波导型定向滤波器的分析与设计-(5976)

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1、ABSTRACTABSTRACTAdirectionalfilterisawell-matchedfour-portdevice，whichispopularlyusedtoseparateaoperationbandfromanotheroperationband,withlittlereflectionattheinputport.Ithasaselectivityfunctionofafilterandadirectionalcharacteristicasacoupler.Inatransmit-rece

2、ivesystemwherethetransmitterfrequencydiffersfromthereceiverfrequency,adirectionalfilterisoftenusedasacomplementarydiplexer.Awaveguidedirectionalfiltercanalsobeusedasaabsorptivefilterinhigh-powertransmitter,whichcanfilterouttheharmonicorothernoises,withlittler

3、eflectedpowerbacktohighpowergenerator.Therearemainlythreekindsofdirectionalfiltersinpracticaluse:half-wavelengthorfull-wavelengthresonatordirectionalfilters,traveling-wave-loopdirectionalfiltersandwaveguidedirectionalfilters.Thefirsttwokindscanberealizedbystr

4、ip-linesormicro-strip-lineswhichbelongtoplanestructure.Theyhaveattractivecharacteristicssuchascompact-sizeandlight-weight,however,theirapplicationsareusuallylimitedbytheirhighlossesandlowpower-handingcapabilities.Inthehighpowerorlowlossapplications,waveguided

5、irectionalfiltersarebetterchoices.Conventionalwaveguidedirectionalfiltersusuallyusecircularly-polarizedmodesinoneormorethanonecylindricalcavitieswhicharecoupledtotworectangularwaveguidesthroughcouplingholes.Theycanalsobeconstructedbyapairofdirectly-coupledcav

6、ityfilters,whicharecoupledtotworectangularwaveguidesthroughcouplingholes.Themaindisadvantageofthesetwokindsofwaveguidedirectionalfiltersisthattheiroperationbandwidthisusuallylimitedtolessthan1%,andtheirthree-dimensionalstructuresarecomplicatedforfabricationan

7、dassembling.Theresearchfocusofthisthesiswillbeonthedesignofwaveguidedirectionalfilterswithwidebandwidthsandsimplestructures.Inthisthesis,theauthorwillproposeanddesigntwowaveguidedirectionalfilters.Thefirstisabroadbanddirectionalfilter,whichincludestwoRibletco

8、uplersandtwoevanescentmodewaveguidefilters.Itcanbeusedasabroadbandcomplementaryduplexerandaabsorptivefilter.Themoreimportantapplicationsofsuchabroadbanddirectionalfilterisinthedesignofmul