PRINTED-CIRCUIT REALIZATION OF A TAPPED COMBLINE BANDPASS FILTER .pdf

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1、PRINTED-CIRCUITREALIZATIONOFATAPPEDCOMBLINEBANDPASSFILTERChing-KuangC.TzuangandWen-TengLoInstituteofCommunicationEngineeringNationalChiaonngUniversityNo.75,Po-AiStreet,Hsinchu,'hiwan,R.O.C.AbstractThedesignofatappedcomblinebandpassfilterrealizedbyplanarorquasi-planarcommensuratelengthtran

2、smissionlinesispresented.Thedesignproceduretakesintoaccountthecompositeeffectsofmultiplequasi-TEMmodes,couplingsbetweennon-adjacentmicrostrips,andcoverheight.An8-to-12GHzbandpassprototypeisbuiltandtested.Itsperform-anceagreesfavorablywiththetheoreticalresult.Fig.1ConventionalTappedComblin

3、eFilter(Sim-plifiedDrawing)I.IntroductionComblinefilterisoneofthewidelyFig.1arenotcommensurate.usedbandpassfiltersemployedinmanycommunicationsystems.ItfeaturesmanyAsthefrequencyofoperationin-usefulproperties[11andbecomesevencreases,saybeyond20GHz,theconven-morecompactandeasytofabricatewhe

4、ntionalcomblinefilterbecomestoosmalltousingtapped-linearrangementatinput/machineit.Analternativefilterconfigura-output[2].AsimplifieddrawingofFig.1tionshowninFig.2istheuseofmicrostripshowsavariantofcomblinefilterinalinesintegratedonaprinted-circuitboard.tappedfashion.Todesignthefiltershow

5、nThisseemstosolvethedifficulitysinceinFig.1,oneneedstomakecertainapproxi-typicalphotolithographytechniquecanmationsduetothefactthattheexacteasilyhandlethetolerancerequirementtheoryofcomblinefiltersynthesisonlyneededformakingthefilter.However,worksforcommensuratelengthTEM-anotherproblemsur

6、faces.Thisistheexis-modeelements[3].Here,however,thetenceofmultiplequasi-TEMmodesassoci-exactequivalentcircuitforthetappedatedwiththeparallelmicrostriplinesusedcombline[4]andthelumpedelementsininFig.2.Thusamoreelaborateapproachto131CH2848-0/90/0000-0131$01.~01990IEEE1990IEEEMTT-SDigesttac

7、klethisproblemisneeded.matrixoftheequivalentcircuit,weoptimizeanerrorfunctionintheleast-squareerrorSectionI1describesaniterativedesignsensebyadjustingthevaluesofW1,Sl,proceduretodeterminethestructuralpara-W2,S2,...inFig.2untilthesolutionscon-metersofFig.2.SectionI11