Filter Design Toolbox

isstable

Test whether a quantized filter is stable

Syntax

• r = isstable(hq)
  r = isstable(hq,k)
  

Description

r = isstable(hq) tests quantized filter hq to determine whether its poles are inside the unit circle. If the poles lie on or outside the circle, isstable returns r = 0. If the poles are inside the circle, isstable returns r = 1.

r = isstable(hq,k) returns the stability of the kth-section of a multiple section quantized filter. Based on the locations of the poles of the specified section, isstable returns r = 1 if the filter section is stable, and 0 otherwise.

To determine the filter stability, isstable checks the quantized filter coefficients. When the poles lie on or inside the unit circle, the quantized filter is stable. FIR filters are stable by design since the defining transfer functions do not have denominator polynomials.

Examples

Since filter stability is very important in your design process, use isstable to deterime whether you quantized IIR filter is indeed stable:

• hq = qfilt;
  isstable(hq)
  ans =
      1
  

See Also

isallpass, isfir, islinphase, ismaxphase, isminphase, isreal, issos, zplane

issos

length