Signal Toolkit - isstable

Function File: FLAG = isstable (B, A)

Returns a logical output equal to TRUE, if the filter is stable. This can be done with coeffients of the filer B and A. Alternatively by using a second order sections matrix (SOS).

Inputs:

• B: Numerator coefficients of the filter
• A: Denominator coeffients of the filter. Can be an empty vector.

Output:

• FLAG: Returns a logical output, equal to TRUE if the filter is stable.

Examples:

   b = [1 2 3 4 5 5 1 2];
   a = [4 5 6 7 9 10 4 6];
   flag = isstable (b, a)
   flag = 0
 

Using SOS

   [z, p, k] = butter (6, 0.7, 'high');
   sos = zp2sos (z, p, k);
   flag = isstable (sos)
   flag = 1