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simulation of multistrip

Question asked by brecht.machiels on Mar 4, 2010

I am trying to simulate a multistrip transmission line in Momentum. It consists of two signal lines and one ground plane (all modeled as strip conductors) in a microstrip configuration. There is no infinite ground plane in the substrate stack. As this is a transmission line and to obtain properly de-embedding S-parameters, I opt to use single ports. The ground reference for each of the signal ports is the ground metal. Unfortunately, it is not possible to specify the same ground reference for the two signal ports on one end of the multistrip. Therefore, I attach a normal single port to the ground metal and have Momentum output 6-port S-parameters which I convert to 4-port S-parameters afterward (using an ADS S-parameter simulation or a custom tool that transforms the Z-matrix).

The results obtained from this simulation however do not seem to be correct (when I compare them to a Momentum simulation with internal ports, a Sonnet simulation. Can this port setup and 6-port to 4-port conversion result in correct S-parameters? Or can this only work with internal ports. If so, how would I obtain de-embedded results? I have come across this: ... +Technique
This seems like a less involving solution however: ... yPaper.pdf
Would it be a good idea to use this de-embedding technique?

Kind regards,
Brecht Machiels
PhD student