noscillatoris,infact,atraactiontoameasurementoftimeorfrequency.determiningtheperiodofanoscillatorwithprecisionplaysaveryimportantrolebecausetheaccuracyofmeasuringperiodgreatlyaffectsthatofexperimentalresults.thetraditionalmethodssuchasthefastfouriertraform(fft)method,the“all-poles”methodandthenonlinearleast-squarefittingmethodcanprovidemoreinformationaboutsignal,buttheywillbefadingtodeterminefundamentalfrequencywithhighprecisionintheexperimentofmeasuringg.aperiodfittingmethod,whichisavariantoftheclaicalleast-squarefittingmethod,isproposedtodeterminethefundamentalfrequencyofaphysicaloscillator.therootmeansquaredeviationusedasthecriterioninthismethodisasingle-parameterfunctionofthefundamentalfrequencyoftheoscillator,soitmakesthefittingproceoptimizeattheexpeeofaleerevaluationoftheotherparameterssuchastheamplitudeandthephase.theoreticalanalysisshowsthatthismethodisintriicallyindependentofthedisturbancesofthehighorderharmonicfrequenciesoscillation,andthecomputersimulationexperimentsshowthatitiseffectivetoovercomethedisturbancesofthefinitequalityfactorandthemonotonicdriftofanoscillatorsystem,aswellasthewhitenoise,andthismethodcandeterminethefundamentalfrequencyorperiodofaphysicaloscillatorwitharelativeprecisionof10-7orders,whilethestandardnonlinearleast-squarefittingmethodcanonlydetermineitwitharelativeprecisionof10-5orders.thereasonisthatthestandardnonlinearleasts-quarefittingproceisdemocraticinitstreatmentofallunknownparameterssuchastheamplitude,thephaseandtheperiod,andtheperiodf
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