Hi folks,
           I have a transformer 4 port s-parameter data set. I also have the lumped element model from the manufacturer. I did a sim with s-paramters . In this case none of the 2 primary terminals was grounded. Just a port (cadence component) was connected to primary side. A load was inserted bw two Secondary terminals.
            In the 2nd sim I just grounded one terminal of the primary (and that of source port). Secondary side remained the same. In both cases I see different S11. But this problem does not show up if I use model of the transformer instead of the measured s-parameters. We have very carefully measured the s-parameters. I am trying to explain it. Any words of wisdom??
           Thanks alot
            Shaf