Also, considering the NEXT, the conditions to have the insertion loss dips
due to the energy transferred to the NEXT port is just more difficult to
satisfy for typical PCB configurations. Not seeing it in a particular
example does not mean that this is not possible. A superposition of the
modes can cause peak of energy transfer into the NEXT port - backward wave
directional couplers use this phenomenon. A good book on the behavior of the
coupled lines is R. Mongia, I. Bahl, P. Bhartia, RF and Microwave Coupled
Line Circuits.
Best regards,
Yuriy
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Yuriy Shlepnev
Sent: Friday, June 23, 2017 8:54 AM
To: aakash6164@xxxxxxxxx; 'Mike Brown'
Cc: tom@xxxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: NEXT and FEXT Profile for a Pulse
Aakash,
You see a dip in the insertion loss because of the energy "escapes" in the
adjacent trace - it goes into the FEXT port. Difference in the propagation
velocities of modes in coupled traces causes the FEXT. When a harmonic
signal is applied to one of the traces, it travels along the line as a
superposition of the modes. Depending on the distance and the difference of
the propagation velocities, signal can be partially or completely
transformed into the adjacent trace(s). This is the result of the
superposition of the modes. The signal is not transformed if all modes
travel with the same velocity (never happen in lossy lines - guess why).
This is one of many possible "explanations" of reality. You can literally
see how it happens in demo-video #2016_11 at
http://www.simberian.com/ScreenCasts.php - see "How Interconnects Work";
section.
Speaking of the x-talk, I should note that the simulation of the cross-talk
is not so simple task, if it has to correlate with the measurements. Results
of one of the validation projects were reported at #2011_02 at
http://www.simberian.com/AppNotes.php and Wild River Technology has XTALK-32
platform designed specifically for the x-talk validation - see more at
https://wildrivertech.com/ ;
Best regards,
Yuriy
Yuriy Shlepnev, Ph.D.
President, Simberian Inc.
2629 Townsgate Rd., Suite #235, Westlake Village, CA 91361, USA Office
+1-702-876-2882; Fax +1-702-482-7903 Cell +1-206-409-2368; Virtual
+1-408-627-7706
Skype: shlepnev
www.simberian.com
Simbeor - Accurate, Productive and Cost-Effective Electromagnetic Signal
Integrity Software
2010 and 2011 DesignVision Award Winner, 2015 Best In Design&Test Finalist
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Aakash Gupta
Sent: Monday, June 19, 2017 6:29 PM
To: Mike Brown
Cc: tom@xxxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: NEXT and FEXT Profile for a Pulse
Thanks for all your responses... I simulated and have some better
understanding now.
I also noticed the following behavior.
I see a dip in Insertion loss of my aggressor when I have FEXT.
Why don't I see a dip in insertion loss when there is only NEXT and no FEXT?
Is it because magnitude of NEXT (iC - iL) is less than FEXT (iC + iL)?
On Mon, Jun 19, 2017 at 8:12 PM, Mike <bmgman@xxxxxxxxxx> wrote:
Tom,noise.
I think the original query under this heading was from an entry-level
person trying to intuitively grasp the crosstalk mechanism and
waveforms. Hence my suggestion to consider the victim line ideally
terminated. Unless you have a well-tutored intuition, it is hard to
consider the superposition of crosstalk from both edges and the
reflections that are usually present on the victim line. A simulation
can handle it all, but often fails to provide the insight needed by a
beginner.
In most practical cases, the victim line should be terminated as in
the application, so that the totality of the crosstalk and reflections
caused by it may be evaluated.
Regards to all.
Mike Brown
ex Tandem/Compaq/HP
- - - - -
On 06/19/2017 07:12 PM, Tom Dagostino wrote:
Aubreyvictim
Nice to hear from you, haven't see you much these past few years.
Agree, an open is an termination, so is a short. My first statement, "
terminated as they are on the DUT" is the real answer.
The second statement " there is no reason to terminate the victim
in the simulation" should have read " there is no reason to
terminate the
differently in the simulation".that
From the context of the statement it was implied (at least in my
head)
a Zo termination should be applied to each end of the victim. I wasapplied
just trying to say not to add anything, just use what the DUT has in
its
configuration.On
Regards,
Tom Dagostino
971-279-5325
tom@xxxxxxxxxxxxxxxxx
Teraspeed Labs
9999 SW Wilshire Street
Suite 102
Portland, OR 97225
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
Behalf Of Aubrey Sparkmannets
Sent: Monday, June 19, 2017 4:54 PM
To: tom@xxxxxxxxxxxxxxxxx
Cc: riaziabe@xxxxxxxxx; Hermann.Ruckerbauer@xxxxxxxxxxxxx;
aakash6164@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: NEXT and FEXT Profile for a Pulse
Tom,
I agree with your comment, "any simulation should have the ends of
the
terminated as they are on the DUT of interest." But your commentEven if
about unterminated line? Every useful line has a termination of some
kind,
it's just the input capacitance of the receiver. Often there arewhich
vias
can really add to the crosstalk.wrote:
Aubrey
Sent from my iPhone
On Jun 19, 2017, at 5:14 PM, Tom Dagostino <tom@xxxxxxxxxxxxxxxxx>
Abe
Your comment : " A crosstalk simulation of a topology consisting of
an aggressor line and a victim, usually requires terminating both
ends of the victim line."
I think should read more along the lines of "any simulation should
have the ends of the nets terminated as they are on the DUT of
interest." If the victim is a source only terminated line there is
no reason to terminate the victim in the simulation.
Thoughts?
Tom Dagostino
971-279-5325
tom@xxxxxxxxxxxxxxxxx
Teraspeed Labs
9999 SW Wilshire Street
Suite 102
Portland, OR 97225
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Abe Riazi
Sent: Monday, June 19, 2017 2:48 PM
To: Hermann.Ruckerbauer@xxxxxxxxxxxxx
Cc: aakash6164@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: NEXT and FEXT Profile for a Pulse
Hi,
Since crosstalk is such an important topic in field of signal
integrity, numerous tools and methodologies have been developed for
analysis of crosstalk effects.
For instance, there exist rules of thumb, mathematical equations
and calculators for obtaining a first order estimate of crosstalk
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