[SI-LIST] Re: How many simulated bits are confident using HSPICE generating eyediagram.
- From: Hermann Ruckerbauer <hermann.ruckerbauer@xxxxxxxxxxxxx>
- To: "Sharma, Rajeev" <rajeev.sharma@xxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 07 Jul 2011 13:34:30 +0200
Hello Rajeev,
good question .. it's some time ago that I came to this conclusion :-)
I think that (multiple) reflections of the X-talk induced noise on the
Victim is not considered with this approach. These reflections are
somehow uncorrelated to the original pattern due to the different flight
times of FEXT and NEXT. So the worst case X-talk might be an overlay of
the 1-st order Xtalk and a specific situation where the Reflected X-talk
hits the receiver at the worst case ISI pattern.
So the worst case X-talk pattern might be not even/odd, but might be
generated by Even/Odd X-talk pattern at the time where the Worst case
ISI is generated + a specific different Pattern on the Aggressors sent
before that Triggers the worst case reflection (from X-talk) on the Victim.
Not sure what other effects might be not included ...
Any ideas (and approaches to include this effects) are welcome!
Best Regards
Hermann
EKH - EyeKnowHow
Hermann Ruckerbauer
www.EyeKnowHow.de
Hermann.Ruckerbauer@xxxxxxxxxxxxx
Veilchenstrasse 1
94554 Moos
Tel.: +49 (0)9938 / 902 083
Mobile: +49 (0)176 / 787 787 77
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schrieb Sharma, Rajeev:
> Hi Hermann,
> Why do you say that Odd mode/even mode crosstalk(that you described below)
> might not be able to capture the worst crosstalk?
> What is missed out in this approach?
>
> BR,
> Rajeev
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of Hermann Ruckerbauer
> Sent: Monday, July 04, 2011 4:02 PM
> To: si-list@xxxxxxxxxxxxx; emcesd@xxxxxxx
> Subject: [SI-LIST] Re: How many simulated bits are confident using HSPICE
> generating eyediagram.
>
> Hi Tesla,
>
> Steve already mentioned most of my thoughts:
>
> What I usually do is to simulate a step response and take a look how
> long it takes until the signal has setteled. Based on this you can
> select which PRBS length you need to take in order to capture the worst
> case ISI (there are some papers out describing this approach).
>
> On the X-talk there is the brute force method as Steve describes, but as
> this is very time consuming (especially when having more aggressors). I
> use a different method that is not that accurate, but captures most of
> X-talk effects while minimizing runtime:
> Take the PRBS pattern that you run on the Victim and run the same
> pattern on all agressors (even X-talk) in the second step (same
> simulation) take the PRBS pattern from the Victim and run an inverted
> pattern on all Aggressors. This approach might not capture the worst
> case X-talk, but limits the simulation time to running the PRBS sequence
> two times at a reasonable accuracy.
>
> The better option might be to use a statistical approach for your
> simulation (not sure if HSPICE includes such thing in the meantime).
> Simulate a stepresponse to characterize the Channel (or use
> S-Parameters), and based on frequency domain characteristics a dataeye
> (including X-talk) can be calculated. There are many simulators out that
> can do such stuff in the meantime ...
>
> Best regards
>
> Hermann
>
> EKH - EyeKnowHow
> Hermann Ruckerbauer
> www.EyeKnowHow.de
> Hermann.Ruckerbauer@xxxxxxxxxxxxx
> Veilchenstrasse 1
> 94554 Moos
> Tel.: +49 (0)9938 / 902 083
> Mobile: +49 (0)176 / 787 787 77
> Fax: +49 (0)3212 / 121 9008
>
>
> schrieb steve weir:
>> The answer depends on what you want to know.
>>
>> If you want to capture your basic channel characteristics under the
>> intended encoding scheme, then figure out your maximum run length and
>> pick a PRBS sequence that is long enough to capture that run length and
>> simulate the entire sequence.
>>
>> If you are trying to do something like evaluation of crosstalk on the
>> eye, then brute force starts to get expensive in simulation time. The
>> brute force method is to use a different PRBS on each aggressor than the
>> victim, and then run the product of the two sequence lengths.
>>
>> Steve.
>> On 7/4/2011 12:42 AM, Tesla wrote:
>>> Hi All,
>>> I will simulate a Multi-Gigabit Serial Link(10Gbps) using HSPICE. I
>>> want to generating eye diagram as the final result, But i don't know how
>>> many bits to run ? Can someone give me some hints?
>>> Best Regards.
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