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edge-coupled, embedded, differential waveguide geometry.

Perhaps I made an incorrect assumption analyzing the Molex FPC flatcable, but I don't see how Zdm is 100+/-10 ohms

Critical ratios:  

Trace width/height ratio = 2.7:1

Coplanar trace space/height = 1.6

This results in Zo much less than 45 Ohms, so how can Zdm reach 90 Ohms over a dielectric comm mode coupling to a ground plane?

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Molex show the ground plane on top and the critical dimensions are for the connector fit and not to control Zo but the  critical dimension between stiffener and alum foil inside the connector.  I show this on my top left and rotated below bottom right in plan view or below this in in the tail cross-section.  Again I ignored this short wavelength sensitive zone ~ above say 300 MHz.in this thread.

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