Crosstalk Coupling: Single-Ended vs. Differential:The paper begins with four propositions. 1), the
effects of crosstalk coupling decrease with trace
separation. 2), crosstalk coupled to a differential pair
has meaning only for the differential component of the
crosstalk on the differential pair, not the common
mode component of the crosstalk. A differential
component only exists because the outside trace is
(perhaps only slightly) further away from the source
than is the inside trace. 3), crosstalk caused by a
differential pair would be equal and opposite, and
therefore cancel, on a victim trace were it not for the
(perhaps only slight) separation of the differential
traces themselves. Since one trace (of the pair) is
(slightly) closer to the victim trace than is the other
trace of the differential pair, that trace will couple
slightly more strongly and there will be a small
differential coupling to a victim trace. 4), differential
pair coupling to another differential pair would
combine these last two effects and should be quite small.