Filter Design Process Overview
Note
You must have the Signal Processing Toolbox installed
to use fdesign and filterbuilder.
Advanced capabilities are available if your installation additionally
includes the Filter Design Toolbox license. You can verify the
presence of both toolboxes by typing ver at the
command prompt. |
Filter design through user-defined specifications is the core
of the fdesign approach. This specification-centric
approach places less emphasis on the choice of specific filter algorithms,
and more emphasis on performance during the design a good working
filter. For example, you can take a given set of design parameters
for the filter, such as a stopband frequency, a passband frequency,
and a stopband attenuation, and— using these parameters—
design a specification object for the filter. You can then implement
the filter using this specification object. Using this approach, it
is also possible to compare different algorithms as applied to a set
of specifications.
There are two distinct objects involved in filter design:
The distinction between these two objects is at the
core of the filter design methodology. The basic attributes of each
of these objects are outlined in the following table.
| Specification Object | Implementation Object |
| High-level specification | Filter coefficients |
| Algorithmic properties | Filter structure |
You can run the code in the following examples from the Help
browser (select the code, right-click the selection, and choose Evaluate
Selection from the context menu), or you can enter the
code on the MATLAB command
line. Before you begin this example, start MATLAB and verify
that you have installed theSignal Processing Toolbox. If you wish
to access the full functionality of fdesign and filterbuilder,
you should additionally obtain the Filter Design Toolbox software.
You can verify the presence of these products by typing ver at
the command prompt.
 | Filter Design with Fdesign and Filterbuilder | | Basic Filter Design Process |  |
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