Since we first introduced Fourier analysis in Lecture 7, we have relied heavily on its properties in the analysis and representation of signals and linear, time-
invariant systems. The Fourier transform was developed from the concept of representing signals as a linear combination of basic signals that were chosen
to be eigenfunctions of linear, time-invariant systems. With the eigenfunctions chosen to be the signals e j(t, this representation led to the Fourier transform synthesis equation, and a given LTI system could then be represented by the spectrum of eigenvalues as a function of W, that is, the change in amplitude that the system applies to each of the basic inputs e ".
In this and the next several lectures we introduce a generalization of the Fourier transform, referred to as the Laplace transform. In addition to leading to a number of new insights, the use of the Laplace transform removes
some of the restrictions encountered with the Fourier transform. Specifically, the Laplace transform converges for a broader class of signals than does the
Fourier transform.