On Tue, 16 Jun 2015 22:08:17 -0500, "Pszemol" <P...@P...com>
wrote:
> 1.5 Differential Signals
> In the case of differential signals, the negative effect of
crosstalk is a
> positive one. The signals on each trace are in theory exactly equal
in
> magnitude and opposite in their sign. So, their electromagnetic
fields
> cancel each other and the return current on the ground plane, as
well. To
> achieve this, the traces for both signals must have the same length
in order
> that the propagation delay times are equal. The receiver is
sensitive to the
> differences of the signals and not to an absolutely level
reference, e.g.,
> to ground. If any signal radiated equally into both differential
traces, the
> receiver would not recognize it. Therefore, the designer has to
make sure
> that radiation affects both traces equally. This can be realized by
routing
> differential traces as close as possible.

Znaczenie prowadzenia linii blisko siebie wyczuwam, tylko ten wpływ
niewielkiej różnicy w długości mnie męczy. Poniższy dokument zaczyna
wyjaśniać problem długości dla takiej linii transmisyjnej i wpływ
różnicy jej długości dla poszczególnych częstotliwości:

http://www.ultracad.com/mentor/differential%20design
%20rules.pdf

--
Marek