FSK传输系统实验.docx

上传人:b****4 文档编号:26998019 上传时间:2023-06-25 格式:DOCX 页数:21 大小:15.83MB
下载 相关 举报
FSK传输系统实验.docx_第1页
第1页 / 共21页
FSK传输系统实验.docx_第2页
第2页 / 共21页
FSK传输系统实验.docx_第3页
第3页 / 共21页
FSK传输系统实验.docx_第4页
第4页 / 共21页
FSK传输系统实验.docx_第5页
第5页 / 共21页
点击查看更多>>
下载资源
资源描述

FSK传输系统实验.docx

《FSK传输系统实验.docx》由会员分享,可在线阅读,更多相关《FSK传输系统实验.docx(21页珍藏版)》请在冰豆网上搜索。

FSK传输系统实验.docx

FSK传输系统实验

FSKtransmissionsystemexperiment

1.Theexperimentpurpose

1.UnderstandthebasicworkingprincipleofFSKmodulation.

2.TomasterthebasicworkingprincipleofFSKorthogonalmodulationandtheimplementationprocess.

3.MasteringtheFSKperformancetest.

4.ThebasicpropertiesoftheunderstandingofFSKundernoise.

2.Experimentalapparatus

1.JH5001communicationprinciple,integratedexperimentsystem

2.20MHZoscilloscope

3.JH9001typeerrortester

3.Theexperimentalprinciple

1.FSKmodulation

Inbinaryfrequencyshiftkeying,constantamplitudeofthecarriersignalfrequencywiththechangeoftheinputstreamandswitch(knownasthetrebleandbass,representingbinary1sand0s).Usually,theexpressionofFSKsignalareasfollows:

(binary1)

(binary0)

The2πΔfrepresentsaconstantoffsetofthesignalcarrier.

IsthesimplestwayofFSKsignalbasedontheinputdatabitis0or1,switchinthetwoindependentoscillator.Usingthemethodofwaveformatthemomentofswitchingphaseisdiscontinuous,sotheFSKsignaliscalleddiscontinuousFSKsignal.DiscreteexpressionsforFSKsignal:

(binary1)

(binary0)

Itsimplementationisshowninfigure3.11:

Figure3.11noncontinuousphaseFSKmodulationblockdiagram

Duetotheexpansionofphasediscontinuitymadespectrum,theFSKmodulationmodeintraditionalcommunicationequipmentusedmore.Withnodevelopmentofdigitalprocessingtechnology,evenafterthephaseFSKmodulationtechnologyareusedmoreandmore.

AtpresentcommonlyusedmethodistheFSKsignal,FSKbasebandsignalfirst,basebandsignalisusedtoanalysethesinglecarrierwaveoscillatorfrequencymodulation.Therefore,FSKcanbeexpressedasfollows:

Itshouldbenotedthatalthoughthemodulationwaveformm(t)discretewhenbittransformation,butthephasefunctionistheta(t)andm(t)isproportionaltotheintegral,soitisacontinuous,itscorrespondingwaveformasshowninfigure3.12:

Figure3.12continuousphaseFSKmodulationsignal

AsaresultoftheFSKsignalcomplexenvelopeisthenonlinearfunctionofmodulationsignalm(t),toidentifyaspectrumofFSKsignalisusuallyverydifficult,oftenadoptthemethodofaveragereal-timemeasurement.BinaryFSKsignalpowerspectraldensityofthediscretefrequencycomponentfc,fc+nΔf,fc-nΔf,wherenisaninteger.ContinuousphaseFSKsignalpowerspectraldensityfunctionoffinallyaccordingtothefrequencyoffsetminusfourpowerdecline.Ifthephasediscontinuity,powerspectraldensityfunctionaccordingtothefrequencyoffsetthenegativequadraticpowerdecline.

TheFSKsignalspectrumisshowninfigure3.13.

Figure3.13spectrumofFSKsignal

FSKsignaltransmissionbandwidthofBr,givenbyCarsonformula:

Br=2Δf+2B

OneoftheBforthedigitalbasebandsignalbandwidth.Assumesthatthesignalbandwidthlimitsthescopeofmainlobe,thebandwidthoftherectangularpulsesignalB=R.Therefore,FSKtransmissionbandwidthto:

Br=2(Δf+R)

Iftheascendingcosinepulsefilter,transmissionbandwidthreducedto:

Br=2Δf+(1+α)R

Theαrollreductionfactorforfilter.

Inthecommunicationchannelplatform,FSKmodulationschemeisasfollows:

FSKsignal:

Itis:

Amongthem:

Ifthequantizedtreatmenttothejunction,thesamplingrateforfs,cycleforTs,haveestablishedundertype:

Accordingtotheaboveprinciple,therealizationoftheFSKquadraturemodulatorfor3.14structureasshowninfigure:

Figure3.14FSKquadraturemodulatorstructure

Ifsenda0,thephaseaccumulatoronthebasisofayardbeforetheyuanattheendofthephase,arriveateachsamplingtimephaseaccumulation,untiltheendoftheelement;Ifsend1yd,thephaseaccumulatorbasedonyardbeforetheyuanattheendofthephase,arriveateachsamplingtimephaseaccumulation,untiltheendoftheelement.

IncommunicationchannelmodelofFSKbasebandsignalinmarkingthe32KHZfrequency,spaceusing16KHZfrequency,datatransferrateof8KBPS.

Controllerprovidesthedatasourcesare:

1.Plusdata:

throughthechannelinterfacemoduleprovidesdata.

2.Allcode:

1cantestmarksendfrequency.

3.Zero:

allcantestspacesendingfrequency.

4.01code:

0101...Alternatetype,usedasageneraltest.

5.Specialcodesequence:

cycleof8codesequence,sothattheconventionaloscilloscopetoobserve.

6.Msequence:

canbeusedtochannelperformancetest.

ThestructureoftheFSKmodulatorasshowninfigure3.15:

Figure3.15FSKmodulatorstructurediagram

2.FSKdemodulation

ForFSKsignaldemodulationwaymany:

coherentdemodulation,filternoncoherentdemodulation,orthogonalmultiplicationofnoncoherentdemodulation.

1.FSKcoherentdemodulation

FSKcoherentdemodulationwanttorestorethemarkingfrequency(

)andthespacefrequency(

),restorethecarriersignalandreceivingtheFSKofintermediatefrequencysignalmultiplicationrespectively,andthenwithinaelementpointsrespectively,afterintegralresultispresupposed,ifthedifferenceiscurrentlyreceivingsignalsgivengreaterthan0to1,otherwise0.CoherentFSKdemodulationblockdiagramasshowninfigure3.21:

Figure3.21coherentFSKdemodulationblockdiagram

CoherentFSKdemodulatorisbestunderadditivewhitegaussiannoisechannelreceiving,itserrorrateis:

CoherentFSKdemodulationunderadditivewhitegaussiannoisehasgoodperformance,butundertheotherchannelcharacteristicisnotexactlythesame,suchasunderthewirelessfadingchannel,theperformanceispoorer,generallyUSESnoncoherentdemodulationscheme.

2.FSKfilteringofnoncoherentdemodulation

CommonlyusedforFSKnoncoherentdemodulationfilternoncoherentdemodulation,asshowninfigure3.22.InputFSKintermediatefrequencysignalis

respectively,afterthecenterfrequencyandbandpassfilter,andthenthroughtheenvelopedetectionrespectively,theoutputoftheenvelopedetectionatt=kTbsampling(includingkasaninteger),andcomparedthesevalues.Accordingtothesizeoftheenvelopedetectoroutput,comparatordecisiondatabitsare1or0.

Figure3.22incoherentFSKreceiverblockdiagram

WhenusingthenoncoherentdetectionFSKsystemofaveragebiterrorrateis:

InwhitegaussiannoisechannelenvironmentnoncoherentdemodulationFSKfilteringperformanceiscoherentFSKperformanceispoor,butinwirelessfadingenvironment,FSKfilteringnoncoherentdemodulationhasshowngoodrobustness.

NoncoherentdemodulationmethodgenerallyUSESFSKfilteringsimulationmethod,thismethodisnotsuitablefordigitaldemodulationofFSK.FordigitalrealizationmethodoftheFSKgeneralorthogonalmultiplicationmethod.

3.OrthogonalmultiplicationofFSKnoncoherentdemodulation

OrthogonalmultiplicationofFSKnoncoherentdemodulationblockdiagramasshowninfigure3.2-3:

Figure3.23FSKorthogonalmultiplicationofnoncoherentdemodulationschemes

Fortheinputsignal

Markfrequencyasfollows:

Thespacefrequencyis:

Inthediagramabove,timedelaysignalis:

Theτforthedelay.

Aftermultiplyingresultsasfollows:

Inthetype,thefirstafterlowpassfiltercanfilterout.When

Thetypecanbesimplifiedas:

Soafterintegrator(lowpassfilter),theoutputsignalofsize:

soastorealizetheorthogonalmultiplicationofFSKnoncoherentdemodulation.

ABtwowaveformasshowninfigure3.24:

Figure3.24differentialdemodulationwaveform

SeeatimingrecoveryinFSKBPSKdemodulationmethod.

In‘communicationchannelplatform’FSKmode,samplingrateof96KHZsamplingrate(everybitby16samples),FSKbasebandsignalcarrierfrequencyfor24KHZ,thereforeintheprocessofDSPprocessing,sampletaking1timedelayvalue.

TheFSKdemodulationblockdiagramasshowninfigure3.25:

Figure3.25FSKdemodulationblockdiagram

4.Theexperimentcontent

Testbeforeinspection,communicationprincipleoftheintegratedexperimentsystemmodesettoFSKmodulationtransmissionsystem.TPMZ07signaltestpointsismeasuredwiththeoscilloscope,ifthereisapulsewaveform,experimentalsystemhasbeennormalwork.Ifthereisnopulsewaveform,theneedtopresstheresetbuttononthepaneltoinitializedtohardware.

1.FSKmodulation

1.FSKbasebandsignalobservation

TPi03isbasebandFSKwaveform.Throughthemenuchoicefor1codeinputdatasignal,theobservedTPi03signalwaveform,measuringthebasebandsignalcycleandsymbolrate.

Throughthemenuchoiceforzeroinputdatasignals,observationTPi03signalwaveform,measuringthebasebandsignalcycle.Measurementresultswillbecomparedwith1yards.

1.Originatedinphasebranchandorthogonalbranchsignaltimedomainwaveformobservations

TPi03andTPi04werebasebandFSKoutputsignalsofin-phasebranchandorthogonalbranch.Measuringthetwosignalsinthetimedomainwaveformwillenter1yards,measuringthetwosignalwhethermeettheorthogonalrelation.

2.OriginatedinphaseLiShaeducationbranchandorthogonalbranchsignal(x-y)waveformobservations

Settheoscilloscopein(x,y),canbeobservedfromthephaseplaneTPi03andTPi04orthogonality,anditsLiShaeducationshouldbeacircle.

Throughthemenuchoicemeasuredunderdifferentinputtype.

3.ContinuousphaseFSKmodulationbasebandsignalobservation

TPM02issendingdatasignals,TPi03isbasebandFSKwaveform.Measurement,throughthemenuchoose0/1codeinputdatasignals,andtheTPM02assynchronoussignal.ObservationTPM02withTPi03pointwaveformcorrespondingrelationshipshouldhaveaclearsignal.And,intheelementofswitchingpointsendwaveformphasecontinuous.

Throughthemenuselectionforaparticularsequencecodeinputdatasignal,repeatth

展开阅读全文
相关资源
猜你喜欢
相关搜索

当前位置:首页 > 幼儿教育 > 育儿理论经验

copyright@ 2008-2022 冰豆网网站版权所有

经营许可证编号:鄂ICP备2022015515号-1