亚马逊意外错误报歉，由于程序执行时，遇到意外错误，您刚刚操作没有执行成功，请稍后重试。或将此错误报告给我们的客服中心：推荐您，确认您的操作无误后，再继续其他操作。您可以通过亚马逊，获得更多的帮助。WIFI Antennas On Mobile Phones
WIFI Antenna Design
WIFI antennas are on just about every cell phone these days. The WIFI frequencies are the highest
of all frequency on the device (relative to cell frequencies, gps, nfc, etc). The WIFI frequency
is divided into two bands:
MHz (which also includes bluetooth) and
All WIFI antennas support the
MHz band, and typically the WIFI antenna is connected to a chip
that does both WIFI and bluetooth. This means designing antennas for WIFI and bluetooth is basically
the same thing. Phones now are shipping with the
MHz band included in WIFI, so that the WIFI
antenna is often dual band. It is also possible to have two wifi antennas, one for 2.4 GHz and one for the 5 GHz
band, although this is less common.
Because WIFI is the highest frequency on the mobile device, the WIFI antenna will be the smallest antenna.
A half-wavelength at 2.4 GHz is 6.25 cm (2.5"), and a half-wavelength at 5 GHz is 3 cm or just over an inch.
Hence, using quarter-wavelength antennas leveraging the devices groundplane can make for very small
wifi antennas. Good quarter-wavelength antennas for WIFI include
WIFI antennas are simultaneously used for transmit and receive. Hence, WIFI antennas must
abide by FCC and governmental
In addition, there are peak
rules that are specified in dBm. Typically, antenna gain is specified in dB, such as peak antenna gain
equals +2 dB. This means that the efficiency times the directivity is +2 dB.
FCC rules often specify gain in dBm. This means that they might say the wifi antenna gain must be
less than 10 dBm. This means that the peak
must be less than 10 dBm. This number is a function of the conducted power (the power the radio outputs
at its terminals, which is typically something on the order of 15 dBm for WIFI), the wifi antenna
efficiency, and the
of the antenna.
Peak gain [dBm] is basically equal to Conducted_Power [dBm] + Antenna Efficiency [dB] + Directivity [dB].
For instance, if the conducted power is 15 dBm, the antenna efficiency is -3 dB, and the directivity is +4 dB,
then the peak gain would be 16 dBm. If the spec for peak gain was 14 dBm, the system could achieve the spec
by dropping the conducted power to 14 dBm (a drop of 2 dB).
WIFI antenna efficiencies for handheld mobile devices are typically on the order of -6 dB to -2 dB.
The efficiency is decreased due to
lossy resistance of all the components around the antenna (camera, PCB, glass on the screen, etc).
The WIFI antenna is typically located on the top of the device (near the GPS antenna and diversity cellular
antenna). Note that there are no
specs, so in general you don't want the WIFI
antenna to have too high of an efficiency, or the SAR and peak gain values will require a large conducted
power backoff.
[Different Site]
This page on WIFI mobile phone antenna design for smartphones is copyrighted. No portion can be reproduced without permission
from the webmaster. Copyright , , wifi antennas.IEEETRANSACTIONSONMICROWAVETHEORYANDTECHNIQUES,VOL.59,NO.10,OCTOBER
DesignandLinearizationofConcurrentDual-BandDohertyPowerAmplifierWithFrequency-DependentPowerRanges
WenhuaChen,Member,IEEE,SeyedAidinBassam,Member,IEEE,XiangLi,YuchengLiu,
KarunRawat,StudentMember,IEEE,MohamedHelaoui,Member,IEEE,FadhelM.Ghannouchi,Fellow,IEEE,andZhengheFeng,SeniorMember,IEEE
Abstract—Adesignmethodologyforaconcurrentdual-bandDohertypoweramplifier(PA)withfrequency-dependentbackoffpowerrangesispresentedinthispaper.Basedonadual-bandT-shapednetworkandacoupledlinenetwork,differentdual-bandcomponentsneededinDohertyPAtopology,includinga3-dBbranch-linecoupler,anoffsetline,andaquarter-wavelengthtransformer,aredeveloped.Twoprototypeswithbalancedandimbalancedbackoffpowerrangemodesareimplementedtoverifythefeasibility.Continuouswavesignaltestresultsshowthattheproposeddual-bandPAsuccessfullyachievesapower-addedefficiencyof33%and30%atthe6-dBbackoffpointfromthesaturatedoutputpowerat880and1960MHz,respectively.Tomeetlinearityrequirements,thePAnonlinearbehaviorischar-acterizedbyusingdigitalmultitonesignals,whichcategorizethedistortionsofaconcurrentdual-bandPAintointermodulationandcross-modulation.Finally,a2-DdigitalpredistortiontechniqueisusedtocompensateforthenonlinearityofPAindualbands.Twotwo-tonesignalsareappliedtothedualbandsforlinearization,andtheexperimentalresultsshowthatthistechniqueachievesimprovementsofbetterthan19.1and24.6dBfortheintermodu-lationandcross-modulationinthedualbands,respectively.IndexTerms—Digitalpredistortion(DPD),Dohertypoweramplifier(PA),dualband,widebandcodedivisionmultipleaccess(WCDMA).
I.INTRODUCTION
ITHTHErapidevolutionofcommunicationtech-nologies,mobilecommunicationsystemsshould
accommodatemanystandardssimultaneously,suchaswide-
ManuscriptreceivedFebruary07,2011;revisedJuly18,2011;acceptedJuly28,2011.DateofpublicationSeptember06,2011;dateofcurrentversionOc-tober12,2011.ThisworkwassupportedbyAlbertaInnovateTechnologyFu-tures(AITF),theNaturalSciencesandEngineeringResearchCouncilofCanada(NSERC),theCanadaResearchChairsProgram,andtheMinistryofScienceandTechnologyofChinaNationalScienceandTechnologyMajorProjectunderGrant-003andGrant09-003.
W.Chen,S.A.Bassam,K.Rawat,M.Helaoui,andF.M.GhannouchiarewiththeIntelligentRFRadioLaboratory(iRadioLab),DepartmentofElec-tricalandComputerEngineering,SchulichSchoolofEngineering,UniversityofCalgary,Calgary,Alberta,CanadaT2N1N4(e-mail:whchen@ucalgary.ca).X.LiandZ.FengarewiththeDepartmentofElectronicEngineering,Ts-inghuaUniversity,Beijing100084,China.
Y.LiuwaswiththeDepartmentofElectronicEngineering,TsinghuaUni-versity,Beijing100084,China.HeisnowwiththeSchoolofElectricalandComputerEngineering,PurdueUniversity,WestLafayette,IN47907USA.Colorversionsofoneormoreofthefiguresinthispaperareavailableonlineathttp://ieeexplore.ieee.org.
DigitalObjectIdentifier10.1109/TMTT.
bandcodedivisionmultipleaccess(WCDMA)andWorldwideInteroperabilityforMicrowaveAccess(WiMAX).Inaddition,forsmoothnetworkmigrationandupgrades,itisessentialtoguaranteethebackwardcompatibilityoflong-termevolutionadvanced(LTE-advanced).Therefore,theRFfront-endinfuturesystemsshouldbeabletosupportmultibandoperations.Inthissituation,amultibandpoweramplifier(PA)ishighlydesirable,especiallyfortheconcurrentmode.ManyeffortshaverecentlybeencarriedouttorealizeconcurrentmultibandPAs[1]–[3].
Atthesametime,nonconstantenvelopemodulationschemes,suchashigh-orderquadratureamplitudemodulation(QAM)andorthogonalfrequency-divisionmultiplexing(OFDM),havebeenwidelyusedforhighcapacityinwirelesscommunica-tions.Anonconstantenvelopesignalleadstoahighpeak-to-av-eragepowerratio(PAPR),whichsignificantlydecreasestheef-ficiencyofthePAinordertomeetthelinearityrequirementsofwirelesscommunicationstandards.Toenhancetheefficiencyinthelow-powerregion,theDohertyPAhasbeenstudiedex-tensivelyandadoptedinbasestations[4],[5].Recently,somenewtechniquestodesignaDohertyPAthatsupportsconcurrentdual-bandoperationhavebeenproposedbyusingdual-bandtransformers[6],[7].
Infact,theefficiencyoftheDohertyPAisenhancedatthecostoflinearitydeterioration,comparedwithtraditionalclassA/ABPAs,ifnoneofintermodulationcancellationtechniquesisused.TosatisfythelinearityspecificationinWCDMA,lin-earizationtechniquesshouldbeemployedfortheDohertyPA.Asshownin[8]and[9],acombinationoftheDohertyanddig-italpredistortion(DPD)techniquesisapromisingsolutionforahigh-efficiencyhigh-linearityPA.Inordertoapplyadual-bandDohertyPAinarealsystem,thelinearizationschemefortheproposedPAshouldbedetermined.
Inconcurrentdual-bandPAs,thedistortionsduetothetransmitter’snonlinearbehaviorareclassifiedasintermodu-lationandcross-modulationdistortions[10],whichintroduceundesiredsignalsatadjacentchannels,resultingindegradedadjacentchannelpowerratio(ACPR)performance.
Inthispaper,aconcurrentdual-bandDohertyPAwithfre-quency-dependentbackoffpowerrangesisproposedandinves-tigated.Thedesignprocedureforthedual-bandpassiveandac-tivecomponentsinvolvedintheproposeddual-bandDohertyPAisbrieflypresented,anddifferentimplementationmethodsarecompared.
/$26.00(C)2011IEEE
2538IEEETRANSACTIONSONMICROWAVETHEORYANDTECHNIQUES,VOL.59,NO.10,OCTOBER
Fig.1.Circuitdiagramofthedual-bandDohertyPA.
Fig.2.Equivalent-circuitmodelofthedual-bandDohertyPA.
Inordertolinearizetheproposeddual-bandDohertyPA,itsnonlinearbehaviorischaracterizedbyusingtwo-tonesig-nals.Accordingtothischaracterization,afrequency-selectivetwo-cellprocessingpredistortionarchitecturethatcansimulta-neouslycompensateforthedistortionineachbandforthelin-earizationofaconcurrentdual-bandPAisdemonstrated.
II.DUAL-BANDDOHERTYPACONCEPT
Thecircuitdiagramoftheproposedconcurrentdual-bandDohertyPAisshowninFig.1.Itconsistsofadual-band3-dBbranch-linecoupler,twosingle-branchdual-bandPAs,twodual-bandoffsetlines,andtwodual-bandquarter-wavelength
transmissionlines.AsimplifiedmodelofthisDohertyPA,asshowninFig.2,isusedtodescribetheoperationmechanism.Contrarytotheconventionalsingle-bandDohertyPA,theconcurrentdual-bandDohertyPAcontainsadual-band
transformer,whichhasfrequency-dependentcharacteristicimpedances.
Asshownin[14],thetransistoroutputsaremodeledascur-rentsourcescontrolledthus,theoutputvoltagesofthecarrieramplifierandtheloadarecalculatedtobe
Intheaboveequation,
arethecharacteristicimpedancesofthe
transformer.Thesecharacteristicimpedancescanbeuniformordistinguishedinthedualbands,inwhichsubscripts1and2relatetothelowerandupperbands,respectively.
Toillustratethepowerbackoffrangeinducedbydifferent
characteristicimpedances,thevalueof
whenthecarrieramplifierreachessaturationisdefinedas
Fig.3.SimulateddrainefficiencyoftheDohertyPAinthebalancedpowerrangemode.
isadesignparameterthatdeterminesthevalueofinrelationto.Consequently,thecurrentinthepeakingamplifiercanbewrittenas
Bysubstituting(2)and(3)into(1)andsolvingforthethatmakesconstant,wecanobtain
Itcanbefoundthatisdistinctifthecharacteristicimped-ancesofthetransformeraredifferentinthetwobands.Fromanotherpointofview,thebackoffpowerrangesoftheDohertyPAindualbandswillbedifferentbydevelopingafre-quency-dependentcharacteristicimpedancetransformer,whichcanprovideuswithmoredesignfreedomandeventuallyim-provetheaverageefficiencyofdifferentsignalstatisticaldistri-butions.
A.BalancedPowerRangeMode
Toverifytheaboveanalysis,conceptualsimulationsarecar-riedout,andthetargetfrequenciesare900and2000MHz.First,
adual-band
transformerwithuniformcharacteristicimped-ancesisusedforpowercombiningintheDohertyPA.Thechar-acteristicimpedancesare50inthebands,meaningthatandarebothequalto2.ThesimulateddrainefficiencyispresentedinFig.3,andascanbeseen,theefficienciesversusbackoffpoweraresimilarinthetwobands.B.ImbalancedPowerRangeMode
Alternatively,thecharacteristicimpedancesofaquarter-wavelengthtransmissionlinearesetas50and100inthelowerandupperbands,respectively,meaningthatandareequalto2and4,respectively,whichcanberegardedasafrequency-dependenttransformer.ThesimulatedefficiencyisgiveninFig.4withthedistinctbackoffpowerrangesthatareachieved.Inthelowerband,thebackoffpowerrangeisalmost
CHENetal.:DESIGNANDLINEARIZATIONOFCONCURRENTDUAL-BANDDOHERTYPA
Fig.4.SimulateddrainefficiencyoftheDohertyPAinanimbalancedpowerrangemode.
constant,whilethePAhasabouta8-dBbackoffpowerrangeintheupperband.
III.DESIGNOFDUAL-BANDCOMPONENTS
AsshowninFig.1,thekeytotherealizationofaconcur-rentdual-bandDohertyPAisthedevelopmentoftherelateddual-bandcomponents,includingactiveandpassivecircuits.Fortunately,therearesomedual-bandcircuittopologiesthatcanbeadopteddirectlyormodifiedaccordinglyforthisspecificap-plication,suchasT-shapedandcoupledlinenetworks.Withthehelpofdual-bandtransmissionlines,thedual-band3-dBbranch-linecoupler,dual-bandoffsetline,and
dual-bandtransformercanberealized.Inparallel,severaldesignmethodsforconcurrentdual-bandPAdesignhavebeenproposed.Briefdescriptionsofthemethodsadoptedtodesignthesedual-bandcomponentsofthedual-bandDohertyPAarereportedbelow.A.
BasicDual-BandTransmissionLine
Oneapproachinrealizingadual-bandtransmissionlineisthedevelopmentofacircuitwithfixedcharacteristicimped-ancesandelectricallengthsofand
atand,respec-tively.AsshowninFig.5,thetypicalstructuresthatmeettheserequirementsincludethecoupledlineandT-shapednetworks.Thefunctionofthesecandidatesisequivtherefore,wecanselecttheappropriatestructuredependingonitsdimensionsandfabricationtolerance.Detaileddesignequa-tionshavebeenrigorouslyderivedin[16]and[21].Moreover,frequency-dependentcharacteristicimpedancescanberealizedbytakingadvantageofthedifferentoddandevenphaseveloci-tiesofatwo-sectionmicrostripimplementedcoupledline.B.Dual-Band3-dBBranch-LineCoupler
Thebranch-linecouplerisusuallyusedtodividepowerequallyandcompensateforphasedelaytosingle-branchPAsintheDohertytopology.Tofulfilldual-bandoperationintheDohertyPA,adual-band3-dBcouplershouldbeimplemented.Asstudiedin[15]–[17],severalpassivedesignmethodscanbeemployedforadual-bandcoupler.Bytakingthefrequencybandwidthandfabricationerrortoleranceintoaccount,theT-shapednetworkisutilizedinthisdesign.AsshowninFig.1,
itcontainspairsofequivalent
transmissionlines.ForFig.5.(a)Conceptofdual-bandtransmissionline,(b)single-sectioncoupledline,(c)two-sectioncoupledline,(d)shortedstubT-shapednetwork,and(e)openstubT-shapednetwork.
Fig.6.Simulatedandmeasuredresultsofthedual-bandbranch-linecoupler.
compactcircuitdimensions,ashort-circuitedstubinsteadofan
open-circuitedstubisusedfortheequivalenttransformerinthisstructure(onecanrefertothedetaileddesignequationsin[16]).
Forverification,thedual-bandbranch-linecouplerwasfab-and,thesimulatedandmeasuredresultsareshowninFig.6.Analmostequalpowerdivisionandthetargetedphasedelayatdesignedfrequencieswereachieved,withthemagni-tudeerrorlowerthan1dB,andthephaseerrorwasnotmorethan2.Theadvantageoftheshorted-circuitedstubisareduc-tioninthewholedimensions.Incontrast,thelengthofthestubwouldbemuchlonger,ifanopen-circuitedstubwasadopted.C.Single-BranchDual-BandPA
SincetheproposedDohertyPAisdesignedfordual-bandop-eration,thePAineachbranchshouldalsoexhibitdual-bandproperties.Thecircuitdesignofthesingle-branchdual-bandPAbasedonasiliconcarbide(SiC)metalsemiconductorfieldeffecttransistor(MESFET)(CREE,CRF24010)isshowninFig.7.Topursueconcurrentdual-bandoperation,theinputandoutputmatchingnetworksshouldprovidetheoptimalimpedanceforeachbandatthesametime.Load–pullsimulationbasedonalarge-signalmodelwasperformedtoobtaintheoptimalloadsin
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