无线系统的微波与射频设计课件.ppt

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1、MicrowaveandRFDesignofWirelessSystemsChapter10ReceiverDesignDr.ZhangYonghongThepurposeofreceiver:recoveringthedesiredsignalfromawidespectrumoftransmittingsources,interference,andnoise.§10.1ReceiverArchitectures§10.2DynamicRange§10.3SelectionofIFFrequency§10.1ReceiverAr

2、chitectures1.ReceiverRequirements2.TunedRadioFrequencyReceiver3.DirectConversionReceiver4.SuperheterodyneReceiver5.Deplexing①Highgain:SpreadovertheRF,IFandbasebandstagestoavoidinstabilityoroscillation.Avoidmorethan50~60dBofgainatanyonefrequency.②Selectivity:itismoreeff

3、ectivetouseasharpcutoffBPFatIFstagetoselectonlythedesiredfrequencyband.③Down-conversion.④Detection.⑤Isolation.Duplexingfilter1.ReceiverRequirements①Tuningisverydifficultbecauseoftheneedtotuneseveralstagesinparallel.②Selectivityispoorbecausethepassbandofsuchfilterisfair

4、lybroad.③Limitingtheamountofgainthatcanbeobtainedbeforeoscillation.④Increasingthecostandcomplexityofthereceiver.2.TunedRadioFrequencyReceiverDrawback:3.DirectConversionReceiver①ForAMreception,thereceivedbasebandsignalwouldnotrequireanyfurtherdetection.②Selectivitycanbe

5、controlledwithasimplelow-passbasebandfilter.③GainmaybespreadthroughtheRFandbasebandstages.Characteristic:BeusedinDopplerradars.LOcanbeobtainedfromthetransmitter.④Itissimplerandlesscostly.⑤1/fnoisehaseffectonthesystem.⑥LOmusthaveaveryhighdegreeofprecisionandstabilitytoa

6、voiddriftingofthereceivedsignalfrequency.4.SuperheterodyneReceiver①AmidrangeIFallowstheuseofsharpercutofffilterforimprovedselectivity.②HigherIFgainthroughtheuseofIFAmplifier.③TuningisconvenientlyaccomplishedbyvaryingthefrequencyoftheLO,sothattheIFfrequencyremainsconsta

7、nt.Characteristic:④Decreasingtheinfluenceof1/fnoise.⑤UsingtwostagesofdownconversiontoavoidproblemduetoLOstability.Itisthemostpopulartype.Applications:broadcast,television,radarssystem.5.DeplexingHalf-duplex:transmitterandreceiverwiththesamefrequencyarenotoperatingsimul

8、taneouslyTDD,bySPDT(+limiter)Full-duplex:Useingseparatetransmitandreceivefrequencybandswithbandpassfilterstoprovidedu