Signal Processing Toolbox

Designing Digital FIR and IIR Filters

Signal Processing Toolbox enables you to design, analyze, and implement FIR and IIR digital filters in MATLAB.

Filter Responses and Design Methods

The toolbox supports a wide range of response types and design methods, including:

• Filter responses for lowpass, highpass, bandpass, bandstop, Hilbert, differentiator, pulse-shaping, and arbitrary magnitude filters
• Parks-McClellan and Kaiser window for FIR filter design
• Butterworth, Chebyshev Type I and Type II, and elliptic filters for IIR filter design

MATLAB code and corresponding plots for FIR (top right) and IIR (bottom right) filter design using algorithms in Signal Processing Toolbox.

Analyzing Filters

You can analyze your filter design by simultaneously viewing multiple characteristics in the Filter Visualization Tool (FVTool):

• Magnitude response, phase response, and group delay in the frequency domain
• Impulse response and step response in the time domain
• Pole-zero information

FVTool also helps you evaluate filter performance by providing information about filter order, stability, and phase linearity. Once you design your filter, you can implement it using FIR and IIR filter structures.

Analysis of a lowpass FIR filter designed using a Kaiser window method. Example plots from Signal Processing Toolbox include (clockwise from top left): Magnitude and phase responses, impulse response, pole-zero plot, and filter order and stability information.

Interactive Filter Design and Analysis

Signal Processing Toolbox provides FDATool, FVTool, and Filterbuilder for interactive filter design and analysis. Together, these tools enable you to:

• Explore FIR and IIR design methods for a given filter specification
• Analyze filters by viewing filter characteristics, including magnitude response, phase response, group delay, pole-zero plot, impulse response, and step response
• Obtain filter information, such as filter order, stability, and phase linearity
• Import previously designed filters and filter coefficients stored in the MATLAB workspace and export filter coefficients

Filter Design and Analysis Tool (FDATool) showing magnitude response, filter order, and stability information for a lowpass FIR filter.

Designing Analog Filters

Signal Processing Toolbox provides functions for analog filter design and analysis. Supported analog filter types include Butterworth, Chebyshev, Bessel, and elliptic. The toolbox also contains discretization functions for analog-to-digital filter conversion.