===LinearTimeInvariantSystems(LTISystems)===Alineartimeinvariantsystemisonethatislinear(superpositionandproportionalityapply)andonethatdoesn′tchangewithtime.Forexampleacircuitwithfixedcapacitors,resistors,andinductorshavinganinputandanoutputislinearandtimeinvariant.Ifacapacitorchangedvaluewithtime,thenitwouldnotbetimeinvariant.===EigenfunctionsandEigenvaluesofanLTISystems===Itisaninterestingexercisetoshowthat<math>ejωt are eigenfunctions of any LTI system. The eigenvalues are ω.
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