Design Techniques for EMC – Part 4Shielding 电磁兼容设计内容技术——第4部分 屏蔽.pdf

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1、DesignTechniquesforEMC–Part4ShieldingByEurIngKeithArmstrongCEngMIEEMIEEEPartner,CherryCloughConsultants,AssociateofEMC-UKThisisthefourthinaseriesofsixarticlesonbest-practiceEMCtechniquesinelectrical/electronic/mechanicalhardwaredesign.Theseriesisintendedforthedesignerofelectronicproducts,f

2、rombuildingblockunitssuchaspowersupplies,single-boardcomputers,and“industrialcomponents”suchasmotordrives,throughtostand-aloneornetworkedproductssuchcomputers,audio/video/TV,instruments,etc.Thetechniquescoveredinthesixarticlesare:1)Circuitdesign(digital,analogue,switch-mode,communications)

3、,andchoosingcomponents2)Cablesandconnectors3)Filtersandtransientsuppressors4)Shielding5)PCBlayout(includingtransmissionlines)6)ESD,electromechanicaldevices,andpowerfactorcorrectionAtextbookcouldbewrittenaboutanyoneoftheabovetopics(andmanyhave),sothismagazinearticleformatcanonlyintroducethe

4、variousissuesandpointtothemostimportantbest-practicetechniques.Manyofthetechniquesdescribedinthisseriesarealsoimportantforimprovingsignalintegrity:reducingthenumberofiterationsduringdevelopmentandreducingmanufacturingcosts.Tableofcontentsforthispart4.Shielding4.1Shieldingandthecommercialim

5、perative4.2Generalconceptsinshielding4.3Biggerandrectangularisbetter4.4Skineffect4.5Apertures4.6Lowfrequency(magneticfield)shielding4.7Waveguidesbelowcutoff4.8Gasketting4.9Shieldingofdisplays(andthelike)4.10Shieldingventilationapertures4.11Shieldingwithpaintedorplatedplastics4.12Shieldingw

6、ithoutmetal4.13Failingconductedtestsduetoinadequateshielding4.14Installationofshieldedenclosures4.15UsingPCB-levelshielding4.16FurtherreadingDesigntechniquesforEMC–Part4–ShieldingCherryCloughConsultantsPage1of234.Shielding4.1ShieldingandthecommercialimperativeAcompletevolumetricshieldisof

7、tenknownasa"FaradayCage",althoughthiscangivetheimpressionthatacagefullofholes(likeMrFaraday’soriginal)isacceptable,whichitgenerallyisn’t.Thereisacosthierarchytoshieldingwhichmakesitcommerciallyveryimportanttoconsidershieldingearlyinthedesignprocess.Shieldsmayb