MW & RF Design of Wireless System ch10

MicrowaveandRFDesignofWirelessSystemsChapter10ReceiverDesignChapter10Receiverdesign1Thepurposeofreceiver:recoveringthedesiredsignalfromawidespectrumoftransmittingsources,interference,andnoise.§10.1ReceiverArchitectures§10.2DynamicRange§10.3SelectionofIFFrequencyChapter10Receiverdesign2§10.1ReceiverArchitectures1.ReceiverRequirements2.TunedRadioFrequencyReceiver3.DirectConversionReceiver4.SuperheterodyneReceiver5.Duplexing3Chapter10.1Receiverarchitectures4ParametersmeasuredbyEWreceivers:Frequency,pulseamplitude,pulsewidth,timeofarrival,angleofarrivalChapter10.1ReceiverarchitecturesESMsystem5BasicreceiversystemChapter10.1Receiverarchitectures6Chapter10.1ReceiverarchitecturesAccordingtothereceiverstructures,EWreceiverscanbeclassifiedas:1)Crystalvideo2)Superheterodyne3)Instantaneousfrequencymeasurement4)Compressive5)Braggcellreceivers7Chapter10.1ReceiverarchitecturesChannelizedreceiver8Chapter10.1Receiverarchitectures9TypicalradioreceiverChapter10.1Receiverarchitectures10TransceiverblockdiagramforwirelesscommunicationsChapter10.1Receiverarchitectures11TypicalmobilephonetransceiversystemChapter10.1Receiverarchitectures①Highgain:(～100dB)SpreadovertheRF,IFandbasebandstagestoavoidinstabilityoroscillation.Avoidmorethan50~60dBofgainatanyonefrequencyband.②Selectivity:itismoreeffectivetouseasharpcutoffBPFatIFstagetoselectonlythedesiredfrequencyband.③Down-conversion.④Detection.⑤Isolation.Duplexingfilter1.ReceiverRequirements12Chapter10.1Receiverarchitectures13Chapter10.1ReceiverarchitecturesFrequencyspectrumshowingvariousapplicationsandpotentilalblockers802.11b/g:2.4GHz802.11a:5GHzMobile:825-960MHz,1710-1955MHz,2010-2145MHzReceiverdesignissues:14BlockdiagramshowingpotentialleakagepathsfortheLOChapter10.1Receiverarchitectures15PathsfortransmitterleakageintothereceiverandpotentialfeedbackChapter10.1ReceiverarchitecturesResultindeseningofthereceiverbysaturatingthereceiverfront-endorcausingoscillationsItisverydifficulttointegratebothtransmitandreceivefunctionsofaduplexsystemonasinglechip16Chapter10.1ReceiverarchitecturesFrequencyspectrumshowingimageinterferenceUsingeitherfilteringorimage-rejectmixingtopologiestosolvetheproblem17①Tuningisverydifficultbecauseoftheneedtotuneseveralstagesinparallel.②Selectivityispoorbecausethepassbandofsuchfilterisfairlybroad.③Limitingtheamountofgainthatcanbeobtainedbeforeoscillation.④Increasingthecostandcomplexityofthereceiver.2.TunedRadioFrequencyReceiverDrawback:18Chapter10.1Receiverarchitectures3.DirectConversionReceiver①ForAMreception,thereceivedbasebandsignalwouldnotrequireanyfurtherdetection.②Selectivitycanbecontrolledwithasimplelow-passbasebandfilter.③GainmaybespreadthroughtheRFandbasebandstages.Characteristic:19Chapter10.1ReceiverarchitecturesBeusedinDopplerradars.LOcanbeobtainedfromthetransmitter④Itissimplerandlesscostly.⑤1/fnoisehaseffectonthesystem.⑥LOmusthaveaveryhighdegreeofprecisionandstabilitytoavoiddriftingofthereceivedsignalfrequency.20Chapter10.1ReceiverarchitecturesDirectconversionreceiver4.SuperheterodyneReceiver①AmidrangeIFallowstheuseofsharpercutofffilterforimprovedselectivity.②HigherIFgainthroughtheuseofIFAmplifier.③TuningisconvenientlyaccomplishedbyvaryingthefrequencyoftheLO,sothattheIFfrequencyremainsconstant.Characteristic:21Chapter10.1Receiverarchitectures④Decreasingtheinfluenceof1/fnoise.⑤UsingtwostagesofdownconversiontoavoidproblemofRFimagefrequency.Itisthemostpopulartype.Applications:broadcast,television,radarsystem.22Chapter10.1Receiverarchitectures5.DuplexingHalf-duplex:transmitterandreceiverwiththesamefrequencyarenotoperatingsimultaneously.TDD,bySPDT(+limiter)Full-duplex:Usingseparatetransmitandreceivefrequencybandswithbandpassfilterstoprovideduplexing.FDD,byCirculatororfilters23Chapter10.1Receiverarchitectures§10.2DynamicRangeInchapter3,DRlforsingle-carrierDRfformuti-carrier1.MinimumDetectableSignal(MDS)2.Sentivity3.DynamicRange4.AutomaticGainControl(AGC)24Chapter10.2Dynamicrange1.MinimumDetectableSignal(MDS)Theoutputsignalpoweris:S0=GSiThetotaloutputnoisepoweris:N0=GNi=kBG(TA+Te)Receivingsystem25Chapter10.2Dynamicrangemin000min00minmin000mink1oiAeASNSSSBTTGGNNSkBTFTNmin00NSTheminimumdetectableinputsignalpoweris:hastherelationshipwiththedemodulator.000bbESBnNR000minebbpSERNnB26Chapter10.2DynamicrangeIfTA=T0①Itisvalidwhentheantennatemperatureis290K,thissituationisseldomtrue.②Theminimumdetectablesignalleveldoesnotdependonthegainofthereceiver.0min00min0017410lgiSSkBTFNSdBmBFdBdBNEXAMPLE10.2,page342.27Chapter10.2Dynamicrange28Chapter10.2Dynamicrange2.Sensitivity=Thereceivervoltagesensitivitymin0min2iiSZV3.DynamicRangemaximumaallowablesignalpowerminimumdetectablesignalpowerrDRThemaximumallowablesignalpowercouldbedefinedbytheP-1orthethird-orderinterceptpoint,P3,attheinputofthereceiver.EXAMPLE10.3,page343.29Chapter10.2Dynamicrange4.AutomaticGaincontrol(AGC)①MostofgainoccurringattheIFstagebecauseofthecheaperIFAmplifier.②AvoidveryhighlevelsofgainatRFfrequencytoextendtheP-1.③Haveamoderatelevelofg