Z-Domain Fit


System identification in z-domain is performed with the function ao/zDomainFit . It is based on a modeified version of the vector fitting algorithm that was chenged to fit in z-domain. Details on the agorithm can be found in [1 - 3].

Call

  mod = zDomainFit(a, pl)
 [mod, resp] = zDomainFit(a, pl)
 [mod, resp, resids] = zDomainFit(a, pl)
 [mod, resp, resids, rmse] = zDomainFit(a, pl)

Inputs

Outputs

Algorithm description

The function performs a fitting loop to automatically identify model order and parameters in z-domain. Output is a z-domain model expanded in partial fractions:

Identification loop stops when the stop condition is reached. Stop criteria are based on two different approachs:

  1. Log residuals difference and root mean squared error
  2. Residuals spectral flatness and root mean squared error
Fitting loop stops when the two stopping conditions are satisfied, in both cases.

The function can also perform a single loop without taking care of the stop conditions. This happens when 'AutoSearch' parameter is set to 'off'.

Parameters

References

  1. B. Gustavsen and A. Semlyen, "Rational approximation of frequency domain responses by Vector Fitting", IEEE Trans. Power Delivery vol. 14, no. 3, pp. 1052-1061, July 1999.
  2. B. Gustavsen, "Improving the Pole Relocating Properties of Vector Fitting", IEEE Trans. Power Delivery vol. 21, no. 3, pp. 1587-1592, July 2006.
  3. Y. S. Mekonnen and J. E. Schutt-Aine, "Fast broadband macromodeling technique of sampled time/frequency data using z-domain vector-fitting method", Electronic Components and Technology Conference, 2008. ECTC 2008. 58th 27-30 May 2008 pp. 1231 - 1235.




©LTP Team