# Wolfram Language & System 10.4 (2016)|Legacy Documentation

This is documentation for an earlier version of the Wolfram Language.
BUILT-IN WOLFRAM LANGUAGE SYMBOL

creates a lowpass biquadratic filter using the characteristic frequency ω and the quality factor q.

creates a filter of a given .

expresses the model in terms of the variable var.

## DetailsDetails

• BiquadraticFilterModel returns the filter as a TransferFunctionModel.
• Biquadratic filters are second-order filters defined by a ratio of two quadratic polynomials. They are among the most commonly used circuits in analog and digital signal processing.
• Filter specifications can be any of the following:
•  {"Lowpass",{{ω,q}}} uses cutoff frequency ω and quality factor q {"Highpass",{{ω,q}}} uses cutoff frequency ω and quality factor q {"Allpass",{{ω,q}}} uses frequency ω and quality factor q {"Bandpass",{ω1,ω2}} uses corner frequencies and {"Bandpass",{{ω,q}}} uses center frequency ω and quality factor q {"Bandstop",{ω1,ω2}} uses corner frequencies and {"Bandstop",{{ω,q}}} uses center frequency ω and quality factor q
• The following filter specifications can be given to create equalizers:
•  {"Peaking",{{ω,q}},g} peaking equalizer using gain value g {"LowShelf",{{ω,q}},g} lowpass shelving equalizer using gain value g {"HighShelf",{{ω,q}},g} highpass shelving equalizer using gain value g
• Given the gain value , the attenuation is .

## ExamplesExamplesopen allclose all

### Basic Examples  (3)Basic Examples  (3)

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Bode plot of the filter:

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A bandpass filter using the full specification:

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Bode plot of the filter:

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Create a lowpass filter and apply it to a dual-tone signal:

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