面向毫米波陣列的寬帶線性射頻發(fā)射機(jī) Towards Wideband Linear RF Transmitters for Millimeter-Wave Arrays

TowardsWidebandLinearRFTransmittersforMillimeter-

WaveArrays

YikuanChen

ElectricalEngineeringandComputerSciencesUniversityofCalifornia,Berkeley

TechnicalReportNo.UCB/EECS-2025-53

/Pubs/TechRpts/2025/EECS-2025-53.html

May14,2025

Copyright?2025,bytheauthor(s).

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TowardsWidebandLinearRFTransmittersforMillimeter-WaveArrays

by

YikuanChen

Areportsubmittedinpartialsatisfactionofthe

requirementsforthedegreeof

MasterofScience,planII

in

Engineering-ElectricalEngineeringandComputerSciences

inthe

GraduateDivision

ofthe

UniversityofCalifornia,Berkeley

Committeeincharge:

ProfessorAliM.Niknejad,Chair

ProfessorKristoferPister

Spring2025

ThereportofYikuanChen,titledTowardsWidebandLinearRFTransmittersforMillimeter-WaveArrays,isapproved:

Chair

Date

Date

Date

5/4/2025

5/12/2025

UniversityofCalifornia,Berkeley

TowardsWidebandLinearRFTransmittersforMillimeter-WaveArrays

Copyright2025

by

YikuanChen

1

Abstract

TowardsWidebandLinearRFTransmittersforMillimeter-WaveArrays

by

YikuanChen

MasterofScienceinEngineering-ElectricalEngineeringandComputerSciences

UniversityofCalifornia,Berkeley

ProfessorAliM.Niknejad,Chair

Thisreportfocusesondesigningahigh-linearitytransmitter(TX)formillimeter-wave(mm-Wave)wirelesscommunication.Torealizeacommonmoduletransceiverthatinterfaceswithdiferentfrontendmodulesfordiferentfunctionalities,theTXisrequiredtocoverawidefrequencybandwithhighinstantaneousradio-frequency(RF)bandwidth,lownoise,andhighlinearityatRFandbasebandports.Diferentarchitecturestorealizethesegoalsforamm-WaveTXareinvestigatedanddiscussed.Ahigh-linearityactivemixerisproposedtoachievea?atinputimpedancecurveversusvaryingbasebandinputfromthedigital-to-analogconverter(DAC).Thisdesignwasfabricatedin28nmbulkcomplementarymetal-oxide-semiconductor(CMOS)technology.Next,acompleteTXwith10-bitbasebandDAC,?lter,anddistributedactivemixerwithtransmissionline(T-Line)powercombinerandlocaloscillator(LO)chain,fabricatedinthesameprocess,isdiscussed.Thisdesignoperatesfrom

13GHzto50GHzanddemonstrates2.5dBmcompressionpointandpowerconsumptionof

71mWona1.2Vsupplyinsimulations.

i

Tomyfamily.

ii

Contents

Contentsii

ListofFiguresiii

ListofTablesv

1Introduction1

1.1TraditionalTransmittervs.DistributedRF-DAC 1

2HighLinearityActiveMixer4

2.1High-LinearityMixer 4

2.2PassiveMixer 5

2.3ActiveMixer 6

3High-LinearityDACwithDistributedMixer14

3.1Overview 14

3.2High-LinearityDAC 14

3.3High-SpeedFPGA-to-ChipCDR 18

3.4CurrentMirrorFilter 20

3.5DistributedActiveMixer 22

3.6DualModeWidebandLOChain 24

3.7TransmitterOverview 29

3.8TestSetup 30

3.9Measurement 32

4Conclusion36

Bibliography37

iii

ListofFigures

1.1Proposedwideband“commonmodule”covers28-50GHzRFbandwidthatthe

inputwith200MHzbasebandbandwidthandcaninterfacetomanydiferent

front-endmodulestorealizediferentfunctionality 2

1.2Traditionaltransmitterblockdiagram 2

1.3RF-DACblockdiagram 3

2.1Passivemixerschematic.NotetheoutputcapacitorsrepresenttheESDdiodes.

TheoutputismatchedviaanasymmetricT-coil.TheresistorsbootstraptheIF

signaltothemixergates,toremoveIF-dependentlinearityefects 6

2.2Passivemixerlayout,viewedinCadenceVirtuoso.TheT-coilmatchingisatthe

top,thedriverchokeisbelow 7

2.3Simpli?edmodelforsingle-balancedactivemixer 8

2.4GmcurveshiftingduetoasymmetricdiferentialMOSFETpair,citedfrom[6].8

2.5Linearity-improvedactivemixer 9

2.6Schematicand?oorplanofthelinearity-improvedactivemixer 10

2.7Layoutoflinearity-improvedactivemixer 10

2.8Comparisonofgaincompressionoftraditionalmixerandtheproposedmixer 11

2.9ComparisonofSignal-to-Noise-and-DistortionRatiooftraditionalmixerandthe

proposedmixer 11

2.10FundamentalandIM3outputpowermeasurements 12

2.11Chipphotoforthepassiveandactivemixers 13

3.1Systemblockdiagramofthetransmitter 15

3.2Conventionalcurrent-steeringDAC 15

3.3ConventionalandCascodedcurrent-steeringDAC 16

3.4Folded-Cascodecurrent-steeringDAC 17

3.5Six-bitbinary-weightedinputbranchesareconnectedtothesamefoldedbranch.17

3.6Layoutofthefolded-cascodecurrent-steeringDAC 18

3.7BlockDiagramofClock-DataRecovery(CDR)circuittoalignthebits 19

3.8Clock-DataRecovery(CDR)circuittoalignthebits 19

3.9Currentmirror?lterschematic.Theinputisontheleftside,andtheoutputis

ontheright 20

3.10Currentmirror?lterBodeplot.Notethezerofromthem-derivedsections 21

iv

3.11Layoutofthecurrentmirror?lter 21

3.12SimulationoftheDACwiththe?lter 22

3.13Distributedmixerandoutputmatchingnetwork 23

3.14Double-Balancedactivemixerquad 23

3.15Distributedmixerlayout 24

3.16Distributedmixerlayoutonthechip 25

3.17Simulateddistributedmixergain 26

3.18DistributedmixerwithI/QpullingatOP1dB 26

3.19DistributedmixerwithoutI/QPullingatOP1dB 27

3.20DistributedmixerwithI/QpullingatOP0.5dB 27

3.21DistributedmixerwithoutI/QPullingatOP0.5dB 28

3.22LOchainconcept.Lowandhighfrequencyampli?erpaths,followedbyaswitch

networktoselectthedesiredfrequencyband.TheLOsignalisthenfedintothe

distributedmixer(thetransmissionline) 28

3.23ThelowfrequencyLOchain,priortothe?naldriverstage.Notethattheam-

pli?ersaresimplyinverters.Anarti?cialtransmissionlineLChybridisbasedon

[2],with4-bittunedcapacitors 29

3.24Thefour?ngerLangecoupler.Thedummymetal(blue)?llsthesurrounding

regionstopassthedi”cultdensityDRCrules 29

3.25CompletelayoutoftheLOchains.ThelumpedandLangehybridsareinthe

centerofthechip,withtheI/Qampli?erchainslaidoutsymmetricallyaround

themixer 30

3.26Architectureofthetransmitter 31

3.27Testsetupblockdiagram 32

3.28Probestationsetupofthechip 33

3.29Layoutofthewidebandlineartransmitter 34

3.30DiePhotoofwidebandlineartransmitter 35

v

ListofTables

2.1SimulatedOIP3oftheproposedactivemixer.......

.............

5

2.2SimulatedOIP3oftheproposedactivemixer.......

.............

9

2.3MeasuredP1dBoftheproposedactivemixer........

.............

11

3.1Summaryoftheperformanceofthedistributedmixer..

.............

25

3.2Summaryoftheperformanceoftheoverallsystem....

.............

30

vi

Acknowledgments

Iwouldliketobeginbyexpressingmydeepestgratitudetomyadvisor,ProfessorAliNikne-jad.Hisunwaveringsupportthroughoutmydegreehasbeeninstrumentalinshapingmeintoawell-roundedengineer,andhisprofoundexpertisehasbeenaconstantsourceofin-spirationformyresearch.IamalsoimmenselythankfultoProfessorKristoferPisterforhisinsightfulguidanceandadvice.

Aspecialthanksgoestomycolleague,RohitBraganza,withwhomIcollaboratedcloselyontheMIDASproject,successfullycompletingtwotapeoutstogether.IamalsogratefultoSashankKrishnamurthyandNimaBaniasadifortheirinvaluablesuggestionsandassistancethroughoutthisresearch,aswellastoHeshamBesharyandAliAmerifortheirhelpwithtesting.

IextendmyappreciationtoAveralKandalaforhisthoughtfulfeedback,whichgreatlyimprovedtheclarityandprofessionalismofmywriteup.Additionally,IthankDARPAforfundingthisprojectandacknowledgethemembersofDARPA,Intel,andTexasInstrumentsfortheirconstructivefeedbackduringourdiscussions.

1

Chapter1

Introduction

ThisprojectispartoftheMillimeter-waveDigitalArrays(MIDAS)researchprogramwhichaimedtoadvancethestate-of-the-artdesignofcomplementarymetal-oxide-semiconductor(CMOS)wirelesstransceiverstoaddressemergingapplicationsindigitalbeamforming.5Gcommunicationutilizesarichspectruminmillimeter-wave(mm-Wave)bands.Inparticular,theFR2spectrumextendsfrom26.5GHzto71GHzindiferentcountries/regions.Tosupportthesedisparatebands,diferenttransceiversdesignedforspeci?cfrequencyrangesarerequired.Thisapproachisnotonlycostly,butdemandslotsofvaluableprintedcircuitboard(PCB)area,especiallyonmobiledevices.Hence,itishighlybene?cialtodesignasingletransceiverthatsupportsawideRFfrequencyrange,toallowthesystemtosupportmultipleapplications,suchasMultiple-InMultiple-Out(MIMO)communicationandmm-Waveradar.

Theaimoftheprojectistoprovidea”commonmodule”,realizedinlow-costCMOStechnology,thatcaninterfacewithahighperformanceTX/RXfront-endmoduledesignedforaspeci?cbandorapplication,asshowninFig.1.1.ForTXapplications,the“com-monmodule”shouldbeas?exibleaspossible,accommodatingdiferentPAoutputpower,modulationschemes,andothertransmitterspeci?cations.

Toachievesuchversatility,thetransceiverisrequiredtohavewideoperationalband-width,highinstantaneousRFbandwidth,lownoise?gure,aswellashighlinearityatbothRFandbasebandports.

1.1TraditionalTransmittervs.DistributedRF-DAC

Atraditionaltransmittertypicallyconsistsofthefollowingstages:aDigital-to-AnalogCon-verter(DAC),abasebandFilter,anup-convertingMixer,anRFFilter,andaPowerAm-pli?er,asshowninFig.1.2.Thisapproachbene?tsfromsimpleLOdistributiontotheup-convertingmixer.However,toachievehighlinearityintheoveralltransmitter,eachstagemustbeextremelylinearbyitself.Often,thelinearitydegradesduetosignal-dependentcurrentthroughthemixerand?niteoutputimpedanceintheDAC.

2

CHAPTER1.INTRODUCTION

Figure1.1:Proposedwideband“commonmodule”covers28-50GHzRFbandwidthatthe

inputwith200MHzbasebandbandwidthandcaninterfacetomanydiferentfront-end

modulestorealizediferentfunctionality.

Figure1.2:Traditionaltransmitterblockdiagram.

Incontrast,anRF-DACtransmitterusesadistributeddesign,asshowninFig.1.3,whereeachelementconsistsofaDACandamixerwithlessoutputpowerthanthetraditionalcounterpart.NsuchelementsarethencombinedtogetherattheRFoutput.ThereisnoexplicitPAinthetransmitter,asapowercombiner,suchasthatformedoftransmissionlines(T-lines),sumsupthepowerdeliveredbyeachcellfordeliverytotheoutput.Toobtainhighlinearityattheoutput,considerabledesignoptimizationisrequired.LOdistributiontoeachmixerisneeded,andthematchingbetweeneachelementlimitstheoveralllinearityofthesystem.ThekeyadvantageofthisapproachiseliminatingthePA,whichavoidsthenonlinearityande”ciencytrade-ofsinherentinsingle-stagePAs.Bydistributingpowergenerationacrossmanylow-power,linearelements,theRF-DACachieveshighoutputpower

3

CHAPTER1.INTRODUCTION

withimprovedlinearityande”ciency.

Figure1.3:RF-DACblockdiagram.

Thisprojectexploresthepotentialandlimitsofdi!erentdesignsonthisspectrum.High-linearityglobalmixers(passiveandactive),describedinCh.2,aredesignedandfabricated,alongwithacompleteRF-DACtopologyutilizingdistributedcombining,withabasebandDAC,analog?lters,anddistributedup-conversionmixerstodrivedi!erentpointsonatransmissionlinetocombineIandQsignalswhileboostingtheoutputpowercompressionpoint.TheRF-DACprototypeisdescribedinCh.3.Thetransmitterwasjointlydesignedandfabricatedbytheauthor(high-linearityDAC,high-speeddigitallinkwithclock-data-recoverycircuit),RohitBraganza(baseband?lter,LOchains)andSashankKrishnamurthy(distributedmixer).

4

Chapter2

HighLinearityActiveMixer

2.1High-LinearityMixer

Inatransmitter,anidealmixertranslatesthebasebandsignaltoahigherfrequencywithoutdistortingtheinformationcontainedinthesignal.Amixeritselfisanon-linearsystemwithrespecttobothitsbaseband(orintermediatefrequency,IF)inputandthelocaloscillator(LO)inputbecausenewfrequencycontentiscreatedattheoutputport.However,agoodmixershouldstillbehave”linear”inthesensethatitsRFoutputamplitudeshouldbeproportionaltotheIFinputamplitude.Inotherwords,theconversiongain,whichisde?nedforatransmittermixerastheratioofthedesiredRFoutputsignalamplitudetotheIFinputsignalamplitude,shouldbeconstantandindependentoftheinputsignalvalue.Inrealmixers,therearelimitsbeyondwhichtheRFoutputhasasub-lineardependenceontheIFinput[9].Theoutputcompressionpointforatransmittermixeristhepoweroftheoutputsignalatwhichtheconversiongaindecreasesfromtheidealconstantgainvalue.Usuallya1-dBcompressionvalue(knownasOP1dB)isspeci?ed.Theoutputtwo-tonethird-orderinterceptpoint(OIP3)isalsooftenusedtocharacterizethelinearityoftransmittermixers.Itisanextrapolatedvalueoftheoutputpoweratwhichthethird-orderintermodulationcomponentswouldbeequaltothatofthedesiredRFoutputsignal(calledthefundamental).

Oneofthekeyspeci?cationsofagoodtransmittermixerisitslinearity.ThehighertheP1dBorOIP3is,thebetterthelinearity.Therearemanywaystoimprovethelinearityofthemixer:[4]usesdynamiccurrentinjectiononadouble-balancedactivecurrentmixerinareceiverforsub-6GHz.[1]introducedfully-diferentialDarlingtoncellsintheRFtransconductancestagetoreducethethird-ordernon-linearity.[7]improvedthelinearityofanup-convertingmixerusingtheImprovedDerivativeSuper-Position(I-DS)techniquecascadedbetweenthemixer’stransconductanceandswitchingstage.Thistechniqueen-hancesmixerlinearitybycancelingthird-orderdistortion(IM3)usingopposingnonlinearcurrentsfromcarefullybiasedtransconductancedevices.Thismaintainsgainande”ciencybutrequiresprecisedevicematchingandbiasing,makingitsensitivetoprocessvariations

5

CHAPTER2.HIGHLINEARITYACTIVEMIXER

andtemperaturechanges.Imperfectionscandegradeperformance,complicatingdesignandmanufacturing.Mostoftheaforementionedmethodscomewithincreasedcurrentconsump-tion.Infact,improvingtheP1dBby1dBusuallyrequiressigni?cantlyincreasedcurrentconsumptionanddegraded?ickernoiseperformance.

Themethodproposedhererelieson?atteningthelargesignaltransconductanceGmofthe”switching”stage(thedevicesalwaysworkinsaturationregion,sotechnicallytheyarenotswitchingdevices,buttheterm”switching”isusedheretoindicatethatitisthestagethathascommon-sourceLOandcommon-gateIFinput)acrossVGSduetothechangingIFcurrent.Thesimulationshowsthattheresultingmixerwithextracteddeviceshasbettersignal-to-distortion-ratio(SNDR)thanaconventionaldoublebalancedactivemixer,withatrade-ofinsignal-to-noiseratioatlowIFinputamplitude.

ThemixerchipdiscussedinthissectionwasdesignedandsubmittedforfabricationinaTSMC28nmBulkCMOSprocessinOctober2019.Themixersareassumedtobeusedinatraditionaltransmitterarchitectureastheglobalmixer,sothekeydesigngoalwastoachievehighlinearitywithasinglemixer.Twomixerdesignswereinvestigated:apassivemixer,designedbyRohitBraganza,andanactivemixer,bothofwhichwereaimedtoachievehighlinearitybyreducingthesignal-dependentquantitiesinthecircuit.Theprincipleoftheproposedactivemixerwillbediscussedindetail.

2.2PassiveMixer

TheschematicofthedesignedpassivemixerisshowninFig.2.1.Itconsistsofthestandarddouble-balancedmixertopology,withtheadditionofbootstrappingresistorsfromtheIFinputtothegateofthemixertransistorstofurtherimprovethelinearity.Theseresistorscausethegatetotrackthe(lowfrequency)IFport,keepingthetransistors’VgsindependentoftheIFsignal,whichreducesintermodulation(IM)productsduetotheIFsignal[8].

Themixerisdrivenbyasimplecommonsourceampli?erwithachokeinductorload.Tokeepthestructurebroadband,asymmetricT-coilswereusedasoutputmatchingnetworkstotheprobepadsandtheirESDdiodes.TheoveralllayoutisshowninFig.2.2.ThemeasuredresultsaregiveninFig.2.1,andwerewithin1-2dBofsimulation;themixershowedareasonableOIP3foralowpowerconsumption(8.4mWat24GHz,15.6mWat40GHz),andwascapableofoperatingacrossawidebandwidth.

Frequency(GHz)MeasuredP1dB(dBm)MeasuredOIP3(dBm)SimulatedOIP3(dBm)

24

-4.3

4.16

5.25

32

-9.1

1.89

3.1

40

-8.9

0.41

1.5

Table2.1:SimulatedOIP3oftheproposedactivemixer.

6

CHAPTER2.HIGHLINEARITYACTIVEMIXER

Figure2.1:Passivemixerschematic.NotetheoutputcapacitorsrepresenttheESDdiodes.

TheoutputismatchedviaanasymmetricT-coil.TheresistorsbootstraptheIFsignalto

themixergates,toremoveIF-dependentlinearityefects.

2.3ActiveMixer

Anactivemixerisnamedsobecauseitprovidespowergainwithactivedevices.Fig.2.3showsthecurrent?owinasingle-balancedactivemixer.Foranalysispurposes,wesimplifytheIFinputtobeacurrentsourcewithsome?niteoutputconductance,G0.Thediferentialpairforthecommon-source(CS)LOinputisbiasedinsaturationmodeatalltimesandthereissomeconstantDCbleedingcurrentsunkbythetaildevice.Atanygivenmoment,thefollowingequationsdescribetherelationshipbetweenthecurrentindiferentbranches:

i1+i2=iin+GoVs

i1≈f(VG0+,Vs)(2.1)

i2≈f(VG0-,Vs)

Ifwewritei1intermsoftheDCtermandthederivativeofi1withrespecttoVGandVS

7

CHAPTER2.HIGHLINEARITYACTIVEMIXER

Figure2.2:Passivemixerlayout,viewedinCadenceVirtuoso.TheT-coilmatchingisat

thetop,thedriverchokeisbelow.

timesthediferentialquantities,wewillget:

The?rsttermistheDCcurrentwithnosignal.ThesecondistheLOfeedthroughtermwhichwillgetcancelledinthedouble-balanceddiferentialoutput.Thethirdterm,whichisalittlebitmorecomplicatedifwetakethefullderivative,isanon-linearandtime-varyingterm(astheIFsignalchanges),whichgeneratesdistortionandmixing.Thefourthtermisalsonon-linearandtime-varying,anditalsochangesastheIFsignalchanges.ThissimpleTaylorSeriesexpansionshowsthattheoutputcurrentdepends,inanon-linearway,onboththesource(input)voltageandgate(LO)voltage.TheLOcontrolsthegatesinatimeperiodicway,andthesourcevariesduetotheDACandthesecondharmonicoftheLO.Atanygivenmoment,thevalueofvS,and,consequently,thecurrentthat?owsintothediferentialpairversusthecurrentthat?owsintotheloadGodependsontheratiobetweenGo(t)andGm(t).EvenwithanidealDACwithoutputimpedanceindependentofthesignal,thedesignwouldstillsuferfromnon-linearitybecauseGm(t)variesinmagnitudeduetothesourcevoltagevarying.Therefore,?atteningtheGmwithrespecttothevaryingsourcevoltage,wouldallowthetotalproportionalcurrent?owingintothediferentialpaircomparedtowhatthecurrentsourcegeneratestobemoreconstant.AstheGmis?attened,theinputimpedanceseenbytheDACstaysconstantacrossinputpower,andtheoutputamplitudeofthemixerwillbelinearizedasthebasebandDACcurrentchanges.

8

CHAPTER2.HIGHLINEARITYACTIVEMIXER

Inadiferentialampli?erwithtailcurrentISS,ifthetwoinputMOSFETsarediferentinsize,thelargesignaltransconductanceGmvs.VGScurvewillshifttotheleftortotheright,asshowninFig.2.4[6].Ifthedrainsofthetwooppositecopiesofsuchanampli?erarecombined,theoverallGmcurvecouldbe?attened,andthisisexactlywhatisneeded.

ThearchitectureoftheproposedactivemixerisshowninFig.2.5.Itisamodi?edcurrent-commutatingmixer(Gilbert-typemixer).Insteadofonecurrent-steeringDAC(+and–outputs),weusetwo,buteachonlyburnshalfofthecurrent.Thetopologyisadaptedfromtheampli?erbyconnectingthedrainsofthetwoGm-linearizedampli?erstogether.BypurposelyintroducingasymmetrybetweentheLO+andLO-transistors,wecanreducethenon-linearmixingtermattheoutput.

Figure2.3:Simpli?edmodelforsingle-balancedactivemixer.

Figure2.4:GmcurveshiftingduetoasymmetricdiferentialMOSFETpair,citedfrom[6]

Fortestingpurposes,wereplacedeachofthetwoDACswithacommon-gateinputstagetoallowenoughheadroomforswingattheoutput.TheIFinputisAC-coupledtothesources

9

CHAPTER2.HIGHLINEARITYACTIVEMIXER

Figure2.5:Linearity-improvedactivemixer.

ofthesecommon-gatetransistorswithDCsettogroundthroughbaluns.Theschematicandlayout?oorplanisshowninFig.2.6andFig.2.7.TheDCcurrentconsumptionofthemixeris13.5mAunder1.2Vsupply,butthiscurrentwillbesharedwiththeDAC.Wesimulateditsperformanceatrelativelyhighoutputpower(non-linearitydominatingthesignal-to-interference-and-distortionratio(SINAD))incomparisontoatraditionaldouble-balancedmixeratthesameoutputpowerandtotalDCcurrentconsumption,andtheresultisshowninFig.2.8andFig.2.9.NotethatbecausemoreactiveMOSFETsareusedinthisdesign,theSINADwillbelowerthanthatofatraditionaldouble-balancedmixerwhenthesignalpowerisverylow(suchthatthenoisepowerdominatestheSINAD).TheOIP3simulatedat25.6GHzwith200MHzbandwidthIFinputusingextractedtransistorsandideal50Ωsource/loadimpedanceis10.96dBm,anditis10.38dBmat50GHz,asshowninTable2.2.Theoutput50OhmloadsaredirectlyconnectedtotheVDD.

Frequency

25.6GHz

50GHz

OIP3

10.96dBm

10.38dBm

Table2.2:SimulatedOIP3oftheproposedactivemixer.

ThemixerchipwasfabricatedinTSMC28nmbulkCMOStechnology.Thechipphotoisshownin2.11.Theoutputpowerat24,28,32,and36GHzwith200MHzIFbandwidthwasmeasuredandshowninFig.2.10.Theconversiongainsarelessthanunityduetothelossoftheprobes,cables,andmatchingnetworks.FortheOIP3test,oneIFtoneat150MHzandoneat200MHzarepower-combinedbeforeconnectingtothepowerdividerfortheIFinput.NotethattheOIP3extrapolatedatdiferentpointsvaries,astheslopeofthethird-orderharmonics(indBscale)isnotconstant,asopposedtothecommonlyseen3dB/dB

10

CHAPTER2.HIGHLINEARITYACTIVEMIXER

Figure2.6:Schematicand?oorplanofthelinearity-improvedactivemixer.

Figure2.7:Layoutoflinearity-improvedactivemixer.

slope,andhencetheintersectionsofthetrend-linesdoesnotrepresenttheIP3points.Thisislikelycausedbyhigher-ordernonlineartermsthatfallattheIM3frequencies,causingtheamplitudetochange.Table2.3showstheP1dBmeasuredatdiferentfrequencies.ThemeasuredOIP3valuesarelowerthanthesimulatedOIP3values(loadedwitha50Ohmloaddirectly)ateachfrequencyduetotheoutputmatchingontheactualfabricatedchip.

11

CHAPTER2.HIGHLINEARITYACTIVEMIXER

Figure2.8:Comparisonofgaincompressionoftraditionalmixerandtheproposedmixer.

Figure2.9:ComparisonofSignal-to-Noise-and-DistortionRatiooftraditionalmixerandthe

proposedmixer.

Frequency

24GHz

28GHz

32GHz

36GHz

P1dB

-4.71dBm

-9.29dBm

-7.74dBm

-8.82dBm

OIP3(extrapolated)

4.89dBm

0.31dBm

1.86dBm

0.78dBm

Table2.3:MeasuredP1dBoftheproposedactivemixer.

12

CHAPTER2.HIGHLINEARITYACTIVEMIXER

Figure2.10:FundamentalandIM3outputpowermeasurements.

13

CHAPTER2.HIGHLINEARITYACTIVEMIXER

Figure2.11:Chipphotoforthepassiveandactivemixers.

14

Chapter3

High-LinearityDACwithDistributedMixer

3.1Overview

AsdiscussedinCh.1,thetraditionaltransmitterarchitecturewithglobalDAC,mixer,andPAandthedistributedRF-DACarchitecturewithNDAC-mixerelementsareonoppositeendsofthedesignspectrum.Thereis,however,stillalargedesignspacebetweenthetwoextremes.OnepossiblechoiceistoeliminatetheexplicitPAasprescribedbytheRF-DACarchitecture,butinsteadofusingthe