lab 5: s-parameter simulation, matching and optimizationrmh072000/site/software_and... · lab 5:...

ADS Fundamentals - 2009

LAB 5: S-parameter Simulation, Matching and Optimization

Overview‐Thisexercisecontinuestheamp_1900design.Itteacheshowtosetup,run,optimizeandplottheresultsofvariousS‐parametersimulations.Also,theoptimizerisusedtocreatetheimpedancematchingnetworks.

OBJECTIVES • Measuregainandimpedance.

• Setupandusesweepplans,parametersweeps,andequationbasedimpedance.

• Calculatevaluesforamatchingnetwork.

• Designamatchingnetwork.

• Useoptimizationtomeetdesigngoals.

• UseNoiseandGaincircles.

• WriteafilewiththeDataFileTool.

©CopyrightAgilentTechnologies2009

Lab 5: S-parameter Simulations and Optimization

5‐2©CopyrightAgilentTechnologies2009

Table of Contents

1. Set up the simulation and circuit with ideal components......................................3

2. Simulate and plot data with marker readout modifications...................................4

3. Write an equation to vary the Term port impedance. ...........................................4

4. Calculate L and C values in the data display. ......................................................5

5. Replace L and C with calculated values and simulate. ........................................6

6. Use the Smith Chart utility to build a simple matching network. ..........................7

7. Add output matching components......................................................................11

8. Set up an Optimization controller and Goals......................................................12

9. Enable the components to be optimized. ...........................................................14

10. Plot the results. ...............................................................................................16

11. Update optimized values and disable the opt function....................................17

12. Simulate the final matched circuit. ..................................................................18

13. Stability equations with gain and noise circles................................................19

14. OPTIONAL – Read and Write S-parameter Data with an S2P file .................21

15. OPTIONAL – YIELD analysis .........................................................................23



PROCEDURE

1. Setupthesimulationandcircuitwithidealcomponents.

a. Savethelastschematic(ac_sim)designas:s_params.

b. Modifythedesigntomatchtheschematicshownhere:

• DeletetheACsourceandcontroller.Alsodeletethemeasurementequations,parameterssweep,andanyunwantedvariables,etc.

• Insertterminations(Term)fromtheS‐parameterpalette.

• FromtheLumpedComponentspalette,inserttwoidealinductors:DC_FeedtokeeptheRFoutoftheDCpath

• InserttwoidealDCblockcapacitors.

• DeletethenodenamesbyclicktheNameiconand,leavingitblank,clickingonthenodenames(VinandVout).ForS‐parametersimulation,theportterminations(num1andnum2)providenodes.

c. InsertanSParametersimulationcontrollerandset:Start=100MHz,Stop=4GHz,andStep=100MHz.

d. Savethedesign.



2. Simulateandplotdatawithmarkerreadoutmodifications.

a. Besurethenameofthedatasetis:s_paramsandthensimulate.

b. Whenthesimulationisfinished,insertarectangularplotofS21(dB).Insertamarkeron1900MHzandverifythatthegainisabout20dB.

c. InsertaSmithchartofS11andplaceamarkeron1900MHz.Tomovethemarker,selectthereadoutandusethearrowkeys.

d. Editthemarkerreadout(doubleclick).GotothetheFormattabandchangeZoto50asshown.ClickClickOKandthemarkerwillnowreadthevalueinvalueinohms,referencedto50ohms.

3. WriteanequationtovarytheTermportimpedance.

a. Inschematic,writeanequationforport2TermZtobe35ohmsabove400MHz:Z=iffreq<400MHzthen50else35endif.

b. SimulateandtheninsertalistofPortZ(2).VerifythatZis35Ohmsabove400MHz.

c. Resetthevalueofport2Termto50ohms:Z=50Ohm.

Typedirectlyon‐screen.



4. CalculateLandCvaluesinthedatadisplay.

Thetransmissionandreflectioncharacteristicsofthebiasedcircuitshowabout20dBofgainbutwithamismatchto50ohmsattheinput.Also,theDCfeedsandblocksareidealandneedtobereplacedwithrealvalues.

a. Indatadisplay,writeanequation,XC,forthecapacitivereactanceof10pFat1900MHz.ThenlistequationXCasshownhere.Ifdesired,titlethelistusingPlotOptions.Withthislowreactance,10pFwillbetheblockingcapacitorvalues.

b. ChangethevalueofthecapacitorintheequationandverifythatXCisautomaticallyupdatedinthelist.

c. Createatableforarangeofinductorvaluesandreactances.L_valisarangeofsweptvaluesfrom1nanoto200nanoin10nanosteps.InADS,thesyntaxoftwocolonsisawildcard(allvalues)andcanalsobeusedtoindicatearangeasshownhere.Thesquarebracketsareusedtogeneratethesweep.Afterwritingtheequationsandlistingthemasshownhere,scrollthroughthelist.Astheinductorvalueincreases,thereactanceat1.9GHzincreases.Therefore,avalueof120nHshouldbeenoughfortheDCfeed(RFchoke).

NOTEonequationsandtablesYoucancopytheequationsandtables(CtrlC/CtrlV)tootherdatadisplays.OrusethecommandFile>SaveAsTemplatetosavethedatadisplayasatemplatethatcanbeinsertedinotherprojects.

d. Savethecurrentdatadisplayandtheschematic.

NOTE:TheXLequationwillbered(invalid)untilL_valiswritten.



5. ReplaceLandCwithcalculatedvaluesandsimulate.

a. Savetheschematicwithanewname:s_match.

b. Changethecomponentname(DC_Block)ofbothblockingcapacitorstoCandtheywillautomaticallybecomelumpedcapacitorsasshownhere.AssignthevalueforeachC=10pF.

c. Changetheidealinductors(DC_Feed)inthesamemannerandsetL=120nHforeach.AccordingtotheXLandL_valtable,thereactanceat1900MHzisabout1.5K,whichisreasonableatthispointinthedesign.

d. Theschematicshouldnowlookliketheoneshownhere.CheckyourvaluesandthenSimulate.

Highlightthecomponentname,typeinC,andpressEnter:DC_BlockwillbecomeC.Thenchangeto10pF.



e. Inthedatadisplay,plotthetransmission(S12andS21)andreflection(S11andS22)datawithmarkersasshownhere.Noticethegainstaysrelativelyflat,theleakageisreasonable,buttheimpedanceisnotnear50ohms.Thenextstepistocreateaninputmatchingnetwork.

6. UsetheSmithChartutilitytobuildasimplematchingnetwork.

a. Inthecurrentschematic,clickonthecommands:Tools>SmithChart(thisisthesameasDesignGuide>FilterandthenselectingtheSmithChartControlwindow).

b. ClickthePaletteiconshownhere‐thisaddstheSmithChartpalettewiththeSmithCharticontoyourschematic.

Smith Chart Control Window



TypeintheZvalue:554‐j*220here.

c. Intheschematic(s_match),inserttheSmithChartMatchingNetworkcomponent(alsoknownasaSmartSmartComponent)neartheinputoftheamplifier–no–noneedtoconnectit–butitisrequired.Also,clickOKclickOKwhenamessagedialogappears.

d. GobacktotheSmithChartcontrolwindowandtypeintheFreq(GHz)to1.9asshownhere.

e. InthelowerrightcorneroftheSmithChartChartutilitywindow,selecttheZLcomponentandtypeintheimpedanceimpedancelookingintotheamplifierfromfromthelastsimulation:554‐j*220asasshownhereandclickEnter.

f. NoticethattheloadsymbolontheSmithcharthasrelocatedasshownhere.Next,selecttheshuntcapacitorfromthepaletteandmovethecursorontheSmithchart:whenyougettothe50Ohmcircleofconstantresistance,clicktostop,asshownhere(itdoesnothavetobeexactforthisexercise).

Loadsymbolisat554‐j220.Sourcesymbolisat50+j0.

Shuntcapallowsyoutomovetothe50ohmcircle.



g. Next,selecttheseriesinductorandmovethecursoralongthecircleuntilyoureachthecenteroftheSmithchartandthenclick.

Nowyouhavea50Ohmsmatchbetweentheloadandsource.

h. MovethecursorintothelowerrightcornerofthewindowandclickoneachofthecomponentsintheSchematicasshownhere.Youwillseethevaluesfortheinductorandcapacitor:approximatelyL=14nHandC=400fFor0.4pF.

i. Toclearlyseetheresponseofthisnetwork,changetheStopFreqto4GHz(4.0e9)andyouwillseethenull(S11)at1900MHz.Also,setTrace2toS21toseebothreflectionandtransmission.

j. TohavetheDesignGuidebuildthecircuit,clickthebuttonbuttononthebottomofthewindow:BuildADSCircuit.Circuit.ClickOKtoanymessagesthatappear.

SeriesLallowsyoutomovealongthe50ohmcircletothecenteroftheSmithChart.



k. Ontheschematic,pushintotheSmithChartcomponentandyoushouldseethenetworksimilartotheoneasshownhere.YouvaluesmaybeslightlydifferentwhichisOK.Popoutwhenfinished.

Nowitistimetousethematchingnetworkwiththeamplifier.Youcouldusethecomponentbyconnectingittotheamplifierinput.However,becauseyouwillbeusingtheoptimizer,itisbettertohavetheL‐Ccomponentsontheschematic.

l. Eithercopy/pastetheL‐CandgroundcomponentsontotheamplifierorsimplyinsertanLandConyourschematic.ThensetthevaluestoL=14.3nHandC=0.4pF.Theamplifierinputshouldnowbeasshownhere.

m. DeletetheSmithChartcomponentfromtheschematicandclosetheSmithChartutilitywindow.



n. Simulatewiththeinputnetwork.

o. Setthesimulationstepsizeto10MHz,andsimulate.

p. Whenthesimulationiscomplete,addS‐22totheSmithchart.PlaceamarkeronS‐22at1.9GHz.TheresultsshowS‐11isgoodbutS‐22isnotmatchedasshownhere.

7. Addoutputmatchingcomponents.

BecauseS‐22issimilartotheunmatchedimpedanceoftheinput,itisreasonabletoputasimilartopologyontheoutputandsimulatetheresponse.

a. SelecttheinputL‐Cnetworkandusethecopyicon(shownhere)tomakeacopytothecomponents.Thenplacethemneartheoutput,withagroundonthecapacitor.Deletethewiresandinsertthemasshownattheoutput.

b. Simulateandchecktheresponse.YourdatashouldbesimilartotheresultsshownherewhereS22isnowcloserto50ohms.However,S11hasshifted,asyoushouldexpect.SettheS‐22markerreadouttoZo=50.

c. Savethedesignbutdonotclosethewindow.

DoubleclicktoeditthemarkerreadoutandsetZo=50.



8. SetupanOptimizationcontrollerandGoals.

a. Savethes_matchschematicdesignwithawithanewname:s_opt.

b. GototheOptim/Stat/Yield/DOEpalettepaletteandinsertanoptimizationcontrollerandonegoalasshownhere.here.

c. Editthegoalbydoubleclicking.Inthethedialogbox,typeinthefollowingfollowingsettingsandclickApplyafteraftereachoneandOKwhendone.

• Expr:dB(S(1,1))SimInstanceName:SP1.

• Max=10(S11mustbeatleast–10dBtoachievethegoal)

• RangeVar=freqRangeMin=1850MHzRangeMax:1950MHz

Noteonquotationmarks‐Therangevaluesdonotneedquotesbecausetheyarevaluesandnotstrings(variables).

Noneedtotypequotationmarkswhenusingdialogbox.



d. CopytheS11goal‐selectitandusethecopyicon.

e. Onscreen,changethegoalexpressionto“dB(S(2,2))”asshownhere.Now,youhavetwogoalsfortheinputandoutputmatch.

f. SetuptheOPTIMcontroller.Forthislabexercise,mostofthedefaultsettingscanremain,includingtheRandomtype.However,editthecontrollerandsettheMaxIter=125andsettheFinalAnalysis=“SP1”.Thesesettingsmeanthattheoptimizerwillrunforupto125iterationstoachievethegoals.TheNormalizegoalssettingmeansthatallgoalswillhaveequalweighting.Also,afinalanalysisisautomaticallyrunwiththelastvaluessothatyoucanplottheresultswithoutrunninganothersimulation.

NoteonOptimparametersettings–

NormalizeGoals=nomeansthatmultiplegoalsarenotequallyweighted.Toequallyweightallgoals,setthistoyes.Forthislabitisnotrequired.

SetBestValues=yesmeansthatthecomponentsonschematiccanbeupdatedwiththebestoptimizedvalues.TheSavesettingsallsavedatatothedataset.Insomecases,thiscanbealotofdataandusealotofmemory.Also,thedefaultistouseallgoalsandallenabledcomponents(nextsteps)ontheschematic.However,youcanedittheOPTIMcontrollerandselectwhichgoalsorvariablestouse.AllofthesettingsareexplainedintheHELP(manuals).

NOTE:The‘Save’parametersthataresetto‘no’meanthatthosevalueswillnotbewrittenintothedataset.



9. Enablethecomponentstobeoptimized.

a. Inschematic,gotoOptions>Preferences>andselectthetabtabmarked:ComponentText/WireLabel.TurnontheFullFulldisplayforOptasshownhereandclickOK.Thiswillallowallowyoutoseetherangesettings.

b. Edit(doubleclick)theinductorL_match_in.Whenthedialogdialogappears,clicktheTune/Opt/Stat/DOESetupbutton.IntheOptimizationtab,settheinductortobeEnabledasshownandtypeinthecontinuousrangefrom1nHto40nHasshownhere.ClickOKandthecomponenttextwillshowtheoptfunctionandrange.

c. GoaheadandEnabletheotherthreematchingcomponentsasshown.Editeachoneusingthedialogboxoryoucantypedirectlyon‐screenusingtheoptfunctionandcurlybracesfortherange.Also,usetheF5keytomovecomponenttextasneeded:



d. CheckthecircuitasshownhereandthenSimulateandwatchthestatuswindow.

e. Thestatuswindowreportsprogress.Ifthegoalsaremet,theEF(errorfunction)=0.AsuccessfuliterationoccursiftheEFmovesclosertozero.WithEF=0(orcloseinsomecases),thenextstepistoupdatecomponentvaluesandplottheresults.IfyourEFisnotzero,checktheschematicandtryitagain.



NOTEonoptimizationEFthatdoesnotreachzeroIfanoptimizationdoesnotmeetthegoal,youcanloosenthegoalsorDesiredError.Also,lookforcomponentsthatarebeingdriventotheendsoftheiroptrangeandwidenthem.Also,tryanotheroptimizationmethod,increasethenumberofiterations,ortryanothertopology.

10. Plottheresults.

a. Inthedatadisplay,insertarectangularplot.Then,asshownhere,addthecompleteSmatrixofthefinalanalysisindBtoseeallfourSparameters.Thiswayyoucanquicklyverifytheresults.Yourvaluesmaydifferslightlybutthegoalsfromtheoptimizationshouldbemet.

b. PlottheimpedanceS11andS22onaSmithchart.ChangethemarkerreadouttoZo=50.Asyouwillsee,theimpedanceisnotcloseenoughto50ohms,eventhoughthegoalsweremet.Therefore,somemodificationswillbemadeinthenextsteps.Butfirst,youwillupdatetheschematicwiththevaluesfromtheoptimization.



11. Updateoptimizedvaluesanddisabletheoptfunction.

a. Clickthecommand:Simulate>UpdateUpdateOptimizationValues.Theenabledenabledcomponentsshouldnowhavethethefinal(best)valuesasthenominalvalues.values.Forexample,theinputinductormayinductormaylookliketheoneshownhere‐here‐yourvaluesmayvaryalittlebecauseofbecauseoftherandommodeandnoseeding.seeding.

b. Disableacomponent.Edit(doubleclick)L_match_ininductor.ThenclicktheTune/Opt/Stat/DOEbutton.SelectDisabledDisabledasshownhereandclickOK.NoticeNoticethatthecomponentfunctionchangeschangesfromopttonoopt.Thismeansthecomponentwillnotbeusedinanoptimization.Youcanalsodisableacomponentbyinsertingthecursoron‐screenandtypingnoinfrontoftheoptfunctiontomakeitnoopt–tryit.

c. Savethes_optschematic.Inthenextsetofsteps,youwillsetupafinalmatchedcircuit.

NOTEondeactivatingtheoptimizationcontroller‐Ifyouwanttosimulatewithoutrunninganoptimization,youmustdeactivatetheoptimizationcontroller.

Disabledoptfunction=noopt, or {-o} if the Options>Preferences (Display Format) is set to Short.



12. Simulatethefinalmatchedcircuit.

a. Savethes_optschematicas:s_final.

b. Deactivate(usetheicon)theoptimizationcontrollerandgoals.

c. ModifythefourLandCmatchingcomponentvalues,addingresistancetotheinductorsasshownhere.Thiswillresultinagoodmatchandwillbeusedfortheremainderofthelabexercisessothatallstudentshavethesamecircuit.Goaheadandchangethevaluesbytypingdirectlyon‐screenasshownhere:

L_match_in=18.3nH&R=12Ohm L_match_out=27.1nH&R=6Ohm

C_match_in=0.35pF C_match_out=0.22pF

d. WiththenewfinalcomponentvaluesandSimulate.

e. Whenthedatadisplayopens,plottheentireSmatrixbyselectingSinthedataset.AlsoplottheS11andS22ontheSmithcharttoverifythematchiscloseto50ohmsat1900MHz.Withtheseresults,thenextstepswillbetosimulatestability,gainandnoisecircles.

f. Savethefinaldesignanddatadisplay.Closethedatadisplaybutkeeptheschematicwindowopened.

Improvedgainwithimprovedmatch.



13. Stabilityequationswithgainandnoisecircles.

a. Savethes_finaldesignas:s_circles.

b. GototheS‐parametersimulationpaletteandinserttwostabilitymeasurementequationsMuandMuPrime(iconsshownhere).Thesecanbeusedwiththeirdefaultsettings..

c. Scrolldowninthepaletteandinserttwomeasurementequations:GaCircleandNsCircleasshown.Also,inserttheOptionscontrollerandsetTemp=16.85toavoidthewarningmessagefornoise.Tnomisthetemperatureatwhichadevicemodelisextractedanyshouldnotapplyhere.AllotherOptionsdefaultsettingsareOK.

d. ChangethedBgainintheGaCircleto30asshown.NosettingisrequiredfortheNsCircle–itwilluseNFmin(calculatedminimumnoisefigure)fromthesimulationdata.

Gain:30dB.



e. Changethesimulationfrequency=1850MHzto1950MHzsothatfewerdatapoints(circles)willbecreated.Checktheschematic,besurethenoisecalculationisturnedONinthecontroller,andSimulate.

f. Whenthedatadisplayopens,plotthemeasurementequations:NsCircle1andGaCircle1onaSmithchartasshown.

g. Inarectangularplot,addMu1andMuPrime1asshown.

h. Also,insertalistofnf(2),NFmin,andSopt.

NOTEonresults‐OntheSmithchart,theareainsidetheGainCircleindicatestheloadimpedancethatwillresultin30dBofgain.TheNoiseCircleisdifferentbecauseitscenterindicatestheoptimumvalueofsourcereflectioncoefficientthatwillresultintheminimumnoisefigure(NFmin).WiththecenteroftheNoiseCircleiswithintheGainCircle,bothGainandNFmincanbeachieved.Thetwostabilitytraces,Mu(load)andMuPrime(source),aregreaterthanone.Thismeansthecircuitisstable(itwillnotoscillate)withinthe100MHzbandwidth.Finally,thelistedvalueofnf(2)isthenoisefigurewhenport2istheoutputport.ThisvaluewouldimproveifthesourcereflectioncoefficientwereequaltoSopt(optimumsourcematch).

Ifsourcereflectioncoefficientisequaltothecenterofthenoisecircle,yougetminimumnoisefigure.



i. Saveandcloseallthedesignsanddatadisplaysintheproject.Atthispoint,theamplifierisreadytobetestedwiththenon‐linearsimulator,HarmonicBalance.However,beforedoingso,youwillreturntothesystemprojectinthenextlabandbuildthetwofiltersfortheRFsystem.

14. OPTIONALReadandWriteSparameterDatawithanS2Pfile

YoucanreadorwritedatainTouchstone,MDIF,orCitifileformats.ADScanconvertsupporteddataintotheADSdatasetformat.Typically,thesedatafilesareputintheprojectdirectorybuttheycanalsobesenttothedatadirectory.Youcancontrolwheretheyreside.

a. Openanewschematicandsaveitas:s2p_data.

b. ClickontheDataFileToolicon.

c. Whenthedialogboxopens,clicktheboxtoWritedatafilefromdataset,thenselecttheTouchstoneformat.Youaregoingtowrite(convert)yourexistingADSdataset(s_params)intoaTouchstonefile.Itwillrepresentmeasurementdatafromanetworkanalyzer.

d. IntheOutputFileNamefield,type:my_file.s2p.ThiswillbethenameofthetheTouchstoneformatfilethatwillbeconvertedfromADSdata.

e. SelecttheOutputDataFormatasMag/Angle.Mag/Angle.

f. IntheDatasetsfield,selectthedataset:s_params.Thiswasthedatasetfromthethesimulationusingtheidealcomponents.components.

g. ClickWritetoFile.ChecktheStatusWindow.Window.Ifsuccessful,youwillseeamessage.message.Thismeansmy_file.s2pisnowaaTouchstonefileinthedatadirectoryofthetheamp_1900project.Youcancheckthisifyouthisifyouwantandyoucanuseatexteditoreditor(ADSMainwindow:Tools>TextEditor)Editor)tolookatortomodifythefile.



SimulationController:Frequencytab‐

h. ClosetheDataFiletoolwindow.

i. Intheemptyschematic,insertanS2PcomponentfromtheDataDataItemspalette.Youwillnoticethatthecomponentvariablevariable(File=)isnotyetassigned

j. Toassignthedata,edittheS2Pcomponentandanotherdialogdialogboxwillappear.Next,browseforthefilename.WhentheWhenthenextdialogappears,selectmy_file.s2pandclickthetheOpenbuttonandthefilenamewillbeassigned(shownhere).

(shownhere).

k. Intheschematic,insertanS_Paramstemplate(Insert>Template)andwiretheS2PcomponenttotheTermswithgroundsasshownhere.

l. FromtheSimulation‐S_Parampalette,insertaSweepPlanandsetittoStart=100MHz,Stop=3GHzandStep=100MHzasshown.SweepplansarenormallyusedforfrequencysweepswithinsweepsbutyoucanuseitheretoseehowitreplacestheFrequencysettingsintheS‐parametersimulationcontroller.

m. TousetheSweepPlan,editthesimulationcontroller.IntheFrequencytab,selecttheSwpPlan1asshownhere.GototheDisplaytab,tab,selectSweepPlanandremovethestart,stopandstopandstepasshownhere.



n. SimulateandtheresultswillautomaticallyappearintheDataDisplaywindowbecausethetemplatehasaDDSdisplaytemplatealso.

o. ZoominontheS21measurementandaddtheS21simulationdatafromyouroriginals_paramsdatasettoverifythattheTouchstonefilecorrectlyrepresentedthedata.Asyouwillsee,thetwotracesareidenticalexceptthattheS2Psimulationonlygoesto3GHz.Here,thetracethicknessandtypeshavebeenadjusted(usingTraceOptions)toshowbothtracesmoreclearly.Markershavealsobeenadded.

15. OPTIONAL–YIELDanalysis

Refertothetheoryslidesandruntheyieldanalysisexamplewithadifferentyieldspec(15dBforexample)usingadifferentfrequencyrange.Examinetheresultsinthedatadisplay.



EXTRA EXERCISES:

1. Z_PORTS‐Inaseparateschematic,setupanSparametersimulationofimpedancethatisdescribedbyanequationasshownhere.Plottheresponseandtryadjustingthevalues.

2. SetupthesimulationusingasweepwithinasweepusingtwoormoreSweepPlans.

3. Gobacktotheoptionalexerciseandusethetexteditortoeditthes2pfile,changesomevalues,andsimulatetoverifythatyoucandothis.

lab 5: s-parameter simulation, matching and optimizationrmh072000/site/software_and... · lab 5:...

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