Istvan, That would be great. It always helps to see meaured results. Lee > [Original Message] > From: Istvan Novak <istvan.novak@xxxxxxxxxxx> > To: <leeritchey@xxxxxxxxxxxxx> > Cc: Istvan Novak <Istvan.Novak@xxxxxxx>; Steve Weir <weirsi@xxxxxxxxxx>; Charles Harrington <ch_harrington@xxxxxxxxx>; <shlepnev@xxxxxxxxxxxxx>; <scott@xxxxxxxxxxxxx>; <sunil_bharadwaz@xxxxxxxxx>; SI LIST <si-list@xxxxxxxxxxxxx> > Date: 11/24/2007 7:33:50 AM > Subject: [SI-LIST] Re: Signal crossing Split plane > > Lee, > > Agree, it is better to speak about data than verbal arguments. Will > write it up and publish. > > Hope you have a great Thanksgiving weekend. > > Istvan > > > > > Lee Ritchey wrote: > > 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. > >>>>>> > >>>>>> > >>>>>> > >>>>>> > >>>>>> > >>> > >>> > >>> > >>> > >>> > >> ------------------------------------------------------------------ > >> To unsubscribe from si-list: > >> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > >> > >> or to administer your membership from a web page, go to: > >> //www.freelists.org/webpage/si-list > >> > >> For help: > >> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > >> > >> > >> List technical documents are available at: > >> http://www.si-list.net > >> > >> List archives are viewable at: > >> //www.freelists.org/archives/si-list > >> or at our remote archives: > >> http://groups.yahoo.com/group/si-list/messages > >> Old (prior to June 6, 2001) list archives are viewable at: > >> http://www.qsl.net/wb6tpu > >> > >> > > > > > > ------------------------------------------------------------------ > > To unsubscribe from si-list: > > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > > > or to administer your membership from a web page, go to: > > //www.freelists.org/webpage/si-list > > > > For help: > > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > > > > List technical documents are available at: > > http://www.si-list.net > > > > List archives are viewable at: > > //www.freelists.org/archives/si-list > > or at our remote archives: > > http://groups.yahoo.com/group/si-list/messages > > Old (prior to June 6, 2001) list archives are viewable at: > > http://www.qsl.net/wb6tpu > > > > > > > > > > > > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > List technical documents are available at: > http://www.si-list.net > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu