WCDMA前馈功放的分析与设计(英文)-豆柴文库

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WCDMA前馈功放的分析与设计(英文)
AnalysisandDesignofWCDMAPowerAmplifier
Introduction
Wirelesscommunicationsystemshavebecomeintegralintoday'smoderneraandWCDMA(WidebandCodeDivisionMultipleAccess)isoneofsuchsystems.WCDMAisathird-generation(3G)cellularcommunicationtechnologythatprovideshigh-speedwirelessdatatransmission.PowerAmplifier(PA)playsacrucialroleintheoperationofWCDMAsystems.Ithastoprovidehighoutputpowerwhilemaintaininglinearamplificationforthetransmissionofdigitalsignals.
Inthispaper,wewillanalyzeanddesignaWCDMAPowerAmplifier.
Analysis
WCDMAspecificationsrequireapoweramplifierwithhighlinearityandefficiency.Thepoweramplifiershouldprovidehighoutputpowerwhilemaintaininglowdistortion.WCDMAsystemsrequireaconstantenvelopesignalwithhighpeak-to-averagepowerratio(PAPR).Thisnecessitatestheuseofaspecificamplifierarchitecture.
ThemostsuitableamplifierarchitectureforWCDMAsystemsistheClass-Eamplifierbecauseofitshighefficiencyandlinearity.TheClass-EamplifierisaswitchingamplifierthatusesaresonantcircuittomaintainanalmostconstantvoltageacrosstheLoadResistance(RL)duringswitching.Theswitchoperatesatafrequencyf,whichistheresonantfrequencyoftheresonantcircuit.TheoutputvoltageoftheamplifierisasquarewavewithitsamplitudeequaltothesupplyvoltageVCC.Thewaveformisfilteredtoproduceasinusoidalwaveformthathashighlinearity.
Design
ThedesignoftheWCDMApowerAmplifierinvolvestheselectionofcomponentsthatwillmeetthespecificationsrequired.Thecomponentsincludethetransistor,resonantcircuit,biasingnetwork,matchingnetwork,andsupplyvoltage.
TransistorSelection:Thetransistoristheheartoftheamplifierandshouldbecarefullyselected.Thetransistorshouldhavehighgain,lownoisefigure,highbreakdownvoltage,andhigh-frequencyperformance.Thechoiceoftransistordependsontherequiredoutputpowerandfrequency.ForWCDMAsystemsoperatingat2.14GHz,asuitabletransistorwouldbetheMRF901.
ResonantCircuit:Theresonantcircuitisusedtomaintainanalmostconstantvoltageacrosstheloadresistancewhileswitching.TheresonantcircuitshouldhaveaQualityFactor(Q-value)that