[SI-LIST] Re: SI Simulation of GHz signals
- From: "Russell D. Moser" <r.moser@xxxxxxxxxxxxxxxxx>
- To: <fzanella@xxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 27 Jul 2004 11:32:05 -0400
I am proud to see such spirited discussion and questions especially from
those with who I have had the opportunity to work with.
I propose a thought that has been discussed over time.
We feel (@ Orion) that we are at a point (and have been for awhile) in our
SI efforts where computational capacity and modeling methods are approaching
the variability of the components.
Simply put, we have seen that variations in PWB, connector and cable
assemblies have finally been able to be discerned due to the granularity of
our models and simulators.
In a former capacity, way back in the late 80's, we had customers ask how
our models correlated with manufacturing variability. As you'd expect, we
were working at edge rates of 1-5ns where such perturbations were not
discernable.
Noting edge rates under 150ps (although those edges are quickly slowed),
our once lumped devices have now exposed their internal variability such as
those of internal geometries (in the case of connectors), materials (PWB
resin pooling, dielectric variability) and lay (in the case of cables.
Many of us who have been around for quite awhile keep this in mind while
developing product, models and designs, I offer this as a bit of wisdom for
those whom are just entering into the field of SI. Do not de-focus on the
real-world nature of the components that we wish to model.
Regards,
___________________
Russell D. Moser
Orion Group
r.moser@xxxxxxxxxxxxxxxxx
www.theoriongroup.net
717.914.0116
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> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Zanella, Fabrizio
> Sent: Tuesday, July 27, 2004 10:12 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: SI Simulation of GHz signals
>
> Does anyone have pointers to detailed explanations of the
> techniques required for the following techniques required for
> 5Gbs and above SI simulations?
> Probability Distribution Function (PDF) plots, Bathtub Curves (CDF).
> Also, what is the maximum allowable crosstalk in dB from the
> surrounding channels at the operating frequency when measured
> with respect to the insertion loss on the channel?
>
> Thanks,=20
> Fabrizio Zanella
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Craig Clewell
> Sent: Tuesday, July 27, 2004 8:48 AM
> To: clifford@xxxxxxxxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: SI Simulation of GHz signals
>
> Hi Clifford,=20
>
> If you are really interested in running the s parameters in
> HSPCIE to speed up your simulation times (and your part
> vendor won't supply them) you may want to set up an ac
> analysis for the "parts" and run each one individually. You
> can generate the S parameters within HSPICE, or any other
> simulator using discrete components. I keep some handy
> netlists available that I re-use over and over again that
> allow me to just drop in single part models. You also may
> want to create a macro in Excel, or a script in MatLab,
> etc... that will take your output and format it into a
> Touchstone file. =20
>
> If you do this work up front you can train your monkey to
> re-use the netlist and macro over and over again. This will
> also allow you to quickly go back and investigate each piece
> of the system on its own, and build up a library of S
> parameter files for devices that you re-use.
> When you want to put the system together you can then drop in
> all the s parameter files from your library.
>
> ...just an idea
>
> Craig
>
> =20
>
> >Hello
> >I would like to perform reliable simulation of GHz signals (up to
> >3.125GHz), specifically Xilinx RocketIO. I would like to
> include in the
> >simulation the effects of the following:
> >Driver->PCB trace (incl. vias)->connector->cable->connector->PCB
> >trace(incl. vias)->Receiver
> >
> >The models that I have obtained from the various vendors are HSPICE
> >models. I have evaluated two of the most recommended S.I. toolchains:
> >Mentor G. HyperLynx and Cadence Spectraquest. Both tools use
> HSPICE as
> >the simulation engine, and essentially act as a front-end gui to
> HSPICE,
> >as well as extracting the PCB trace/via models. My
> experiences thusfar
> >with both tools have not been good. Anything but the most
> simplistic of
> >traces causes the tools to either crash or take rediculous time to
> >process (of the order of hours for even a simple net). A
> further issue
> >is that both of these tool vendors claim that the HSPICE
> simulator is
> >not necessary, and that the simulation can be performed
> without it, but
> >practically this is not the case, due to a lack of availability of
> >reliable models in anything other than HSPICE format. The conversion
> >from HSPICE to any of the custom modelling types is also, in my
> opinion,
> >non-trivial and potentially an extremely tedious manual process.
> >
> >I believe that S-Parameter based simulation provides much faster
> >simulation, but again there is a lack of availability of S-Parameter
> >models.
> >
> >Can anyone recommend a method for simulating the above
> signals that is
> >simple, robust and reliable, or is the simulation of such
> signals still
> >premature? Coming from a HW design background, I am fairly
> new to S.I.,
> >but it seems surprising that there is no industry-standard
> modelling
> >type (equivalent of IBIS) that cable/connector vendors will provide,
> but
> >maybe this level of simulation is in its infancy, and S-Parameter
> models
> >will emerge as the standard?
> >
> >Is the simulation of such signals entirely necessary? I am dubious
> about
> >the reliability of the results of such simulations, and I am
> wondering
> >whether it is not more practical to just take all the precautions
> >possible and hope for the best!
> >
> >Please let me know if you have any advise, or a good solution to my
> >dilemma!
> >
> >Kind regards,
> >Clifford
> >
> >
> >
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