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Microstip coupled line - Models and Momentum simulation

Question asked by CYBERPHOX on May 28, 2010
Hi All,

I am trying to model coupling between two pcb traces. Something simple at the momemt to just try and understand things better.

What I have is a simulation test bench (s-parameters) with a standard MCLIN model set up as follows:-
Width = 70um, S = 4mm and L = 2mm

The substrate is as follows:
H=70um, Er = 4.3, T=17um, Tand=0.02

With the simulation I look at the coupling between one trace and the other. Port 1 and Port2.
S21 with this setup is -52.2dB @ 1.6GHZ

If I then create a momentum layout view and simulate in momemtum (uW mode) the same thing, I get S21 = -102dB!  In microwave mode I had to also resort to using internal ports and not single ports. The results with single ports (or thickness modelled for the sheet metal) is not normal with uW. With uW when setup ok the result is similar to RF mode. With EMDS i get S21 = -86dB.

I don't trust the Momentum or EMDS results, can anyone help me with this?

(ADS2009 is used here)

Many thanks,