[SI-LIST] Re: Differential Impedance; Traces w/o Ref Plane

Hi Bob,

You could try the differential embedded coplanar waveguide
in the Polar Si6000, you would need to set the "D" dimension large
so the coplanar grounds were out of the sphere of influence...

www.polarinstruments.com/products/cits/Si6000.html


Kind regards
Martyn Gaudion
www.polarinstruments.com


At 10:51 09/12/2002 -0600, you wrote:
>         I am trying to calculate the differential impedance of two pcb
>traces (ie a balanced pair) when they are routed in the area of a pcb with
>NO power/gnd plane to use as a reference.  The available tools that I have
>access to only treat the cases that include a reference plane; ie
>microstrip, stripline, edge-coupled traces over a plane, etc.  I also
>tried digging into a few of my old ElectoMagnetics textbooks, but those
>formulas for parallel-plate transmission lines make assumptions that
>handle only the case in which the plate width >> separation distance.  I
>am having trouble finding a transmission line model that reflects pcb
>trace geometries.
>
>         Any helpful information, formulas, links to websites, etc.,  would
>be greatly appreciated.
>
>Thanks in Advance,
>
>Bob Tarasewicz
>Westell, Inc.
>ph 630-375-4461
>btara@xxxxxxxxxxx
>
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