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ADS Fundamentals – 2009
LAB 2: System Design Fundamentals
Overview‐Thischapterintroducestheuseofbehavioralmodelstocreateasystemsuchasareceiver.Thislabwillbethefirststepinthedesignprocesswherethesystemlevelbehavioralmodelsaresimulatedtoapproximatethedesiredperformance.Bysettingthedesiredspecificationsinthesystemcomponents,youcanlaterreplacethemwithindividualcircuitsandcomparetheresultstothebehavioralmodels.
OBJECTIVES • Usetheskillsdevelopedinthefirstlabexercise.
• CreateasystemprojectforanRFreceiverusingbehavioralmodels(filter,amplifier,mixer)where:RF=1900MHzandIF=100MHz.
• UseanRFsource,LOwithphasenoise,andaNoiseController.
• Testthesystem:S‐parameters,Spectrum,Noise,etc.
©CopyrightAgilentTechnologies2009
Lab 2: System Design Fundamentals
2‐2 ©CopyrightAgilentTechnologies2009
Table of Contents
1. Create a New Project (system) and schematic. ...................................................3
2. Build a behavioral RF receiver system. ..............................................................3
3. Set up an S-parameter simulation with frequency conversion. ............................6
4. Plot the S-21 data. ..............................................................................................9
5. Increase gain, simulate, and add a sccond trace. ..............................................9
6. Set up an RF source and LO with Phase Noise.................................................10
7. Set up a HB Noise Controller.............................................................................12
8. Set up a HB simulation. ......................................................................................13
9. Simulate and plot the response: pnmx and Vout. ..............................................14
10. OPTIONAL - SDD (Symbolically Defined Device) simulation..........................15
Lab 2: System Design Fundamentals
2‐3©CopyrightAgilentTechnologies2009
PROCEDURE
1. CreateaNewProject(system)andschematic.
a. UsetheFile>NewProjectcommandandnamethenewproject:system.
b. Openandsaveanewschematicwiththename:rf_sys.rf_sys.
2. BuildabehavioralRFreceiversystem.
a. Butterworthfilter:GototheComponentPalettelistPalettelistandscrolldowntoFiltersBandpass.Bandpass.InsertaButterworthfilter.Setitasshown:Fcenter=1.9GHztorepresentthecarriercarrierfrequency.SetBWpass=200MHzandandBWstop=1GHz.
b. Amplifier:GototheSystem‐Amps&MixerspalettepaletteandinserttheAmp.SetS21=dbpolardbpolar(10,180).
Foron‐screenediting,usetheEnterkeytosteptothenextparameter.
Lab 2: System Design Fundamentals
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c. Term:Insertaterminationattheinputforport1.TermsareintheSimulationS_ParampaletteortypeinthenameTermintheComponentHistoryandpressEnter.
NOTEonButterworthfilterThebehavioralButterworthresponseisideal;thereforethereisnorippleinthepassband.Lateron,whenthefilterandamplifierarereplacedwithcircuitmodels,therewillberipple.Forsystemfiltermodelingwithripple,usethebehavioralEllipticalfilter.
Lab 2: System Design Fundamentals
2‐5©CopyrightAgilentTechnologies2009
ThenextstepswilladdabehavioralmixerandLOtotheRFsystem.
d. FromtheSystem‐Amps&Mixerspalette,insertabehavioralMixerattheattheampoutput‐becarefultoinserttheMixerandnotMixer2.Mixer2Mixer2issimilarandalsofornonlinearanalysisbutdoesnotworkwithwiththesmall‐signalfrequencyconversionfeatureofS‐parameteranalysisthatyouwilluseinthisexercise.
e. SettheMixerConvGain=dbpolar(3,0).Also,settheMixerSideBand=LOWERbyinsertingthecursorinfrontofthedefault(BOTH)andusingthekeyboardUPandDOWNarrowkeystotogglethesettingtoLOWER.Leaveallothersettingsinthedefaultcondition.
f. MovecomponenttextclicktheF5keyboardkeyandthenclickonacomponenttomoveitstext.Dothissothatyoucanclearlyseethecomponents.
g. AddtheLObyinsertinga50ohmresistorinserieswithaV_1TonesourcefromtheSourcesFreqDomainpalette.SettheFreqto1.8GHz.ThiswillprovideanIFof100MHzattheoutput.Don’tforgettheground.
LocalOscillator:resistor,voltagesource,andground.
Lab 2: System Design Fundamentals
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h. AddalowpassBesselfilteratthemixeroutputasshownhere.ThefilterisintheFiltersLowpasspalette.SetFpass=200MHz.
i. InsertaTermforport2.Thefinalsystemcircuitshouldlookliketheoneshownhere:
NOTE:YoucansettheNparameter(order)onthefiltersbutitisnotrequired.Bydefault,ADSwillcalculatetheorder(N)basedonthespecifications.IfNisspecified,ADSwilloverwritethefilterspecifications.
3. SetupanSparametersimulationwithfrequencyconversion.
a. Insertthecontrollerandsetupthesimulation:1GHzto3GHzin100MHzstepsasshownhere.
Formatted: Bullets and NumberingDeleted:
Lab 2: System Design Fundamentals
2‐7©CopyrightAgilentTechnologies2009
b. EdittheSimulationcontrollerand,inthetheParametersTab,EnableACfrequencyfrequencyconversionbycheckingtheboxtheboxasshownhere.
c. GototheDisplaytabandcheckthetwotwoboxestodisplaythesettingsshownshownhere:FreqConversionandFreqConversionPort.Thedefault(port1)(port1)isusedbecauseitistheportwherewherefrequencieswillbeconvertedusingusingthemixersettingsalso.NOTE:thisNOTE:thisconversiononlyworkswithwiththisADSmixer.
TheS‐parametersimulationcontrollershouldnowlookliketheoneshownhere:
d. Click:Simulate>SimulationSetup.WhentheWhenthedialogappears,changethedefaultdefaultdatasetnametorf_sys_10dBtoindicateindicatethatthissimulationdatarepresentstherepresentsthesystemwith10dBofamplifieramplifiergain.
e. ClickApplyandSimulate.
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Lab 2: System Design Fundamentals
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Lab 2: System Design Fundamentals
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4. PlottheS21data.
a. IntheDataDisplaywindow,insertarectangularplotofS(2,1).
b. Putamarkeronthetracenear1.9GHzwiththemouse.Theninsertyourcursorandtypeinthevalue:1.9inthereadoutbox.Thegainincludesmixerconversiongainminussomelosstoduemismatches.
5. Increasegain,simulate,andaddasecondtrace.
a. GobacktotheschematicandchangetheamplifiergainS21from10to20dBasshownhere.
b. InSimulate>SimulationSetup,changethedatasetnametorf_sys_20dB.ClickApplyandSimulate.
c. Whenthesimulationfinishesyouwillbepromptedtochangethedefaultdataset–answer:No.No.
d. Edittheexistingplot(doubleclickonit)–thisisthisistheonewiththe10dBtrace.Whenthethedialogappears,clickthearrowtoseethetheavailableDatasetsandEquations(shownhere)andselecttherf_sys_20dBdataset.
e. SelecttheS(2,1)dataandAdditindB,clickingOK.Noticethattheentiredatasetpathnameappearsbecauseitisnotthedefaultdataset.
f. PutaMaxMarkeronthenewtrace.Selectbothmarkers(selectthe(selectthereadouts)andclicktheicontoTurnonDeltaMode(select(selecteitherasareference)toseethe10dBdifferencebetweenthebetweenthetwosimulations.BesuretosavetheDataDisplay.
Deleted: ,t
Deleted: n
Deleted: ewmarker
Deleted: commandMa
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Lab 2: System Design Fundamentals
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Display.
6. SetupanRFsourceandLOwithPhaseNoise.
Thisnextstepshowshowtosimulatephasenoise,contributedbyabehavioraloscillator,usingtheHarmonicBalancesimulator.Atthispointinthecourse,itisnotrequiredthatyouunderstandalltheHarmonicBalancesettings(coveredlater).
a. Savethecurrentschematicwithanewname.Click:File>SaveDesignAsandtypeinthename:rf_sys_phnoise.
b. Inthesavedschematic,deletethefollowingcomponents:S_paramsimulationcontroller,theV_1ToneLOsource,its50ohmresistorandground.
c. Replacetheport1TermwithaP_1Tonesource(Sources‐FreqDomainpalette)andsetthepowerandfrequencyasshown:Freq=1.9GHzandP=polar(dbmtow(40),0).Also,renamethesourceasRF_sourceandchangetheNumparametertoNum=1.
d. InsertawirelabelVout(node)andsotheschematiclooksliketheoneshownhere:
e. GotoSourcesFreqDomainpalette,scrolltothebottom,selecttheOSCiconandinserttheOSCwPhNoise‐connectittothemixer.SetFreq=1.8GHzandchangethePhaseNoiselistasshown.ThedefaultvalueofPisthepowerindBmandithas50ohmsZ(Rout).
ConnecttoMixerLOinput.
Lab 2: System Design Fundamentals
2‐11©CopyrightAgilentTechnologies2009
Lab 2: System Design Fundamentals
2‐12 ©CopyrightAgilentTechnologies2009
7. SetupaHBNoiseController.
a. GototheSimulationHBpaletteandinsertaNoiseCon(NoiseController)ontheschematicasshownhere.
NOTEonNoiseCon:ThiscomponentisusedwiththeHBsimulator.Itallowsyoutoconvenientlykeepallnoisemeasurementsseparatefromthesimulationcontroller.Also,youcansetupandusemultiplenoiseconsfordifferentnoisemeasurementswhileonlyusingonlyoneHBcontroller.
b. FreqtabEdittheNoiseCon–gototheFreqtabandsettheSweepTypetoLogfrom10Hzto10KHzwith5pointsperdecade.
c. Nodestab–ClickthePosNodearrow,selecttheVoutnode,andclicktheAddbutton.Thenoisecontroller,likeotherADScomponets,canreadandidentifynodenamesintheschematic.
d. PhaseNoisetab–SetthePhaseNoiseNoiseType:PhaseNoisespectrumspectrumandsetthecarrierFrequencyto100MHz.ThisistheIFtheIFfrequencywhichhasphasenoisephasenoiseduetotheLO.
e. Displaytab–GototheDisplaytabandchecktheboxesforthesettingsyoumade(shownhere).Inthefuture,youmayprefertodisplaythedesiredsettingsfirstandtheneditthemontheschematic.
Displaythesesettings:
Deleted: 10KHz
Lab 2: System Design Fundamentals
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8. SetuptheHBsimulation.
a. GototheSimulation‐HBpaletteandinsertaHBsimulationcontrolleroncontrollerontheschematic.
b. EdittheHBcontroller(doubleclick).IntheFreqFreqtab,changethedefaultfreqsettingto1.8GHz1.8GHzusingtheApplybutton.ThenaddtheRFtheRFfrequency1.9GHzandclickApplyagain.again.
c. IntheDisplaytab,checktheboxtodisplayMaxOrderandclickApplyatthebottom
NOTEonHBfreqsettings‐YouonlyneedtospecifytheLOfreq(1.8GHz)andtheRFfreq(1.9GHz)inthecontroller.ThereisnoneedtospecifyanyotherfrequenciesbecausethedefaultsforOrder(harmonics)andMaximumorder(mixingproducts)willcalculatetheothertonesinthecircuit,includingthe100MHzIF.
d. GototheNoisetabandchecktheNoiseConsboxasshown.ThenusetheEditbuttontoselectNC1whichistheinstancenameoftheNoiseCon.ClickAddandApply.
e. Displaytab–GototheHBDisplaytabandchecktheboxesforthesettingsshownhere.Thenoiseconsettingsarenearthebottomofthelistasyouscrolldown.
Lab 2: System Design Fundamentals
2‐14 ©CopyrightAgilentTechnologies2009
ThecompleteschematicforsimulatingLOPhaseNoiseattheIFisshownhere.Checkyourschematicbeforesimulating:
9. Simulateandplottheresponse:pnmxandVout.
a. Insertarectangularplotofpnmx.UsePlotOptionstosettheX‐axistoLogscale.NoticetraceshowsthedecreasingdBvaluesassignedintheoscillatorsetting(forexample:about30dBat1KHz).Also,insertarectangularplotofVoutindBmwithamarkeronthe100MHzIFsignal.At‐40dBminput,plusabout23dBofampandconversiongain,theoutputshouldbeabout–17.7dBmasshown.
b. Saveallyourwork.YouhavenowcompletedthefirststepinthedesignprocessfortheRFreceiver.Inthefollowinglabs,youwillbuildthecircuitsthatwillreplacethesystemmodelcomponents.
NOTE:YoucanchangetheminimumYaxisvalueto–100foramorerealisticnoisefloor.
Lab 2: System Design Fundamentals
2‐15©CopyrightAgilentTechnologies2009
10. OPTIONALSDD(SymbolicallyDefinedDevice)simulation
SDDsallowyoutowriteanequationtodescribethebehavioratthenodesofacomponent,eitherlinearornonlinear.Forthisstep,youwillwriteasimplelinearequationdescribingsumsanddifferencesthatappearattheoutputofa3portSDD.
a. UseSaveDesignAstogivethecurrentdesign(rf_sys_phnoise)thename:rf_sys_sdd.
b. Deletethebehavioralmixerinthecircuit.
c. GotothepaletteEqnBasedNonlinearandinsertthe3the3portSDDinschematic,inplaceofthemixer.ConnectConnectgroundsonthenegativeterminalsasshownhere.here.
d. EdittheI[2,0]valuebyinsertingthecursordirectlyontheonthetextandaddingthevaluesshown:_v1*_v3.BysubtractingthevoltageofthemixingtermsoftheRF(_v1)andLO(_v3),theIF(_v2)voltageremains.TheSDDisnowamixerwithnoconversiongain,andboththesumandthedifferencefrequencieswillappearattheoutput.
e. SimulateandplotthespectrumofVoutindBm.indBm.Asyoucansee,withoutconversiongain,conversiongain,theIFsignalismuchlower.lower.Also,boththedifferenceandthesumsum(RF+LO)appear(marker:SUM).AlthoughAlthoughSDDscanbeusefultodescribebehavior,writingtheproperequationscanbebecomplicated(requiresadvancedcourse).course).
NOTE:SDDsperformnumericaloperations.Thismeansv1*v3isaproductofthevoltagesatterminals1and3.
Lab 2: System Design Fundamentals
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f. DeactivatetheHBandNCcontrollers.
g. InsertaTransientsimulationcontrollerandusethesetupshownhere.Also,useSimulation>Setuptochangethedatasetnameto:rf_sys_sdd_trans.
h. RuntheTransientsimulation.
i. DonotchangedefaultdatasetsintheDataDisplay.
j. Insertanequation(shownhereasVout2)thatusesthefs()functiontotransformthedata–besuretoincludethe7commasafterVout(theseskiparguments).The10nargumentisthestarttimeof10nanosecondsand40nisthestoptimeof40nanoseconds.NOTE:YoucouldalsouseTraceOptions>TraceExpressiononVoutandthenmodifytheexpressioninsteadofwritinganequationandthenplottingit.
k. Insertaplotoftheequation.Asyoucansee,the100MHztonecompareswiththeHBdataextremelywell(<0.1dBdifference).
IMPORTANTNOTE:thisstepisusedonlytoshowhowtosetupanSDDmixer(especiallythemultipliersettings).Ifyouuseothermodelsinthissamesetupforacomparison,youmaygetdifferentresults(especiallyTransient)becausesuchmodelsmayhavenon‐causalresponses.Also,delaycanbeaddedtosomefilterstoeliminatethenon‐causaleffect.
l. Savethedesignanddata.
Lab 2: System Design Fundamentals
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EXTRA EXERCISES:
1. Usingtherf_sys_phnoisedesign,runaTransientsimulationforthesystem(notusingtheSDD)andcomparetheresultswiththefsfunction.
2. GobackandreplacetheButterworthfilterwithanellipticalfiltermodelshownhereandsimulate.TrysettingdifferentrangesfortheRipplevalueortryusingthetunertoadjusttherippleparameter.Thendisplaytheresultsandlookattherippleinthepassband.Todothis,youwillhavetousethezoomcommandsonthedatadisplay.
3. Trytuningvariousparametersinthedesign.
4. EntervaluesofLOandRFrejectiontothebehavioralmixerandlookatthesimulationresults.