Signal Processing Toolbox

Overview

Filter Design Methods

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

Design Method	Function
Butterworth	butter
Chebyshev Type I	cheby1
Chebyshev Type II	cheby2
Elliptic	ellip
Equiripple	remez
Least squares	firls
Bartlett window	bartlett
Bartlett-Hanning window	barthannwin
Blackman window	blackman
Blackman-Harris window	blackmanharris
Bohman window	bohmanwin
Chebyshev window	chebwin
Flat top window	flattopwin
Gaussian window	gausswin
Hamming window	hamming
Hann window	hann
Kaiser window	kaiser
Nuttall (Nuttall's Blackman-Harris) window	nuttallwin
Parzen or de la Vallé-Poussin window	parzenwin
Rectangular window	rectwin
Triangular window	triang
Tukey (tapered cosine) window	tukeywin

You can implement any of the above windows manually using fir1 or fir2. You can also specify a user-defined window by entering its function name and input parameter.

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). See Analyzing the Filter for more information.

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

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 Panels

The Filter Design and Analysis Tool has sidebar buttons that display particular panels in the lower half of the tool. The panels are

• Design Filter. See Choosing a Filter Design Method for more information. You use this panel to
• Design filters from scratch.
• Modify existing filters designed in FDATool.
• Analyze filters.
• Import filter. See Importing a Filter Design for more information. You use this panel to
• 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, two additional panels are available--Set Quantization Parameters and Transform Filter. Use the Set Quantization Parameters panel to

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

Use the Transform Filter panel to change a filter from one filter type to another.

If you have the DSP Blockset installed, a Realize Model panel is available. Use this panel to create a Simulink block containing the filter structure.

Getting Help

At any time, you can right-click or click the What's this? button, , to get information on the different parts of the tool. You can also use the Help menu to see complete Help information.

Filter Design and Analysis Tool

Opening the Filter Design and Analysis Tool