Domov Technika Analogový signál

Analogový signál



Úvod

Analogový signál se vztahuje k informaci vyjádřené průběžně se měnícími fyzikálními veličinami, jako je teplota, vlhkost, tlak, délka, proud, napětí atd. Analogový signál obvykle nazýváme jako spojitý signál, může mít nekonečně dlouhý počet různých hodnot. uoussignalinvalue.

Variousphysicalquantitiesinactualproductionandlife,suchasimagestakenbycameras,pressure,flowrate,speed,humidity,etc.recordedintheworkshopcontrolroom,areallanalogsignals.Thedigitalsignalisformedbysampling,quantizingandcodingonthebasisoftheanalogsignal.Specifically,samplingistoobtainthesamplevalueofeachmomentoftheinputanalogsignalatanappropriatetimeinterval.Quantizationistousethebinarycodesystemtorepresentthevalueofeachmomentmeasuredbysampling,andtheencodingistogeneratethequantizationBinarynumbersarearrangedtogethertoformasequentialpulsetrain.

Intheprocessofanalogsignaltransmission,theinformationsignalisfirstconvertedintoalmost"identical"fluctuatingelectricalsignals(hencethename"analog"),andthentransmittedthroughwiredorwirelessmeans,andtheelectricalsignalsarereceivedAfterthat,itisrestoredtoaninformationsignalthroughthereceivingdevice.

Fornearlyahundredyears,whetheritisawiredtelephoneoraradioandtelevisionthatissentwirelessly,analogsignalshavebeenusedtotransmitsignalsforalongtime.Itcanbesaidthattheanalogsignalisalmost"exactlythesame"astheoriginalsignal,anditseemsthatitshouldachieveagoodtransmissioneffect.However,thefactisonthecontrary.Inthepast,weoftenencounteredunintelligiblephenomenawhencalling;radiostationsalwayshavetheeffect.Largershortcomings;snowflakesflickeronTVimagesfromtimetotime.Thisisbecausethesignalhastoundergoalotofprocessingandtransmissionduringthetransmissionprocess,andthesedeviceswillinevitablyproducesomeinterference;inaddition,ifitiswiredtransmission,electricalequipmentnearthelinewillalsoproduceelectromagneticinterference;ifitiswirelesstransmission,itisevenmore""Open",allkindsofinterferenceintheairaresimplyirresistible.Theseinterferencescaneasilycausesignaldistortionandsomenoise.Thesedistortionsandadditionalnoisewillalsoaccumulateasthetransmissiondistanceincreases,whichwillseriouslyaffectthecommunicationquality.Inthisregard,peoplethoughtofmanyways.Oneistotakevariousmeasurestoresistinterference,suchasimprovingthequalityofinformationprocessingequipmentandminimizingitsinterference;anotherexampleistoshieldthetransmissionline;anotherexampleistouseafrequencymodulationcarrierinsteadofanamplitudemodulationcarrier.However,noneofthesemethodscanfundamentallysolvetheproblemofinterference.Anotherwayistotrytoremovethenoiseinthesignalandrecoverthedistortedsignal.However,foranalogsignals,sincetheoriginalundistortedsignalcannotbemoreaccuratelyinferredfromthedistortedsignal,thismethodisveryuseful.Itisdifficulttobeeffective,andsomeevengetworse.

Analogsignalsaremainlycontinuoussignalsrelativetodiscretedigitalsignals.Analogsignalsaredistributedinallcornersofthenaturalworld,suchastemperaturechanges,whiledigitalsignalsareartificiallyabstractedintermsofamplitudevalues.Discontinuoussignal.Electricalanalogsignalsmainlyrefertoelectricalsignalswithcontinuousamplitudeandphase.Thissignalcanbeusedbyanalogcircuitstoperformvariousoperations,suchasamplification,addition,andmultiplication.

Digitalizace analogových signálů

Převod analogových signálů na digitální signály vyžaduje čtyři základní kroky: vzorkování signálů, zadržení signálu, kvantování signálu a kódování signálu.

Samplingistodiscretethecontinuoussignalintime,thatis,collecttheinstantaneousvaluepointbypointontheoriginalanalogsignalaccordingtoaspecifictimeinterval.Fromtheeffectpointofview,thehigherthesamplingfrequency,theclosertheobtaineddiscretesignalistotheoriginalanalogsignal,butthehigherthesamplingfrequency,thehighertherequirementsfortheactualcircuit,whichwillalsobringalotofcalculationandstorage.Ifthesamplingfrequencyistoolow,itwillcauselossofinformation.Aftertakingitsinstantaneousvalue,itshouldbekeptintheoriginalpositionforaperiodoftime,andthesawtoothwavesignalformedinthiswayisprovidedforsubsequentsignalquantization.

Toquantizethecollecteddiscretesignalistoconvertasignalofaspecificamplitudeintoanintegermultipleofthesmallestunitoftheanalog-to-digitalconverter.Thissmallestunitisalsocalledthequantizationunitoftheanalog-to-digitalconverter.Eachsampledvaluerepresentstheinstantaneousamplitudeoftheanalogsignalobtainedbyonesample.Usuallythequantizationunitisamultipleof2.Themorequantizationbits,thesmallerthequantizationerror,andthebettertheresultofquantization.Intheactualquantizationprocess,approximateprocessingisrequired,sotheremustbeaquantizationerror.Thiserrorwillbereproducedinthefinaldigital-to-analogconversion.Thiserrorisusuallycalledquantizationnoise.Thisquantizationerrorcanusuallybereducedbyincreasingthenumberofquantizationbits,butwhenthesignalamplitudeisreducedtoacertainvalue,thecorrelationbetweenthequantizationnoiseandtheoriginalanalogsignalbecomesmoreobvious.

Encodingthequantizeddiscretesignalisthefinalstepofconvertinganalogsignalsintodigitalsignals.Itiscommonlyimplementedbyparallelcomparisonandsuccessiveapproximationcircuits.Withthehelpofcertaincircuits,thequantizedThediscretesignalisconvertedtothecorrespondingdigitalsignal.

Signaladvantages

Themainadvantageofanalogsignalsistheirpreciseresolution.Underidealconditions,ithasinfiniteresolution.Comparedwithdigitalsignals,analogsignalshavehigherinformationdensity.Sincethereisnoquantizationerror,itcandescribethetruevalueofthephysicalquantityinnatureascloseaspossible.

Anotheradvantageofanalogsignalsisthatwhenthesameeffectisachieved,analogsignalprocessingissimplerthandigitalsignalprocessing.Theprocessingofanalogsignalscanbeimplementeddirectlythroughanalogcircuitcomponents(suchasoperationalamplifiers,etc.),whiledigitalsignalprocessingofteninvolvescomplexalgorithmsandevenrequiresspecializeddigitalsignalprocessors.

SignalDisadvantages

Themaindisadvantageofanalogsignalsisthattheyarealwaysaffectedbynoise(undesiredrandomchangesinthesignal).Afterthesignalisduplicatedmanytimes,orafterlong-distancetransmission,theinfluenceoftheserandomnoisesmaybecomeverysignificant.Inelectricity,theuseofgroundedshields,goodlinecontact,andtheuseofcoaxialcablesortwistedpairscanalleviatethesenegativeeffectstoacertainextent.

Noiseeffectscancausesignalloss.Itisalmostimpossibletorestorethedamagedanalogsignalagain,becausetheamplificationofthedesiredsignalwillamplifythenoisesignalatthesametime.Ifthereisalargegapbetweenthenoisefrequencyandthefrequencyofthedesiredsignal,anelectronicfiltercanbeintroducedtofilteroutthenoiseofaspecificfrequency,butthissolutioncanonlyreducetheimpactofnoiseasmuchaspossible.Therefore,undertheinfluenceofnoise,althoughtheanalogsignaltheoreticallyhasinfiniteresolution,itisnotnecessarilymoreaccuratethanthedigitalsignal.

Althoughthedigitalsignalprocessingalgorithmisrelativelycomplex,theexistingdigitalsignalprocessorcanquicklycompletethistask.Inaddition,thegradualpopularizationofcomputersandothersystemshasmadethespreadandprocessingofdigitalsignalsmoreconvenient.Devicessuchascamerashavegraduallyrealizeddigitalization,althoughtheymustinitiallyreceiveinformationofrealphysicalquantitiesintheformofanalogsignals,andfinallytheywillbeconvertedintodigitalsignalsbyanalog-to-digitalconverterstofacilitatecomputerprocessingortransmissionviatheInternet.

Tento článek je ze sítě, nereprezentuje pozici této stanice. Uveďte prosím původ dotisku
HORNÍ