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Integrated Frequency Synthesizers for Wireless Systems
Theincreasinglydemandingperformancerequirementsofcommunicationssystems,aswellasprob-
lemsposedbythecontinuedscalingofsilicontechnology,presentnumerouschallengesforthedesign
offrequencysynthesizersinmoderntransceivers.
Thisbookcontainseverythingyouneedtoknowfortheefficientdesignoffrequencysynthesizers
fortoday’scommunicationsapplications.Ifyouneedtooptimizeperformanceandminimizedesign
time,youwillfindthisbookinvaluable.
Usinganintuitiveyetrigorousapproach,theauthorsdescribesimpleanalyticalmethodsforthe
designofphase-lockedloop(PLL)frequencysynthesizersusingscaledsiliconCMOSandbipolar
technologies.Theentiredesignprocess,fromsystem-levelspecificationtolayout,iscoveredcom-
prehensively.Practicaldesignexamplesareincluded,andimplementationissuesareaddressed.
Akeyproblem-solvingresourceforpractitionersinintegrated-circuitdesign,thebookwillalsobe
ofinteresttoresearchersandgraduatestudentsinelectricalengineering.
AndreaLacaitaisFullProfessorofElectricalEngineeringatthePolitecnicodiMilano,Italy.
SalvatoreLevantinoisAssistantProfessorofElectricalEngineeringatthePolitecnicodiMilano.
CarloSamoriisAssociateProfessorofElectricalEngineeringatthePolitecnicodiMilano.
Integrated Frequency
Synthesizers for
Wireless Systems
Andrea Lacaita, Salvatore Levantino, and
Carlo Samori
PolitecnicodiMilano,Italy
CAMBRIDGEUNIVERSITY PRESS
Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo
Cambridge University Press
The Edinburgh Building, Cambridge CB2 8RU, UK
Published in the United States of America by Cambridge University Press, New York
www.cambridge.org
Information on this title: www.cambridge.org/9780521863155
© Cambridge University Press 2007
This publication is in copyright. Subject to statutory exception and to the provision of
relevant collective licensing agreements, no reproduction of any part may take place
without the written permission of Cambridge University Press.
First published in print format 2007
ISBN-13 978-0-511-29521-8 eBook (EBL)
ISBN-10 0-511-29521-9 eBook (EBL)
ISBN-13 978-0-521-86315-5 hardback
ISBN-10 0-521-86315-5 hardback
Cambridge University Press has no responsibility for the persistence or accuracy of urls
for external or third-party internet websites referred to in this publication, and does not
guarantee that any content on such websites is, or will remain, accurate or appropriate.
Contents
Preface pagevii
Acknowledgments viii
1 Localoscillatorrequirements 1
1.1 AMandPMsignals 2
1.2 Effectofphasenoiseandspurs 6
1.3 Frequencyaccuracy 9
1.4 Switchingspeed 12
1.5 References 12
2 Phase-lockedloops 14
2.1 Basics 14
2.2 PLLforfrequencysynthesis 23
2.3 Discrete-timeandnon-linearityeffects 32
2.4 Spectralpurity:spursandphasenoise 38
2.5 References 47
3 Fractional-NPLLs 49
3.1 Beyondtheinteger-Napproach 49
3.2 Fractional-Ndivision 50
3.3 (cid:1)(cid:2)controlofdivisionfactor 58
3.4 (cid:1)(cid:2)fractional-NPLL 65
3.5 References 72
4 Electronicoscillators 74
4.1 Introduction 74
4.2 PrinciplesofLCoscillators 74
4.3 Single-transistoroscillators 82
4.4 Differentialoscillators 91
4.5 References 101
5 Noiseinoscillators 103
5.1 Introduction 103
5.2 Linearandtime-invariantmodel 103
5.3 Noise–powertrade-offandscalingissues 105
v
vi Contents
5.4 Time-variantmodels 108
5.5 Applicationtosomepracticalcases 116
5.6 Additionalissuesinlow-phase-noisedesign 131
5.7 References 131
6 Reactivecomponentsinoscillators 133
6.1 Introduction 133
6.2 Integratedinductors 133
6.3 Inductortopologies 141
6.4 Integratedvaractors 146
6.5 Switchedtuning 153
6.6 References 155
7 Noiseup-conversioninVCOs 157
7.1 Introduction 157
7.2 Tuningcurveandsensitivitycoefficients 157
7.3 Noiseup-conversionfromvaractors 161
7.4 Topologiesandmethodstominimizeforup-conversion 166
7.5 Othermechanismsofnoiseup-conversion 175
7.6 References 180
8 Frequencydivision 182
8.1 Introduction 182
8.2 Digitalfrequencydividers 182
8.3 Programmabledividers 188
8.4 Dual-modulusprescalers 193
8.5 Circuitimplementation 198
8.6 Noiseindigitaldividers 204
8.7 References 209
9 Phasecomparison 211
9.1 Introduction 211
9.2 Phasecomparisonpath 211
9.3 Phase/frequencydetectors 214
9.4 Chargepump 224
9.5 Phase-detectionnoise 229
9.6 References 234
Index 236
Preface
The phase-locked loop (PLL) concept is about 70 years old and a wealth of literature is
alreadyavailableonthesubject.SomeonemaythereforeaskwhyanotherbookaboutPLLs.
The first reason is related to the specific application considered here, namely the sili-
conintegrationoffrequencysynthesizers.Classicaltextsdonotdealindepthwithissues
related to the design of frequency synthesizers in modern transceivers. In particular, the
designguidelinesandtheperformanceofsomeimportantbuildingblocksandtheirimpact
onthewholesystemaresometimesbarelymentioned.Theattempt,here,hasbeeninstead
toprovideabroaddescriptionofthemosttypicalcircuittopologiesofvoltage-controlled
oscillators,frequencydividersandphaseandfrequencydetectors,andtodiscusstheirper-
formanceintermsofpowerconsumption,phasenoise,spurs,andsoforth.Achapterisalso
devotedtointegratedpassivecomponents,suchasvaractorsandinductors,sincetheability
tooptimizetheirperformancejudiciouslyisbecomingakeyskillrequiredoftheRFdesigner.
ThesecondreasonisthatthebookattemptstoprovideanalternativeapproachtoPLL
theory and design. After years of research and study on the subject, the authors propose
an analysis methodology that is both rigorous and intuitive. The ability to simplify the
picture and to address schematicallythe impact of complex, often non-linear, effects is a
fundamentalskillofanygoodengineer.ThePLLisagoodtrainingexampleforthedesigner.
In this respect, the book provides many examples of models, starting from a schematic
and simplified description of the circuit operation and then leading to estimates, which
arecomparedwithsimulationresults.Theseexamplesareintendednotonlytoprovidea
deeperinsightintocomplexandintriguingeffects,butalsotoencouragestudentsandyoung
analoguedesignerstokeepexercisingtheabilitytofigureouttheconsequencesoftechnical
choicesbeforeperformingcircuitsimulations.
ThebookstartswiththreechaptersaddressingthePLLasasystem.Chapter1pointsout
thetypicalrequirementsofthefrequencysynthesizerinRFsystems.Chapter2coverssome
PLLbasics.ItdoesnotdealwiththewholePLLtheory,whichisanalyzedindepthinmany
classical books. The chapter highlights only the concepts needed for understanding the
subsequenttopics.Chapter3finallyanalyzesfractional-divisionPLLs,whichareseldom
discussedinothertexts.
Chapters4to9arethendevotedtodiscussingindetailthedesignissuesrelatedtothePLL
buildingblocks.Chapters4to7dealwithvoltage-controlledoscillatorsandtheirpractical
implementationsinbipolarandCMOStechnologies,includingresonatordesignandlayout.
Chapters8and9arefocusedonthedesignofprogrammabledividersandphase-comparison
circuits,includingissuesrelatedtonon-linearities.
vii
Acknowledgments
Theresearchactivitybehindthisbookhasbeeninprogressformorethantenyears.Itwas
madepossiblethankstothefinancialsupportprovidedbytheItalianMinistryofUniversities
andResearchandbyindustry.Inthisrespect,manythanksgotoMarioPaparoofSTMi-
croelectronics (Catania, Italy), Maurizio Pagani of Ericsson Lab (Vimodrone, Italy), and
toMihaiBanuofthe(formerly)SiliconCircuitResearchDepartmentofBellLaboratories
(MurrayHill,NJ),fortheirstrongsupport.
Theauthorsareindebtedtoalltheirpastgraduatestudents,MrFrancescoVilla,DrAlfio
Zanchi,DrAndreaBonfanti,DrLucaRomano`,DrStefanoPellerano,DrMarcoMilaniand
DrLuigiPanseri,whosharedtheexcitementsofthisresearchandcontributedtomostof
theunderstandingreportedinthefollowingpages.Theauthorsarealsoextremelygrateful
to their current Ph.D. students, Paolo Madoglio and Marco Zanuso, who worked out the
examples and the simulations, providing critical revisions of the text. Clearly, only the
authorsareresponsibleforanyerrorsthatmaystillbepresent.
viii
