Radio-Frequency Digital-to-Analog Converters Radio-Frequency Digital-to-Analog Converters Implementation in Nanoscale CMOS Morteza S. Alavi Jaimin Mehta Robert Bogdan Staszewski AMSTERDAM (cid:129) BOSTON (cid:129) HEIDELBERG (cid:129) LONDON NEW YORK (cid:129) OXFORD (cid:129) PARIS (cid:129) SAN DIEGO SAN FRANCISCO (cid:129) SINGAPORE (cid:129) SYDNEY (cid:129) TOKYO Academic Press is an imprint of Elsevier AcademicPressisanimprintofElsevier 125LondonWall,LondonEC2Y5AS,UnitedKingdom 525BStreet,Suite1800,SanDiego,CA92101-4495,UnitedStates 50HampshireStreet,5thFloor,Cambridge,MA02139,UnitedStates TheBoulevard,LangfordLane,Kidlington,OxfordOX51GB,UnitedKingdom ©2017ElsevierLtd.Allrightsreserved. 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LibraryofCongressCataloging-in-PublicationData AcatalogrecordforthisbookisavailablefromtheLibraryofCongress BritishLibraryCataloguing-in-PublicationData AcataloguerecordforthisbookisavailablefromtheBritishLibrary ISBN978-0-12-802263-4 ForinformationonallAcademicPresspublications visitourwebsiteathttps://www.elsevier.com/ Publisher:JoeHayton AcquisitionEditor:TimPitts EditorialProjectManager:CharlotteKent ProductionProjectManager:NickyCarter CoverDesigner:VictoriaPearson TypesetbySPiGlobal,India Preface The work on this RFDAC idea can be traced all the way back to 2001 when our small group at Texas Instruments (TI) was busy inventing new digital methods of realizing the traditional analog-intensive RF transceiver functions. The design of our first digital RF processor (DRP) for Bluetooth in 130nm CMOS was coming to an end but we still needed to obtain some form of RF power regulation so that the transmitter (TX) would not produce too little or too much RF power. Hence, we added a few other transistors parallel to the main transistor of the switched- mode (thus, digital!) power amplifier operating in class-E mode (theoretically, up to 100% efficient!). Little did we know that those extra transistors would become extremely handy when another group from TI-Israel asked us to add amplitude modulation(AM)totheoriginalfrequency-modulated(FM)Bluetoothsignalforthe new extended data rate mode. The fully digital vector modulation (AM combined with FM) could not be made any much simpler: We just expanded the number of transistors from 8 to 256 to get the sufficient AM resolution in addition to the fine frequency resolution from an all-digital phase-locked loop (ADPLL), which was invented a couple of years earlier in the same DRP group as part of my part-time PhD research. That SoC went into high-volume production in 90nm and then in 45nm CMOS, while we got busy at applying these newly invented techniques to cellularstandards.EnterJaiminMehta,whojoinedmyTXDRPgrouptoworkout preciselyallthesystem,architectural,andcircuitsissuesaswellasthoserelatedto calibration and compensation for high-volume production of cellular radios. Given the pioneering work and enormous amount of research issues solved throughout this cycle, Jaimin was able to turn his full-time industrial work into a PhD thesis guidedbymyoldadvisorfromnearbyUniversityofTexasatDallas,ProfessorPoras T.Balsara.Chapters2–5andAppendixAaretheoutcomeofthatindustrialwork. AfterIlefttheUSindustryforacademiainEuropein2009,Ihadplentyoftime tothinkaboutfutureapplicationsofRFDACs.Andthefuturelookedunmistakably broadband.Itwasclearthatthepolartopologywouldcometoacrashinghaltdueto its>10×bandwidthexpansion.EnterMortezaAlavi,hewasthenanewbright-eyed PhDstudentatDelftUniversityofTechnology,extremelyhungryfornewknowledge and eager to prove himself with almost impossible tasks. He took upon himself to adapt the polar RFDAC approach to the in-phase/quadrature (I/Q) topology, which wouldentirelyavoidthatpeskybandwidthexpansion.InthenextfourPhDyears,he workedfuriouslyatsolvingalltheissuesandthenetresultisthatwecannowdirectly gofrom2×13I/Qbitsofthedigitalbasebandsignalto150MHzwideband23dBm ofoutputRFpowerwith1024-QAMconstellation.Chapters6–12andAppendixB aretheoutcomeofhisresearchwork. My coauthors and I strongly believe in the huge potential of RFDACs not only incommercialapplicationsbutalsoasanavenueforfurtheracademicresearch.Our belief seems to be shared with our collaborators and industrial partners. We would like to sincerely thank all our collaborators and supporters, as well as critics, at xi xii Preface TI and Delft University of Technology who have helped to turn the idea of digital RFmodulationintoareality.Iwouldliketoconcludewithastatementfrommydear TImentor,Dr.BillKrenik:“Thebestisyettocome.” RobertBogdanStaszewski (onbehalfofcoauthors,MortezaS.AlaviandJaiminMehta) Dublin October2016 Acknowledgment TheauthorsacknowledgehelpfromthefollowingPhDstudentsinfindingtyposand minormistakesduringfinalproofreading:MiladPiri,FeifeiZhang,andKaiXu. xiii Acronyms 1D one-dimensional 2D two-dimensional ADC analog-to-digitalconverter ADPLL all-digitalPLL AM amplitudemodulation balun balanced-unbalanced BER biterrorrate CML current-modelogic CMOS complementarymetal-oxide-semiconductor CORDIC coordinaterotationdigitalcomputer DAC digital-to-analogconverter DAT distributedactivetransformer DC directcurrent DCO digitallycontrolledoscillator DNL differentialnonlinearity DPA digitallycontrolledpoweramplifier DPD digitalpredistortion DRAC digital-to-RF-amplitudeconverter DSP digitalsignalprocessing EDGE enhanceddataratesforGSMevolution ESD electrostaticdischarge EVM errorvectormagnitude FFT fastFouriertransform FIR finiteimpulseresponse GSM globalsystemformobilecommunications I in-phase IC integratedcircuit IQ I/Qvector ISI intersymbolinterference LO localoscillator LPF low-passfilter LSB leastsignificantbit LTE long-termevolution MSB mostsignificantbit NF noisefigure OFDM orthogonalfrequency-divisionmultiplexing OSR oversamplingratio PA poweramplifier PAPR peak-to-averagepowerratio PLL phase-lockedloop PM phasemodulation xv xvi Acronyms PSD powerspectraldensity PVT process,voltage,andtemperature Q quadrature-phase QAM quadratureamplitudemodulation QPSK quadraturephase-shiftkeying RF radiofrequency RF-DAC RFdigital-to-analogconverter RMS rootmeansquare RRC rootraisedcosine RX receiver SAW surfaceacousticwave SDT software-defined-transmitter SNR signal-to-noiseratio SRAM staticrandomaccessmemory SRC sample-rateconverter TDD time-divisionduplexing TX transmitter UART universalasynchronousreceiver/transmitter VCO voltagecontrolledoscillator VSA vectorsignalanalyzer VSWR voltagestandingwaveratio WCDMA widebandcodedivisionmultipleaccess WLAN wirelesslocalareanetwork ZOH zero-order-hold CHAPTER 1 Introduction CHAPTER OUTLINE 1.1 TheConventionalRFRadio................................................................. 2 1.2 Motivation..................................................................................... 4 1.3 TheBookObjectives......................................................................... 6 1.3.1 SystemSimulationofWCDMABasebandData........................... 6 1.3.2 SomeImportantFigures-of-MeritinRFTransmitters.................... 8 1.4 AnalogVersusDigitalRFTransmitters.................................................... 9 1.5 Analog-IntensiveRFTransmitters.......................................................... 9 1.6 DigitallyIntensiveRFTransmitters........................................................ 12 1.7 NewParadigmofRFDesigninNanometer-ScaleCMOS............................... 13 1.8 All-DigitalPolarTransmitter................................................................ 14 1.9 All-DigitalI/QTransmitter................................................................... 16 1.10 Conclusion..................................................................................... 18 1.11 BookOutline................................................................................... 19 Consumerelectronicdevicessuchassmartphones,tablets,andlaptopsareconstantly evaluated against three key criteria: low-cost, high-power efficiency, and support of multimode/multiband communication standards such as Wi-Fi or wireless LAN (IEEE 802.11) [1], Bluetooth [2], GNSS,1 second-generation (2G) cellular using GSM,third-generation(3G)cellularusingWCDMA[3],andfourth-generation(4G) cellularusingeitherofWiMAXor3GPPLTE[4,5].Thesegadgetdevicescomprise a myriad of IC chips to perform an extensive number of distinct functions such as multimedia streaming and gaming as well as supporting the aforementioned communicationstandards.Asanexampleofcontemporarygadgetdevices,Fig.1.1 illustrates the mainboard of a smartphone, for example, the iPhone 5. It consists of anapplicationprocessor(AP)unit,subscriberidentificationmodule(SIM)cardslot, 1GNSSistheabbreviationofglobalnavigationsatellitesystem.ItincludesAmerican’sGPS,Russian’s GLONASS,EuropeanUnion’sGalileo,andChina’sBeidounavigationsystem. Radio-FrequencyDigital-to-AnalogConverters.http://dx.doi.org/10.1016/B978-0-12-802263-4.00001-5 1 ©2017ElsevierLtd.Allrightsreserved. 2 CHAPTER 1 Introduction Multiband/ LTE modem/ SIM card Mode RF TR. GPS slot Apple A6 AP Sensors GSM/GPRS/EDGE PA Memory/ Audio RF ANT. SW. LTE P.M. NAND flash Class-D PA WCDMA PA/ CDMA PA LTE PA/ Power Combo chip : Duplexer LTE-13-PA Duplexer management Wi-Fi/ Bluetooth/FM FIG.1.1 ThefrontandrearmainboardofiPhone-5. CourtesyofAppleInc. NAND flash memory, power management unit, Class-D audio amplifier, and, most significantly, a number of RF transceiver modules that support today’s universal communication standards such as GSM, CDMA, Wi-Fi/Bluetooth/FM, GPS, and LTE in combination with its power management unit. Over the past two decades, therehavebeentremendouseffortstodesignRFradiosthatwillaffordanopportunity toaddressthelow-power,low-cost,andextremelypower-efficientdemandsand,yet, theyhavealsoemployedinventivetransceiverarchitectures. 1.1 THE CONVENTIONAL RF RADIO AsdepictedinFig.1.2A,aconventionalRFtransceiverconsistsofabasebandDSP unit,TX,andRX[6,7].Thetransmitterperformsinthefollowingmanner:Thean- ticipatedtransmittedinformationsuchasvoice,video,ordigitaldataliketext/images areinitiallydigitallyprocessed,thenencoded,andsubsequentlyappliedtoaDACin order to convert the digital data to their corresponding analog counterparts. Due to the fact that these analog signals comprise unwelcome noise and spectral replicas, the transmitter utilizes a low-pass filter (LPF) to reduce those undesirable artifacts. The filtered analog signals are subsequently mixed with an RF LO utilizing an