RF Analog Impairments Modeling for Communication Systems Simulation: Application to OFDM-Based Transceivers

211 Pages·2012·5.89 MB·English

by  Lydi Smaini(auth.)

RF Analog Impairments
Modeling for Communication
Systems Simulation
RF Analog Impairments
Modeling for Communication
Systems Simulation
Application to OFDM-based
Transceivers
Lydi Smaini
MarvellSwitzerland
A John Wiley & Sons, Ltd., Publication
Thiseditionfirstpublished2012
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LibraryofCongressCataloging-in-PublicationData
Smaini,Lydi,1974-
RFanalogimpairmentsmodelingforcommunicationsystemssimulation:
applicationtoOFDM-basedtransceivers/LydiSmaini.
p.cm.
ISBN978-1-119-99907-2(hardback)
1.Radio–Transmitter-receivers–Simulationmethods.2.Electromagnetic
interference.3.Signalintegrity(Electronics)4.Telecommunication
systems–Simulationmethods.5.Orthogonalfrequencydivisionmultiplexing.
I.Title.
TK7867.2.S632012
621.382–dc23
2012016441
AcataloguerecordforthisbookisavailablefromtheBritishLibrary.
PrintISBN:9781119999072
Typesetin10/12.5PalatinobyLaserwordsPrivateLimited,Chennai,India
Tomyparents,ZinaandRabah.
Tomysisters,NadineandAssia.
Tomybrothers,MalikandDalil.
Tomychildhoodfriend,Djamel.
Contents
Preface xi
Acknowledgments xiii
AbouttheAuthor xv
1 IntroductiontoCommunicationSystem-on-Chip,RFAnalog
Front-End,OFDMModulation,andPerformanceMetrics 1
1.1 CommunicationSystem-on-Chip 1
1.1.1 Introduction 1
1.1.2 CMOSTechnology 3
1.1.3 CoexistenceIssues 4
1.2 RFAFEOverview 6
1.2.1 Introduction 6
1.2.2 SuperheterodyneTransceiver 8
1.2.3 HomodyneTransceiver 10
1.2.4 Low-IFTransceiver 11
1.2.5 AnalogBasebandFilterOrderversusADCDynamicRange 12
1.2.6 DigitalCompensationofRFAnalogFront-EndImperfections 13
1.3 OFDMModulation 14
1.3.1 OFDMasaMulticarrierModulation 14
1.3.2 FourierTransformandOrthogonalSubcarriers 15
1.3.3 ChannelEstimationandEqualizationinFrequencyDomain 18
1.3.4 Pilot-Tones 20
1.3.5 GuardInterval 21
1.3.6 WindowedOFDM 21
1.3.7 AdaptiveTransmission 22
1.3.8 OFDMAforMultipleAccess 23
1.3.9 ScalableOFDMA 23
viii Contents
1.3.10 OFDMDBBArchitecture 24
1.3.11 OFDM-BasedStandards 27
1.4 SNR,EVM,andE /N DefinitionsandRelationship 27
b 0
1.4.1 BitErrorRate 27
1.4.2 SNRversusEVM 28
1.4.3 SNRversusE /N 31
b 0
1.4.4 ComplexBasebandRepresentation 32
References 34
2 RFAnalogImpairmentsDescriptionandModeling 37
2.1 Introduction 37
2.2 ThermalNoise 38
2.2.1 AdditiveWhiteGaussianNoise 38
2.2.2 NoiseFigureandSensitivity 40
2.2.3 CascadedNoiseVoltageinICDesign 41
2.2.4 AWGNinSimulations 42
2.2.5 FlickerNoiseandAWGNModeling 43
2.3 OscillatorPhaseNoise 44
2.3.1 DescriptionandImpactontheSystem 44
2.3.2 PhaseNoiseModelingintheFrequencyDomain 45
2.3.3 SimulationinTemporalDomain 49
2.3.4 SNRLimitationduetothePhaseNoise 50
2.3.5 ImpactofPhaseNoiseinOFDM 52
2.4 SamplingJitter 57
2.4.1 JitterDefinitions 57
2.4.2 SamplingJitterandPhaseNoiseRelationship 58
2.4.3 SNRLimitationduetoSamplingJitter 61
2.4.4 ImpactofSamplingJitterinOFDM 63
2.4.5 SamplingJitterModeling 63
2.5 CarrierFrequencyOffset 64
2.5.1 Description 64
2.5.2 ImpactofCFOinOFDM 65
2.6 SamplingFrequencyOffset 67
2.6.1 Description 67
2.6.2 ImpactofSFOinOFDM 68
2.7 IandQMismatch 71
2.7.1 Description 71
2.7.2 IQMismatchModeling 76
2.7.3 SNRLimitationduetoIQMismatch 76
2.7.4 ImpactofIQMismatchinOFDM 78
2.8 DAC/ADCQuantizationNoiseandClipping 79
2.8.1 SNR Limitation due to the Quantization Noise and Clipping
Level 79
Contents ix
2.8.2 ImpactofConverterClippingLevelinOFDM 82
2.8.3 DACandADCDynamicRangeinOFDM 84
2.8.4 DACandADCModeling 86
2.9 IP2andIP3:Second-andThird-OrderNonlinearities 87
2.9.1 Harmonics(Single-ToneTest) 87
2.9.2 IntermodulationDistortion(Two-ToneTest) 89
2.9.3 ReceiverPerformanceDegradationduetotheNon-linearities 92
2.9.4 ImpactofThird-OrderNonlinearityinOFDM 95
2.9.5 SimulationinComplexBaseband 98
2.10 PowerAmplifierDistortion 99
2.10.1 PAModeling 99
2.10.2 ImpactofPADistortionsinOFDM 102
References 104
3 SimulationoftheRFAnalogImpairmentsImpactonReal
OFDM-BasedTransceiverPerformance 107
3.1 Introduction 107
3.2 WLANandMobileWiMAXPHYOverview 108
3.2.1 WLAN:StandardIEEE802.11a/g 108
3.2.2 MobileWiMAX:StandardIEEE802.16e 109
3.3 SimulationBenchOverview 110
3.3.1 WiFiandWiMAXOFDMTransceiverModeling 110
3.3.2 EVMEstimationasPerformanceMetric 112
3.3.3 EVMversusSNRSimulationsinAWGNChannel 113
3.4 WiFiOFDMandMobileWiMAXSignalsPAPR 116
3.5 TransmitterImpairmentsSimulation 117
3.5.1 Introduction 117
3.5.2 DACClippingandResolution 118
3.5.3 IandQMismatch 121
3.5.4 RFOscillatorPhaseNoise 125
3.5.5 PowerAmplifierDistortion 130
3.5.6 TransmitterCompleteSimulation 133
3.6 ReceiverImpairmentsSimulation 134
3.6.1 Introduction 134
3.6.2 CarrierFrequencyOffset 135
3.6.3 SamplingFrequencyOffset 140
3.6.4 Linearity:IIP2andIIP3 146
3.6.5 IandQMismatch 154
3.6.6 RFOscillatorPhaseNoiseandReciprocalMixing 154
3.6.7 SamplingJitter 156
3.6.8 ADCClippingandResolution 158
3.6.9 ReceiverCompleteSimulation 160
3.7 AdaptiveModulationIllustration 162
x Contents
3.8 Summary 164
References 164
4 DigitalCompensationofRFAnalogImpairments 167
4.1 Introduction 167
4.2 CFOEstimationandCorrection 168
4.2.1 CFOEstimationPrinciple 168
4.2.2 CFOEstimationintheTimeDomain 170
4.2.3 CFOEstimationintheFrequencyDomain 172
4.2.4 CFOCorrection 175
4.3 SFOEstimationandCorrection 176
4.3.1 SFOEstimationPrinciple 176
4.3.2 SFOEstimation 178
4.3.3 SFOCorrection 181
4.3.4 JointSFOandCFOEstimation 181
4.4 IQMismatchEstimationandCorrection 183
4.4.1 Principle 183
4.4.2 EffectoftheChannel 186
4.4.3 SimulationResults 187
4.5 PowerAmplifierLinearization 190
4.5.1 DigitalPredistortionPrinciple 190
4.5.2 MemoryPolynomialPredistortion 191
4.5.3 PolynomialCoefficientsComputation 192
4.5.4 SimulationResults 193
4.6 Summary 196
References 197
Index 199
Preface
Moderndigitalcommunicationstransceiverscanbedecomposedintotwomainparts:
the radio frequency (RF) analog front-end, which transmits and receives the analog
signal,andthedigitalbaseband,whichisresponsibleforthedigitalsignalprocessing
(DSP) and data demodulation. The ‘‘virtual’’ frontier is delimited by the digital to
analogconversionintransmission,andbytheanalogtodigitalconversioninreception.
The digital baseband is commonly studied and simulated by communication system
and DSP engineers based on standard requirements, which specify the modulation
typeandthesystemperformanceintermsofbitorpacketerrorrate.Ontheotherhand,
the RF analog front-end specifications are often derived by the RF analog engineers
themselvesusing,forexample,Excelspreadsheetsforcalculatingsignal-to-noiseratio
(SNR) or error vector magnitude (EVM) from basic and classical formulas based on
dual-orsingle-tonetestshistoricallycomingfromlaboratorymeasurements.Actually,
theseRFanaloganalysismethodsdonottakeintoaccountthesignalspectralproperties
and the transceiver bandwidth; consequently, there is a gap between the RF analog
front-end specifications and the digital baseband simulations which often introduces
misunderstandingduringthetransceiverdesign.
Nowadays,withthegrowingcomplexityofpersonalmobilecommunicationsystems
demanding higher data-rates and high levels of integration using low-cost comple-
mentarymetaloxidesemiconductor(CMOS)technology,overallsystemperformance
has become much more sensitive to RF analog font-end impairments. Consequently,
communication system and DSP engineers have to understand and to include these
RFanalogimperfectionsintheirsimulationbenchesinordertomeasuretheirimpact
on the system performance. In addition, in deep-submicrometer CMOS technology
(nanometer)thedigitalpartofthetransceivernaturallyshrinkswiththeprocessratio
whereastheRFanalogpartremainsfairlyconstant(only10%sizereductioningood
cases). As a result, in terms of die area and thus cost reduction, the analog part
remainsthemajorbottleneckofCMOStransceiverintegrationandgenerallyrequiresa
non-negligibleredesigneffortifonewantstoreduceitsareaandpowerconsumption.
To surmount this integration issue, a new trend is to design suboptimal RF analog
xii Preface
front-ends,called‘‘dirtyRF’’inrecentliterature,andtocompensatetheirimpairments
withDSP.Designingsuch integrated transceivers requiresathorough understanding
ofthewholetransceiverchain,includingRFanalogengineeringandDSP.
TheaimofthisbookistoprovidethereaderwiththeoreticalandpracticalRFanalog
systemmodelingknowledgeandexamplesdirectlyapplicabletoadvancedtransceiver
studies and simulations. Furthermore, we endeavor to make a bridge between RF
analog designers and communication system/DSP engineers who often use different
toolsandvocabularyevenwhenspecifyingthesamething.Wetheoreticallydescribethe
impactoftheRFanalogimperfectionsonorthogonalfrequencydivisionmultiplexing
(OFDM)modulation,whichhaswidelyrecognizedadvantagesandisutilizedinlatest
generation communication systems. To illustrate the theory we present simulation
results comparing the impact of the transceiver imperfections on two well-known
deployedstandards,WiFi(802.11a/g)andmobileWiMAX(802.16e).
Theorganizationofthebookisasfollows:
• InChapter1weintroducethechallengesoftheintegrationofcommunicationsystems
on-chip,especiallythoseusingCMOStechnology.Wewillalsogiveanoverviewof
themajorRFanalogfront-endarchitectures,themainprinciplesofOFDMmodulation
whichisnowdeployedin4Gmobilecommunications,andfinallyanintroductionto
RFanalogsystemperformancemetricsandbasebandsimulation.
• Chapter 2 deals with the principal RF analog impairments encountered in commu-
nication transceivers. We describe them mathematically in order to derive models
whichcanbeincorporatedintoanysystemsimulation,andalsotostudytheirtheo-
reticalimpactonthesystemperformancewithaspecialfocusonOFDMmodulation.
• In Chapter 3, system simulation results based on WiFi and mobile WiMAX OFDM
transceiversarepresented.AlltheRFanalogimpairmentsdescribedinChapter2are
modeled and simulated in order to study their impact individually on the system
performance,bothintransmissionandreception.
• Finally, digital estimation and compensation of the RF analog impairments is
overviewedinChapter4:carrierandsamplingfrequencyoffsetsinOFDMreception,
quadratureimbalance,aswelldigitalpre-distortionintransmissionareaddressed.