低成本24GHz天线设计概要文档格式.docx

低成本24GHz天线设计概要文档格式.docx

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Coordinatesystem..........................................52

Layoutspecification.........................................63

Impedancematching.........................................84

Radiationpattern,3-Dvisualization...........................125

Radiationpattern,2-Dvisualization...........................146

Performance..............................................257

Summary.................................................268Revisionhistory...........................................27

DocID018585Rev13/28

Table1.

Specificationoftherecommendedsubstrate....................................7Table2.Documentrevisionhistory.................................................27

AN33594/28DocID018585Rev1

Figure1.

Sphericalcoordinatesystem.................................................5Figure2.

LayoutofMeander-likePCBantennae.........................................6Figure3.

CrosssectionofthePCBatantennaeregion....................................7Figure4.

PartoftheZigBeemodule'

sPCBwithMeander-likeantenna（aroundscale4:

1........8Figure5.

Bypassingimpedancematchingcircuitry-directRFconnection.....................8Figure6.

CompleximpedanceoftheMeander-likeantennaonSmithChart...................9Figure7.

MagnitudeoftheS11parameterinlogarithmicscale（Cartesianplot................10Figure8.

Antenna'

sStandingWaveRatio（SWR.......................................11Figure9.

Threedimensional（3-Dradiationpatternoverview..............................12Figure10.

RadiationpatternonY-Zplane..............................................12Figure11.

RadiationpatternonX-Zplane..............................................13Figure12.

Majorplanesusedtovisualize3-Dradiationpatternusing2-Dplots.................15Figure13.

FarfieldradiationpatternplottedonY-Zplane.................................16Figure14.

normalizedradiationpatternonY-Zplan（Polarplot.............................17Figure15.

normalizedradiationpatternonY-Zplane（Cartesianplot........................18Figure16.

FarfieldradiationpatternplottedonX-Yplane.................................19Figure17.

NormalizedradiationpatternonX-Yplan（Polarplot............................20Figure18.

NormalizedradiationpatternonX-Yplan（Cartesianplot.........................21Figure19.

FarfieldradiationpatternplottedonX-Zplane.................................22Figure20.

NormalizedradiationpatternonX-Zplane（Polarplot............................23Figure21.NormalizedradiationpatternonX-Zplane（Cartesianplot........................24

AN3359CoordinatesystemDocID018585Rev15/281Coordinatesystem

Forthepurposeofthisdocument,thesphericalcoordinatesystemillustratedinFigure1is

used.

Figure1.Sphericalcoordinatesystem

ThePCBmoduleisorientatedvertically（planeX-Z,andlocatedinproximitytotheoriginof

thecoordinatesystem.TheazimuthangleradiatesfromtheX-axistowardstheY-axis,and

theelevationangleradiatesfromtheZ-axistowardsthehorizontalplane,X-Y.Sometimes,

aswithgeographicalandnavigationalsystems,theX-axisiscalledthe"

Nord-axis"

theY-

axisiscalledthe"

East-axis"

andtheZ-axisiscalledthe"

Zenith-axis"

.

LayoutspecificationAN3359

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2

L

ayoutspecification

PCBantennas,includingtheelectricalparametersofPCBmaterialsused,arelayout

sensitive.STMicroelectronicsrecommendsusingalayoutascloseaspossibletothatshowninFigure2.Figure2.

LayoutofMeander-likePCBantennae

TheelectricalparametersandperformanceofthePCBantennaarealsodeterminedbythesubstrateused,inparticularthethicknessofthecoreanddielectricconstants.Figure3illustratesatypicalcross-sectionofthesubstrateinaPCB-antennaearea.

εR

Layoutspecification

DocID018585Rev17/28

Figure3.

CrosssectionofthePCBatantennaeregion

AsubstratewiththeparametersinTable1isrecommended:

Specificationoftherecommendedsubstrate

Pos.Layer

Dimension

DielectricConstantLabel

ValueUnitValueUnit1SolderMask,TopS10.7mil17.78µ

m4.42CopperTraceT1.6mil40.64µ

m---3Core

C28mil711.2µ

m4.44

SolderMask,Bottom

S2

0.7

mil

17.78

µ

m

4.4

ImpedancematchingAN3359

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3Impedancematching

Meander-likePCBantennacanbetunedtotherequired50Ohmimpedancebymatching

theimpedancecircuitrywiththeπtopology.InFigure2theimpedancematchingareaismarkedwithadashedline.Undernominalconditions,thisantennashouldexhibitimpedanceveryclosetotherequirednominalimpedance（50Ohm.

Tochecktheperformanceofthisdesign,asampleantennawasmanufactured（accordingtothespecificationscoveredbythisdocument.Figure4showsthisantenna.Figure4.

sPCBwithMeander-likeantenna（around

scale4:

Assumingthatthemanufacturedsampleexhibitstheexpectedperformance（noimpedancematchingnecessary,theimpedancematchingcircuitrywasbypassedbytwo100pF

capacitorsconnectedinseries,asshowninFigure5:

Figure5.

Bypassingimpedancematchingcircuitry-directRFconnection

Allelectricalparametersofthemeander-likeantennahavebeenmeasuredatconnectiontotheBandPassFilterwiththefrequencyspancoveringfrequenciesfrom2.4GHzto2.5GHz.

CompleximpedanceoftheantennaisshownintheSmithdiagraminFigure6:

Impedancematching

DocID018585Rev19/28

Figure6.

CompleximpedanceoftheMeander-likeantennaonSmithChart

Figure7showsthemagnitudeoftheS11parameter（inlogscale.

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Figure7.

MagnitudeoftheS11parameterinlogarithmicscale（Cartesianplot

Figure8showstheStandingWaveRatio（SWR.

AN3359Impedancematching

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Figure8.Antenna'

sStandingWaveRatio（SWRThefollowingchangeswillaffecttheradiationimpedanceofthePCBantenna:

●

slightboardsizevariation●

metalshielding●

useofplasticcover●presenceofothercomponentsinproximityoftheantenna

Thebestperformanceimpedancematchingcircuitrywillcompensatetheseeffectssothat

foroperatingfrequencies,theoptimum50Ohmimpedanceisachieved.

Radiationpattern,3-DvisualizationAN335912/28DocID018585Rev1

4Radiationpattern,3-Dvisualization

Athree-dimensional（3-Dvisualizationoftheradiationpattern（magnitudeoftheelectrical

farfield|E|isdoneforthecenterISMbandfrequency2.44175GHz.

Figure9.Threedimensional（3-Dradiationpatternoverview

Figure10.RadiationpatternonY-Zplane

AN3359Radiationpattern,3-Dvisualization

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Figure11.RadiationpatternonX-Zplane

Radiationpattern,2-DvisualizationAN335914/28DocID018585Rev1

5Radiationpattern,2-Dvisualization

InthischapterallradiationpatternsarerelatedtothemagnitudeofelectricalfarfieldE,

whichisnormalizedandshowninthelogarithmicscale（indB.Thismeansthatthe

maximumglobalradiationpattern（maximummagnitudeoftheelectricalfar-fieldEis

representedby0dBlevel.Toshowantennaradiationpatternsindetail,threetwo

dimensional（2-Dmajorcutsarepresented.Considertheorientationofthemoduleinthe

sphericalcoordinatesystemasshowninFigure1.

Athreedimensional（3-Dfarfieldradiationpatternisvisualizedasthreetwodimensional

（2-Dcutsthrougha3-Dpattern.Threemajorplanesareusedforthesecuts（Figure12:

OnehorizontalX-Yplane●Twoverticalplanes:

X-ZplaneandY-Zplane.

Forthecol