User`s guide

15 Filter Design Toolbox 2.1 Release Notes
15-4
Transformations Option in FDATool
When you use Filter Design and Analysis Tool (FDATool) with Filter Design
Toolbox 2.1, the Toolbox adds a new menu to the FDATool menu bar. Named
Transformations, the new selection provides direct access to the new FIR and
IIR filter transformation functions added to the Toolbox in this release (refer
to “New Filter Transformation Functions”).
Transformations appears as
shown in this figure only when you have installed the Filter Design Toolbox.
With this new option, FIR and IIR filters whose characteristics are particularly
valuable become the sources for other FIR and IIR filters that share the same
desirable features in a different passband configuration. Transforming a filter
saves you from repeating the filter design process. For more information, refer
to Transforming Filters in your Filter Design Toolbox User’s Guide.
In the figure, the
Targets option is available only when you have the
Developer’s Kit for Texas Instruments DSP installed.
New Analysis Method
Filter Design Toolbox 2.1 includes one new analysis method — zerophase —
that returns the zero-phase response of a linear-phase FIR filter.
[hr,w] = zerophase(b), and the other available syntax options for
zerophase, returns the zero-phase response hr and the frequency vector w (in
rad/sample) at which
hr is computed, given a linear-phase FIR filter b. The
zero-phase response is evaluated at 512 equally spaced points on the upper half
of the unit circle.
Note that the zero-phase response is always real, but it is not equivalent to the
magnitude response. In particular, the zero-phase response can be negative;
the magnitude response is always positive.