[SI-LIST] Re: SI Simulation of GHz signals

Russell,
Very well said indeed.

Michael E. Vrbanac

Russell D. Moser wrote:

> 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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