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ADS Fundamentals – 2009

LAB 7: Harmonic Balance Simulations

Overview‐Thisexercisecontinuestheamp_1900designandshowsthefundamentalsofusingtheHarmonicBalancesimulatortolookatthespectrum,analyzecompression,calculateTOI,andperformothernon‐linearmeasurements.

OBJECTIVES • Setupandperforma1toneHBsimulation.

• Setupandperforma2toneHBsimulation.

• Usevariablesforsimulationandsourcecontrol.

• TestGain,Compression,AvailablePower,NoiseFigure,IP3,andotherspecifications.

• UsethetstransformonHBdata.

• Workwithequations,plots,andtheMixtable.

©CopyrightAgilentTechnologies2009

Lab 7: Harmonic Balance

7‐2©CopyrightAgilentTechnologies2009

TABLE OF CONTENTS

1. Set up the circuit with a P_1Tone source.............................................................3

2. Set up a one-tone Harmonic Balance simulation. ................................................4

3. Write a measurement equation for dBm of Vout and simulate.............................4

4. Plot the spectrum, equation, and ts of the node voltages. ...................................5

5. Operate on Vout and Mix using functions and indexing.......................................6

6. Calculate Delivered Power and Zin using Pin Current .........................................7

7. Test for Gain Compression using the XDB simulator...........................................9

8. Simulate compression with a power sweep. ......................................................10

9. Plot various gain, power, and line equations......................................................11

10. Two-tone HB simulation with variables. ..........................................................12

11. Use equations to access and control HB data. ...............................................13

12. Simulate IP3 or TOI (Third Order Intercept)....................................................13

13. OPTIONAL - Sweep RF power against the TOI measurement ......................16



PROCEDURE

1. SetupthecircuitwithaP_1Tonesource.

a. Closethesystem_prjifitisstillopened.Thenopentheamp_1900projectandschematic:s_final.

b. Savethes_finalschematicwithanewname:hb_basic.ThendeleteallthesimulationandmeasurementcomponentsandtheinputTerm.Beginbuildingthesetupshownhere.

c. InsertaP_1Tone(Sources‐FreqDomainpalette)fortheRFinput.

d. Insert4pinlabels(nodenames)Vin,Vout.VCandVBasshownsothatthevoltageswillbeavailableinthedataset.

e. SettheRFsourceasshown:Freq=1900MH.Also,removeremovethepolarfunctionsothatonlythedbm‐to‐wattswattsfunctionremains:P=dbmtow(40).Also,renamerenamethesourceRF_source.TheportnumberisdefineddefinedbyNum=1.

VC

P_1TonesourceisusedwithHarmonicBalance.Notethedefaultpowersettingisinpolarform.



2. SetupaonetoneHarmonicBalancesimulation.

a. GototheSimulation_HBpaletteandinsertaHarmonicBalancesimulationcontrollerasshownhere.

b. EdittheFreqsettingonthescreen:changeittoFreq[1]=1900MHzsothatitmatchestheFreqsettingintheP_1Tonesource.

3. WriteameasurementequationfordBmofVoutandsimulate.

a. Fromthesimulationpalette,insertameasurementequation.

b. WriteanequationtocalculatetheoutputpoweratVoutindBm:dbm_outdbm_out=dBm(Vout[1]).Thenumberinbraces[1]referstotheindexvalueofthecalculatedfrequenciesintheanalysis.WithOrder=3,theindexvaluesare:index[0]istheDCcomponent,index[1]is1900MHz,index[2]isthesecondharmonicor3800MHz,andindex[3]isthethirdharmonic.Therefore,theequationshouldproducetheoutputpowerindBmfor1900MHzonly.

c. Simulate–youshouldhavenowarningsorerrormessages.

d. ChangetheHBcontrollerto:Freq[1]=1800MHz.Now,simulateagainandreadtheerrormessage‐thesourceis100MHzawayfromtheHBfrequencyof1800MHz.Thisisacommonerrorwhenthesourceandcontrollerdonotagree.

Freq[1]mustbesettomatchthesourcefrequency.

Orderisthenumberofharmonics.



e. ResettheHBcontrollerFreq[1]=1900MHzandsimulateagain.

4. Plotthespectrum,equation,andtsofthenodevoltages.

a. Inthedatadisplay,plotdBmofVout.Also,insertalistofdbm_out.Wheneveryouwriteameasurementequation,itwillappearinthedataset.Thetwovaluesshouldbethesameasshownhere.

b. Putamarkeronthefundamentalandverifythatyouramplifierhasabout35dBofGainwithoutputpowerindBm=‐4.876at1900MHz.

NOTEonresults:WithOrdersetto3inthesimulationcontroller,youget3tones:fundamentalplustwoharmonics.TheDCcomponentalsoshowsupontheplotbecauseHarmonicBalancealwayscomputesDCforconvergence.

c. Insertastackedrectangularplotandinserttwodatatracesastimedomainsignals:VinandVout.Thets(timeseries)functionoperatesonHBandtransformsitintothetimedomain.Inthiscase,youcanseethattheamplifierdoesnotinvertthesignalasyoumightexpect.Thesewillbetwoseparateplotsinoneframe.Putmarkersonthesametimepointasshown.

d. EdittheY‐axislabelonthetracebychangingVouttoVCandchangingVintoVBasshownhere.Nowyoucanseetheinversion.Thismeansthatthematchingnetworkprobablyhasagreateffectonthephase.

Changethesearguments.



5. OperateonVoutandMixusingfunctionsandindexing.

a. InsertalistofMixandVoutasshownhere.WheneveraHBsimulationisperformed,aMixtable(indexvalues)iscreatedinthedataset.NoticethatVoutisalwayscomplex(magandangle),unlessyouoperateonitusingdB,dBm,etc.Inthenextsteps,youwilllearnhowtowriteequationstodisplayoroperateonspecifictonesintheMixtable.Thisisespeciallyusefulformultipletonesormixers.

b. EditthefirstlistandaddVin.ThenselectTraceOptionsandandeditVinbytypinginthedBmfunction:dBm(Vin)andclickandclickOK.NoticethatwheneveryoueditatraceorinsertaninsertanequationthebuttonsappearforVariableInfo(dependencies)orFunctionHelp(manuals).

c. Yourlistshouldnowcontaintheschematicequationdbm_outandtheexpressiondBm(Vin)forallfrequencies.frequencies.Now,editthedBm(Vin)databyinsertingtheinsertingtheindexvalue[1]intheVinargumentasshown–shown–nowyougetthevalueofVinattheindexvalueorvalueor1900MHz.

d. Insertthe[1]inthedbm_outequation‐itbecomesinvalidbecauseitwasindexedas{1}ontheschematic.

e. Remove[1]fromtheinvaliddbm_outequationtomakeitvalidagain.

Adding[1]totheVindatareturnsthe2ndindexvalue=1900MHz.

Adding[1]tothemeasurementequationmakesitinvalid.

Indexvalueof1900MHz=1.TheDCindex=0..HB.



InsertZin:50asthe2ndargumentseparatedbyacomma.

f. InsertthecursorinthedBm(Vin[1])expressionandaddacommaand50asshownhere.ThesecondargumentinthedBmfunctionisZin.Ifnoargumentisgiven,thedefaultis50ohms.Therefore,nochangeshouldoccur.Undothecommafifty(,50)sothatitreadsdBm(Vin[1]again.

NOTEondBmfunctionandZinofyourdesigns‐ThedBmfunctionconvertsavoltageintodBmassuminganexact50ohmimpedance.However,ifZinisnotexactly50ohms+/‐j0,thenthepoweratVinmaybeincorrect.Therefore,youmaywanttousethecorrectvalueofZinasyouwillseeinthenextstep.

6. CalculateDeliveredPowerandZinusingPinCurrent

a. EdittheHarmonicBalancecontrollerandselecttheselecttheOutputtabandchecktheboxforPinPinCurrents(shownhere)andclickOK.ThiswillThiswilladdallthevaluesofcurrenttothedatasetdataset–youwillbeusingtheinputpincurrentinsteadofacurrentprobe.

b. Simulateagain.Whenfinished,gotothesameDataDisplayandwriteanequationfortheinputcurrentwhichusesthetotalcurrentthroughtheinputinductor.Todothis,usetheeditor:writeI_in=andtheninserttheinductorcurrentasshownhere:

Thenaddthebracketed[1]sothatit’sthecurrentat1900MHz.Theresultequationshouldbeasshownhere–youwillusethistocalculateimpedanceandpower.



c. WriteanotherequationtocalculateZinusingVinVinandI_inat1900MHzasshownhere.TheninsertinsertalistoftheZ_inequation.Noticethecomplexcompleximpedanceisnot50ohms!

d. WriteanequationtocalculateaveragedeliveredpowerusingthenodevoltageVinandtheinputcurrentequationI_in:

Notethat0.5givestheaverageofthepeakvalue,theconjfunctionconvertsthecomplexcurrenttoitsconjugatebecauseV&Imustbeinphasetodissipatepowerand+30convertsthevaluetodBm(sameasdividingby0.001).

e. EdityourearlierlistofdBm(Vin[1])anddeletedbm_outandaddtheequationP_del_dBm.Also,addanotherVintraceandeditthetraceexpressiontoread:dBm(Vin[1],Z_in).Nowyouhavethreewaysofcomputinginputpowertocompare.Noticethattwoofthevaluesarethesame:

NOTEonpincurrentsvscurrentprobes:Youcouldhaveusedacurrentprobeattheinputinsteadofthepincurrentthroughtheinductor.EitherwayisOK.However,thepincurrentscanmakethedatasetslargeifthecircuitisalsolarge.

dBmusingdefaultsdBmusingVandIdBmusingZ_ineqn



7. TestforGainCompressionusingtheXDBsimulator.

TheXDBsimulationcontrollerisaspecialuseHarmonicBalancesimulationforgaincompression.

a. Saveallyoucurrentwork:schematicanddatadisplay.Thensavetheschematicwithanewname:hb_compression.Afterward,closethehb_basicdatadisplay.

b. Inthenewschematic,deactivatetheHB1controller.

c. GototheSimulationXDBpaletteandinserttheXDBcontroller.EditthecontrolleronscreensothatFreq[1]andGCinputandoutputfrequenciesareall1.9GHzasshown.TheparameterGC_XdB=1meansthatthetestwillbefor1dBcompression.Later,ifyouwanted3or6dBcompression,simplychangethevalue.

d. IntheSimulationSetup,changetheDatasetnametohb_xdbandthenSimulate.

e. Whenthedatadisplayopens,insertalistofofinpwrandoutpwr.Theneditdirectlyontheonthelistbyinsertingabracketedone[1]after[1]aftereachdataitemasshownhere.IfIfdesired,titletheplotasshown.Youjustjustperformeda1dBgaincompressiontestintestinonlyafewseconds!Becausethisamplifierisbiasedquitehigh,the1dBcompressionpointoccurswhentheinputinputpowerisabout–30dBmasshownhere.here.Inthenextsteps,youwillmodifythetheschematicandsetupapowersweepwithwithharmonicbalance–anotherwaytotesttestcompression!

1.9 GHz



8. Simulatecompressionwithapowersweep.

a. DeactivatetheXDBandactivatetheHBcontroller.

b. InsertavariableequationVARforRF_pwr=40.

c. SettheRFsourcepowertothevariable:P=dbmtow(RF_pwr).

d. EdittheHBcontroller.Inthesweeptab,settheRF_pwrsweepasshownfrom–50to–20,step1.

e. GototheDisplaytabandsettheSweepVaranditsvaluestobedisplayedontheHBcontrollercomponentasshownhere.

f. Changethedatasetnameto:hb_compandsimulate.Whenthedatadisplaywindowopens,answerNotochangingthedataset‐thiswillkeeptheXDBdatavalidasthedefaultdataset.Now,youwillhavetoexplicitlyplotthehb_compdata–thisiscommonpractice.

g. Insertaplotandselectthehb_compdataset.Thenplottheschematicmeasurementequationdbm_out.InsertamarkeronthetracewherethevalueofRF_pwrisneartheXDBinpwrvalue:‐31.Asyoucansee,thetwovaluesareclosebuttheydifferbecausethesweepresolutionsresolutionsaredifferent–theXDBsimulation(differentDDSDDSanddataset)usedmanycloselyspacedsweepvalues.

1dBcompressionpointfromXDB


7‐11


values.

9. Plotvariousgain,power,andlineequations.

a. Writeanequation,dB_gainthatusesthedbm_outmeasurementequation.BysubtractingthelinearinputRF_pwrfromdbm_out,theresultisthegainatallvaluesofRFinputpower:

b. Edittheplotofdbm_outandaddthedB_gainequation‐theYaxisscalewillautomaticallyadjust.YoucanaddmarkerstoseebothvaluesatoneRFpowerlevelasshown.

c. ToplotdB_gainagainstoutputpower,insertanewplot,addthedB_gainequationandthenclickAddVs.Next,selectthehb_compdatasetandtheindependentvariablefortheXaxis:dbm_out.ClickOKandthesharpfallofgainwillbeplottedasshown.Usemarkerstoreadthevalues.

d. Writeonemoreequation,line,tocreatealinearline(extrapolateddata)

thatrepresentstheidealoutputpowerwithnocompression.Byaddingtheuncompressedgainatthefirstdatapoint[0]totheRFpowerateverypoint,yougettheidealgainorline.

e. Insertanewplotofdbm_out(usinghb_compdata)andaddlinealso.Thisvisuallyshowstheamplifier’sdeviationfromlinearoutputpower.

f. Saveallyourwork.



10. TwotoneHBsimulationwithvariables.

Thenextfewstepsshowmoreuseofvariablesinsimulationcontrol.Thisisimportantformorecomplexcircuitrefinement,calculationsintheremaininglabs,andworkingwithADSexampleswhichusethismethodofsimulationcontrol.

a. Savethelastschematicdesignwithanewname:hb_2Tone.

b. EdittheVARandaddvariablesforRF_freqandspacingasshownhere.Vbiasisnotrequired‐youmayormaynothaveVbiasifyoudidanoptionalstepearlier.

NOTEonunitsinVARs–Ifyousetunitsheredonotsetthemanywhereelseortheymaymultiplyinthesimulation.

c. ChangethesourcetoaP_nTone.Editthesourcesothatithastwotones:Freq[1]and[2]withRF_pwrforeachasshownhere.

d. EdittheHarmonicBalancecontrollerasshownherebyaddinganotherfrequency,Freq[2],andthevaluesasshown,usingthespacingvariable/2.Also,setOrder=4forbothandsetMaxOrder=8.Inthiscase,thetwoRFtonesarespaced5MHzapart(channelspacing).

e. RemovetheRF_pwrsweepfromthecontrollerbyerasingiton‐screenorinthedialoganddisplay.Also,removeanyothercontrollersorunwantedcomponentsandsavethedesignagain.

MaxOrder=numberofmixingproducts.

Freq[1]isavariableoranumber.Order[1]=4meansFreq[1]willbecalculatedwith4harmonics.


7‐13


f. SimulateandplotthespectrumofVoutindBm.Putamarkeronatonenear1900MHz.Noticethatyoucannotclearlyseetheadjacenttones.Toseetheinter‐modulationtones,youcaneitherzoominontheplotortrychangingtheXaxisscaling.Trybothofthesemethodsquicklybecausethenextstepshowsatechniqueusingequations.

11. UseequationstoaccessandcontrolHBdata.

a. Createamatrixwithvectors(indexvalues)tothedesiredtones.Todothis,writethetonesequationshownhere.Thisequationcreatesamatrixusingthesquarebrackets.Withinthebracketsarecurlybraceswithindexvaluesforthemixtable.Inthiscase,thenumber1representstheRFtonewithspacing.Zeromeansthatnoothertoneisdesired(sameasDC),and2representstwotimestheRFsimulationtone.

b. InsertarectangularplotofVout–spectrumindBm.ThenuseTrace

OptionstoedittheTraceExpressionasshownhere,usingparenthesis–typein:dBm(mix(Vout,tones)).Also,settheTraceTraceTypetoSpectral.

c. Theplotshouldnowshowonlythefourtonestonesyouspecified(10MHzapart).Toverifyverifythis,insertalistofMix(Mixtable).TheTheindexvaluesfromtheMixtablearethetonesthetonesthatyouspecifiedwiththetonesequation.ThisishowHarmonicBalancedatacanbeaccessedandcontrolledusingequations.

12. SimulateIP3orTOI(ThirdOrderIntercept)

Usecurlybraceswithinbrackets.



a. Onthehb_2Toneschematic,inserttwoHarmonicBalanceIP3outmeasurementequations:onefortheupperandoneforthelowerspacedtone.Manymeasurementsrequiretwo‐tonessonametheinstancesupperandlowerasshownhere.

b. Notethedefaultnodelabel(vout),vectors{1,0},andimpedance50.Tomatchthesevaluestoyourcircuit,changevouttoVout(uppercaseV).ThensettheindexvaluestocorrespondtoyourMixtableshownherefromthelastsimulation(onlylower_toineedstochange).

c. ChecktheequationstobesuretheyarecorrectandthenSimulate.

d. IntheDataDisplay,listthetwomeasurementequationvaluesasshownhere.RemovetheindependentvariableusingPlotOptions.HeretheamplifierTOIvaluesappearreasonableandalmostsymmetrical.

e. AsanexerciseincontrollingdatawithADSfunctions,writeanequationintheDataDisplayforthesamemeasurementasshownhere.Thenlistit(my_toi)asshownhere.Yougetthesameresultsbecauseyouusethesamefunction:ip3_out.Theonlydifferenceisthatthisisafterthesimulation.Also,thisequationisusedintheoptionalstepattheendofthislab.

2‐toneMixHBdata


7‐15


f. PlotthespectrumofVoutindBmandthenzoominontheplottoseethetwotonesyoujustsimulated.Putmarkersontheupperfundamentalandthe3rdordertone–theseshouldmatchthefrequencyvaluesintheMixtable.

NOTE–Youcouldeasilygobacktotheschematic,changethespacingVARvalueandsimulateagain.Alltheequations,plotsandtableswouldsimplyfillupwiththenewdata.Thisisthevalueofusingvariablesforsimulationanddatadisplays.

g. Savetheschematicanddatadisplay.

NOTEforMixermeasurements–Ifyoudesignmixers,theLOshouldbeFreq[1]inthesimulationcontrollerbecauseithasthemostpower.Also,inmeasurementequations,youwillhavetotreat2‐tonedataasifitwere3‐tone:LO,RF1andRF2forupperandlowertones.Forexample,theupperIP3equationsforadown‐converterwouldhavethefollowingindexvalues:{‐1,1,0},{‐1,2,1}where–1inthefirstrepresentstheLOtone.

Mixingproducts:MaxOrder



13. OPTIONALSweepRFpoweragainsttheTOImeasurement

ThisstepshowstheeffectsonTOIwhentheinputpowerbeginstodrivethedevicetowardcompression.Ingeneral,manymeasurementscanberefinedtogetabettermeasureofcircuitperformance,beyondtherequiredspecifications.Todothis,youmusthaveapowerfulnon‐linearsimulatoranddatadisplaytoolsuchasADS.

a. Usingthesamehb_2Tonedesign,setuptheHBsimulationcontrollertosweeptheRFpowerasshownherefrom–45to–30dBm.Youalreadytested1dBcompression(about–31dBmRFinputpower)andyoujustfinishedmeasuringTOIwhich(about15dBm).

b. Simulateandwatchthechangesinthedatadisplay.

c. Editthemy_toilisttoincludetheindependentdata(RF_pwr).Thenincreasethelistsizesothatallthevaluesappear.Asyoucansee,TOIbeginstochangegreatlyasRF_pwrmoveshigher.However,thechangeisnotlinear.Thenextstepwillshowthiswithmorerefinement.

d. Changethelistofmy_toitoarectangularplot(PlotOptions‐clicktheplottypeicon).Then,onthesameplot,insertVoutindBmandeditthetraceexpressiontoreturntheupperRFtoneasshownhere.NowyoucanseehowtheTOImeasurementtrackswiththattone:

dBm(mix(Vout,{1,0}))

NOTEonVoutdata–YoumustusethemixfunctionbecauseVoutcontains41totalfrequencytones:2spacedfundamentalswith4harmonics(thismeans8tones),with8max_order(thismeans32moreintermodtones),plusthedccomponent.These41tonesarepresentateachofthe16valuesofRFpower.

2traces:my_toianddBmofupperRFtone.


7‐17


e. AddonemoreVouttracetotheplot.Again,editthetrace(TraceExpression)sothatisbecomestheupper3rdorderproduct:

dBm(mix(Vout,{2,1}))

f. Yourplotshouldnowlookliketheoneshownhere.ItshouldcontaintheupperRF_freq,theupper3rdorderproduct,andtheequationmy_toi(uppertoi).Now,editthemy_toitraceandselectPlotAxesasshownhere.ThenselectRightYaxisforthistraceandwatchthechange.

g. YourplotshouldnowhavetheTOIvaluefromyourequationontheRightYaxisandthetwotonesusedtocalculateTOIontheleft.Now,usePlotOptions,selectYAxis,andremovetheAutoScale(uncheckthebox).ThenincreasetheMaxto10andclickOK.Finally,placeamarkeronthepointwheretheslopeofthetwotonesisnolonger3:1.Asyoucansee,IP3wascalculatedinthecorrectregion.However,afterthemarker,the3rdorderproductbeginstoriseatasharperrate.ThisisagoodexampleofusingADStolearnmoreabouttheperformanceofyourdesign,beyondthespecification.

Clickhere:

MakeyourplotlooksimilarusingtheDataDisplaytextanddrawingfeatures.



EXTRA EXERCISES:

1. SweptRFfrequency‐CopytheschematicandthenchangethesweptvariablefromRFpowertoonetoneRFfreq.Todothis,setuptheVARforRF_freqinboththecontrollerandthesource.SweepRF_freqfrom100MHzto3GHzin100MHzsteps.Besuretochangethedatasetname,thensimulateandplottheoutputpowerequationagainstthesweptfrequencyasshown.Also,notethatthedatasetwillcontainalistoftheharmonicindexasshown.

2. Trywritinganequationtopassallthe5thorderproductstoaspectralplot.

3. Usethepspecfunctiontocalculatepowergaintotheload.Todothis,firstlookattheHelpforpspec.TheninsertacurrentprobeattheVoutnode.