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Varying Lowpass Filter

Butterworth filter with varying coefficients

  • Varying Lowpass Filter block

Control System Toolbox / Linear Parameter Varying


The block implements an analog Nth-order Butterworth filter with unit DC gain and varying cutoff frequency that you provide as an input to the block.

Use this block and the other blocks in the Linear Parameter Varying library to implement common control elements with variable parameters or coefficients. For more information, see Model Gain-Scheduled Control Systems in Simulink.


Avoid making the cutoff frequency depend on the block output y. If you have such dependence, the resulting filter causes an algebraic loop, because computing the block output value requires knowing the block output value. This algebraic loop is prone to instability and divergence.



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Lowpass filter input signal.

Filter cutoff frequency, specified in rad/s.


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Lowpass filter output signal.


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Lowpass filter order, specified as a positive integer.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2017b