Signal Processing Toolbox

Filter Design and Analysis Tool

Overview

You can use the Filter Design and Analysis Tool (FDATool) as a convenient alternative to the command line filter design functions. This chapter contains the following sections, which walk you through a typical filter design session using the FDATool:

• Opening the Filter Design and Analysis Tool
• Getting Help
• Choosing a Filter Type
• Choosing a Filter Design Method
• Setting the Filter Design Specifications
• Computing the Filter Coefficients
• Analyzing the Filter
• Converting the Filter Structure
• Importing a Filter Design
• Exporting a Filter Design
• Saving and Opening Filter Design Sessions

Below is a brief introduction to the FDATool that will give you a better understanding of how it can be used.

Filter Design Methods

The tool gives you access to all of the filter design methods in the Signal Processing Toolbox:

• Butterworth (butter)
• Chebyshev type I (cheby1)
• Chebyshev type II (cheby2)
• Elliptic (ellip)
• Equiripple (remez)
• Least squares (firls)
• Windows
• Bartlett (bartlett, fir2)
• Blackman (blackman, fir2)
• Boxcar (boxcar, fir2)
• Chebyshev (chebwin, fir2)
• Hamming (hamming, fir2)
• Hann (hann, fir2)
• Kaiser (kaiser, fir1)
• Triangular (triang, fir1)

Additional filter design methods are available to users of the Filter Design Toolbox.

Using the Filter Design and Analysis Tool

There are different ways that you can design filters using the Filter Design and Analysis Tool. For example:

• You can first choose a filter type, such as bandpass, and then choose from the available FIR or IIR filter design methods.
• You can specify the filter by its type alone, along with certain frequency- or time-domain specifications such as passband frequencies and stopband frequencies. The filter you design is then computed using the default filter design method and filter order.

Analyzing Filter Responses

Once you have designed your filter, you can analyze different filter responses:

• Magnitude response (freqz)
• Phase response (freqz)
• Pole-zero plots (zplane)
• Impulse response (impz)
• Group delay (grpdelay)
• Step response

You can also display the filter coefficients.

Filter Design and Analysis Tool Modes

The Filter Design and Analysis Tool operates in two modes:

• Design mode. In this mode, you can:
• Design filters from scratch.
• Modify existing filters designed by FDATool.
• Analyze filters.
• Import mode. In this mode, you can:
• Import previously saved filters or filter coefficients that you have stored in the MATLAB workspace.
• Analyze imported filters.

There is one more mode available to you if you also have the Filter Design Toolbox: the quantize mode. Use this mode to:

• Quantize double-precision filters that you design in FDATool.
• Quantize double-precision filters that you import into FDATool.
• Analyze quantized filters.

Getting Help

At any time, you can right-click or press the What's this? button,

, to get information on the different parts of the GUI.

Selected Bibliography

Opening the Filter Design and Analysis Tool