[SI-LIST] Follow-up on Vector Fitting Matlab code.

From: Raymond Anderson <Raymond.Anderson@xxxxxxx>
To: "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
Date: Thu, 06 May 2004 10:00:21 -0700

After my recent posting regarding the Vector Fitting Matlab code by Dr. 
Gustavsen several members of si-list contacted me directly to obtain 
copies of the code. It was suggested by some that it might be nice if 
the code could be placed on the si-list web site for others to access.

I contacted Dr. Gustavsen to determine if it was OK if we posted his 
code. He gave the go ahead. However he also indicated that he had his 
own web site at the following URL:
 
http://www.energy.sintef.no/produkt/VECTFIT/home.asp


That site is dedicated to his Vector Fitting activities and has his code 
available for download (including another package beyond what I passed 
around earlier this week), along with some additional info on the 
subject and a nice listing of references on the subject.

His code as it stands does not produce a "black-box" model appropriate 
for Hspice. It does produce a model suitable for a simulator called 
EMTP-ATP which is used by power engineers for transient simulations 
(like on 500kv power lines...) He actually takes the derived rational 
polynomial function and then extracts a lumped element model for the 
EMTP simulator. To utilize this code for producing a Spice black-box 
model realized as rational polynomials one would want to take the poles 
and residues the program calculates and use them in a subcircuit 
comprised of Laplace defined G elements (in Hspice) in the proper 
topology similar to what the ADS Spice Model Generator or Sigrity 
Broadband Spice or Apsim SPAR programs emit as a spice model.

In any event, Dr Gustavsen's vectfit code does the "heavy lifting" in 
creating an accurately fitted rational polynomial approximation to a 
frequency response submitted to it as admittance values. Presently the 
code does enforce stability by a rather simplistic scheme using 
"pole-flipping", however Dr. Gustavsen tells me that he is currently 
working on a more sophisticated passivity enforcement program based on 
the more powerful QP approach and plans on releasing the code later this 
year.

-Ray Anderson

Staff SI Engineer
Sun Microsytems.




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[SI-LIST] Follow-up on Vector Fitting Matlab code.

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