A good white paper is linked here:
http://www.polarinstruments.com/support/si/AP8164.html
Kb, the near end crosstalk coefficients, is indeed calculated with L and C
between interconnects. However, L & C values are both frequency dependent.
For example, a tabular model for coupled lines has frequency dependent
R/L/G/C content. So the Kb value calculated is also frequency dependent,
not a constant.
For comparison of different models, one may pick a measurement frequency,
say 1GHz, to compare their crosstalk. In reality (e.g. circuit simulation),
all these frequency dependency will be taken into account when producing
final response.
MH
On Thu, Jun 18, 2015 at 3:58 PM, Conrad Herse <herse@xxxxxxxxxxxxx> wrote:
My response was incomplete. As I understand it reverse crosstalk will
reach some maximum magnitude and then level off. Achieving this maximum
magnitude is a function of both coupled length and rise time, hence the
sensitivity to frequency.
Conrad
From: Conrad Herse <herse@xxxxxxxxxxxxx>
To: "scott@xxxxxxxxxxxxx" <scott@xxxxxxxxxxxxx>; Boris Bakshan <
bbakshan@xxxxxxxxx>
Cc: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
Sent: Thursday, June 18, 2015 5:44 PM
Subject: [SI-LIST] Re: NEXT vs. Frequency
Does rise time not also effect the *duration* of reverse crosstalk and
NEXT?
Conrad
From: Scott McMorrow <scott@xxxxxxxxxxxxx>
To: Boris Bakshan <bbakshan@xxxxxxxxx>
Cc: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
Sent: Thursday, June 18, 2015 4:01 PM
Subject: [SI-LIST] Re: NEXT vs. Frequency
You are mixing up NEXT with Reverse Crosstalk, and FEXT with Forward
Crosstalk
Reverse and Forward crosstalk are traveling waves the propagate on coupled
conductor in the forward and reverse directions.
NEXT and FEXT are the measurements made at the near end and far end sides
of the victim interconnect. NEXT is subject to discontinuities in
interconnect, including imperfect termination at the near and far ports.
These discontinuities give rise to frequency dependent variations in NEXT.
Scott McMorrow
Consultant - R&D
Teraspeed Consulting - A Division of Samtec
16 Stormy Brook Rd
Falmouth, ME 04105
(401) 284-1827 Business
http://www.teraspeed.com
On Thu, Jun 18, 2015 at 4:46 PM, Boris Bakshan <bbakshan@xxxxxxxxx> wrote:
Hello experts!the
It is well known that NEXT coefficient is dictated by the properties of
interconnect (mutual capacitance and inductance between the two
interacting lines). I do not see why is it that NEXT should change with
respect to frequency?
With FEXT, since we have rise time taken into account then the frequency
dependence is more trivial.
What am I missing with NEXT?
Thanks,
Boris.
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