[Qucs-help] FW: transformer difference, Sparams vs AC

[Claudio G. <cla...@vi...>]

(forwarding message, as it was rejected due to size. I have removed the attachment with the big simulation results and enclosed only the schematic)

>From a quick test, it really seems there is an issue with the "N coupled inductors" model for the AC simulation; if you use the simple "coupled inductors" model the results seem fine.

Regards,
  Claudio




----Messaggio originale----

Da: "cand brick" <can...@gm...>

Data: 13-ott-2017 5.37 AM

A: <Quc...@li...>

Ogg: transformer difference, Sparams vs AC



Hi,
I am having an issue where the input impedance to a transformer with a capacitive load results in a different answer when I use Sparameter compared to the AC simulation. Note that this is a simplified version of the actual problem.
I have gone through the math on this problem and measured an experimental version of this with a VNA and the Sparameter simulation matches theory and the experiment. The AC simulation does not get the same answer. I am curious if this is due to an error in my setup of the problem and if so what am I doing different between the two, other than the source impedance. 
I have tried the AC version of this in a variety of ways with various diagnostics, but I tried to boil down the issue to be clear on this request for further insight into what I a may be missing.
When I simulate this with a different software, these two cases seem to match, is this a limitation of mutual inductors or AC?
I attempted to attach the file package, let me know if I should attach the file in a different manner.
Thanks,
Brick