简介：Amorerelaxedsufficientconditionfortheconvergenceoffiltered-XLMS(FXLMS)algorithmispresented.Itispointedoutthatifsomepositiverealconditionforsecondarypathtransferfunctionanditsestimatesissatisfiedwithinallthefrequencybands,FXLMSalgorithmconvergeswhateverthereferencesignalislike.Butiftheabovepositiverealconditionissatisfiedonlywithinsomefrequencybands,theconvergenceofFXLMSalgorithmisdependentonthedistributionofpowerspectraldensityofthereferencesignal,andtheconvergencestepsizeisdeterminedbythedistributionofsomespecificcorrelationmatrixeigenvalues.ApplyingtheconclusionabovetotheDelayedLMS(DLMS)algorithm,itisshownthatDLMSalgorithmwithsomeerroroftimedelayestimationconvergesincertaindiscretefrequencybands,andthewidthofwhicharedeterminedonlybythe"time-delayestimationerrorfrequency"whichisequaltoonefourthoftheinverseofestimatederrorofthetimedelay.

简介：Simpleandefficientsurfaceacousticwave(SAW)two-portresonatorswithlowinsertionlossandhighQ-valuesonST-Xquartzsubstrateusingacorrosion-proofA1/Au-stripeelectrodestructurearedevelopedforgassensing.Itwascomposedoftwoshortedgratingreflectorsandadjacentintedigitaltransducers(IDT),andanactivemetalfilminthecavitybetweentheIDTsforthesensitivefilmcoating.Thedevicesareexpectedtoprovidegoodprotectiontowardsmetalelectrodeforgassensorsapplicationinchemicallyreactiveenvironments.Excellentdeviceperformanceaslowinsertionloss,highQfactorandsingle-modeareachievedbycarefullyselectingthemetallicelectrodethickness,cavitylengthandacousticaperture.Priortofabrication,thecouplingofmodes(COM)modelwasperformedfordevicesimulationtodeterminetheoptimaldesignparameters.Thefabricatedsingle-modeSAWresonatoratoperationfrequencyof300MHzrangeexhibitsmatchedinsertionlossof~6.5dBandloadedQfactorinthe3000range.Usingthefabricatedresonatorasthefeedbackelement,adualresonator-oscillatorwithexcellentfrequencystability(0.1ppm)wasdevelopedandevaluatedexperimentally,anditissignificantforperformanceimprovementofSAWgassensor.