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Design >> RF Design >> S-parameter puzzle
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Message started by jefkat on Jul 27^th, 2007, 2:35am

Title: S-parameter puzzle
Post by jefkat on Jul 27^th, 2007, 2:35am

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

Title: Re: S-parameter puzzle
Post by pancho_hideboo on Jul 27^th, 2007, 4:35am

Hi.

(1) Balanced Drive
NPORT1 (1 0 2 0 3 0 4 0) nport thermalnoise=yes
PORT1 (1 2) port r=50 num=1 type=dc
R0 (3 4) resistor r=1K

(2) Unbalanced Drive
NPORT1 (1 0 0 0 3 0 4 0) nport thermalnoise=yes
PORT1 (1 0) port r=50 num=1 type=dc
R0 (3 4) resistor r=1K

Your s-parameters are measured with unbalanced,
so results of S11 from aboves are different.