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.

Design a Filter with fdesign and filterbuilder

Basic Filter Design Process

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