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1、TransmissionMar.2007JournalofElectronicScienceandTechnologyofChinaV.01.5No.1TransmissionPropertiesdarWave1-ropertiesoIarwavethroughReentryPlasmaSheathGAOZheng-pingl,-,MAZhao.guol,.,LIUJingl,.,LIZhong-ping3,ZHANGDa-hai31.EngineeringResearchCenterofElectromagneticWaveAbsorbingMaterials,MinistryofEduca
2、tice,UniversityofElectronicScienceandTechnologyofChinaChengdu610054China2.StateKeyLab.ofElectronicThinFilms&IntegratedDevices,UniversityofElectronicScienceandTechnologyofChinaChengdu610054China3.NationalKeyLaboratoryofAdvancedFunetienalCompositeMaterials,9200BoxBing100076ChinaAbstractInthispaper
3、,bytakingintoaccountthecouplingoftheionizationofablationgasandatmosphere,anelectronsdensitydistributionmodelisbuflLUsingthismodel,thetransmissionpropertiesof蟠erentpolarizationradarwavethroughsheathareevaluatedonthebasisofthetransmissionmatrixtheory.Then.wediscusstheeffectsoftheelectronsdensity,thead
4、dedmagneticfield,andtheradarwavefrequencyonthetransmissionproperties.Asaresultofthisinvestigation,greatertransmissionpowercouldbegainedinordertoefficientlyshortencommunicationblackout,byreducingtheelectronsdensityorchoosingproperaddedmagneticlieIdandthefrequencyoftheradarwaveaccordingtothedilferentp
5、olarizationformoftheradarwave.Keywordscommunicationblackout;plasmasheath;radarwave;reentry;transmissionproperties;wllenmilitarymissileslikeintercontinentalmissileandlong-rangestrategicmissilereenterstheaerosphereathypersonicspeeds,theatmosphereinfrontofthemissilesiScompressedandheatedup.Thesharplyin
6、creasingtemperaturecausestheablationofradomeandionizationoftheablationgas.Then,aplasmasheathisformedwhichseriouslyattenuatesandreflectsthemicrowavestransmission,resultinginthecommunicationblackoutbetweenthemissileandtheland.Anumberofexperimentsandtheoreticalinvestigationshavebeenproposedinrecentyear
7、storesolvethisproblem.Theabsorptionpowerandreflectionpoweroftheelectromangnatic(EM)waveweretreatedthroughmagnetized,stationary,seconddimensional,nonuniformplasmaandgottheirnumericalrelationshipswiththeparametersoftheplasmat.HucalculatedtheabsorptionpowerofEMwavefromnonuniformmagnetizedplasmaslabutil
8、izingscatteringmatrixmethod.HelalyinvestigatedthescatteringphenomenaoftheEMwavethroughthenonuniformmagnetizedplasmaslabL耳|.Petrindealtdewiththenonlinearmutua1.influencebetweentheEMwaveandthemagnetizedplasmaL.Abovestudiesmainlyfocusontheabsorptionfromplasmasheath,seldomwithexplicitdiscussionaboutthee
9、ffectsoftheelectronicdensity,EMwavefrequency,andappliedmagneticfieldonthetransmissionpower.Inthispaper,weproposethedistributionmodeloftheelectronicdensitybycombiningatmosphereionizationandablationgasionizationandevaluatetheeffectsoftheelectronsdensity,radarwavefrequency,andappliedmagneticfieldonthet
10、ransmissionpoweroftheradarwavethroughplasmasheathduringreentry.Theconclusionismadeofhowtoenhancetransmissionpowerandshortencommunicationblackoutinpractice.1ModelDefineInthepreviousstudieselectronicdensitydis仃ibutionssuchasquadricmode1.exponentialmodeletc.,onlyatmosphereionizationistakenintoconsidera
11、tion.Greaterrorexistsinthesemodels.Analyzingfromaphysicalperspective,wecanseethatelectronicdensitygoestozeronearthemissilesurfaceandintheplacefarawayfromthemissile,withoneorsevellextremumsinlimiteddistance,andiswithsmoothvariationinthewholeplasmasheath.Obviously,thedis仃ibutionmodelsmentionedabovecou
12、ldnotsatisfythephysicaldistributionwel1.Toobtainabetterdistributionmodel,theelectronsgeneratedbymaterialablationaretakenintoaccounKwhichfollowthedistributionthattheelectronicdensityreachesthemaximumneartllemissilesurfaceanddecreasesasthedistanceincreases.Bycouplingtheelectronsgeneratedbyatmosphereio
13、nizationand30JournalofElectronicScienceandTcclmologyofChinaV_01.5materialablation,weestablishourelectronsdensitydistributionmodelandtheresultapproachestheexperimentresult.Withthedifferentflyingvelocity,themaximumofelectronsdensitydiffers,asshowninFig.1.963024681012magneticfield.Themagneticfieldhasno
14、influenceontheelectronicmovement.Therefore,thesituationinthisaspectisthesameasthesituationwithoutanappliedmagneticfield.Theradarwavewiththisincidencedirectioniscalledordinarywave.BysolvingtheMaxwellsequations,thecomplexrelativepermittivityoftheplasmacanbeobtainedh=3Okm.whereh=55lmIh0lmIFig.1Theelect
15、ronsdensitydistribution2ResuItandAnalysisAsshownintheFig.1,electronicdensitydjstributionisnonuniformintheplasmasheath.Thus.thepermittivityintheplasmasheathisnonuniformtoo.Sincethetransmissionpropertiesofradarwavethroughreentryplasmasheathisrathercomplex,thereentryplasmasheathisdividedintoseveraIslabsintheperpendiculardirectiontothesurfaceinthisPapertoapproachpropersolutions(seeFig.2).Eachslabcanbeapproximatelytreatedasuniformdistribution.Then,thetransmissionpropertiescanbecalculatedonthebasisofthetransmissionmatrix.ozIzL_l厄+Iz-JFig.2Transmissionmatrixtheory
