Bandpass Filter Design Example

The Matlab code below designs a bandpass filter which passes frequencies between 4kHz and 6kHz, allowing transition bands from 3-4 kHz and 6-8 kHz (i.e., the stopbands are 0-3 kHz and 8-10 kHz, when the sampling rate is 20 kHz). The desired stop-band attenuation is 80 dB, and the passband ripple is required to be no greater than 0.1 dB. For these specifications, the function kaiserord returns a beta value of and a window length of . These values are passed to the function kaiser which computes the window function itself. The ideal bandpass-filter impulse response is computed in fir1, and the supplied Kaiser window is applied to shorten it to length .

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Subsections

• Matlab code
• Results
• In case you don't have the Matlab Signal Processing Toolbox
• Comparison to the Optimal Chebyshev FIR Bandpass Filter
• Matlab code
• Results

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written by Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.