ADS Fundamentals – 2009

LAB 6: Design Guide, Transient, Momentum Simulation and the DAC

Overview‐ThisexerciseteachesthefundamentalsofcreatingfiltersinADSandusingtheTransientsimulator.TheDesignGuideisusedtobuildalumpedcomponentfilterandMomentumisusedtotestamicrostripfilter.

OBJECTIVES • Builda200MHzIFlowpasslumpedfilterusingaDesignGuide

• Builda1900MHzRFbandpassfilterinmicrostrip.

• PerformaTransientanalysisonthemicrostripfilter.

• SimulatethemicrostripfilterinMomentum.

• OPTIONAL–DAC(dataaccesscomponent)exercise.

©CopyrightAgilentTechnologies2009

Lab 6: Design Guide, Transient, Momentum, DAC

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TABLE OF CONTENTS

1. Change projects and start the Design Guide. ......................................................3

2. Insert the LPF Smart Component and design the filter. .......................................3

3. Microstrip 1900 MHz bandpass filter. ...................................................................7

4. Transient Analysis on the microstrip filter. ...........................................................9

5. Momentum simulation from layout. ....................................................................11

6. OPTIONAL - Impedance response Data Access Component. .........................17

Lab 6: Design Guide, Transient, Momentum, DAC

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PROCEDURE1. ChangeprojectsandstarttheDesignGuide.

NOTE:IfyoudonothaveaccesstotheDesignGuide,buildthefilterwithlumpedcomponentsandsaveitasfilter_lpfanduseitforthefinalanalysislab.

Thesestepswillshowhowadesignguidecanquicklyandaccuratelyproduceafilter,similartoE‐syn,butwithmoreoptionsandgreatercontrol.

a. GototheADSMainWindowandclickFile>OpenProject.

b. AnswerYestoAllifyouarepromptedtosaveallyourcurrentwork.Thenopenyourearlierproject:system_prj.

c. Createanewschematicnamed:filter_lpf.

d. Besureitistheonlyschematicopenedonyourscreen.Now,threeNow,threestepsareneededtostarttheprocess:

♦ Clickthecommands:DesignGuide>Filter>FilterControlControlWindow.

♦ Thenewwindow,FilterDesignGuide,DesignGuide,willnotbeactiveuntilyouinsertaschematicsmartcomponentfromthepalette(nextstep).

♦ IntheFilterDesignGuidecontrolwindow,clickontheComponentPalette–Allicon(shownhere).Immediately,thepalettewillappearonyourschematicwindow.Youarenowreadytoinsertsmartcomponent.YoucouldalsoinsertthecomponentfirstandthenopentheFilterDesignwindow–eithermethodworks.

2. InserttheLPFSmartComponentanddesignthefilter.

a. IntheFilterDGpalette,selecttheLow­PassLumpedfilterfiltershownhere(DT=dualterminated).Ifamessageappears,(shownhere)clickOKtodismissit.Theninsertthethecomponentontheschematic.UsetheEsckeytoendthethecommand.

Lab 6: Design Guide, Transient, Momentum, DAC

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b. PositiontheFilterDesignGuidewindownexttotheschematicsoitisactiveandclickontheFilterAssistanttab–itshouldactivateasshownhere.Ifnot,selectthefilterintheSmartComponentlist.Youarenowreadytosetthespecifications.

c. IntheFilterDesignGuidewindow(shownhere),enterthefollowingthreefilterspecifications:

(ripple)Ap(dB)=0.1,(passband)Fp=0.2GHz,(stopband)Fs=1.2GHz

d. Aftersettingthefilterresponse,clickRedrawtoseetheresponseplotchange.ThisisaButterworthresponse.ItwillprovidealowpasslumpedfilterforthesystemIFoutput.

e. Todesignthefilter,clicktheDesignbutton.

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f. Inyourschematic,theSmartComponentnowhasyourfilterspecificationsandthefiltercircuitiscreated.Toverifythis,pushintopushintotheDTcomponent.Afterward,popoutasshownhere:here:

g. GototheSimulationAssistantandsetthesweepsweepfrom0MHzto1.3GHzin10MHz10MHzsteps.ThenclicktheSimulateSimulatebuttonandwatchwhathappens:happens:atemplaterunstheS‐parameterparametersimulationanddisplaysthetheresults.

h. ExaminethedatadisplayandmovethethemarkerM1to100MHz.Noticethethespeclineat–20dB(AtoB)andthetheperformancetablethatcomparesthecomparestheinputparameterstotheresults:the–20dBstopbandisat800MHzwhichwillbeOKforoursystem.

i. Scrolldownandexamineallthedata.

j. SaveandcloseallwindowsusingtheADSmainwindowcommand:File>CloseAll.Youwillusethisoutputsignalfilterlateroninthecourse.Next,youwillbuildtheinputfilter.

Thisfilterwillbeavailableinthelibraryforuselater.Editthecomponenttodisplaythedesiredparameters.

filter_lpf

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3. Microstrip1900MHzbandpassfilter.

Inthesenextsteps,youwillbuildandsimulateacoupledlinefilterwiththeADScircuitsimulator.Afterward,youwilltransferittoADSlayoutandsimulateusingMomentum.ThisstepisonlyintendedtobrieflyshowhowMomentumworksinasimplemicrostripapplication.

a. Createanewschematicinthecurrentproject(system_prj)named:named:filter_1900.

b. FromtheTLines­Microstrippalette,insertanMCFILasshown.Becausethetwoendcomponentsaresymmetrical(CLin1andCLin2),savetimebytypingtheW,S,andLparameters(shownhere)forthefirstoneandthencopyit.Theninsertthemiddlecomponent(Clin3)andtypeinitsvalues.

c. Insertportconnectorsoneachendasshownalso.

d. FromtheMicrostrippalette,insertthesubstratedefinitionMSUBasshown‐noothersettingsarerequired–thedefaultsubstratewillbeused.

Thesetwohavethesamevalues.

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NOTEonthefilterS‐21response–TheS‐parametersimulation(S‐21)ofthisfilterisshownhereasareference‐thereisnoneedtosimulateitwiththeS‐parametersimulatoratthistime.

e. Intheschematic,click:File>DesignParameters.Whenthedialogappears,selecttheADSbuilt‐insymbolforabandpassfilter:SYM_BPFandclickOK.

f. Savethedesignagainsothatallthemodificationsarealsosaved.Thisisthefilterthatwillbeusedforthefollowingstepsandforthefinalsystemdesign.

Saveddesign:filter_1900foruselateroninthesystem.

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4. TransientAnalysisonthemicrostripfilter.

a. Savetheschematic(filter_1900)withanewname:filter_trans.

b. Modifytheschematictolookliketheoneshownbelowbydeletingtheportconnectors.

c. FromtheSources‐TimeDomainpalettepaletteinsertaVtSineattheinput(beinput(besuretogrounditasshown).Itshown).ItisrecommendedtouseTimeuseTimeDomainsourcesforTransientTransientanalysis.

d. Inserta50ohmresistorattheinputandontheoutput(withground).

e. Labelpin/nodesVinandVoutasshown.Thecircuitshouldlookliketheoneshownhere.

f. FromtheSimulation­Transientpalette,insertaTransientsimulationcontrollerandsettheStopTimeandMaxTimeStepasshown.Thesimulationwillbeginattimezero(default)andstopafterfifteenperiodsoftheinputsignal(8ns).Inaddition,thetimestepwillsampleattwice(Nyquistrule)therateofthehighestspectralcomponentdesired,herethe15thharmonic.

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g. Simulateandafterthesimulation,insertarectangularplotofVinandVoutandediteachtrace(TraceOptions)toplacesymbolatdata–thiswillshowyouthetimepointstakeninthesimulation.

h. Zoomintotheplotafter5nsandputandputthemarkersonthepeaksofpeaksofVinandVoutasshownhere.here.

i. Writeanequationasshowntocalculatethedelaythroughthefilter:filter:marker_difference.ThiscalculatestheXaxisdifferencebetweenmarkersusingtheindepindepfunction(independentvariable=time).

j. Insertalistofmarker_differenceandusePlotOptionstoremovetheindependentdataasshown.Thevalueisthedelaythroughthefilterafterstartup(settling).Dependinguponwhereyouzoominandwhereyouplacethemarkers,yourvaluemaydifferslightly.Thedelaythroughthefilterisabout44picosecondsasshownhere.

k. Savetheschematicbutkeepitopened.Saveandclosethedatadisplay.

l. ThenextstepswillbetosimulatethisfilterinMomentum.

TraceOptionsTab–LinearTab

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5. Momentumsimulationfromlayout.

a. Openfilter_1900andsaveitwithanewname:filter_mom.

b. Transferthefilter_momschematictolayoutbyclickingclickingtheschematicwindowcommand:Layout>Generate/UpdateLayout.

c. Whenthenextdialogappear,besuretheStartingComponentisP1(portconnector1fromschematic)sothattheleft‐to‐rightlayoutwillbegeneratedcorrectly.ClickOKandyoushouldseeanotherdialogindicatingthatallcomponentshavebeencreatedinthelayoutwindow.

d. ThelayoutwindowandtheLayerscontrolwillopen.Inthethelayout,verifythatyouhavethreelongcoupledlineswithtwowithtwoports.Zoominonaport(shownhere),andverifythatitverifythatitisconnectedtotheedgeofthemetal.FormanymanyMomentumsolutions,itisnotnecessaryfortheporttotoconnecttothemiddleoftheline–itonlyneedstobeonthe

Zoomed‐inportconnector.Momentumportscanbeinsertedinlayoutifthedrawingiscreatedinlayout.

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theedge.

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e. ThenextstepistodefinethesubstrateinMomentum.Todothis,usetheLayoutcommandsshownheretotransfertheschematicschematicMSUBdefinition:Momentum>Substrate>UpdateFromSchematic.

f. Verifythatthe10milsubstratedefinitionisnowinMomentum.Click:Momentum>Substrate>Create/ModifyandyoushouldseetheMSUBvaluesinthedialog.

g. YoucanalsolookattheLayoutLayerstabtoseehowthedrawinglayersinlayoutaremappedtothesubstrate:condisametalstriplayer.ButDONOTchangeanything.ClickOKtodismissthedialog.

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h. Beforesimulating,lookattheMomentummeshfeatures.Click:Momentum>Mesh>Setup.WhentheWhenthedialogappears,noticetherearemanymeshmeshfeatures.Butfornow,besuretheEdgeMeshboxMeshboxisuncheckedasshownandclickOK.

NOTEontheMomentumprocess‐theorderofstepsis:computethesubstratedefinition(Green’sfunctions),createthemeshorgridpattern(cells),andthensimulate.

i. Tosimulate,click:Momentum>Simulation>S­parameters.Whenthedialogappears,typeinthesweepasshown:1GHzto3GHzusing25pointsasthelimit.ClickUpdateanditwillappearintheFrequencyPlan.Next,clicktheSimulatebuttonandclickYesiftheQuestiondialogappears.Watchthestatuswindow‐theAdaptivesweeptypeisthedefaultanditscurvefitting‐likealgorithmwillruntheEM(electro‐magnetic)simulationbysolvingselectedpoints.

Momentumautoplotfeature

Lab 6: Design Guide, Transient, Momentum, DAC

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j. WhentheADSDataDisplayopens,youwillseeamessagemessageabouttheautoplot:checktheboxasshownherehereandclickOKtodismissit.NoticethattheMomentumMomentumautoplottemplatelooksslightlydifferentthanthanADS.

k. ZoomintotheS21plot.Asshownhere,theexpectedresponseissimilartotheresponsethatyouwouldgetfromthecircuitsimulatorwithanysmalldifferenceduetothesolutionmethods.Also,zoominandlookatthemeshpattern.

l. Drawasimplecruderectangle(iconshownhere)alongthelengthofthefilter.Itshouldbeabout2000milslongand60or70milswide.Whenyoudrawtherectangle,noticethatthecursorbeginsdrawingatx‐y0,0asshownhere.Also,youcanmeasureanobject,usingthecursor,byclickinginlayoutandwatchingthevalueschangehere.ThepointofthisstepistoshowhowMomentumcananalyzethecouplingbetweenthefilterandtherectangle(metal).

m.

Zoomintoseethemeshcells.

W:60‐70mils

Click,thenmovethecursorandlookatthewindowbottomor,tomeasureanobject,use:Insert>Measureandclickontwopoints.

L:about2000milsorslightlylongerthenthefilter

Spacingbetweenthefilterandtherectangleisabout10milsonthisend.

Lab 6: Design Guide, Transient, Momentum, DAC

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n. Withtherectangledrawnnexttothelayout,performanotherMomentumsimulation.Click:Momentum>Simulation>S­parametersandwhenthedialogappears,changethedatasetnameasshownhere,filter_mom_stripandclickApplyandSimulate.

o. Thissimulationwilltakealittlelongerbecausetherearenowmoreunknowns(cells)tocalculateandthereforemorecomputationtimeisrequired.Whenthedatadisplayappears,youshouldseethatthereisaresonancesomewherenearthebandpassoritsedges,dependinguponyourrectangle.ThisisthetypeofsimulationthatcanonlybeaccomplishedwithMomentum.ViewtheS‐21resultsandthenclosethelayoutanddatadisplaywindows.Itisnotnecessarytosavethisdesign.

p. YounowhavetwofiltersthatcanbeusedlaterfortheRFsystem.Theyare:1)filter_lpf‐thisisthe200MHzlowpasscreatedfirst,and2)filter_1900‐yousimulatedthismicrostripcoupledlinefilterusingtheTransientsimulatorandMomentum.Atthistime,closeandsavealldesignsandwindows.

EXAMPLE:Narrowresonanceat2.05GHzduetocouplingeffectsofrectangle.

Lab 6: Design Guide, Transient, Momentum, DAC

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6. OPTIONAL­ImpedanceresponseDataAccessComponent.

ADACcomponentisafile‐basedcomponent.Itmaycontainvariousformatsofdatafrommeasurements,listeddata,oranyothervalidfiletypethatADScanread.Inthisstep,youwillcreateasimplefilewithcompleximpedancevaluesthatvaryoverafrequencyrange.KeepinmindthattheDACcanbeusedtocreatesuchmodelsas:frequencysensitiveimpedances,varactors,stepfunctions,bitsequencesforsources,timedomainsequences,andmanyotheruseswhereafileismoreefficientthantypinginlongequationsorlistsonyourschematic.Ingeneral,theDACworkslikethis:itisacomponentthatpointstoafileinthedatadirectory.InthisexampleyoucreateafilethatwillbeusedfortheimpedanceparameterofanADScomponent‐thesimulatorwillsimplyreadthefile.

a. Openanewschematicwiththename:Z_DAC.

b. Refertotheschematicshownhere.Insertaterminationwithground,anequationbaselinearZ1P_Eqn(Z1port)fromtheEqnBasedLinearpalette.TheninsertanS‐parametercontroller,andaDACfromtheDataitemspaletteintheirdefaultstates(nosettingyet).

c. SettheS‐parametersimulationasifitwastheLPF:10MHzto200MHzin10MHzstepsasshownandsavetheschematicagain.

d. OpentheWindowsNotepadprograminStart>>Programs>Accessories.OrusetheADSMainMainWindow(Tools>TextEditor)ifNotepadistheNotepadisthedefaulttexteditor(thiscanbechanged).

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IMPORTANTNOTEonDACtextfiles‐YoushouldnotuseaprogramthathasformattinglikeMSWORD.However,NotepadisOK.

e. Writeanmdf(multi‐dimensionaldatafile)fileshownhereandsaveitintheDATAdirectoryas:z_dac.mdf.

NOTEonfiletype.mdf‐Ifnecessary,usewindowswindowsfileexplorertochangethenameifitisissavedasa.txtfile.Also,thesyntaxinthefirstfirstcolumnis4frequencypoints,thesecondandandthirdcolumnscontaintherealandimaginaryimaginaryimpedancevaluesateachfrequency.frequency.

f. Onschematic,edittheS‐parametercontroller.InParameterstab,settocomputeZparametersnotS.IntheDisplaytab,checkSweepVar,Start,Stopandsetthemasshowntosweepfreqfrom10to200MHzin10MHzsteps.Youwillgetinterpolateddataforallthesteps.

g. Ontheschematic,edit(doubleclick)theZ1P_Eqnanditseditdialogwillappearasshownhere.

h. Asshownhere,selectFileBasedastheParameterEntryMode,andDAC1,andsettheDependentParameterNametomy_zandclickOK.

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i. EdittheDACasshown:Typeinthefilename,selecttheType,etc.Also,iVar1

(my_freq)istheindependentvariablenameandiVal1(freq)istheindependentvariablevalue.As“freq”isswept,“my_freq”willbeindexedinthefileandtheDACwillreturncomplexvaluesof“my_z”interpolatedovertherange.

j. Simulateandplottwotraces,realandimag,ofZ(1,1)asshown.Asyoucansee,theZportcanbeusedwhereverafrequencysensitivecomponentisrequired.Formultiplecomponents,simplycreatedifferentfilesandaccessthemasrequired.

EXTRA EXERCISES:

1. CalculatethebandwidthofthefilterinTransientsimulationusingtherule‐of‐thumb:BW=0.35/risetime.Fromtimezerountilabout6nsshouldbetherisetime.However,usethemarkersandtheequationstodothecalculation.

2. TryusingtheDesignGuideforanothercircuittypeorsomeotherdesign.

3. CreateaDACforafrequencysensitiveinductorandsimulateitinasimpleCLCfilter.TheDACwillcontaintheinductorvaluesateachfrequency.

GenericMDIF

Lab 6: Design Guide, Transient, Momentum, DAC

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