*From*: "Ingraham, Andrew" <a.ingraham@xxxxxxxx>*To*: <si-list@xxxxxxxxxxxxx>*Date*: Tue, 14 Oct 2003 11:03:21 -0400

> Lastly, concerning the effect of plane breaks, differential mode currents > are not affected by the break because they cancel, and the plane acts as a > virtual equipotential surface or plane. I would assume that this is true ONLY when the differential traces are on the same layer and adjacent where they cross the plane break. If they were routed as independent single-ended signals, even with identical length constraints, the return current cancellation would be much less effective if it happens at all (except at low frequencies). For a broadside coupled pair that is sandwiched between ground planes, the return currents would not cancel very effectively unless you provided plenty of paths (vias) from one plane to the other in the vicinity of where the pair crosses the plane break, on both sides of the break. Regards, Andy ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu

**Follow-Ups**:**[SI-LIST] Re: Diff.Pairs - Return current distribution***From:*Charles Grasso

**References**:**[SI-LIST] Re: Diff.Pairs***From:*esayre

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