GMSK英文翻译.docx
- 文档编号:7183677
- 上传时间:2023-01-21
- 格式:DOCX
- 页数:7
- 大小:37.21KB
GMSK英文翻译.docx
《GMSK英文翻译.docx》由会员分享,可在线阅读,更多相关《GMSK英文翻译.docx(7页珍藏版)》请在冰豆网上搜索。
GMSK英文翻译
1.Introduction
Moderncommunicationsystemsusedigitalmodulationtechniques.Advancementsinverylargeintegration(VLSI)anddigitalsignalprocessing(DSP)technologyhavemadedigitalmodulationlesscostthananalogtransmissionsystems.Digitalmodulationoffersmanyadvantagesoveranalogmodulation.Someadvantagesincludegreaternoiseimmunityandrobustnesstochannelimpairments,easiermultiplexingofvariousformsofinformation(e.g.,voice,data,andvideo),andgreatersecurity.Furthermore,digitaltransmissionsaccommodatedigitalerror-controlcodesthatdetectand/orcorrecttransmissionerrors,andsupportcomplexsignalconditioningandprocessingtechniquessuchassourcecoding,encryption,andequalizationtoimprovetheperformanceoftheoverallcommunicationlink.Newmultipurposeprogrammabledigitalsignalprocessorshavemadeitpossibletoimplementdigitalmodulatorsanddemodulatorscompletelyinsoftware.Insteadofhavingaparticularmoderndesignpermanentlyfrozenashardware,embeddedsoftwareimplementationsnowallowalterationsandimprovementswithouthavingtoredesignorreplacethemodem.
Indigitalcommunicationsystems,themodulatingsignal(e.g.~message)mayberepresentedasatimesequenceofsymbolsorpulses,whereeachsymbolhas
finitestates.Eachsymbolrepresents
bitsofinformation,where
bits/symbol.Manydigitalmodulationschemesareusedinmoderncommunicationsystems,andmoreandmorearesuretobeintroduced.Someofthesetechniqueshavesubtledifferencesbetweenoneanother,andeachtechniquebelongstoafamilyofrelatedmodulationmethods.
2.FactorsThatInfluencetheChoiceofDigitalModulation
Severalfactorsinfluencethechoiceofadigitalmodulationscheme.Adesirablemodulationschemeprovideslowbiterrorratesatlowreceivedsignal-to-noiseratios,performswellinmultipathandfadingconditions,occupiesaminimumofbandwidth,andiseasyandcost-effectivetoimplement.Existingmodulationschemesdonotsimultaneouslysatisfyalloftheserequirements.Somemodulationschemesarebetterintermsofthebiterrorrateperformance,whileothersarebetterintermsofbandwidthefficiency.Dependingonthedemandsoftheparticularapplication,tradeoffsaremadewhenselectionadigitalmodulation.
Theperformanceofamodulationschemesisoftenmeasuredintermsofitspowerefficiencyandbandwidthefficiency.Powerefficiencydescribestheabilityofamodulationtechniquetopreservethefidelityofthedigitalmessageatlowpowerlevels.Inadigitalcommunicationsystem,inordertoincreasenoiseimmunity,itisnecessarytoincreasethesignalpower.However,theamountbywhichthesignalpowershouldbeincreasedtoobtainacertainleveloffidelity(i.e.,anacceptablebiterrorprobability)dependsontheparticulartypeofmodulationemployed.Thepowerefficiency,
(sometimescalledenergyefficiency)ofadigitalmodulationschemeisameasureofhowfavorablythistradeoffbetweenfidelityandsignalpowerismade,andisoftenexpressedastheratioofthesignalenergyperbittonoisepowerspectraldensity(
)requiredatthereceiverinputforacertainprobabilityoferror(say
).
Bandwidthefficiencydescribestheabilityofamodulationschemetoaccommodatedatawithinalimitedbandwidth.Ingeneral,increasingthedatarateimpliesdecreasingthepulse-widthofadigitalsymbol,whichincreasesthebandwidthofthesignal.Thus,thereisanunavoidablerelationshipbetweendatarateandbandwidthoccupancy.However,somemodulationschemesperformbetterthantheothersinmakingthistrade-off.Bandwidthefficiencyreflectshowefficiencytheallocatedbandwidthisutilizedandisdefinedastheratioofthethroughputdatarateperhertzinagivenbandwidth.IfRisthedatarateinbitspersecond,andBisthebandwidthoccupiedbythemodulationRFsignal,thenbandwidthefficiency
isexpressedas
Thesystemcapacityofadigitalcommunicationsystemisdirectlyrelatedtothebandwidthefficiencyofthemodulationschemes,sinceamodulationwithagreatervalueof
willtransmitmoredatain88ivenspectrumallocation.
Thereisafundamentalupperboundonachievablebandwidthefficiency.Shannon'schannelcodingtheoremstatesthatforanarbitrarilysmallprobabilityoferror,themaximumpossiblebandwidthefficiencyislimitedbythenoiseinthechannel,andisgivenbythechannelcapacityformula.NotethatShannon'sboundappliesforAWGNnon-fadingchannels.
WhereCisthechannelcapacity(inbps),BistheRFbandwidth,andS/Nisthesignal-to-noiseratio.
Inthedesignofadigitalcommunicationsystem,veryoftenthereisatradeoffbetweenbandwidthefficiencyandpowerefficiency.
Whilepowerandbandwidthefficiencyconsiderations,areveryimportant,otherfactorsalsoaffectthechoiceofadigitalmodulationschemes.Forexample,forallpersonalcommunicationsystemwhichservealargeusercommunity,thecostandcomplexityofthesubscriberreceivermustbeminimized,andamodulationwhichissimpletodetectismostattractive.TheperformanceofthemodulationschemeundervarioustypesofchannelimpairmentssuchasRayleighandRiceanfadingandmulitpathtimedispersion,givenaparticulardemodulatorimplementation,isanotherkeyfactorinselectingamodulation.
3.GMSKdesignprinciples
PARTONE:
Gaussianfilterminimumfrequencyshiftkeying(GaussianMinimumShiftFilteredKeyingshortGMSK)modulationtechnologyfromMSK(MinimumShiftKeying)modulationdevelopedonthebasisofadigitalmodulation,ItscharacteristicsarethedataflowtothefrequencymodulatorpriortotheadoptionofaGaussianfilter(pre-modulationfilter)pre-modulationfilter,toreducethefrequencyoftwodifferentcarrierswitchingthehoppingenergy,makethesamerateofdatatransmissionchannelspacingwhenitbecomesmoreconcentrated.BecausethedigitalsignalmodulationGaussbeforethepre-modulationfilter,ModulationSignal11930.1ismorecontinuousphase,andsmoothingfilter,GSMKmodulationsignalspectrumcompact,BERperformance,andthedigitalmobilecommunicationhasbeenusedextensively,AsisnowwidelyusedGSM(GlobalSystemforMobilecommunication)mobilecommunicationssystemistheuseGMSKmodulation.
PulseresponsewastypicaloftheGaussiandistribution,WhenhispulseterminalandoutputportshaveGaussianoutputresponse.Gaussianfilterthroughthewaveformdatawiththefollowingcharacteristics:
hasnotcurbedthehigh-frequencysignalcomponents.thusenablingthebandwidthandnarrowbandasacute.Impulsetoosmall,notmodulatorunnecessaryinstantaneousfrequencyoffset.ThereforeusingGaussianfilterasapre-modulationlow-passfilterismoreappropriate.ButwhenanpulsewidthofthesquarewaveatTb,andtheresponsewaswideoutput,SuchawidthofTbpulse,theoutputwillbeaffectedbeforeandafterthesymbolofaresponse,Ofcourse,itwasalsothecodebothbeforeandaftertheimpact.Thatistosay,theimportationofrawdatathroughtheGauss-filter,itwillinevitablybringtheinter-symbolinterference.Intentionalintroductionofcontrollableinter-symbolinterferenceandsignalcompressionofthespectrummodulation,demodulationusebeforeandafterthecodetopredicttherelevance,canstillaccuratedemodulationforthejudgment,thisistheso-calledpartial-responsetechnology.GMSKistousethistechnologytorespond,itisamemorysystem,relativelyspeaking,MSKresponsetothewholetechnology,orzero-memorysystem.
PARTTWO:
GMSKinwirelesscommunicationsystems,Gaussmodulationprocessisdividedintopre-modulationfilterandFMmodulation,correspondingdemodulationprocessisdividedintoFMdemodulationandGMSKdemodulation,FMdemodulationcompletionoftheGaussFMsignalwaveformconversion,FMreceptionusuallycompletedemodulationchip(egKA8514Aetc.)GMSKDemodulationcompletedGausswaveformtoadigitalwaveformconversion,usuallyGMSKdemodulatorchipcompleted(suchastheMX589),GMSKsuperheterodynereceiver,AfteranRFsignalormultipleDDCMixersgetalow-frequencysignals(Gausswaveform),thenafteralow-frequencysignalGMSKmodemisdigitaloutput.InGMSKdemodulation,ontheonehand,tobecompletedwiththeGaussiansignalsynchronization,theotherhand,theyhavetousetheappropriatealgorithmtothejudgmentofthejudgmentsignalsandsomecorrection,Traditionaldesignistheuseofanalogintegratedcircuitstocomplete,TheformercansynchronizerorPLL(PhaseLockedLoopPLLforshort)tobeperformedandthejudgmentoftensignalusingaphasejudgment,inabitof/2sampling,IfsamplingalargeparticularreferencevalueA0isabitoutput,theoutputbit0,therefore,GMSKdemodulatorchipsimulationcomplexstructure,lowflexibility,configurationparametersarechangedthroughthechiphardwareparameterstoachieve.SCMsoftwareGMSKdemodulationprocess,facedwiththesamesignalsynchronizationandthetwomajorissuesofjudgment,AsthefiguresSynchronizerissimple,suitableforsoftware,itistheuseofdigitalsynchronizationalgorithmjudgment,adoptionofthe"zero"detection(usedhereasareferencevaluewhichthe"zero"value)andthebit-widthadjustmentstoachievesignalcaptureandsynchronization.
PARTTHREE:
Thewholesystemfromhardwareandsomeexternalmicrocontrollercircuitcomposedoftwoparts,SomeofthesebrokenFMdemodulator.AsGMSKsignalistheanalogsignal,inordertofacilitatetheuseofitssoftwarefordigitalprocessing,SofirstofthesignalforDconversion,thepaperfromtheflexibilityandlow-costperspective,DsuccessiveapproximationbasedonthetheorythatacyclicalpulsecontroloftheSawtoo
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- GMSK 英文翻译
![提示](https://static.bdocx.com/images/bang_tan.gif)