基于labview的锁相放大器实现

锁相放大器的LabVIEW实现-I-摘要锁相放大器（Lock-inAmplifier,LIA）是一种根据相关检测原理设计的同步相干检测仪，能够准确检测提取出淹没在强噪声背景中的周期性有用信号，是微弱信号检测（WeakSignalDetection）领域中最重要和最有效的精密仪器之一，广泛地应用与基础科学研究、国防科技、生物医学信号、物理探伤等领域。相敏检波器（PhaseSensitiveDetector,PSD）是锁相放大器的核心器件，能够实现对待测信号和参考信号进行相关运算；而低通滤波器的通频带宽决定了相敏检波器输出信号的谐波成分，进而对锁相放大器的精度产生影响。因此，本文着重研究了相敏检波器和低通滤波器的设计环节，并在参考信道设置了两路正交的参考信号以避免了输出结果对相位差的依赖。本文通过分析锁相放大器的工作原理，利用虚拟仪器技术，基于LabVIEW软件开发平台实现了双锁相放大器的设计方案。经测试证明，本文设计的正交矢量型数字锁相放大器具有较好的抑噪性能，能够大幅度提高输出信号的信噪比。关键词：锁相放大器；虚拟仪器；相敏检波器锁相放大器的LabVIEW实现-II-Functionrealizationoflock-inamplifierbyLabVIEWprogrammingAbstractLock-inAmplifier(LIA),basedontheprincipleofcorrelation-detecting,isoneofthemosteffectivemeansinweaksignaldetectionsandprovetobeabletodetectandmeasureperiodicalsignals,themagnitudeofwhichareusuallysoweakagainstthesurroundingnoise,widelyusedinthefieldsofscientificresearch,nationaldefensescienceandtechnology,biomedicalengineering,physicaldetection,andsoon.Phasesensitivedetector(PSD)isthecoreofthelock-inamplifierandcanidentifythemeasuredsignalswhosefrequencyisthesameasthereferencesignal;anditsoutputisdeterminedbythepassband-widthoffrequencyoftheLPF,whichalsoaffectstheprecisionofthelock-inamplifier.Thus,thispaperstudiestherealizationofthePSDandtheLPF,andsetuptwoorthogonalreferencesignalchannelstoavoidthedependenceonthephasedifference.Thepaperanalysestherealizationofthelock-inamplifier,anduseLabVIEWtorealizethedual-phaselock-inamplifier.And,itprovestobeeffectivethroughthesimulations,showsagoodperformanceinthedetectionofweaksignals,andgreatlyimprovestheSNRoftheoutputsignals.KeyWords：Lock-inAmplifier；VirtualInstrument；PhaseSensitiveDetector锁相放大器的LabVIEW实现-III-目录摘要.....................................................................................................................................IAbstract..............................................................................................................................II1绪论…………………………………………………………………………...………11.1课题研究背景及意义................................................................................................11.2微弱信号检测............................................................................................................11.3锁相放大器发展概况................................................................................................31.4虚拟仪器技术与LabVIEW简介.............................................................................41.4.1虚拟仪器技术…………………………………………………………...……41.4.2LabVIEW简介…………………………………………………..……...……61.5本章小结...................................................................................................................92锁相放大器的基本理论.............................................................................................102.1相关检测原理..........................................................................................................102.2相关检测技术..........................................................................................................112.3正交矢量型锁相放大器..........................................................................................122.4模拟与数字锁相放大器性能对比..........................................................................122.4数字滤波器的设计..................................................................................................132.5本章小结..................................................................................................................153数字锁相放大器的软件设计.....................................................................................173.1数字锁相放大器的前面板.....................................................................................173.2数字锁相放大器程序框图.....................................................................................183.3各子模块设计及功能介绍.....................................................................................203.3.1信号生成模块...............................................................................................203.3.2前级滤波模块...............................................................................................223.3.3相敏检波模块...............................................................................................233.3.4信号还原模块...............................................................................................253.3.5测量显示模块...............................................................................................263.3本章小结..................................................................................................................274系统性能测试与分析.................................................................................................284.1部分模块功能仿真与调试......................................................................................284.1.1信号生成模块仿真与调试.............................................................................284.1.2前级滤波模块仿真效果分析.........................................................................29锁相放大器的LabVIEW实现-IV-4.1.3相敏检波模块仿真测试.................................................................................294.2整体模块性能测试..............................................................