射频电路理论与技术-Lectrue-9-(signal-flow-graph-2)课件.ppt

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1、射频电路理论与技术2021/8/7SignalFlowGraphsandApplicationsAsignalflowgraphisaconvenienttechniquetorepresentandanalyzethetransmissionandreflectionofwavesinamicrowaveamplifier.Oncethesignalflowgraphisdeveloped,relationsbetweenthevariablescanbeobtainedusingMason’srule.Certain

2、rulesarefollowedinconstructingasignalflowgraph:1.Eachvariableisdesignatedasanode.2.TheSparametersandreflectioncoefficientsarerepresentedbybranches.3.Branchesenterdependentvariablenodesandemanatefromindependentvariablenodes.Theindependentvariablenodesaretheinciden

3、twaves,andthereflectedwavesaredependentvariablenode.4.Anodeisequaltothesumofthebranchesenteringit.2021/8/7SignalflowgraphfortheSparametersequationsSignalflowgraphofatwo-portnetwork2021/8/7Inordertoobtainthesignalflowgraphofamicrowaveamplifier,weneedtoobtainthesig

4、nalflowgraphofasignalgeneratorwithsomeinternalimpedanceandthesignalflowgraphofaloadimpedance.2021/8/72021/8/7Fortheloadimpedance,or2021/8/7Wecannowcombinethesignalflowgraphforthetwo-portnetworkwiththesignalflowgraphsofthesignalgeneratorandtheload.Theresultingsign

5、alflowgraphofamicrowaveamplifierisTodeterminetheratiooftransferfunctionTofadependenttoanindependentvariable,weapplyMason’srule–namely,2021/8/7ThetermsP1,P2,andsoonarethedifferentpathsconnectingthedependentandindependentvariableswhosetransferfunctionTistobedetermi

6、ned.Apathisdefinedasasetofconsecutive,codirectionalbranchesalongwhichnocodeisencounteredmorethanonceaswemoveinthegraphfromtheindependenttothedependentnode.Thevalueofthepathistheproductofallbranchcoefficientsalongthepath.Todeterminetheratiob1/bs,weidentifytwopaths

7、,2021/8/7ThetermsSL(1)isthesumofallfirst-orderloops.Afirst-orderloopisdefinedastheproductofthebranchesencounteredinaroundtripaswemovefromanodeinthedirectionofthearrowsbacktothatoriginalnode.First-orderloops2021/8/7ThetermsSL(2)isthesumofallsecond-orderloops.Aseco

8、nd-orderloopisdefinedastheproductofanytwonontouchingfirst-orderloops.second-orderloopsThetermsSL(3)isthesumofallthird-orderloops.Athird-orderloopisdefinedasthe