Lecture 8: Transforms We Have Met and Loved
Schedule
:: Transforms
::
DTFT
::
System
Analysis
::
Properties
We have studied this year a variety of transforms:
 Laplace transforms
 which are useful for system analysis, including transient and stability analysis. By evaluating at we explored also the concept of frequency response.
 Ztransforms
 which are the transform appropriate for discretetime systems. Like the Laplace transform, it can be used for transient analysis, stability analysis, and, by evaluating at we get the concept of frequency response.
 Fourier series
 which are used to provide a representation of periodic signals. This has some application to circuit analysis for periodic signals, and leads, by taking a limit to signals of increasingly longer period, to the Fourier transform. We also saw that we can take the idea of series representations of functions and use a variety of other basis functions for other useful representations.
 Fourier transforms
 which can be used to examine frequency response of signals. By means of their properties, we are also lead to consider concepts such as modulation. Fourier transforms do not really address the stability issues that Laplace transforms do, nor can they be used as conveniently for transient analysis. However, by not starting at , they simplify some other issues.
 The Discretetime Fourier Transform

is to the Ztransform what
the Fourier transform is to the Laplace transform. That is, we have
an exact frequency component representation of signals that are
not periodic
by evaluating a (possibly twosided) Ztransform at
The DTFT is the study of this set of lecture notes.
 The Discrete Fourier Transform (DFT)

can be used to compute a
transform of a finitelength discretelysampled set of data. The
DFT can be used for computational signal analysis, and its
implementation in the form of the FFT is very common. However,
because the signal is truncated in time and in frequency, it does
not provide an exact frequency analysis (although there are
techniques to get close enough in practice).
Copyright 2008,
by the Contributing Authors.
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admin. (2006, June 05). Lecture 8: Transforms We Have Met and Loved. Retrieved January 07, 2011, from Free Online Course Materials — USU OpenCourseWare Web site: http://ocw.usu.edu/Electrical_and_Computer_Engineering/Signals_and_Systems/8_1node1.html.
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