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1、英文论文翻译天线性能目录PROPERTIESOFANTENNAS22.1ANTENNARADIATION32.2GAIN52.3EFFECTIVEAREA82.4PATHLOSS82.5RADARRANGEEQUATIONANDCROSSSECTION102.6WHYUSEANANTENNA?12天线的功能122.1天线辐射132.2天线增益152.3天线有效面积172.4路径损耗182.5雷达距离方程和截面202.6为什么使用一个天线？21英文原文：PROPERTIESOFANTENNASOneapproachtoanantenna
2、bookstartswithadiscussionofhowantennasradiate.BeginningwithMaxwell’sequations,wederiveelectromagneticwaves.Afterthatlengthydiscussion,whichcontainsalotofmathematics,wediscusshowthesewavesexcitecurrentsonconductors.Thesecondhalfofthestoryisthatcurrentsradiateandproduceel
3、ectromagneticwaves.Youmayalreadyhavestudiedthatsubject,orifyouwishtofurtheryourbackground,consultbooksonelectromagnetics.Thestudyofelectromagneticsgivesinsightintothemathematicsdescribingantennaradiationandprovidestherigortopreventmistakes.Weskipthediscussionofthoseequa
4、tionsandmovedirectlytopracticalaspects.Itisimportanttorealizethatantennasradiatefromcurrents.Designconsistsofcontrollingcurrentstoproducethedesiredradiationdistribution,calleditspattern.Inmanysituationstheproblemishowtopreventradiationfromcurrents,suchasincircuits.Whene
5、veracurrentbecomesseparatedindistancefromitsreturncurrent,itradiates.Simplystated,wedesigntokeepthetwocurrentsclosetogether,toreduceradiation.Somediscussionswillignorethecurrentdistributionandinstead,considerderivedquantities,suchasfieldsinanapertureormagneticcurrentsin
6、aslotoraroundtheedgesofamicrostrippatch.Youwilldiscoverthatweuseanyconceptthatprovidesinsightorsimplifiesthemathematics.Anantennaconvertsboundcircuitfieldsintopropagatingelectromagneticwavesand,byreciprocity,collectspowerfrompassingelectromagneticwaves.Maxwell’sequation
7、spredictthatanytime-varyingelectricormagneticfieldproducestheoppositefieldandformsanelectromagneticwave.Thewavehasitstwofieldsorientedorthogonally,anditpropagatesinthedirectionnormaltotheplanedefinedbytheperpendicularelectricandmagneticfields.Theelectricfield,themagneti
8、cfield,andthedirectionofpropagationformaright-handedcoordinatesystem.Thepropagatingwavefieldintensitydecreases
