[SI-LIST] Re: fiber-weave effect alive and well?
- From: "Christian D'Souza" <christian.dsouza@xxxxxxxxx>
- To: Perry.Qu@xxxxxxxxxxxxxxxxxx
- Date: Fri, 14 Sep 2007 14:58:48 -0500
Perry / Aubrey,
I believe the column that Lee is talking about is:
Intelligent Design
[image: Figure 1 1080 Glass Cloth With 3.5-Mil Wire<br>] Figure 1 1080
Glass Cloth With 3.5-Mil Wire
by Lee Ritchey
April 1, 2007
On the Problem of Jitter and Skew in Gigabit and Faster Signals Caused by
Laminate Weaves
The link is
http://www.circuitree.com/CDA/Archives/BNP_GUID_9-5-2006_A_10000000000000075718
I think that you need to register at www.circuitree.com before you can
access the archives.
Regards,
Christian
On 9/14/07, Scott McMorrow <scott@xxxxxxxxxxxxx> wrote:
>
> Perry
> Fiber-weave effects are alive and well, and IMO should be considered by
> every designer concerned with 6 Gbps or higher differential serial data
> communications channels on PCBs, backplanes, and single-ended skew
> controlled parallel buses. Jeff's paper is real life, building upon
> about 5 years of good research at Intel. The method that is used is
> quite valid and will be seen in real designs. The Intel research is
> able to better characterize weave skew using physical nyquist sampling
> techniques. Yes, with different trace jogs you will see all sorts of
> potential alignments, but in the worst case you will still find that
> traces can have significant lengths of worst case fiber weave
> alignment. If you are trying to design systems with 1000's of
> differential pairs, there is a statistical certainty that one or more of
> those pairs will have skew close to the absolute worst case, if not
> designed to compensate for laminate weave anisotropy.
>
> The problem is most pronounced with weaves that have large holes without
> fiber in the weave pattern, but you will also see issues with core
> materials that are often constructed with large diameter fibers, like
> 7628 material. The fiberglass the Lee proposes to use does have some
> benefits, however, it does not totally eliminate the fiber weave
> problem. It reduces it to a lower level. Unfortunately, it is not a
> widely manufactured laminate weave.
>
> There are patented techniques for improving weave-induced skew, which
> must be licensed. There are also some non-patented techniques, which
> may also be used that are not quite as effective as the patented
> techniques, but nevertheless can be used to design robust systems.
> There is also some silicon IP that can be used to automatically
> compensate for skew, and is finding it's way into test instrumentation.
>
>
> regards,
>
> Scott
>
> Scott McMorrow
> Teraspeed Consulting Group LLC
> 121 North River Drive
> Narragansett, RI 02882
> (401) 284-1827 Business
> (401) 284-1840 Fax
>
> http://www.teraspeed.com
>
> Teraspeed(r) is the registered service mark of
> Teraspeed Consulting Group LLC
>
>
>
> QU Perry wrote:
> > I would be interested to see a link as well.
> >
> > Jeff's paper on DesignCon2007 is convincing to me that this is something
> > we need to pay attention. Real life design will probably not be as bad
> > as the theoretical estimate since most of the diff pair routing we have
> > on the PCB is not likely to run a long length non-stop in parallel with
> > edge. The "jog" as is called in the paper is very common due to vias etc
> > and pretty random.
> >
> > Also from the data we got from PCB vendor, it appears that thinner
> > dielectric substrate the worse fibre weave effect as the gap between the
> > fiber is larger. Has this been looked at ?
> >
> > Regards
> >
> > Perry
> >
> >
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=20
> >
> > Perry Qu=20
> >
> > Design & Qualification, Alcatel-Lucent Canada Inc.
> >
> > 600 March Road, Ottawa ON, K2K 2E6, Canada=20
> >
> > DID: 613-7846720 Fax: 613-5993642=20
> >
> > Email: perry.qu@xxxxxxxxxxxxxxxxxx=20
> >
> >
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=20
> >
> > =20
> >
> >
> >> -----Original Message-----
> >> From: si-list-bounce@xxxxxxxxxxxxx=20
> >> [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of=20
> >> Aubrey_Sparkman@xxxxxxxx
> >> Sent: Friday, September 14, 2007 1:59 PM
> >> To: leeritchey@xxxxxxxxxxxxx; rdudek@xxxxxxxxxxxxxxx;=20
> >> si-list@xxxxxxxxxxxxx
> >> Subject: [SI-LIST] Re: fiber-weave effect alive and well?
> >> =20
> >> Would you like to share a link?=3D20
> >> =20
> >> =20
> >> Aubrey Sparkman=3D20
> >> Enterprise Engineering Signal Integrity Team=3D20 Dell, Inc.=3D20=20
> >> Aubrey_Sparkman@xxxxxxxx=3D20
> >> (512) 723-3592=3D20
> >> "Discovery consists of seeing what everybody has seen and=20
> >> thinking what nobody else has thought." - Jonathan Swift
> >> =20
> >> =20
> >> -----Original Message-----
> >> From: si-list-bounce@xxxxxxxxxxxxx=20
> >> [mailto:si-list-bounce@xxxxxxxxxxxxx]
> >> On Behalf Of Lee Ritchey
> >> Sent: Friday, September 14, 2007 11:36 AM
> >> To: Russell S. Dudek Jr.; si-list@xxxxxxxxxxxxx
> >> Subject: [SI-LIST] Re: fiber-weave effect alive and well?
> >> =20
> >> We already have a glass weave solution. Check my column in=20
> >> the April issue of Circuitree magazine.
> >> =20
> >> Lee Ritchey
> >> =20
> >> =20
> >>
> >>> [Original Message]
> >>> From: Russell S. Dudek Jr. <rdudek@xxxxxxxxxxxxxxx>
> >>> To: <si-list@xxxxxxxxxxxxx>
> >>> Date: 9/12/2007 1:10:28 PM
> >>> Subject: [SI-LIST] Re: fiber-weave effect alive and well?
> >>>
> >>> Steve,
> >>> =3D20
> >>> I agree, Fiber Weave Effect (FEW) has most certainly been=20
> >>>
> >> confirmed by
> >> such
> >>
> >>> research. However, there is a new change in the wind. I=20
> >>>
> >> have the=3D20=20
> >>
> >>> unique opportunity, as a technical liaison, to enable a=20
> >>>
> >> technology=3D20=20
> >>
> >>> that may put
> >>>
> >> an
> >>
> >>> end to FWE as a consideration in high-speed designs. We=20
> >>>
> >> all know that
> >> =20
> >>
> >>> the crux of the matter is the glass weave and its effect on=20
> >>>
> >> localized
> >> Er.
> >>
> >>> Either get ride of the reinforcement layer completely or more=3D20=20
> >>> challenging change the fundamentals of the glass weave fabrication
> >>>
> >> process (GWFP).
> >>
> >>> =3D20
> >>> We have taken the more challenging (and fun) approach and have=20
> >>> rocked=3D20 the fundamentals the GWFP. I cannot disclose much the=20
> >>> specifics of=3D20 the technology and our partners in such an=20
> >>>
> >> open forum. =20
> >>
> >>> However, if=3D20 you are interested learning more feel free=20
> >>>
> >> to contact=20
> >>
> >>> me and we can=3D20 get the proper NDAs in place to facilitate=20
> >>>
> >> such a discussion.
> >>
> >>> =3D20
> >>> RD
> >>> =3D20
> >>> Russell Dudek
> >>> Technology Specialist
> >>> Compunetics, Inc.
> >>> 700 Seco Road
> >>> Monroeville, PA 15146
> >>> 412-858-6264
> >>> rdudek@xxxxxxxxxxxxxxx
> >>> www.compunetics.com <http://www.compunetics.com/> =3D20
> >>>
> >>> To see where no one notices the contrast of white on white is =
> >>>
> > an=3D20=20
> >
> >>> indispensable virtue of infinite potential.
> >>>
> >>> =3D20
> >>>
> >>>
> >>>
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