[SI-LIST] Re: Signal crossing Split plane

Yuriy,
 not only are your slot simulations on your page not so helpful, but your via 
simulations are very misleading. I think you'll run into trouble when you try 
to compare your simulation and measurement results, because your simulation 
models are unrealistic.
At such frequencies (20 GHz and beyond), the via can no longer be considered to 
be just the barrel and the pads, as you did. The modes excited at the via-trace 
interface don't die abruptly, but extend along the traces to the ports. So 
either you seperate these modes from the originally excited modes at the port 
(in order to obtain "clean" S-parameters') or you allow the modes to die before 
they reach the ports (as recommended in most 3D full-wave solvers).
I just read a very interesting research paper the other day on defining the 
boundaries of discontinuties, in which these issues are properly examined. I 
can't really remember the exact title nor its authors at the moment, but the 
paper was presented at a Ph.D. research conference on microelectronics and 
electronics somewhere in Europe (Italy, I presume). You'll be shocked at the 
error you are making when you read this work. 
You also connected the models of the via and transmission lines after the 
simulations, correct? Here you go wrong again, because how do you know where 
the vias "actually" begin and end? And at what freqency? These are very 
complicated issues and I suggest you spend a little more time studying them 
well.
Thanks.
Charles

Yuriy Shlepnev <shlepnev@xxxxxxxxxxxxx> wrote: Scott,

I agree with you. It was just an illustration of a slot-type discontinuity
in general for some stackup configurations. It shows how a slot-type
discontinuity in a reference plane may reflect the signal even in the case
if slot does not cut across the board or around a patch (though, it might be
obvious for you). As soon as the coupling to a slot is strong, it has to be
simulated at the system level with a complete geometry of the slot or split,
with all relevant traces crossing the slot and all de-caps (if any). I
prefer to do it with the hybrid de-compositional approach on the base of
localized models built with an electromagnetic solver. The localized strip
to slot coupling effect can be captured with a 4-port S-parameter model for
strip crossing the slot for instance (two ports for the strip and two for
the slot). Combined with the strip and slot line models, it produces a
simple and computationally efficient system-level model that captures
practically all coupling and resonance effects.
 
Best regards,
Yuriy

Yuriy Shlepnev
Simberian Inc.
www.simberian.com 


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Scott McMorrow
Sent: Sunday, November 18, 2007 12:29 PM
To: shlepnev@xxxxxxxxxxxxx
Cc: sunil_bharadwaz@xxxxxxxxx; 'SI LIST'
Subject: [SI-LIST] Re: Signal crossing Split plane

Yuriy

Actually, these sorts of slot simulations are pretty meaningless.  Slots 
normally occur due to plane splits.  As a result, the either extend from 
one edge of a board to another edge, or when the plane is a square patch 
the slot is a closed loop around the periphery of the plane.  When this 
happens, it is quite interesting to simulate multiple signals crossing 
the slot.  There is a very nice slot resonance mode that occurs that is 
generally in the signal bandwidth (or at least 3rd harmonic) because of 
the length of the slot. This induces a signficant amount of ringing and 
crosstalk into neighboring traces.

scott

Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax

http://www.teraspeed.com

TeraspeedR is the registered service mark of
Teraspeed Consulting Group LLC



Yuriy Shlepnev wrote:
> Sunil,
>
> A simple example of how an electromagnetic solver can be used to
investigate
> the effect of a slot or split in a reference plane is provided at
> http://www.simberian.com/AppNotes.php - see the topmost app note.
>
> Best regards,
> Yuriy
>
> Yuriy Shlepnev
> Simberian Inc.
> www.simberian.com
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On
> Behalf Of sunil bharadwaz
> Sent: Sunday, November 18, 2007 1:26 AM
> To: SI LIST
> Subject: [SI-LIST] Signal crossing Split plane
>
> Hi ,
> I have few signals (@ 80 Mhz & 20 Mhz) crossing the split Power
> plane in the adjacent layer.
>
> The 20 Mhz signal is diffrerential signal.The 80 Mhz is a single
> ended signal.
>
> I want to analyse the affect on Signal Integrity of these two
> signals due to split plane.
>
> I believe one need to define his stack up (Including the 
> split) & then extract the layout to simulate.
>
> I'am not too sure if the prevalent SI tools have an option
> of creating split planes .
>
> Pls suggest me a right tool to carry out this.Also , i'am
> looking for a free tool to start with (even if the accuracy 
> is slightly limited).
>
> Thanks in Advance!!
>
> Regards
> Sunil.Bh
>
>        
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