数据采集系统的模拟抗锯齿滤波器

Analogfilterscanbefoundinalmosteveryelectronic

circuit.Audiosystemsusethemforpreamplification,

equalization,andtonecontrol.Incommunicationsys-

tems,filtersareusedfortuninginspecificfrequencies

andeliminatingothers.Digitalsignalprocessingsys-

temsusefilterstopreventthealiasingofout-of-band

noiseandinterference.

Thisapplicationnoteinvestigatesthedesignofanalog

filtersthatreducetheinfluenceofextraneousnoisein

dataacquisitionsystems.Thesetypesofsystemspri-

marilyutilizelow-passfilters,digitalfiltersoracombina-

tionofboth.Withtheanaloglow-passfilter,high

frequencynoiseandinterferencecanberemovedfrom

thesignalpathpriortotheanalog-to-digital(A/D)con-

version.Inthismanner,thedigitaloutputcodeofthe

conversiondoesnotcontainundesirablealiasedhar-

monicinformation.Incontrast,adigitalfiltercanbeuti-

lizedtoreducein-bandfrequencynoisebyusing

averagingtechniques.AN699Anti-Aliasing,AnalogFiltersforDataAcquisitionSystemsAuthor:BonnieC.BakerANALOGVERSUSDIGITALFILTERSMicrochipTechnologyInc.Asystemthatincludesananalogfilter,adigitalfilterorbothisshowninFigure1.WhenananalogfilterisINTRODUCTIONimplemented,itisdonepriortotheanalog-to-digitalconversion.Incontrast,whenadigitalfilterisimple-Analogfiltersca