Gert, great response post, thanks ! Has anyone investigated extending the
measured S-parameters bandwidth using rational compact modeling methods for
improving time domain eye simulation correspondence with direct measurements of
the eye? My thinking is extending the BW of the S-parameter may reduce impact
of windowing.
Our approach is to benchmark the simulation with direct measurements over short
to long reach with a smattering of crappy return loss channels as well. The
scope bandwidth has a lot of impact (Heidi Barnes discussed this in a
WRT/Keysight tutorial 2016), window impact is significant as well in EDA tool.
- Al
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> On Behalf Of
Havermann, Gert
Sent: Sunday, July 21, 2019 11:30 PM
To: farhilltramper@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] AW: Bandwidth of channel sparameter vs EH/EW
Hi Tramp,
the eye is time domain, thus the S-parameters are Fourier transformed. Fourier
transform expects unlimited bandwidth but every set of S-parameters is band
limited, so there are always artefacts or even errors when handling
S-parameters in time domain.
The time domain signal after Fourier is a repeating (pulse response followed by
pulse response...) and the software defines a window to cut out just a single
response as the final result. If the window is too large, or there is some
causality error, then there is a signal right at the end of the time domain
signal. That means there is more energy in the interval leading to a smaller
Eye opening and thus al following calculations will be incorrect. Causality is
very important for S-Parameters that are translated to time domain.
Mit freundlichen Grüßen / Kind regards.
Gert Havermann
Signal Integrity Engineer
Dept.: Corporate Technology Services
HARTING Stiftung & Co. KG
Marienwerderstraße 3
D-32339 Espelkamp
Phone +49 (0)5772 47 857
Fax +49 (0)5772 47 90857
mailto:gert.havermann@xxxxxxxxxxx
http://www.HARTING.com
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Vorstand: Dipl.-Kfm. Philip F. W. Harting (Vorsitzender), Dipl.-Kffr. Maresa W.
M. Harting-Hertz, Dipl.-Kfm. Dr.-Ing. E. h. Dietmar Harting, Dipl.-Hdl. Margrit
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-----Ursprüngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> Im Auftrag von
Tramp
Gesendet: Sonntag, 21. Juli 2019 21:29
An: si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] Bandwidth of channel sparameter vs EH/EW
Dear SI experts,
It seems that the bandwidth of channel sparameter has influence on the eye
result.Taking 10GKR for example, when comparing the eye obtained w/ the snp of
the BW of 50GHz, 60GHz, and 100GHz, the trend I observed so far is as
follows:
The 50GHz snp gets the smallest EH + largest EW, and vice versa for the 100GHz
snp. The eye obtained w/ 60GHz has the mediate EH/EW in between, Does that make
sense? If, anyone can explain why?
--
Best Regards,
Tramp
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