天线测试方法new

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1、天线测试方法1.BasicAntennaConcepts1.1ELECTROMAGNETICWAVES电磁波Theradiationfield辐射场fromatransmittingantennaischaracterizedbythecomplexPoyntingvector坡印亭矢量ExH*inwhichEistheelectricfield,andHisthemagneticfield.Closetotheantenna,atadistancerfromtheantenna,thePoyntingvectorisimaginary(reactive无功

2、)andthefieldsdecay衰变morerapidlythan1/r,whilefartherawayfromtheantennathePoyntingvectorisreal(radiating辐射)andthefieldsdecayas1/r.Thesetwotypesoffieldsdominate主宰indifferentregionsofthespacesurroundingtheantenna.BasedonthischaracterizationofthePoyntingvector,wecanidentifythreemajorreg

3、ions(Figure1).1.1.1.ReactiveRegionThisregionisthespaceimmediatelysurroundingtheantenna.Theextentofthisregionisgivenapproximatelyas0

4、on,theradiatingfieldsbegintodominate.Theextentoftheradiatingnear-fieldregionisƒÉ/2ƒÎ

5、eld)isdependentonr.ForD2/4ƒÉ

6、egionisoftenreferredtoastheFresnelregion.菲涅耳区域1.1.3RadiatingFar-FieldBeyondtheradiatingNear-Fieldregion,forr>2D2/ƒÉthePoyntingvectorisreal(onlyradiatingfieldsarepresent)andhasonlytwosphericalcoordinate球面坐标components(ƒÆ,ƒÓ).Thefieldsdecayas1/randtheradiationpatternisindependentofr.T

7、heradiationpatterninthisregionisapproximatedbytheFouriertransformoftheaperturedistribution(withaphaseerroroflessthanƒÉ/16).ThisregionisreferredtoastheFraunhoferregion.夫琅和地区1.2ANTENNAPARAMETERS1.2.1Polarization极化Polarizationisthepropertyoftheelectricfieldvectorthatdefinesvariationin

8、directionandmagnitudewitht