Reviews on Digital Filter.docx

Reviews on Digital Filter.docx

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ReviewsonDigitalFilter

ReviewsonDigitalFilter

Abstract—Thispapermakesacomprehensiveintroductionofthedigitalfilterandmakesasummaryofbackgroundknowledge,applicationoffilterandclassificationindetail.Thenwehaveacomparisonofseveralclassicaldigitalfilters.Finallythedigitalfilterandthedevelopmenttrendareprospected.

Keyword—digitalfilterFIRfilterIIRfiltermethod

1.Backgroundandsignificanceofdigitalfilter

Wearenowlivinginaglobalinformationage.Whatwesee,whatwehearorevenwhatwesmellisthesignalaswell.Butfromtheperspectiveofscience,engineeringandoursociallife,wewillencountermanysignals,suchaspressure,temperature,forceandheartrateandsoon.

Asweallknow,signalprocessingdependsonitssystem.Todealwiththeanalogsignal,weneedanalogsystem.Similarly,wewillhavedigitalsystemfordigitalsignalprocessing.However,analogsystemhaslargevolume,lowaccuracyespeciallynointelligence.Onthecontrary,digitalsystemcanbewell-applied.Therefore,thetechnologyofdigitalsignalprocessingispaidextensiveattentionbypeople.

Digitalfilteringtechnologyisanimportantbranchoftheanalysisandprocessingtechnologyofdigitalsignal.Bothsignalacquisition,transmission,processingandexchangeofthesignalcannotdowithoutfilteringtechnology.Itisextremelyimportantforsafe,reliable,effectiveandflexiblesignaltransmission.Inalltheelectronicsystems,thedigitalfiltersincludethemosttechnologyandarethemostcomplex.Digitalfilterdirectlydeterminesthequalityofproduct.

Nowadays,filtershavearelevantimportanceinelectronicsystemsbecausetheyarepresentinalmostanyelectronicsystem,forexamplecommunicationsystemsmakeintensiveuseoffiltertoseparateunwantednoisefromthedesiredsignal.PowersuppliesusefilterstorejectrippleandimprovethequalityoftheDCsignal.Audioequalizersusefilterstoamplifyorattenuatebandsintheaudiorangetoimproveaudioqualitydependinguponroomacousticcharacteristics.Digitalvideoneedsdigitalfilterstoreducenoiseduetocodingandtransmissionthroughanoisychannel,andsoon.

Accompaniedwiththedevelopmentofthetechnologyofcomputerandmicroelectronics,thetheoryandarithmeticofdigitalsignalprocessingdevelopquickly,Digitalfiltersareextensivelyusedinaudioandvideoprocessing,digitalcommunications,frequencyanalyses,automationandsoon.Digitalfilterisoneofthemostimportantpartsofdigitalsignalprocessing.Italmostappearsinalldigitalsignalsprocessingsystem.

2.Therelatedtechnologydevelopmentsituationathomeandabroad

Digitalfilterisanalgorithmoradeviceconsistingofdigitalmultiplier,adderandadelayunit.Anditplaysanimportantroleinvariousapplicationsofdigitalsignalprocessing.Throughthemathematicalprocessingofsamplingdata,itreachesthegoaloffrequencydomainfiltering.Digitalfiltercanextractusefulandimportantinformationveryflexibly,whichbecomeanimportantpartofmodernsignalprocessing.

Digitalfilteriswidelyusedinthedigitalcommunication,voiceandimageprocessing,spectrumanalysis,patternrecognition,automaticcontrolandotherfields.Comparedwithanalogfilter,thedigitalfilterisabletodealwithlowfrequencysignalwithoutdrifting.Thefrequencyresponsecharacteristicscanbeveryclosetotheidealstation.Italsoreachesveryhighprecisionandcanbeintegratedeasily.Itactuallyisappliedmoreandmorewidelywithallthoseadvantagesofdigitalfilter.Atthesametime,theinventionofDigitalSignalProcessor（DSP）andtherapiddevelopmentofFieldProgrammableGateArray（FPGA）alsopromotethedevelopmentofthedigitalfilterwhichprovidesmorechoicesforimplementationofthedigitalfilters.

Inrecentyears,manydomesticandforeignresearchersmakealotofresearchesaboutthedigitalfilterdesign,whichpromotesitsdevelopmentgreatly.Theapplicationofneuralnetwork,thegeneticalgorithm,improvementmodelsandthewaveletapproximationmethodsinoptimizingthedesignofdigitalfilterhasgoodresults.Butitisstillnotofoptimization,sotherearescholarstryingtomakesomeoptimizationonalgorithmlikeplanningalgorithm,particleswarmoptimization,artificialfishswarmalgorithmindesigningofthedigitalfilter.Theresultsofthoseimprovementsareexcellent.

Filtersarebeingextensivelyusedin1950sandtheyaremainlyappliedinspeechpathfilteringandtheroadoffilterwave.Afterhalfacentury’sdevelopment,thedevelopment,productionandapplicationofthefiltersinChinahavecaughtupwiththeinternationalpaces.Butduetothelackofspecializedresearchinstitutions,theintegrationofprocessandmaterialindustrycan'tkeepup,whichmakestheapplicationanddevelopmentoffiltersinourcountrycan’tfollowtheinternationaldevelopment.

Inthesignalprocessing,signalisoftenmixedwithnoise.Toeliminatethenoisefromthereceivedsignalisaveryimportantprobleminsignaltransmissionandprocessing.Accordingtothedifferentcharacteristicofsignalandnoise,theprocessofextractingtheusefulsignaliscalledfilteringsystem.Thefunctionoffilteringiscalledfilter.Inmoderntelecommunicationequipmentandvarioustypesofcontrolsystem,theapplicationofdigitalfilterisveryextensive.Herearethemostsuccessfulpartsoftheapplicationdomain.

1）speechprocessing

Speechsignalprocessingisoneoftheearliestapplicationsofdigitalfilter.Itisalsothefirsttopromotethefieldoftheorydevelopmentofdigitalsignalprocessing.Themaincontentsinclude5aspects.Thefirstisthespeechsignalanalysis.Itisthecalculationandanalysisofwaveformcharacteristics,thestatisticalcharacteristicsandthemodelparametersofspeechsignals.Thesecondisthespeechsynthesis.Itmeanstheutilizingspecial-purposedigitalhardwareorsoftwarerunningonageneralcomputertoproducespeech.Thethirdisthespeechrecognition.Itisusingspecialhardwareorcomputertorecognizehumanspeech,ortoidentifythespeaker.Thefourthisspeechenhancement.Itistoextractthespeechsignalwhichisconcealedfromnoiseorinterference.Thefifthisspeechcoding,whichismainlyusedforvoicedatacompression.Ithasestablishedaseriesofaudiocodinginternationalstandardforalotofcommunicationandaudioprocessing.

2）pictureprocessing

Digitalfilteringtechniquehavebeenappliedsuccessfullytothestillimageandimagerestorationandenhancement,datacompression,noiseandinterferenceremoving,imagerecognitionandtomographyX-ray.Itisalsousedinvisibleimageofradar,sonar,ultrasonicandinfraredsignals.

3）Communication

Inthefieldofmoderncommunicationtechnology,almosteverybranchhasbeeninfluencedbydigitalfilteringtechniques.Sourcecoding,channelcoding,modulation,multiplexing,datacompressionandadaptivechannelequalizationusethedigitalfilterwidely.Particularlyindigitalcommunication,networkcommunication,imagecommunication,multimediacommunicationapplications,withoutthedigitalfilter,wealmostcan'tdoanything.Thesoftwareradiotechnologyisconsideredtobethefuturedirectionofdevelopmentofcommunicationtechnology,whichisbasedonthedigitalfilteringtechnologyaswell.

4）television

DigitalTVreplacinganalogueTVisaninevitabletrend.Popularizationofhighdefinitiontelevisioniscomingnearly.Thevideodisctechnologyhasformedahugemarketindustrytosupportit.Thevideophoneandvideoconferenceproductsareconstantlyupdating.Theachievementandthestandardizingoftheworkinthevideocompressionandaudiocompressionworkcontributetotheflourishingdevelopmentoftelevisionindustry.Therefore,digitalfilteranditsrelatedtechnologyisanimportantbasisforcompressedvideoandaudiocompressiontechnology.

5）Radar

Radarsignalhasaverywidefrequencybandandthedatatransmissionrateisveryhigh.Sotheamountofcompresseddataandreducingthedatatransmissionrateisthemostimportantissuethatthedigitalradarsignalprocessinghastoface.Theinventionofthedigitaldevicespromotestheradarsignalprocessingtechnology.Inmodernradarsystem,thedigitalsignalprocessingpartisindispensable,becausetheestimationandtargetimagingofthesignalgenerating,filtering,processingandthetargetparametersallcannotdowithoutthedigitalfilteringtechnique.Digitalfilterofradarsignalisoneoftheveryactiveresearchfieldsnowadays.

6）sonar

Sonarsignalprocessingisdividedintotwocategories,namelyactivesonarsignalprocessingandpassivesonarsignalprocessing.Activesonarsysteminvolvesmanytheoriesandtechniquesthesameasradarsystem.Forexample,theyhavetogenerateandemitpulsesignaldetectionandsignalprocessingtasksaretodetectandanalyzetheweaktargetechosoastoachievethedetection,localization,tracking,navigation,imagingdisplayoftarget.Themainsignalprocessingtechnologytheyareappliedincludesfiltering,thresholdcomparisonandspectralestimation.

7）biomedicalsignalprocessing

Digitalfilteriswidelyusedinmedicine,suchasEEGandECGanalysis,tomographyXraycomputeraidedanalysisandadaptivedetectionoffetalheartsound.

8）Music

Digitalfilterhasopenedupanewsituationforthefieldofmusic.Thedigitalfilteringtechniqueshaveshownpowerfulinthemusicsignalforediting,synthesis,andjoininginthemusicreverberation,chorusandspecialeffectsandotherspecialaspects.Digitalfiltercanbeusedforcomposing,recordingandplayback,ortheoldtapesoundrecoveryetc.

9）otherfields

Theapplicationfieldso