MATLAB SIGNAL PROCESSING TOOLBOX 6 Bedienungsanleitung PDF herunterladen (Seite 30)

3 Design a Filter with fdesign and filterbuilder

3-2

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 DSP System 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:

• Specification Object — Captures the required design parameters of a filter

• Implementation Object — Describes the designed filter; includes the array of

coefficients and the filter structure

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 the Signal Processing Toolbox software. If

you wish to access the full functionality of fdesign and filterbuilder, you should

additionally obtain the DSP System Toolbox software. You can verify the presence of

these products by typing ver at the command prompt.

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MATLAB SIGNAL PROCESSING TOOLBOX 6 Bedienungsanleitung Seite 30