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1、2.7相位噪声NoiseinOscillatorsV=Acos(ωt+φ)o,idealovφnV=A(t)⋅f(ωt+φ(t))o,practical142o43periodicfunctionwithperiod=2πAMPMω−ωωo−ωmωo+ωmomFMωoωoω+ωPMomAMTotalnoisepowerequallysplitintophasenoisepowerandamplitudenoisepower1.RandomwalkFM(randomwalkoffrequency),Splotgoesdownas1
2、/f4.f2.FlickerFM(flickeroffrequency),Splotgoesdownas1/f3.f3.WhiteFM(whiteoffrequency),Splotgoesdownas1/f2.f4.FlickerPM(flickerofphase),Splotgoesdownas1/f.f5.WhitePM(whiteofphase),Splotisflat.f1.RandomwalkFM(1/f4)noiseisdifficulttomeasuresinceitisusuallyveryclosetothe
3、carrier.RandomwalkFMusuallyrelatestotheOSCILLATOR'SPHYSICALENVIRONMENT.IfrandomwalkFMisapredominantfeatureofthespectraldensityplotthenMECHANICALSHOCK,VIBRATION,TEMPERATURE,orotherenvironmentaleffectsmaybecausing"random"shiftsinthecarrierfrequency.2.FlickerFM(1/f3)isa
4、noisewhosephysicalcauseisusuallynotfullyunderstoodbutmaytypicallyberelatedtothePHYSICALRESONANCEMECHANISMOFANACTIVEOSCILLATORortheDESIGNORCHOICEOFPARTSUSEDFORTHEELECTRONICS,orENVIRONMENTALPROPERTIES.FlickerFMiscommoninhigh-qualityoscillators,butmaybemaskedbywhiteFM(1
5、/f2)orflickerPM(1/f)inlower-qualityoscillators.3.WhiteFM(1/f2)noiseisacommontypefoundinPASSIVE-RESONATORFREQUENCYSTANDARDS.Thesecontainaslaveoscillator,oftenquartz,whichislockedtoaresonancefeatureofanotherdevicewhichbehavesmuchlikeahigh-Qfilter.Cesiumandrubidiumstand
6、ardshavewhiteFMnoisecharacteristics.4.FlickerPM(1/f)noisemayrelatetoaphysicalresonancemechanisminanoscillator,butitusuallyisaddedbyNOISYELECTRONICS.Thistypeofnoiseiscommon,eveninthehighestqualityoscillators,becauseinordertobringthesignalamplitudeuptoausablelevel,ampl
7、ifiersareusedafterthesignalsource.FlickerPMnoisemaybeintroducedinthesestages.Itmayalsobeintroducedinafrequencymultiplier.FlickerPMcanbereducedwithgoodlow-noiseamplifierdesign(e.g.,usingrfnegativefeedback)andhand-selectingtransistorsandotherelectroniccomponents.5.Whit
8、ePM(f)noiseisbroadbandphasenoiseandhaslittletodowiththeresonancemechanism.It0isprobablyproducedbysimilarphenomenaasflickerPM(1/f)no
