[SI-LIST] Re: One stitching via or more vias is better for 25Gbps application???

  • From: steve weir <weirsi@xxxxxxxxxx>
  • To: leeyuyun <leeyuyun@xxxxxxxxxx>
  • Date: Sat, 06 Sep 2014 05:28:33 -0700

Typically, HFSS is used to design structures.
There is not a single correct answer.   Z axis transitions are not 
entirely localized.  One could design a D pair  transition for a single 
pair and then find out when they place that structure, that they have 
important differences in performance due to other surrounding structures 
including other transitions and stitch via patterns.  Simberian has 
several good papers on their web site addressing these types of issues.

Steve
On 9/6/2014 5:16 AM, leeyuyun wrote:
>
> Hi, Steve
> Thanks your information
> I have SI wave and HFSS software, and which one is better for 25Gbps 
> application?
> Do you agree P/N share the same stitching via is a good way?
> Appreciate your teaching
> Regards, Lee
>
> > "steve weir" <weirsi@xxxxxxxxxx> 於 2014/9/6 下午7:45 寫道:
> >
> > "It depends".  In the general sense: Tighter stitching increases the
> > lowest cavity resonant frequencies.  However stitching is not free, and
> > where stitching goes particularly close to signal vias can have a big
> > impact on how the overall structure performs.
> >
> > If you want well controlled results that meet a particular loss budget,
> > then you really need to model in a good solver.  You can always contract
> > with someone to design your transitions for you. There are entire
> > businesses built around getting structures like this right:  Teraspeed,
> > Wild River, etc.
> >
> > Steve
> > On 9/6/2014 4:25 AM, Leeyuyun wrote:
> > > Hi, all
> > > I am doing 100Gbps (4x25Gps) product now
> > > How do we put stitching vias when high speed signal change the layer?
> > > This is a differential pair, which has P and N
> > > Someone told me that one stitching vias is better because P and N 
> share the common return
> > > Someone told me that more stitching vias is better because loop 
> inductance could be reduced more
> > > I am confused which one is better?
> > > Can anyone help me?
> > > Thanks, 
> Lee------------------------------------------------------------------
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> > --
> > Steve Weir
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-- 
Steve Weir
IPBLOX, LLC
1580 Grand Point Way
MS 34689
Reno, NV  89523-9998
www.ipblox.com

(775) 299-4236 Business
(866) 675-4630 Toll-free
(707) 780-1951 Fax

All contents Copyright (c)2013 IPBLOX, LLC.  All Rights Reserved.
This e-mail may contain confidential material.
If you are not the intended recipient, please destroy all records
and notify the sender.



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