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1、基于AD9851的便携式数字扫频仪器的设计(硬件设计)DesignofportabledigitalbasedonAD9851sweepfrequencyinstrument(hardwaredesign)摘要扫频仪是测量网络传输特性的仪器,在现代电子测量中占据着重要的地位。本文着重分析了扫频仪的工作原理,提出了一种基于DDS技术的扫频仪的设计方案。在对市场上扫频仪的研究现状和对系统特性进行分析以后,确定了本设计的性能指标和总体方案。此设计主要有扫频信号发生器电路、增益控制电路、自动电平控制电路、
2、检波头输出电路、单片机ATmega128以及电源模块电路等模块组成,其中扫频信号发生器电路采用DDS纯数字化方法,具有高速的频率转换时间、极高的频率分辨率和较低的相位噪声还具有可编程控制等优点,再加上增益控制电路、自动电平控制电路等,使扫频仪能适应各种测试要求。利用微处理器ATmega128作为控制及处理单元,使用集成化的幅度和相位检测芯片,配有LCD192X64液晶显示,使这种扫频仪设计简单,调试方便,性能稳定可靠,系统界面友好,能够在全频范围内自动步进测量,可预置测量范围及步进频率值,可以更加
3、细致的观察频率特性图,给使用者带来方便。关键词扫频仪DDS技术增益控制IAbstractSweepgeneratorisaninstrumentformeasuringtransmissioncharacteristicsofthenetwork.Inthispaper,theworkingprincipleofsweepgeneratorwereanalysedemphatically,thenadesignschemebasedonDDStechnologywereputforward.Aft
4、eranalysingtheresearchstatusofthesweepgeneratorsinthemarketandthesystemcharacteristics,wemakesuretheperformanceindexandgeneralscheme.Inthisdesign,thesweepgeneratorconsistsofseveralparts,theyrespectivelyaresweptsignalgeneratorcircuit,gaincontrolcircuit
5、,automaticvoltagecontrolcircuit,detectingheadoutputcircuit,atmega128microcontroller,powermodulecircuitInwhichsweptsignalgeneratoradoptthepuredigitaltechniquewhichhashigh-speedfrequencyconversiontime,extremelyhighfrequencyresolution,lowerphasenoiseandt
6、heoutstandingadvantageofprogramecontrol,superaddthegaincontrolcircuitandAutomaticvoltagecontrolcircuit,thesweepgeneratorcanadapttovarioustestrequirements.EmbeddedmicroprocessorAD9851wereusedasthecontrolandprocessingandthecompositivemagnitudeandphasede
7、tectingcircuitLCD192X64makethedesignofsweepgeneratormoresimple,thedebuggingmoreconvenientandtheperformancemorestableandreliable.Inaddition,thissweepgeneratorcanmakesteppingmeasurementautomaticallyinthewholefrequencyrange.Wecanpresetmeasuringrangeandst
8、eppingfrequency,sothedetailedfrequencycharacteristiccurvescanbeseenclearly.Thisfunctionbringsusersmuchconvenience.Keywords:sweepgeneratorDDStechonologygaincontrolI目录摘要IABSTRACTII第一章绪论11.1扫频仪简介11.2扫频仪的分类及其简介2第二章便携式扫频仪器方案的选择72.1扫频仪基本知识72.1.1扫频仪的