I see your problem and I don't think there's any way to express the
impedance of an individual signal track. You have a coupled system, ie
some of the signal on one signal track will appear on the other, and the
only complete description is with a 2x2 impedance matrix. However, your
ground tracks between the signal tracks will mean that the coupling will
be fairly small and you can calculate a good working approximation for
individual impedances. If I may shamelessly plug my company's product
'TrackSim', I used it to calculate the impedances of your 4 track
system. I entered rectangular tracks with a track height and spacing
between tracks equal to the 40% of the track width. I also assumed the
tracks to be embedded in a thick PCB layer with rel. perm. = 4. The
impedances came out as roughly 37 ohms for the left hand signal track
and 58 ohms for the right hand track. The coupling is about 10%.
If you have any further questions I'd be happy to try and help.
Best wishes,
Dr Adam Woolfe,
Softsim.
Email address : [email protected]
Web for demo downloads : http://www.softsim.com
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