外文翻译之滤波器外文原文及翻译.docx

外文翻译之滤波器外文原文及翻译.docx

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外文翻译之滤波器外文原文及翻译

Thisinventionrelatestomechanicalwavefiltersandmoreparticularlytothosewhichcompriseoneormoretransversemembersadaptedforflexuralvibration.

Anobjectoftheinventionistoreducetheminimumwidthoftransmissionbandobtainableinamechanicalwavefilterwhichemploysatransverseflexuralvibratorymember.

Otherobjectsoftheinventionaretosimplifythemechanicalstructureandreducethecostoffiltersofthistype.

Oneformofmechanicalwavefiltercomprisesacentralrodofacousticmaterialandoneormorecentrallylocatedtransversemembersadaptedtobesetintoflexuralvibrationwhenlongitudinalvibrationsareimpresseduponanendoftherod.Foragivenrod,thewidthofthetransmissionbanddecreasesasthemassofthetransversemembersisincreased.Peaksofattenuationoccurattheantiresonantfrequenciesofthetransversemembers,andthesepeaksareusuallylocatedclosetothebandlimitstoobtainsharpcut-offs.

Heretofore,thetransversemembershavebeenmadeintheformofcrossbars.Theflexuralantiresonanceofabarisdirectlyproportionaltoitswidthandinverselyproportionaltothesquareofitslength.Sincetheantiresonantfrequencyisfixed,toincreasethemass,andtherebynarrowtheband,thewidthofthebarmaybeincreasedbyafactorKanditslengthincreasedatthesametimebythesquarerootofK.However,apointisreachedatwhichtheratioofthewidthtothelengthissolargethatthebarwillnolongervibratesatisfactorilyintheflexuralmode.Thereis,therefore,afairlydefinitelimitontheminimumbandwidthobtainablewithfiltersusingcrossbars.

Inaccordancewiththepresentinventionthislimitationonminimumwidthofbandisovercomebyusingaflexurallyvibratingdisc,mountedatitscenter,asthetransversemember.Byusingadiscthemassisgreatlyincreasedandthereforeamuchnarrowerbandmaybeobtained.Asinglediscwillprovideapeakofattenuationeitheraboveorbelowtheband.Twodiscslocatednearthemid-pointofthecentralrodandclosetogetherwillprovideapeakaboveandapeakbelowtheband.Thecentralrodhasasmallcross-sectionaldimensionscomparedtoitslength,whichisapproximatelyequaltoahalfwave-lengthatafrequencywithintheband.

Thenatureoftheinventionwillbemorefullyunderstoodfromthefollowingdetaileddescriptionandbyreferencetotheaccompanyingdrawing,inwhichlikereferencecharactersrefertosimilarpartsandinwhich:

Fig.1isaperspectiveviewofamechanicalwavefilterinaccordancewiththeinventionemployingasingledisc,and

Fig.2isaperspectiveviewofatwo-discfilter.

Takingupthefiguresinmoredetail,Fig.1showsamechanicalwavefilterinaccordancewiththeinventioncomprisingacentralrod1ofcircularcrosssectionandatransversedisc2，bothmadeofsuitableacousticmaterial.ThediameterAoftherod1issmallcomparedtoitslengthB,whichisapproximatelyahalfwave-lengthatacut-offfrequency.Thedisc2hasadiameterCandthicknessDandiscentrallymountednearthecenteroftherod1.Longitudinalvibrationsimpresseduponanendofthebar1byasuitabledrivingdevice,representeddiagrammaticallybythebox3showninbrokenoutline,willcausethedisc2tovibrateintheflexuralmode.Thelongitudinalvibrationsoftherod1maybepickedupattheotherendofthefilterbysomesuitabledevice,representedbythebox4showninbrokenoutline.Apeakofattenuationwilloccurateachfrequencyatwhichthedisc2isantiresonant.ThedimensionsCandDofthedisc2are,therefore,soproportionedthatthefirstflexuralantiresonancefl,givenapproximatelybythefollowingformula,occursatafrequency,usuallynearabandlimit,atwhichapeakisdesired:

（1）

whereCandDareincentimeters,Misthedensityofthematerial,PisPoisson'sratioandYisYoung'smodulus.Ifflisonthelowersideofthetransmissionband,thelengthBoftherod1ismadeapproximatelyequaltoahalfwavelengthattheuppercut-offfrequency.Ifflisabovetheband,Bismadeapproximatelyequaltoahalfwave-lengthatthelowercut-off.

Iftwopeaksofattenuationaredesired,oneoneithersideofthebandandclosetothebandlimits,thestructureshowninFig.2maybeused.Thefiltercomprisesacentralrod1andtwotransverse,centrallymounteddiscs5and6,locatedclosetogetheroneoneithersideofthecenteroftherod1.Oneofthediscshasitsfirstflexuralantiresonanceatafrequencyclosetoonelimitofthebandandtheotherdischasitsfirstflexuralantiresonanceclosetotheotherlimitoftheband.InthiscasethelengthBoftherod1isapproximatelyequaltoahalfwavelengthatthe-bandfrequency.

InmechanicalfiltersofthetypeshowninFigs.1and2,employingtransverseimpedancemembers,foragivenrod1thewidthofthebanddecreaseswithanincreaseinthemassofthetransversemembers.Theuseofdiscs,suchas2,5and6,forthesemembersallowstheirmasstobegreatlyincreasedascompared,forexample,withcrossbars,andthereforeamuchnarrowerbandmaybeobtained.Theformerlimitontheminimumbandwidthobtainablewithfiltersusingtransversemembersisthusgreatlyloweredinthedisc-typefiltersofthepresentinvention.Anotherdistinctadvantageofthedisc-typefilterisitsmechanicalsimplicity.Thefiltermay,forexample,bemadefromasinglepieceofmetalandcheaplyturnedoutonalathe.

TheimageimpedanceZofthefilter,whichshouldmatchtheimageimpedanceofthedrivingmeansatthemid-bandfrequency,isgivenbytheformula:

（2）

wherewistheangularfrequency,jisthequadrantaloperator,Visthevelocityofpropagation,equaltothesquarerootoftheratioofYtoM,Z0isthecharacteristicimpedanceoftherod1andZDistheimpedanceofthedisc2,forthefilterofFig.1,orthesumoftheimpedancesofthetwodiscs5and6,forthefilterofFig.2.Thisimageimpedanceisofatypewhichcanbereadilymatchedbyadrivercomprisingapiezoelectriccrystalattachedatitsendtoanendoftherod1.

Thefilterwillhaveatransmissionbandbelow,andoneormorebandsabove,theprincipalbandwhichhasbeenhereconsidered.Theseextraneousbands,ifobjectionable,maybeeliminatedbyattenuationprovidedbythedrivingmeans,whichshouldbedesignedtohaveatransmissionbandcoinciding，withtheprincipalbandofthemechanicalfilter.Thediscriminationofthefiltermay,ofcourse,beincreaseddyconnectingintandemtwoormoresectionsofthetypeshowninFig.1orFig.2.

Whatisclaimedis:

1.Amechanicalwavefilterfortransmittingabandoffrequenciescomprisingarodandatransversediscbothmadeofacousticmaterial,saidrodhavingalengthapproximatelyequaltoahalfwave-lengthatafrequencywithinsaidbandandsaiddiscbeingcentrallymountednearthecenterofsaidrodandadaptedtobesetintoflexuralvibrationbylongitudinalvibrationsimpresseduponanendofsaidrodandhavingaflexuralantiresonanceatafrequencyclosetoonelimitofsaidband.

2.Afilterinaccordancewithclaim1inwhichsaidrodhasacircularcrosssection.

3.Afilterinaccordancewithclaim1inwhichthecross-sectionaldimensionsofsaidrodaresmallcomparedtoitslength.

4.Afilterinaccordancewithclaim1inwhichsaidrodhasacircular,crosssectionthediameterofwhichissmallcomparedtoitslength.

5.Afilterinaccordancewithclaim1inwhichsaidflexuralantiresonanceofsaiddiscisitsfirst.

6.Amechanicalwavefilterfortransmittingabandoffrequenciescomprisingarodandatransversediscbothmadeofacousticmaterial,saidrodhavingalengthapproximatelyequaltoahalfwave-lengthatafrequencywithinsaidbandandsaiddiscbeingcentrallymountednearthecenterofsaidrodandadaptedtobesetintoflexuralvibrationbylongitudinalvibrationsimpresseduponanendofsaidrodandhavingitsfirstflexuralantiresonanceatafrequencyononesideofsaidbandandsaidrodhavingalengthapproximatelyequaltoahalfwave-lengthatthebandlimitontheothersideofsaidband.

7.Afilterinaccordancewithclaim1inwhichsaidflexuralantiresonanceofsaiddiscisitsfirstandsaidrodhasalengthapproximatelyequaltoahalfwave-lengthattheotherlimitofsaidband.

8.Amechanicalwavefilterfortransmittingabandoffrequenciescomprisingarodandatransversediscbothmadeofacousticmaterial,saidrodhavingalengthapproximatelyequaltoahalfwave-lengthatafrequencywithinsaidbandandsaiddiscbeingcentrallymountednearthecenterofsaidrodandadaptedtobesetintoflexuralvibrationbylongitudinalvibrationsimpresseduponanendofsaidrodandhavingitsfirstflexuralantiresonanceatafrequencyontheuppersideofsaidbandandsaidrodhavingalengthapproximatelyequaltoahalfwave-lengthatthelowerlimitofsaidband.

9.Afilterinaccordancewithclaim1inwhichsaidflexuralantiresonanceofsaiddiscisitsfirstandislocatedabovesaidbandandsaidrodhasalengthapproximatelyequaltoahalfwave-lengthatthelowerlimitofsaidband.

10.Amechanicalwavefilterfortransmittingabandoffrequenciescomprisingarodandatransversediscbothmadeofacousticmaterial,saidrodhavingalengthapproximatelyequaltoahalfwave-lengthatafrequencywithinsaidbandandsaiddiscbeingcentrallymountednearthecenterofsaidrodandadaptedtobesetintoflexuralvibrationbylongitudinalvibrationsimpresseduponanendofsaidrodandhavingitsfirstflexuralantiresonanceatafrequencyonthelowersideofsaidbandandsaidrodhavingalengthapproximatelyequaltoahalfwave-length