[SI-LIST] Re: mode conversion myth
- From: "Yuriy Shlepnev" <shlepnev@xxxxxxxxxxxxx>
- To: "'liuluping 41830'" <liuluping@xxxxxxxxxx>, <Istvan.Novak@xxxxxxx>, <eric@xxxxxxxxxxxxxxx>
- Date: Sat, 3 Jan 2009 13:13:55 -0800
Liu,
Istvan provided some general guidance on how to handle the skew or mode
transformation that may cause the skew. I think to be more specific you have
to run your favorite electromagnetic solver and estimate the amount of the
mode transformation and what it does to the signal. It may require a
compensation or may not. Some examples of such analysis are provided in App
Note #2009_01 at http://www.simberian.com/AppNotes.php Note, that to verify
the theoretical concepts of the mode transformation and compensation,
Teraspeed Consulting Group provided experimental results from their PLRD-1
test board.
Best regards,
Yuriy Shlepnev
www.simberian.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of liuluping 41830
Sent: Friday, January 02, 2009 12:12 AM
To: Istvan.Novak@xxxxxxx; eric@xxxxxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: mode conversion myth
Dear Eric and Istvan:
Yes ,"do not introduce any local skew" ,Istavan's clarification is very
helpful in practical design,
and I also have myth on this problem: How to compensate for the local skew ?
For example ,the bend discontinuities of differential pairs,the msot
common practical routing scheme
using a small detour for the inner trace of coupled bends,but does this
compensation affect the common
mode noise?
Some paper suggest different routing schemes like shunt a compensation
capacitance at the bends,
but it's not very practical to use, Can we find better ways?
Thanks and happy new year!
LIU Luping
Msg: #5 in digest
Date: Tue, 30 Dec 2008 16:59:03 -0500
From: istvan Novak <Istvan.Novak@xxxxxxx>
Subject: [SI-LIST] Re: mode conversion myth
Hi Eric,
Yes, in general I agree with your description, I would add one
clarification, though. With a spatial resolution determined by the
bandwidth of signal we want to push through the differential
interconnect, we need to keep the electrical symmetry between the legs
all along the way. In particular, when it comes to propagation delay,
it is very important that not only the end-to-end propagation delay is
kept similar, but we do not introduce any local skew. This becomes
important when we have to decide where and how we compensate for known
skew contributors.
Regards,
Istvan
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