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THIF-34DigitalGenerationofRFSignalsforWirelessCommunicationsWithBand-PassDelta-SigmaModulationJ.Keyzer,J.Hinrichs,A.Metzger,M.Iwamoto,I.Galton,andP.Asbeck-UniversityofCalifornia,SanDiego,LaJolla,CA92093-0407ABSTRACT-Thispaperdemonstratesahighspeeddigitalstreamswhich,overaspecifiedfrequencyband,aretechniquetoproducebinary(digital)signalsthatencodecapableofmeetingtherequirementsforCDMAsystemsrepresentativeRFsignals(withtimevaryingenvelope)as(IS-95).neededforwirelesscommunications.Specifically,itshowsthatIS-95formatCDMAsignalscanbegeneratedwithasinglebitdigitaldatastreamat3.6Gb/S.Thetechniqueuses11.SIGNALGENERATIONAPPROACHband-passdelta-sigmamodulationsothatthequantizationnoiseisshapedoutofthefrequencybandofinterest.ThisTransmittersimplementedwithanalogandRFapproachpointsthewaytosingle-chip,DSP-basedtransmitters,usedinconjunctionwithswitchingmodepowerelectronicstypicallyincludeavarietyoffunctions.Inamplifiersandsimpleanalogfilters,toimplementallthemanycases,thein-phase(I)andquadrature(Q)basebandfunctionsofawirelesstransmitter.signals,arecomputedatbasebandfrequencieswithdigitalsignalprocessing(DSP),andsubsequentlyconvertedtoI.INTRODUCTIONtheanalogdomainwithdigital-to-analogconverters(DACs)ofmoderateresolution(4-12bits).ThesignalsAsCMOS-basedDSPperformanceincreasesanditscostaresubsequentlyupconvertedtoRF,oftenviaanintermsofpowerdissipationandcircuitareadrops,thereintermediatefrequencystage,usingquadraturemixersandisincreasingopportunitytoimplementRFfunctionswithfilters.Avariablegainstageisoftenincluded.Finally,DSP.AccordingtotheITRSRoadmap,theclockrateofthetransmittercomprisesapoweramplifierandanoutputhighperformancechipswillreach3.5GHzin2005.Thiscoupler.impliesthatCMOSwillhaveasignificantroleinInthispaperwedemonstrateanalternativemicrowavefunctions,notjustasanalog-based“RFCMOS”,butintheformofdigitalcircuits.architecture,whichpotentiallyiseasiertoimplement.DSPbasedsystemspotentiallycanprovidemanyThereisnoneedforahighresolutionD/Aconv
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