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momentum z0 result

Question asked by DROBISON on Oct 11, 2004
Latest reply on Oct 11, 2004 by ALEPEREZ
 I have been having problems with momentum simulations and I would like some help.  The problem occurs when I use a special substrate stackup.  It involves a special metallization layer on top which is cut away in certain areas to allow for surface mount components.  Where it is not cut out, it is to behave like a ground plane, which is accomplished by vias down to the bottom ground plane.
 When I try to simulate anything using this stackup, the "Z0(X)" result turns out to be very off.  If I use an ideal ground for the top plane, the Z0(X) result comes close to the port impedance, which is expected with this design (as the line should be matched to the port).  If you need further explanation of the problem, please contact me.  Thank you!

 I have already sent this to agilent support along with an attached project, but have not heard back from them.

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