基于DDS的信号源设计资料.doc

摘要本文主要介绍了采用直接数字频率合成DDS芯片实现正弦信号输出，并完成调频，调幅功能。它采用美国模拟器件公司（AD公司）的芯片AD9851，并用AT89C51单片机对其控制，首先从DDS芯片的输出，经低通滤波得到正弦信号，然后对该信号进行调频，调幅。其中调频部分可以通过在软件中修改DDS芯片的频率控制字，相位控制字等来实现，而调幅部分需在DDS输出正弦信号之后外加一调幅器实现。调幅部分将DDS输出作为载波信号，RC振荡器提供1KHz振荡作为调幅信号，它利用了乘法器MC1496完成对正弦信号调制。该系统输出稳定度、精度极高，适用于当代的尖端的通信系统和精密的高精度仪器。本文首先介绍了直接数字合成的原理，然后提出了系统总体设计方案，还有系统硬件电路和软件编写设计等，其中如采用的AD9851芯片和调幅模块电路设计作了详细介绍。关键词：直接数字频率合成(DDS)；AD9851；调频；调幅AbstractThisarticlemainlyintroducedusesthedirectdigitalfrequencytosynthesizetheDDSchiptorealizethesinesignaloutput,andcompletesthefrequencymodulation,theamplitudemodulationfunction.ItusestheAmericansimulationcomponentcompany(ADCorporation)chipAD9851,andwiththeAT89C51monolithicintegratedcircuittoitscontrol,firstfromtheDDSchipoutput,obtainsthesinesignalafterthelowpassfilter,thencarriesonthefrequencymodulationtothissignal,theamplitudemodulation.FrequencymodulationpartialmaythroughrevisetheDDSchipinsoftwarethefrequencycontrolword,thephasecontrolwordandsoonrealizes,buttheamplitudemodulationarepartialmustaftertheDDSoutputsinesignalsur-amplitudemodulatorrealization.TheamplitudemodulationpartiallytheDDSoutputtooktheintelligencesignal,theRCoscillatorprovidesthe1KHzvibrationtotaketheamplititude-modulatedsignal,itusedmultiplierMC1496tocompletetothesinesignalmodulation.Thissystemoutputstability,theprecisionareextremelyhigh,issuitableforthecontemporaryacmecommunicationssystemandthepreciseprecisioninstrument.Thisarticlefirstintroducedthedirectdigitalsynthesisprinciple,thenproposedthesystemsystemdesignplan,butalsohasthesystemhardwareelectriccircuitandthesoftwarecompilationdesignandsoon,likeusestheAD9851chipandtheamplitudemodulationmodulecircuitdesignhasmadethedetailedintroduction.Keyword:Directdigitalfrequencysynthesis(DDS)；AD9851；frequencymodulation；amplitudemodulation目录TOC\o"1-3"\h\zHYPERLINK\l"_Toc137740327"引言PAGEREF_Toc137740327\h1HYPERLINK\l"_Toc137740328"1直接数字频率合成（DDS）原理及性能综述PAGEREF_Toc137740328\h1HYPERLINK\l"_Toc137740329"1.1DDS原理PAGEREF_Toc137740329\h1HYPERLINK\l"