Varying Lowpass Filter

Butterworth filter with varying coefficients

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Libraries:
Control System Toolbox / Linear Parameter Varying

Description

The block implements an analog N^th-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.

Caution

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.

Ports

Input

u — Filter input

scalar

Lowpass filter input signal.

freq — Cutoff frequency

scalar

Filter cutoff frequency, specified in rad/s.

Output

y — Filter output

scalar

Lowpass filter output signal.

Parameters

Filter order — Lowpass filter order

1 (default) | positive integer

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