[SI-LIST] WG: Re:AW: A query in High speed Signal Integrity analysis
- From: "Havermann, Gert" <Gert.Havermann@xxxxxxxxxxx>
- To: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 21 Feb 2013 09:45:13 +0000
Hi Tesla,
Return Loss is basically the same as vswr, thus a bad RL means a bad vswr,
means that the standing waves amplitudes are stronger.
When you simulate or measure a transmission line, you see RL ripples. The
“amplitude” of these ripples is directly related to the impedance of the line:
the further off the impedance is in regards to the termination and source, the
higher the ripples. This is valid for common mode as well as differential mode.
BR
Gert
Von: Tesla [mailto:emcesd@xxxxxxx]
Gesendet: Donnerstag, 21. Februar 2013 09:59
An: Havermann, Gert
Cc: si-list@xxxxxxxxxxxxx
Betreff: Re:[SI-LIST] AW: A query in High speed Signal Integrity analysis
Hi, Gert
Could you explain a little more about high common mode impedance resulting in
high common mode return loss?
Thanks.
Tesla
At 2013-02-20 16:40:26,"Havermann, Gert" <Gert.Havermann@xxxxxxxxxxx> wrote:
>Yes, the problem is tight coupling. the tighter you couple, the higher the
>single ended impedance must be, resulting in high common mode impedance
>resulting in high common mode return loss.
>
>If you will have EMI problems or not can't be judged just by the trace, but a
>high common mode return loss opens the door for EMI problems, therefore I
>would try to keep this door closed.
>
>BR
>Gert
>
>
>----------------------------------------
>Absender ist HARTING Electronics GmbH, Marienwerderstraße 3, D-32339
>Espelkamp; Registergericht: Amtsgericht Bad Oeynhausen; Register-Nr.: HRB
>8808; Vertretungsberechtige Geschäftsführer: Dipl.-Kfm. Edgar-Peter Düning,
>Dipl.-Ing. Torsten Ratzmann
>
>
----------------------------------------
Absender ist HARTING Electronics GmbH, Marienwerderstraße 3, D-32339 Espelkamp;
Registergericht: Amtsgericht Bad Oeynhausen; Register-Nr.: HRB 8808;
Vertretungsberechtige Geschäftsführer: Dipl.-Kfm. Edgar-Peter Düning,
Dipl.-Ing. Torsten Ratzmann
-----Ursprüngliche Nachricht-----
>Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im
>Auftrag von Syed Razeen Raj Mohamed - ERS, HCL Tech
>Gesendet: Dienstag, 19. Februar 2013 08:17
>An: Mohanty, Sarada; O Nithin Bharadwaj; si-list@xxxxxxxxxxxxx
>Betreff: [SI-LIST] Re: A query in High speed Signal Integrity analysis
>
>Is this a problem of Tight coupling? The lengths of the P/N are the same,
>since it is a Pre-SI analysis.
>Single end imp was 113ohms and diff imp was 95 ohms
>
>Is it recommended to use loose coupling or can we proceed with the current
>trace width n spacing. Will ter be a EMI problems because of that ??
>Kindly clarify
>
>Thanks & Regards
>Razeen.
>
>-----Original Message-----
>From: Mohanty, Sarada [mailto:Sarada.Mohanty@xxxxxxx]
>Sent: Tuesday, February 19, 2013 12:04 PM
>To: O Nithin Bharadwaj; si-list@xxxxxxxxxxxxx
>Cc: Syed Razeen Raj Mohamed - ERS, HCL Tech
>Subject: RE: A query in High speed Signal Integrity analysis
>
>Hi Nitin,
>
>Common mode return loss issue could be reason of mismatching differential Skew
>between P/N pair and tight coupling between P/N pair. Common mode could not
>always terminated because of mismatching ground reference between P/N (P with
>ground & N with ground). It Can be reduced by properly terminating with common
>model termination or matching with P/N differential skew with tight tolerance.
>
>Thanks,
>Sarada
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
>Behalf Of O Nithin Bharadwaj
>Sent: Tuesday, February 19, 2013 11:39 AM
>To: si-list@xxxxxxxxxxxxx
>Cc: Syed Razeen Raj Mohamed - ERS, HCL Tech
>Subject: [SI-LIST] A query in High speed Signal Integrity analysis
>
>Hi ,
>
>I'm currently working on a design that operates at 6GBps. It's a Pre-SI
>analysis and when I look at the s-parameters the Differential Return loss and
>Insertion loss meets the requirement.
>And when i observe the common mode return loss fails to meet the requirement.
>What is the impact if I violate the common mode return loss spec? What is the
>benefit to me beating it?
>
>Kindly let me know your valuable comments so I can give my recommendations to
>my layout team for routing.
>
>Thanks & Regards
>Razeen.
>9176668688
>
>
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