[SI-LIST] Re: Signal crossing Split plane
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Istvan Novak" <Istvan.Novak@xxxxxxx>
- Date: Wed, 21 Nov 2007 16:00:18 -0800
Istvan,
If your data is public, why not share it with us. It would make your case
solidly.
Lee
> [Original Message]
> From: istvan novak <Istvan.Novak@xxxxxxx>
> To: <leeritchey@xxxxxxxxxxxxx>
> Cc: Steve Weir <weirsi@xxxxxxxxxx>; Charles Harrington
<ch_harrington@xxxxxxxxx>; <shlepnev@xxxxxxxxxxxxx>; <scott@xxxxxxxxxxxxx>;
<sunil_bharadwaz@xxxxxxxxx>; SI LIST <si-list@xxxxxxxxxxxxx>
> Date: 11/21/2007 1:08:00 PM
> Subject: [SI-LIST] Re: Signal crossing Split plane
>
> Lee,
>
> You are correct in saying that how much problem we have from plane
> splits strongly depends on how the split is done and how the PDNs
> are designed on those planes. If, for instance, we have a solid ground
> plane behind the split planes, the return loop size just temporarily
> expands, signal degradation may be minimal, crosstalk may go up
> proportionally to how much the normalized spacing of traces over the
> split decreases. If the split is narrow, the extra crosstalk pulse will
> be similarly narrow. With today's sub 100-ps edges it still may come
> close to the saturated crosstalk value over the gap.
>
> I dont claim that I have analyzed all possible practical parameter
> combinations, but those that I have looked at, it WAS NOT the
> signal integrity of a particular signal that suffered first when traces
> crossed plane splits. First suffers crosstalk and EMI radiation.
> I have 12-year-old measured data to show this, though it has not
> been published. The data is not confidential, it just happens to be
> part of the SI courses I do.
>
> Regards,
> Istvan
>
>
>
>
> Lee Ritchey wrote:
>
> >Iv've got the test PCBs, do you have the tools?
> >
> >Lee
> >
> >
> >
> >
> >>[Original Message]
> >>From: steve weir <weirsi@xxxxxxxxxx>
> >>To: <leeritchey@xxxxxxxxxxxxx>
> >>Cc: Charles Harrington <ch_harrington@xxxxxxxxx>;
> >>
> >>
> ><shlepnev@xxxxxxxxxxxxx>; <scott@xxxxxxxxxxxxx>;
> ><sunil_bharadwaz@xxxxxxxxx>; SI LIST <si-list@xxxxxxxxxxxxx>
> >
> >
> >>Date: 11/20/2007 5:45:16 PM
> >>Subject: [SI-LIST] Re: Signal crossing Split plane
> >>
> >>Lee I don't think the original problem would have warranted
> >>measurements. But the thread has moved significantly since then. It
> >>might be a fun test of Simbeor to model your test vehicle and compare
> >>results. Rather than just drive with a TDR, it might be fun to drive
> >>with a pulse generator that can be set to the simulated resonant
> >>frequency and see if doing so impacts measured results in real life the
> >>way simulation predicts.
> >>
> >>Best Regards,
> >>
> >>
> >>Steve.
> >>Lee Ritchey wrote:
> >>
> >>
> >>>I've watched this thread for a while now and haven't seen anyone
suggest
> >>>making measurements. I've done lots of that and have several test
> >>>
> >>>
> >boards
> >
> >
> >>>in my lab that represent the kind of plane splitting that is done to
> >>>accommodate two Vdds in the same plane. I've run traces over these
> >>>
> >>>
> >splits
> >
> >
> >>>and measured them with a TDR with a rise time of 40 pSEC. There is no
> >>>detectable disturbance of the signal when this is done. (Of course,
the
> >>>Vdd PDS designs need to be done such that the frequencies in the
signals
> >>>crossing the planes can be properly supported. If that has not been
> >>>
> >>>
> >done,
> >
> >
> >>>worrries about crossing plane splits will be the minor problem.)
> >>>
> >>>I've also measured hundreds of vias used to change layers from top to
> >>>bottom of a PCB and from adjacent layer to adjacent layer. Again,
> >>>measuring these vias with the same TDR they behave as though someone
has
> >>>attached a very small parasitic capacitor, on the order of .5 pF for a
> >>>
> >>>
> >12
> >
> >
> >>>mil drill in a 100 mil thick PCB. There has been no detectable
> >>>
> >>>
> >coupling of
> >
> >
> >>>energy into the space between planes.
> >>>
> >>>Same thing for right angle bends. Not a detectable source of signal
> >>>degradation or EMI.
> >>>
> >>>Sometimes a little lab time saves a lot of agony and speculation.
> >>>
> >>>If there are those out there who have tests that prove otherwise,
> >>>
> >>>
> >perhaps
> >
> >
> >>>they should publish the results. I've published mine several times as
> >>>
> >>>
> >have
> >
> >
> >>>others.
> >>>
> >>>Hope this helps those who are confused by all of the complex
> >>>
> >>>
> >explanations
> >
> >
> >>>that have been offered without any supporting measurements.
> >>>
> >>>Lee Ritchey
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>>[Original Message]
> >>>>From: Charles Harrington <ch_harrington@xxxxxxxxx>
> >>>>To: <shlepnev@xxxxxxxxxxxxx>; <scott@xxxxxxxxxxxxx>
> >>>>Cc: <sunil_bharadwaz@xxxxxxxxx>; SI LIST <si-list@xxxxxxxxxxxxx>
> >>>>Date: 11/20/2007 2:45:54 PM
> >>>>Subject: [SI-LIST] Re: Signal crossing Split plane
> >>>>
> >>>> Yuriy,
> >>>> I agree with some of your views. However, they contradict your via
> >>>>
> >>>>
> >>>>
> >>>models.
> >>>
> >>>
> >>>
> >>>> I couldn?t reply yesterday, because I was trying search for the
> >>>>
> >>>>
> >>>>
> >>>reference I mentioned, since you needed it. Many other people replied
> >>>off-line and so needed the reference. Got it from IEEE Xplore.
> >>>
> >>>
> >>>
> >>>>
> >>>>
> >>>> A Novel Methodology for Defining the Boundaries of Geometrical
> >>>>
> >>>>
> >>>>
> >>>Discontinuities in Electronic Packages
> >>>
> >>>
> >>>
> >>>>Ndip, I.; Reichl, H.; Guttowski, S.;
> >>>>Research in Microelectronics and Electronics 2006, Ph. D.
> >>>>12- 15 June 2006 Page(s):193 - 196
> >>>>
> >>>>
> >>>> You mentioned in your mail that the near field zone as a result of
> >>>>
> >>>>
> >the
> >
> >
> >>>>
> >>>>
> >>>>
> >>>higher-order modes excited at the via expands with frequency and is
very
> >>>small. I agree with you.
> >>>
> >>>
> >>>
> >>>> But the question is this. How small is it? How small or big is at 1
> >>>>
> >>>>
> >>>>
> >>>GHz, 10 GHz, 20 GHz? Have you ever studied it? You have to take this
> >>>
> >>>
> >zone
> >
> >
> >>>into consideration when studying vias or any other structures that
> >>>
> >>>
> >excite
> >
> >
> >>>higher order modes.
> >>>
> >>>
> >>>
> >>>> The method proposed in this paper is quite illustrative and
> >>>>
> >>>>
> >useful. I
> >
> >
> >>>>
> >>>>
> >>>>
> >>>understand it this way (Please correct me if I understand it wrongly):
> >>>
> >>>
> >>>
> >>>> These higher-order modes (e.g., TE, TM...) are characteristics of
> >>>>
> >>>>
> >the
> >
> >
> >>>>
> >>>>
> >>>>
> >>>trace or transmission line and they die exponentially away from the
> >>>
> >>>
> >point
> >
> >
> >>>of excitation, i.e., the via-trace interface. S-parameters, like other
> >>>network parameters, give us the relation between input and output
> >>>
> >>>
> >signals.
> >
> >
> >>>Now, to obtain S11, for example, you need to get the ratio of the
> >>>
> >>>
> >reflected
> >
> >
> >>>and input signals. Both signals must be of the same "type". We can not
> >>>directly compare cars and aeroplanes, though both are used for
> >>>transportation. You know your input signal (e.g., a transverse
> >>>electromagnetic wave), because you excited it at the port. At
> >>>discontinuities, an infinite order of given higher-order modes can be
> >>>excited. The orders or strength of the excited modes differ from one
> >>>discontinuity to another, although the modes can be the same. So, there
> >>>
> >>>
> >is
> >
> >
> >>>no way you can know all the orders of the higher-order modes excited
and
> >>>how they interact. Now if you place your ports quite close to the point
> >>>
> >>>
> >>>
> >>>> of excitation of these modes, then your S-parameters must be wrong.
> >>>>
> >>>>
> >Why?
> >
> >
> >>>>
> >>>>
> >>>>
> >>>In this case, to obtain S11, you need to obtain the ratio of the
unknown
> >>>higher-order modes and your known excited transverse electromagnetic
> >>>
> >>>
> >wave
> >
> >
> >>>at the port. That?s why in most 3D full-wave solvers, it is recommended
> >>>that ports should be placed far away from the discontinuities, so as to
> >>>enable these higher-order modes to die. When they die, then you can
> >>>
> >>>
> >easily
> >
> >
> >>>define your S-parameters which will then be the ratio of the input
> >>>
> >>>
> >signal
> >
> >
> >>>you know (transverse electromagnetic wave) and the reflected signal you
> >>>know (transverse electromagnetic wave). To define the points where
these
> >>>modes die or have attenuated substantially, these authors argued that
> >>>
> >>>
> >near
> >
> >
> >>>the discontinuity, the imaginary part of the Poynting vector describes
> >>>
> >>>
> >the
> >
> >
> >>>reactive energy associated with these higher-order modes. So they
> >>>
> >>>
> >studied
> >
> >
> >>>this imaginary part and used it to define the point where the modes
> >>>
> >>>
> >die. I
> >
> >
> >>>think they mentioned that only
> >>>
> >>>
> >>>
> >>>> at a distance of about 1mm away from the via-trace interface, at 20
> >>>>
> >>>>
> >GHz
> >
> >
> >>>>
> >>>>
> >>>>
> >>>(or may be 30 GHz) may you place your ports, to get correct results.
> >>>Certainly, this depends on the via geometry and trace type. But I find
> >>>
> >>>
> >the
> >
> >
> >>>results very helpful and can be used as a base for further experiments.
> >>>
> >>>
> >You
> >
> >
> >>>can get the details from the paper.
> >>>
> >>>
> >>>
> >>>> Unfortunately in your case, you compare what you don?t know
> >>>>
> >>>>
> >(reflected
> >
> >
> >>>>
> >>>>
> >>>>
> >>>signal) and what you know (excited input signal). In your via models,
> >>>neither did you define the required distance away from the via-trace
> >>>interface needed for these modes to die nor did you follow the advice
> >>>
> >>>
> >given
> >
> >
> >>>in full-wave solvers to be far way from the via-trace interface. You
> >>>considered the via just as the barrel and the pads at 20 GHz and
beyond.
> >>>That?s why I mentioned yesterday that your via models are not correct
> >>>
> >>>
> >and
> >
> >
> >>>your S-parameter results are misleading. If you wish to study only the
> >>>behaivor of the barrel alone at lower frequencies (for what ever reason
> >>>
> >>>
> >-
> >
> >
> >>>but not for realistic designs), then you don't even need a field
solver.
> >>>You can get formulas from good SI texts like that of Horward Johnson or
> >>>from papers.
> >>>
> >>>
> >>>
> >>>> At first I was also making the same mistakes as you are making right
> >>>>
> >>>>
> >>>>
> >>>now. I had a lot of difficulties to correlate my simulation and
> >>>
> >>>
> >measurement
> >
> >
> >>>results. So I learnt a lot from this paper, from Professor C. Balanis
> >>>(Advanced engineering electromagnetics) and from Professor R. Collins
> >>>(Field theory of guided waves). I think these references will be good
> >>>
> >>>
> >for
> >
> >
> >>>you. You need all three of them.
> >>>
> >>>
> >>>
> >>>> There are also a lot of points that you need to modify in your
> >>>>
> >>>>
> >models.
> >
> >
> >>>> It?s ridiculous when you talk of -30 dB attenuation of
higher-order
> >>>>
> >>>>
> >>>>
> >>>modes. Which higher-order mode? Which order of this mode? Basic
> >>>electromagnetic theory teaches us that an infinite order of a given
> >>>higher-order mode can be excited at any discontinuity. An interaction
> >>>between makes matters worst. So how do you separate the different
> >>>
> >>>
> >orders of
> >
> >
> >>>the modes and tell which one attenuates by -30 dB? Are the modes
> >>>propagating or evanescent? Never use rule of thumbs that have no base.
I
> >>>supposed you meant attenuation of the fundamental mode which is
> >>>propagating.
> >>>
> >>>
> >>>
> >>>> I don?t know anything about the lumped ports you use. All I know is
> >>>>
> >>>>
> >>>>
> >>>that some lumped ports in some field solvers assume perfect H boundary
> >>>conditions on the sides. Consequently, depending you may not even
> >>>
> >>>
> >capture
> >
> >
> >>>stray fields. So you can even get the worst results with lumped ports.
> >>>
> >>>
> >>>
> >>>> You can only shift your reference S-parameters plane and get
accurate
> >>>>
> >>>>
> >>>>
> >>>results if your model captured all the necessary field behavior. But
you
> >>>can not simulate the via and traces differently and then do some
> >>>post-processing or circuit modeling afterwards and expect to get
correct
> >>>results at higher frequencies. The traces too are part of the ?via
> >>>
> >>>
> >effect?
> >
> >
> >>>at least, at the frequencies you are interested in (20 GHz and beyond),
> >>>because the stored higher-order modes give rise to additional
> >>>
> >>>
> >inductances
> >
> >
> >>>and capacitances. These inductances and capacitances can not be
> >>>
> >>>
> >captured if
> >
> >
> >>>you analyze the vias separately from their traces.
> >>>
> >>>
> >>>
> >>>> Finally, the theory of multi-modal decomposition means different
> >>>>
> >>>>
> >things
> >
> >
> >>>>
> >>>>
> >>>>
> >>>to different electrical engineers. So I don?t know what you mean. If
you
> >>>mean that different parts of a system can be analyzed separately and
> >>>
> >>>
> >then
> >
> >
> >>>put together, then it?s true that it has been done for decades now. But
> >>>
> >>>
> >the
> >
> >
> >>>question is this. How do you bring the different parts together in the
> >>>
> >>>
> >case
> >
> >
> >>>where there are discontinuities like vias? How do you define the via?
> >>>
> >>>
> >How
> >
> >
> >>>small or big is your near field zone? I bet you, we have not yet
> >>>
> >>>
> >understood
> >
> >
> >>>this type of decomposition and it has not been done, or at least
> >>>
> >>>
> >published
> >
> >
> >>>for decades. Whenever we have to deal with vias and other
> >>>
> >>>
> >discontinuities
> >
> >
> >>>at higher frequencies, straight-forward modeling can not be used.
> >>>
> >>>
> >>>
> >>>> Please Yuryi, don?t get me wrong. I?m not trying to highlight on
> >>>>
> >>>>
> >your
> >
> >
> >>>>
> >>>>
> >>>>
> >>>errors. I have mine too, like any body else. No one is perfect. I?m
just
> >>>trying to raise the point that we need to be careful when modeling vias
> >>>
> >>>
> >at
> >
> >
> >>>your frequencies. I agree with most of the points you made, but
> >>>
> >>>
> >disagree on
> >
> >
> >>>the ones stated above. We learn from each other when we exchange ideas
> >>>about such fundamental issues that affect our modeling results. I think
> >>>that is one of the reasons why Ray and his team set up this forum.
> >>>
> >>>
> >>>
> >>>>
> >>>>Best regards.
> >>>> Charles
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>Yuriy Shlepnev <shlepnev@xxxxxxxxxxxxx> wrote: Charles,
> >>>>
> >>>>I am sorry that the simulation examples were not helpful to you. I
will
> >>>>appreciate if you send me the reference you mentioned - I am preparing
> >>>>
> >>>>
> >to
> >
> >
> >>>>
> >>>>
> >>>>
> >>>be
> >>>
> >>>
> >>>
> >>>>shocked:)
> >>>>
> >>>>You are absolutely right, the via-holes are not just pads and barrels
> >>>>
> >>>>
> >and
> >
> >
> >>>>there is no one solution that covers all possible cases. Analysis of
> >>>>different vias has to be done in different ways. Transition to the
> >>>>
> >>>>
> >traces
> >
> >
> >>>>have to be almost always included in the final model for analysis of
> >>>>multi-gigabit channels. Moreover sometime the via-hole problem cannot
> >>>>
> >>>>
> >be
> >
> >
> >>>>solved locally and require analysis of parallel plane structures with
> >>>>
> >>>>
> >all
> >
> >
> >>>>decoupling structures attached (see technical presentation #1 at
> >>>>http://www.simberian.com/Presentations.php for more details on
> >>>>
> >>>>
> >different
> >
> >
> >>>>structures).
> >>>>
> >>>>Considering the ports and excitation. Analysis of via-holes with
lumped
> >>>>ports provides just rough idea about the via-hole behavior. It is
> >>>>
> >>>>
> >similar
> >
> >
> >>>>
> >>>>
> >>>>
> >>>to
> >>>
> >>>
> >>>
> >>>>what you would see from a differential probe attached to the pads of
> >>>>
> >>>>
> >the
> >
> >
> >>>>via-holes. Transition to traces and transmission line or wave-ports
> >>>>
> >>>>
> >have
> >
> >
> >>>>
> >>>>
> >>>>
> >>>to
> >>>
> >>>
> >>>
> >>>>be used for the final extraction of S-parameters for the system-level
> >>>>analysis (I am sorry that you missed this part in app notes). Note
> >>>>
> >>>>
> >that it
> >
> >
> >>>>is possible only for the localizable via-holes or via-holes not
> >>>>
> >>>>
> >coupled to
> >
> >
> >>>>parallel planes in general. Such t-line ports have to be positioned at
> >>>>
> >>>>
> >a
> >
> >
> >>>>distance from the via-hole that guaranties that the high-order modes
> >>>>
> >>>>
> >are
> >
> >
> >>>>attenuated substantially (for practical applications we usually use
> >>>>
> >>>>
> >-30 dB
> >
> >
> >>>>threshold at the highest frequency of interest). After such analysis,
> >>>>
> >>>>
> >the
> >
> >
> >>>>phase reference planes of S-parameters can be safely shifted closer to
> >>>>
> >>>>
> >the
> >
> >
> >>>>via-hole at the position where t-lines are still continuous to
preserve
> >>>>causality (to the edges of anti-pads for instance). Such
transformation
> >>>>
> >>>>
> >>>>
> >>>does
> >>>
> >>>
> >>>
> >>>>not affect the near field or high order modes around the via-holes and
> >>>>
> >>>>
> >the
> >
> >
> >>>>final model can be safely connected with the transmission line
segments
> >>>>
> >>>>
> >>>>
> >>>in a
> >>>
> >>>
> >>>
> >>>>system-level solver. Though, the model have to be used with
> >>>>
> >>>>
> >transmission
> >
> >
> >>>>line segments with length not less than in the electromagnetic
analysis
> >>>>
> >>>>
> >>>>
> >>>(to
> >>>
> >>>
> >>>
> >>>>avoid the near-field interaction between the vias and possible
> >>>>discontinuities). This technique called the multi-modal
> >>>>
> >>>>
> >de-compositional
> >
> >
> >>>>analysis and used in microwave engineering for decades at frequencies
> >>>>
> >>>>
> >even
> >
> >
> >>>>higher than 20 GHz.
> >>>>Note, that in typical PCB trace the cut-off frequencies for high-order
> >>>>
> >>>>
> >>>>
> >>>modes
> >>>
> >>>
> >>>
> >>>>are extremely high. 10 mil trace on 10 mil dielectric with dielectric
> >>>>constant 4.2 have cut-off frequency about 120 GHz, and the cross-over
> >>>>
> >>>>
> >with
> >
> >
> >>>>the surface TM mode may happen only at 200 GHz. Before 120 GHz the
> >>>>high-order modes are evanescent and essentially form the via-hole near
> >>>>field. This near-field zone is expanding with the frequency, but at 20
> >>>>
> >>>>
> >GHz
> >
> >
> >>>>the area is still relatively small. Thus S-parameters only for the
> >>>>
> >>>>
> >>>>
> >>>dominant
> >>>
> >>>
> >>>
> >>>>modes can be safely extracted and used as the via-hole model.
> >>>>Cases when via-hole excite the non-evanescent parallel-plane modes and
> >>>>planes are not stitched close to the via-hole cannot be solved locally
> >>>>
> >>>>
> >>>>
> >>>(non
> >>>
> >>>
> >>>
> >>>>localizable) and may require the system-level analysis with all
> >>>>
> >>>>
> >decoupling
> >
> >
> >>>>structures attached.
> >>>>
> >>>>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 Charles Harrington
> >>>>Sent: Monday, November 19, 2007 8:33 AM
> >>>>To: shlepnev@xxxxxxxxxxxxx; scott@xxxxxxxxxxxxx
> >>>>Cc: sunil_bharadwaz@xxxxxxxxx; 'SI LIST'
> >>>>Subject: [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 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
> >>>>>
> >>>>>
> >>>>>---------------------------------
> >>>>>Be a better pen pal. Text or chat with friends inside Yahoo! Mail.
See
> >>>>>
> >>>>>
> >>>>>
> >>>>how.
> >>>>
> >>>>
> >>>>
> >>>>
> >
> >
> >
> >
>
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