# Discrete Varying Notch

Discrete-time notch filter with varying coefficients

**Libraries:**

Control System Toolbox /
Linear Parameter Varying

## Description

The block implements the Tustin discretization of a continuous-time notch filter with
varying coefficients. Feed the continuous-time values of the notch frequency, minimum
gain, and damping ratio to the **freq**, **gmin**, and
**damp** input ports, respectively. These parameters control the
notch depth and frequency of the continuous-time notch frequency as shown in the
following illustration. The damping ratio **damp** controls the notch
width *Δ*; larger **damp** means larger
*Δ*.

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 filter coefficients 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

### Output

## Parameters

## Extended Capabilities

## Version History

**Introduced in R2017b**