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基于MEMS开关的射频衰减器的设计制作.docx

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基于MEMS开关的射频衰减器的设计制作 Introduction Radiofrequency(RF)attenuatorsareusedtoreducetheintensityofRFsignalsbyintroducingacontrolledlossinthetransmissionline.Attenuatorsarecommonlyusedincommunicationsystemstoadjustsignallevels,matchimpedance,andprotectsensitivecomponentsfromhighpowersignals.Inthispaper,wepresentthedesignandfabricationofanRFattenuatorbasedonMEMSswitches. MEMSswitchesaremicromechanicaldevicesthatusemechanicalcontactstoswitchRFsignals.MEMSswitchesofferseveraladvantagesovertraditionalelectromechanicalswitches,includingsmallsize,lowpowerconsumption,lowinsertionloss,andhighisolation.MEMSswitchescanalsobeintegratedwithotherRFcomponentsonasinglechip,makingthemattractiveforRFsystem-on-a-chip(SoC)applications. Design TheRFattenuatorisdesignedusingastandardRFtransmissionlinetopologywithMEMSswitchesplacedatspecificintervalstoprovidevariableattenuationlevels.Thedesignincludesasingle-pole,double-throw(SPDT)MEMSswitchcontrolledbyelectrostaticactuation.TheSPDTswitchisusedtoselectbetweentwopaths:adirectpathwithnoattenuationandapathwithattenuationprovidedbyaseriesofMEMSswitches. TheattenuationleveliscontrolledbyabinarycontrolcircuitthatactivatestheMEMSswitchesinsequencetoprovideincrementallyincreasingattenuationlevels.Thebinarycontrolcircuitconsistsofaseriesofdigital-to-analogconverters(DACs)andamplifiersthatgeneratethecontrolvoltagesfortheMEMSswitches. Fabrication TheRFattenuatorisfabricatedusingstandardMEMSfabricationprocesses,includinglithography,etching,anddeposition.TheMEMSswitchesarefabricatedusingasurfacemicromachiningprocessthatinvolvesdepositingalternatinglayersofsacrificialandstructuralmaterialsonasiliconsubstrate.Theswitchcontactsareformedusingalift-offprocess,andthesacrificialmaterialisetchedtoreleasetheswitches. ThecontrolcircuitryisfabricatedusingstandardCMOSprocessesonaseparatechip,whichisthenbondedtotheMEMSchipusingaflip-chipbondingprocess.ThecontrolcircuitrychipincludestheDACs,amplifiers,andothercontrolcircuitryneededtoactivatetheMEMSswitches. Results TheRFa