Signal Processing Toolbox

Filter Design and Analysis Tool

Overview

Note    The Filter Design and Analysis Tool (FDATool) requires resolution greater than 640 x 480.

The Filter Design and Analysis Tool (FDATool) is a powerful user interface for designing and analyzing filters. FDATool enables you to quickly design digital FIR or IIR filters by setting filter performance specifications, by importing filters from your MATLAB workspace, or by directly specifying filter coefficients. FDATool also provides tools for analyzing filters, such as magnitude and phase response plots and pole-zero plots. You can use 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
• Choosing a Filter Type
• 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.

Note    If you have installed external hardware or targets that interact with FDATool, you may see additional options in FDATool. Refer to the specific hardware or target manual for information on these options. These toolboxes/targets are integrated with FDATool.                                         Filter Design Toolbox     Developer's Kit for Texas InstrumentsTM DSP

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-Hanning (barthannwin)
• Bartlett (bartlett)
• Blackman (blackman)
• Blackman-Harris (blackmanharris)
• Bohman (bohmanwin)
• Chebyshev (chebwin)
• Gaussian (gausswin)
• Hamming (hamming)
• Hann (hann)
• Kaiser (kaiser)
• Nuttall's Blackman-Harris (nuttallwin)
• Rectangular (rectwin)
• Tapered cosine (tukeywin)
• Triangular (triang)

You can implement any of these windows manually using fir1 or fir2.

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 in FDATool or in a separate Filter Visualization Tool (fvtool):

• 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, export the coefficients to the MATLAB workspace, and create a C header file containing the 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.

If you also have the Filter Design Toolbox installed the additional quantize mode is available. 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