[SI-LIST] Re: Far-end crosstalk over long PCB trace
- From: "Sogo Hsu" <sogo.hsu@xxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 07 Jun 2005 04:01:56 -0000
Dear Istvan and Craig,
Thank you for your response. However, Far-end crosstalk is indeed
getting saturation. You can easily find lots of related information
by Googling "crosstalk saturation". Dr. Zhen Mu has several papers
addressed on this topic. Elie Michael Issa also mentioned the
saturation length condition. Typically, the far-end crosstalk is
assumed to be proportional to coupled length. However, the
estimation of linear far-end crosstalk is correct only if the system
is weakly coupled transmission. From conservation point of view, it
is not reasonable that the coupled energy is increased without
limitation. Meanwhile, the saturation phenomenon can be explained by
Modal Velocity. The mechanism of "crosstalk" is the result of
velocity discrepancy of different modes.
BRs,
Sogo Hsu, Ph. D.
Foxconn
--- In si-list@xxxxxxxxxxxxxxx, Istvan Novak <istvan.novak@xxxx>
wrote:
> Near-end crosstalk saturates at a length matching the
> quarter wavelength in the coupled section. Far-end
> crosstalk, however, does not saturate any 'fixed' length;
> the saturation depends also on the coupling. The weaker
> the coupling, the longer coupled length you need for saturation.
>
> Regards,
>
> Istvan Novak
> SUN Microsystems
>
> Sogo Hsu wrote:
>
> >Hi, SI Gurus,
> >
> >It seems a old question in SI-list. Right now, we evaluated the
> >crosstalk noise cased by neighboring aggressors. As we know, the
far-
> >end crosstalk noise is proportional to coupled length and will be
> >saturation if the coupled etching length is greater than
constraint
> >length. The phenomenon can be easily explained by the discrepancy
of
> >modal velocity in coupled-transmission line. However, we found
the far-
> >end crosstalk simulated by Hspice, PCB SI and SPEED XP etc.,
will not
> >behave the saturation even the coupled length is 100in. In my
opinion,
> >it is not reasonable. Pls help me to verify the solver. Thank you
in
> >advance.
> >
> >* I briefly describe the scenarios as below
> >3-line coupled transmission line
> >Tr=1ns
> >
> >Best Regards,
> >Sogo Hsu
> >
> >
> >
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