简介：Inthispaperwedescribeafull-integratedcircuitcontainingallbuildingblocksofacompletedPLL-basedsynthesizerexceptforlowpassfilter(LPF).Thefrequencysynthesizerisdesignedforafrequencyhopping(FH)transceiveroperatingupto1.5GHzasalocaloscillator.ThearchitectureofVoltageControlledOscillator(VCO)isoptimizedtogetbetterperformance,andaphasenoiseof-111.85-dBc/Hz@1MHzandatuningrangeof250MHzaregainedatacentrefrequencyof1.35GHz.AnovelDual-ModulusPrescaler(DMP)isdesignedtoachieveaverylowjitterandalowerpower.ThesettlingtimeofPLLis80μswhilethereferencefrequencyis400KHz.ThismonolithicfrequencysynthesizeristointegrateallmainbuildingblocksofPLLexceptforthelowpassfilter,withamaximumVCOoutputfrequencyof1.5GHz,andisfabricatedwitha0.18μmmixedsignalCMOSprocess.Lowpowerdissipation,lowphasenoise,largetuningrangeandfastsettlingtimearegainedinthisdesign.
简介：磁电机眼(瞬间)与微波magnetostatic波浪(MSW)指导光波浪联合同时由信号能导致的多重收音机频率(RF)激动RF信号的multifrequency衍射效果然后并行处理能被衍射效率(Des)是的特征使用认识到近似在里面到RF信号紧张和衍射角度的直接比例与在线性瞬间相互作用区域以内的相应RF信号的频率有关。在这份报纸，学习了是在一阶的瞬间相互作用近似的multifrequency瞬间布拉格衍射，并且获得是为原则衍射效率(PDE)的近似分析表示。另外，提出基于单个频率的衍射是RF信号的相对紧张的一个平行成像方法。由计算和分析，相对错误是为在内的三个RF信号的盒子的不超过0.3dB60MHz的频率空间，这被显示出。
简介：OneoftheprincipaldisadvantagesofOrthogonalFrequencyDivisionMultiplexing(OFDM)isverysensitivetocarrierfrequencyoffset.Theintegerfrequencyoffsethasnoeffectontheorthogonalityamongthesubcarriers,butitcausesacircularshiftandphaserotationofthereceiveddatasymbolssequence,resultinginaBitErrorRate(BER)of0.5.Inthispaper,anovelintegerfrequencyoffsetestimatorforOFDMisderivedbasedonmaximumlikelihoodestimationtechniqueandexplorationofthedifferentialrelationbetweentwoconsecutiveOFDMdatasymbolsequencesinfrequencydomain.ItsperformanceiscomparedwiththeconventionalmethodbycomputersimulationsfortheadditivewhiteGaussiannoisechannelandamultipathfadingchannel.Simulationresultsshowthattheperformanceoftheproposedestimatorisbetterthantheconventionalestimator.
简介：Anovelfinite-difference(FD)approximationinfrequency-domainfortheMurboundaryconditionispresentedinthispaper.CombinedwiththeFDequationsderivedforinhomogeneousanisotropicmedia,thisboundaryconditionisconvenientandeffectivetobeappliedtotheEMscatteringbyelectricallylargeobjectsofcomplexmedia.Boththememoryrequirementandthecomputingtimearedramaticallysaved,comparedwiththeMM,withthecompressedstoragetechnique.Forthecasesofdifferentmedia,RCSofcircularandrectangularcylindersarecomputed.Goodagreementisobtainedbetweentheresultsbythismethodandthoseavailable.
简介：Erroranalysismethodsinfrequencydomainaredevelopedinthispaperfordeterminingthecharacteristicrootandtransferfunctionerrorswhenthelinearmultipassalgorithmsareusedtosolvelineardifferentialequations.therelationbetweenthelocaltruncationerrorintimedomainandtheerrorinfrequencydomainisestablished,whichisthebasisfordevelopingtheerrorestimationmethods.TheerrorestimationmethodsforthedigitalsimulationmodelconstructedbyusingtheRunge-Kuttaalgorithmsandthelinearmultisteppredictor-correctoralgorithmsarealsogiven.
简介：Basedonthetheoryofthepassivehydrogenmaser,alongwiththetechnologyoffrequencymodulationandmodulationtransferspectroscopy,thetheoreticalexpressionofthesinglefrequencymodulationforthepassivehydrogenmaserandthefunctionofthecavityandHlineerrorsignalsseparationarederived,whicharebasicallycoincidentwiththeexperiment.Theabsorptionanddispersionspectrumcurveswithdifferentresonancewidthsshowthatthecavityandhydrogentransitionserveasdiscriminators,andthetwoerrorsignalscanbeseparated.Throughthecalculationsofthetwoerrorsignalsinthepassivehydrogenmaser,itanalyzesthetraditionalmethodofthetwoerrorsignalsseparation,andthendescribesanewimprovedmethodforthepassivehydrogenservoloopsconsistingintheuseofasinglemodulationfrequencyandfrequencydiscrimination.Anullinteractionofthetwoerrorsignalsforthenewselectionofthephasesettingisdeducedtheoreticallyandvalidatedbythesimulation.Thepreliminaryexperimentalresultconfirmsthefeasibilityofthisnewapproach,whichcanreducetheinfluencefromthecavityfrequencyvarietyonthecrystaloscillatorandcontributesignificantlytothelongtermperformanceofthepassivehydrogenmaser.
简介：Toimprovethefrequencystabilizationoflaserdiodeinthelaserfrequencyscannedinterferometricmetrology,amodifiedmethodisproposedbyusingafiberringresonator.Thetheoreticalanalysisofthismodifiedmethodisperformed.Moreover,thePound-Drever-Hall(PDH)techniqueisemployedtoobtainthefrequencydiscriminationcurveofafiberringresonator,whosefinesseis1260andline-widthis270kHz.Thesimulatedresultsshowthatthecurvehasasteepslopeneartheresonantfrequency,whichprovesthesensitivityofthissystemtothefrequencydeviation,sothemodifiedmethodhasgreatpotentialforthefrequencystabilizationofalaserdiode.
简介：Thephaseandfrequencylockingofmicrowave,millimeterwavepowercombiningwereanalysedandsummarizedinanall-roundway.Themaster/slavephaselockingofcavityoscillators,thepeerphaselockingofmutuallycoupledoscillators,andthepeerphaselockingofring-connectedmultipleoscillatorswereinvestigated.Theresultsofnumericalcalculations,andtherelationsofphasetophaselockingmodelandoscillatorparametersweregiven.Andthecavityandspacepowercombiningaspectsformicrowaveandmillimeterwavewerepresented.
简介：Themethodformeasuringthestrainofanobjectusinganopticalfiberandafrequencymodulation(FM)coupledcaritysemiconductorlaserispro-posed.ThismethodusesthecoherentFMheterodyneprincipleoftheMichelsonin-terferometerandcanavoidtheπ/2nonreciprocalphasebiasandphaseshiftingproblemexistingingeneralfiberopticinterferentialsensors,themaximumdetec-tionrangeislimitedbythecoherentlengthofthesemiconductorlaseranditsrela-tivefactor.
简介：ThePMD-inducedpulsebroadeningmaycausethedegradationofreceiversensitivityandhasnegativeeffectsonthepowerspectrumofreceivedsignals.TheexpressionsofPMD-inducedpulsebroadeningeffectsonreceiversensitivityarederivedbasedontheconceptofmeansquarepulsewidth.TheeffectsofPMDonthespectrumofreceivedpowerareanalyzedindetail.Finally,theschemeisdiscussedwithwhichthepowerofacertainfrequencycomponentisextractedasafeedbackcontrolsignalinaPMDcompensationsystem.
简介：Theattempttorepresentasignalsimultaneouslyintimeandfrequencydomainsisfullofchallenges.TherecentlyproposedadaptiveFourierdecomposition(AFD)offersapracticalapproachtosolvethisproblem.ThispaperpresentstheprinciplesoftheAFDbasedtime-frequencyanalysisinthreeaspects:instantaneousfrequencyanalysis,frequencyspectrumanalysis,andthespectrogramanalysis.AnexperimentisconductedandcomparedwiththeFouriertransforminconvergencerateandshort-timeFouriertransformintime-frequencydistribution.TheproposedapproachperformsbetterthanboththeFouriertransformandshort-timeFouriertransform.
简介：Theprincipleandmethodofbothradartargetimagingandvelocitymeasurementsimultaneouslybasedonstepfrequencywaveformsispresented.VelocitycompensationisnecessaryinordertoobtainthegoodHighresolutionrangeprofilesincethiswaveformisgreatlysensitivetotheDopplershift.Thevelocitymeasurementperformanceofthefourstylesisanalyzedwithtwopulsetrainsconsistedofpositiveandnegativestepfrequencywaveforms.Thevelocityoftargetscanbeestimatedfirstcoarselybyusingthepulsetrainswithpositive-positivestepfrequencycombination,andthenfinebypositive-negativecombination.Simulationresultsindicatethatthemethodcanaccomplishtheaccurateestimationofthevelocitywithefficientcomputationandgoodanti-noiseperformanceandobtainthegoodHRRPsimultaneously.
简介：Nonlinearfrequencyconversionisoneofthemostfundamentalprocessesinnonlinearoptics.Ithasawiderangeofapplicationsinourdailylives,includingnovellightsources,sensing,andinformationprocessing.Itisusuallyassumedthatnonlinearfrequencyconversionrequireslargecrystalsthatgraduallyaccumulateastrongeffect.However,thelargesizeofnonlinearcrystalsisnotcompatiblewiththeminiaturisationofmodernphotonicandoptoelectronicsystems.Therefore,shrinkingthenonlinearstructuresdowntothenanoscale,whilekeepingfavourableconversionefficiencies,isofgreatimportanceforfuturephotonicsapplications.Inthelastdecade,researchershavestudiedthestrategiesforenhancingthenonlinearefficienciesatthenanoscale,e.g.byemployingdifferentnonlinearmaterials,resonantcouplingsandhybridizationtechniques.Inthispaper,weprovideacompactreviewofthenanomaterials-basedefforts,rangingfrommetaltodielectricandsemiconductornanostructures,includingtheirrelevantnanofabricationtechniques.
简介：Thetraditionalsuper-resolutiondirectionfindingmethodsbasedonsparserecoveryneedtodividetheestimationspaceintoseveraldiscreteanglegrids,whichwillbringthefinalresultsomeerror.Tothisproblem,anovelmethodforwidebandsignalsbysparserecoveryinthefrequencydomainisproposed.Theoptimizationfunctionsarefoundandsolvedbythereceiveddataateveryfrequency,onthisbasis,thesparsesupportsetisobtained,thenthedirectionofarrival(DOA)isacquiredbyintegratingtheinformationofallfrequencybins,andtheinitialsignalcanalsoberecovered.Thismethodavoidstheerrorcausedbysparserecoverymethodsbasedongriddivision,andthedegreeoffreedomisalsoexpandedbyarraytransformation,especiallyithasapreferableperformanceunderthecircumstancesofasmallnumberofsnapshotsandalowsignaltonoiseratio(SNR).
简介：Steppedfrequencysignalisoftenusedtosynthesizehigh-resolutionrangeprofile,butredundanthigh-resolutionrangeprofileexistsbeforesynthesis.Twomethodshavebeengiventoextracttargetfromoverlappedhigh-resolutionrangeprofileandanalyzedtoshowhowspuriouspeaksappear.Thispaperprovidesareverse-countalgorithmtoresolvetheproblemofspuriouspeaksformovingtarget.Thisproposedmethodselectsthepeakwithmaximumamplitudeastheextractedtargetandgetsitspositionbyusingthenumberofsamplesprcedingbeforethepresentsamplepositionandthenumberofhigh-resolutionrangecellofthetarget.Thisproposedmethodiscomparedwiththealreadygivenmethodandtheresultshowstheabilityoftheproposedmethodtoremovespuriouspeaks,itprovidesthefoundationforhigh-resolutionrangeprofile.
简介：Theproblemofdistributedproportionalfairinter-cellfrequencyallocationforflat-structuredcellularsystemsisstudiedinthispaper.Wefirstlyproposeaframeworkofthefrequencyallocationinwhichthewholefrequencyallocationprocessisdecomposedintomanyconsecutivestages,thenidentifythatforeachstagethekeyistofindtheMaximumWeightIndependentSet(MWIS)inagivenweightedconflictgraphinthedistributedmanner.AnewdistributedalgorithmforMWISisdescribedinwhicheachnodeiterativelyexchangesmessageswithneighbors.WiththisdistributedMWISalgorithm,anewdistributedproportionalfairfrequencyallocationschemeispresented.TheperformanceoftheproposedalgorithmistestedincomputerexperimentssimulatingtheLongTermEvolution(LTE)cellularsystems.Simulationresultsshowtheperformanceoftheproposeddistributedproportionalfairfrequencyallocationschemeiscomparablewiththecentralizedones.
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