理工大学毕业设计IIAbstractVirtualInstrumentisthenewestdevelopmentorientationofinstrument.Ithasbecomeanimportantareaofinformationtechnology.Thedesignmethodofvirtualfrequencycharacteristictesterisputforwardbasedontheideaofvirtualinstruments.Itmainlyaimstorealizefrequencycharacteristictestsystemusingvirtualinstrumentdevelopment——LabVIEWprovidedbytheNICompanyintheUnitedStatesandcombingthecorrespondinghardwarecondition.Thesystemincludedthethreemodulessuchassignalproduced,dataacquisitionandfrequencycharacteristicanalysis.Thepurposeandsignificanceoffrequencycharacteristictestinginstrumentdevelopmentbasedonvirtualinstrumentwasdiscussedinthispaper.Itintroducesthecharacteristics,structureanddevelopmentofvirtualinstrument.ThroughLabVIEWprogramming，thefunctionsignalgeneratortoproducesweep-frequencysignalneededinthetest.ThesweepsignalandtheresponsesignalofanetworkundertestarecollectedbyDAQNIUSB-6251.Thefrequencycharacteristicmeasurementisimplementedeffectivelybyanalysis，computationanddisplayincomputer.Thisnew-stylefrequencycharacteristictestmeterutilizesfullyvirtualinstrumentaltechnology,newlystronglysoftwarefunctionandgraphicsofcomputer.Thisnew-styletestmetercanwellsatisfyscienceresearchandengineeringdesignbyitsnovel,vividcurvedisplaying.KeyWords:Virtualinstrument；LabVIEW；Amplitude-frequencycharacteristic；Phase-frequencycharacteristic；Frequency-sweepsignal兰州理工大学毕业设计III目录第一章绪论..........................................................................................................................11.1毕业设计的技术背景及任务和要求.........................................................................11.1.1毕业设计的技术背景.....................................................................................11.1.2毕业设计的任务和要求.................................................................................11.2虚拟仪器的技术概述.................................................................................................21.2.1虚拟仪器的基本概念及特点.........................................................................21.2.2虚拟仪器的分类及组成.................................................................................31.3本章总结.....................................................................................................................6第二章虚拟频率特性测量仪的系统设计..............................................................................72.1频率特性测试仪的概述.............................................................................................72.1.1频率特性测试仪的发展现状.........................................................................72.1.2频率特性测试仪的基本原理.........................................................................82.2频率特性的基本概念及测量方法.............................................................................82.3系统结构及总体设计方案.......................................................................................102.4本章总结...................................................................................................................11第三章各模块的详细设计方案............................................................................................123.1扫频信号源设计.......................................................................................................123.1.1激励信号频率点的分配方案.......................................................................123.1.2激励信号的产生...........................................................................................143.2数据采集模块设计...................................................................................................193.2.1数据采集基础...............................................................................................193.2.2数据采集卡及其设置...................................................................................213.2.3采集程序设计方法介绍...............................................................................233.3数据处理模块设计...................................................................................................293.3.1数据处理总体设计.......................................................................................293.3.2巴特沃斯滤波器的选择...............................................................................303.3.3幅度谱和相位谱VI的使用.........................................................................313.3.5频率特性曲线显示.......................................................................................323.4前面板设计.............................................................................................................333.5本章总结...................................................................................................................34第四章测试方案与测试结果...........................................................