# Wolfram Language & System 10.3 (2015)|Legacy Documentation

This is documentation for an earlier version of the Wolfram Language.
WOLFRAM LANGUAGE TUTORIAL

# Analog Filter Design

The Wolfram Language provides a comprehensive set of methods for designing analog filters.

## Analog Filter Transfer Functions

 ButterworthFilterModel Butterworth filter model Chebyshev1FilterModel Chebyshev type 1 filter model Chebyshev2FilterModel Chebyshev type 2 filter model EllipticFilterModel elliptic filter model BesselFilterModel Bessel filter model

Analog filter design methods.

Each one of the classic filters is defined by a particular choice of the function , where defines the order of the filter.

Here is the Chebyshev polynomial of the first kind of order and is the Chebyshev rational function.
The Bessel filter is another popular analog filter with a formulation in terms of rational polynomials.

 TransferFunctionModel transfer function of the analog filter TransferFunctionExpand expanded transfer function TransferFunctionFactor factored transfer function

Representation of analog filters.

A second-order Butterworth filter model with cutoff frequency at .
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Plot the magnitude of the transfer function of an order 5 Butterworth filter.
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Transfer functions of selected orders of lowpass analog filters.
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Plot the magnitude of the transfer functions of selected orders of lowpass analog filters.
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## Poles and Zeros of Analog Filters

 TransferFunctionPoles extract poles of analog filters TransferFunctionZeros extract zeros of analog filters

Poles and zeros of analog filters.

Show poles of a Butterworth filter.
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Poles and zeros of an elliptic filter.
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## Frequency Response of Analog Filters

Squared frequency response of a second-order Butterworth filter.
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Plot the magnitude squared of the frequency response.
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Bode plot of the filter.
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Bode plots of the selected orders of lowpass analog filters.
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## Output Response

Symbolic step response of a Butterworth filter.
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Step response of the filter computed numerically.
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Plot the step response.
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Sinusoidal response of a Butterworth filter as a function of frequency.
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Filter out the high-frequency sinusoid.
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Filter out the low-frequency sinusoid.
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## Different Types of Analog Filters

### Create Filters of Different Types

Create a lowpass Butterworth filter with edge frequencies at 500Hz and 1000Hz and attenuations of 1dB and 20dB for passband and stopband respectively.
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Create a highpass Butterworth filter with edge frequencies at 500Hz and 1000Hz and attenuations of 1dB and 20dB for passband and stopband respectively.
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Create a bandpass Butterworth filter with edge frequencies at 500Hz and 1000Hz and attenuations of 1dB and 20dB for passband and stopband respectively.
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Create a bandstop Butterworth filter with edge frequencies at 500Hz and 1500Hz and attenuations of 1dB and 20dB for passband and stopband respectively.
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### Convert between Filter Types

 TransferFunctionTransform transform a transfer function

Convert between different filter types.

Convert a lowpass analog prototype to highpass, bandpass, and bandstop.
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