FreeLists / si-list / [SI-LIST] Re: Help - experience with Ansoft "F"dependentsources????

["Neeraj Pendse" <cnepsc@xxxxxxxxxxx>]

Hi Ed:

F elements are current-controlled-current-sources, and they are a way of
expressing mutual inductance.  F elements are good for two reasons: (a)
It is easier to represent than K elements, because the direction of
coupling is hard to work out when you have n-coupled inductors. (b) Some
versions of SPICE have trouble when many mutual inductance elements are
in a circuit.

If you draw yourself a circuit diagram for the CCCS connections in a
simple SPICE subcircuit generated by Ansoft, you will realize that there
is no approximations made while using the F-element to represent mutual
inductnace ... ie it is a theoratically correct substitution. Just a
small arithematic excercise to figure out a transformation from K to F.
I believe Ansoft has a paper on this, I suggest you ask them to provide
you a copy. 

Regards,

- Neeraj.

National Semiconductor Corporation
http://www.national.com, NYSE: NSM

> "Dr. Edward P. Sayre" wrote:
> 
> Folks:
> 
> Does anyone have specific experience of the satisfactory use of the Ansoft
> Maxwell "F" dependent source modes to model multiple coupled inductors.  I
> am trying to do an RF crosstalk and transmission analysis using a Maxwell
> derived model in SPICE. The answers do not reduce to the correct answers at
> low frequencies or for that matter do they make sense at any other
> frequency.  Range of operation I am looking at is 50 MHz thru 1 GHz.
> 
> I am looking for the basic derivation of how the "F" model (Current
> controlled current source) expresses coupled inductors, or how it is
> related to the coupled transformer coupling coefficient "k" which is the
> more conventional way of expressing coupled inductors.
> 
> Thanks in advance -
> 
> ed sayre
> 
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-- 
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