Polynomial Stability Test
Use SchurCohn algorithm to determine whether all roots of input polynomial are inside unit circle
Libraries:
DSP System Toolbox /
Math Functions /
Polynomial Functions
Description
The Polynomial Stability Test block uses the SchurCohn algorithm to determine whether all roots of a polynomial are within the unit circle.
Here is the equivalent MATLAB^{®} code.
y = all(abs(roots(u)) < 1)
This block is most commonly used to check the pole locations of the denominator polynomial, A(z) of a transfer function H(z).
$$H(z)=\frac{B(z)}{A(z)}=\frac{{b}_{1}+{b}_{2}{z}^{1}+\dots +{b}_{m}{z}^{(m1)}}{{a}_{1}+{a}_{2}{z}^{1}+\dots +{a}_{n}{z}^{(n1)}}$$
The poles are the n − 1 roots of the denominator polynomial A(z). When any poles are located outside the unit circle, the transfer function H(z) is unstable. As is typical in DSP applications, the transfer function above is specified in descending powers of z^{−1} rather than z.
Ports
Input
Output
Parameters
Block Characteristics
Data Types 

Multidimensional Signals 

VariableSize Signals 

Extended Capabilities
Version History
Introduced before R2006a