transmission line transformer ads

With Pspice transmission T model and an optional parallel inductance, if a common mode voltage along the line is implied.

You can see this inductor e. g. in Polyfet application notes. If no core is used, the loop inductance still exists. Using an inductance to model the common mode component, however is only a lunped element estimation. A second, common mode transmission line may be more appropriate for higher frequencies. General, this component depends on exact geometry and may be difficult to determine.

Hello,

I reviewed the Polyfet application note and am somewhat confused.

http://www.polyfet.com/broadbandmatch.PDF

They are using a transmission line (equivalent to PSpice T model) and two inductors, one parallel to the outer conductor and one to the inner. My intuitive understanding is, that only one inductor should be used, parallel to outer conductor. But I'm not sure about. I think however, that the Polyfet equivalent circuit would show incorrect behaviour when operating the line in regular single ended mode, while a single inductor would be ignored then, as necessary.

Regards,
Frank