Simulink Reference

Discrete Filter

Implement IIR and FIR filters

Library

Discrete

Description

The Discrete Filter block implements Infinite Impulse Response (IIR) and Finite Impulse Response (FIR) filters. You specify the coefficients of the numerator and denominator polynomials in ascending powers of z^-1 as vectors using the Numerator and Denominator parameters. The order of the denominator must be greater than or equal to the order of the numerator. See Discrete Transfer Fcn for more information about coefficients.

The Discrete Filter block represents the method often used by signal processing engineers, who describe digital filters using polynomials in z^-1 (the delay operator). The Discrete Transfer Fcn block represents the method often used by control engineers, who represent a discrete system as polynomials in z. The methods are identical when the numerator and denominator are the same length. A vector of n elements describes a polynomial of degree n-1.

The block icon displays the numerator and denominator according to how they are specified. For a discussion of how Simulink displays the icon, see Transfer Fcn.

Data Type Support

A Discrete Filter block accepts and outputs a real signal of type double.

Parameters and Dialog Box

Numerator

The vector of numerator coefficients. The default is [1].

Denominator

The vector of denominator coefficients. The default is [1 2].

Sample time

The time interval between samples. See Specifying Sample Time in the online documentation for more information.

Characteristics

Direct Feedthrough	Only if the lengths of the Numerator and Denominator parameters are equal
Sample Time	Discrete
Scalar Expansion	No
States	Length of Denominator parameter -1
Dimensionalized	No
Zero Crossing	No

Direct Look-Up Table (n-D)

Discrete State-Space