It seems that if you had a wide buss, and the spacing on the buss was not the same frequency as the spacing on the fiber, you could just about guarantee a worst case pair. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of QU Perry Sent: Friday, September 14, 2007 5:02 PM To: Scott McMorrow Cc: si-list Subject: [SI-LIST] Re: fiber-weave effect alive and well? Scott: =20 Thanks for your comments. I agree the probability of hitting a worst case mis-alignment can be high, especially for large backplane where trace tends to run in parallel with board edge for a long length. Hopefully we can find some less painful fix soon, e.g., Board manufacturer to provide us dielectric panel with rotated glass as suggested in Jeff's paper. =20 Regards =20 Perry =20 =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 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 ________________________________ From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx]=20 Sent: Friday, September 14, 2007 3:49 PM To: QU Perry Cc: si-list Subject: Re: [SI-LIST] Re: fiber-weave effect alive and well? =09 =09 Perry =09 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.=20 =09 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. =09 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. =09 =09 regards, =09 Scott =09 =09 Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax =09 http://www.teraspeed.com =09 Teraspeed(r) is the registered service mark of Teraspeed Consulting Group LLC QU Perry wrote:=20 I would be interested to see a link as well. =09 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. =09 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 ? =09 Regards =09 Perry =09 =09 =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D= 3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D =3D3D=3D = =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D= 20 =09 Perry Qu=3D20 =09 Design & Qualification, Alcatel-Lucent Canada Inc. =09 600 March Road, Ottawa ON, K2K 2E6, Canada=3D20 =09 DID: 613-7846720 Fax: 613-5993642=3D20 =09 Email: perry.qu@xxxxxxxxxxxxxxxxxx=3D20 =09 =09 =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D= 3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D =3D3D=3D = =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D= 20 =09 =3D20 =09 =20 -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx=3D20 [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of=3D20 Aubrey_Sparkman@xxxxxxxx Sent: Friday, September 14, 2007 1:59 PM To: leeritchey@xxxxxxxxxxxxx; rdudek@xxxxxxxxxxxxxxx;=3D20 si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: fiber-weave effect alive and well? =3D20 Would you like to share a link?=3D3D20 =3D20 =3D20 Aubrey Sparkman=3D3D20 Enterprise Engineering Signal Integrity Team=3D3D20 Dell, Inc.=3D3D20=3D20 Aubrey_Sparkman@xxxxxxxx=3D3D20 (512) 723-3592=3D3D20 "Discovery consists of seeing what everybody has seen and=3D20 thinking what nobody else has thought." - Jonathan Swift =3D20 =3D20 -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx=3D20 [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? =3D20 We already have a glass weave solution. Check my column in=3D20 the April issue of Circuitree magazine. =3D20 Lee Ritchey =3D20 =3D20 =20 [Original Message] From: Russell S. Dudek Jr. <rdudek@xxxxxxxxxxxxxxx> <mailto:rdudek@xxxxxxxxxxxxxxx>=20 To: <si-list@xxxxxxxxxxxxx> <mailto:si-list@xxxxxxxxxxxxx>=20 Date: 9/12/2007 1:10:28 PM Subject: [SI-LIST] Re: fiber-weave effect alive and well? =09 Steve, =3D3D20 I agree, Fiber Weave Effect (FEW) has most certainly been=3D20 =20 confirmed by such =20 research. However, there is a new change in the wind. I=3D20 =20 have the=3D3D20=3D20 =20 unique opportunity, as a technical liaison, to enable a=3D20 =20 technology=3D3D20=3D20 =20 that may put =20 an =20 end to FWE as a consideration in high-speed designs. We=3D20 =20 all know that =3D20 =20 the crux of the matter is the glass weave and its effect on=3D20 =20 localized Er. =20 Either get ride of the reinforcement layer completely or more=3D3D20=3D20 challenging change the fundamentals of the glass weave fabrication =20 process (GWFP). =20 =3D3D20 We have taken the more challenging (and fun) approach and have=3D20 rocked=3D3D20 the fundamentals the GWFP. I cannot disclose much the=3D20 specifics of=3D3D20 the technology and our partners in such an=3D20 =20 open forum. =3D20 =20 However, if=3D3D20 you are interested learning more feel free=3D20 =20 to contact=3D20 =20 me and we can=3D3D20 get the proper NDAs in place to facilitate=3D20 =20 such a discussion. =20 =3D3D20 RD =3D3D20 Russell Dudek Technology Specialist Compunetics, Inc. 700 Seco Road Monroeville, PA 15146 412-858-6264 rdudek@xxxxxxxxxxxxxxx www.compunetics.com <http://www.compunetics.com/> <http://www.compunetics.com/> =3D3D20 =09 To see where no one notices the contrast of white on white is =3D =20 an=3D3D20=3D20 =20 indispensable virtue of infinite potential. =09 =3D3D20 =09 =09 =09 =09 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the=3D20 =20 Subject field =20 or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list =09 For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field =09 =09 List technical documents are available at: http://www.si-list.net =09 List archives are viewable at: =3D3D20 =09 //www.freelists.org/archives/si-list or at our remote archives: =09 http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: =09 http://www.qsl.net/wb6tpu =3D3D20 =20 =3D20 =3D20 =09 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field =3D20 or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list =3D20 For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field =3D20 =3D20 List technical documents are available at: http://www.si-list.net =3D20 List archives are viewable at: =3D3D20 =09 //www.freelists.org/archives/si-list or at our remote archives: =09 http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =3D3D20 =09 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field =3D20 or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list =3D20 For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field =3D20 =3D20 List technical documents are available at: http://www.si-list.net =3D20 List archives are viewable at: =3D20 =09 //www.freelists.org/archives/si-list or at our remote archives: =09 http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =3D20 =3D20 =3D20 =20 =09 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field =09 or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list =09 For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field =09 =09 List technical documents are available at: http://www.si-list.net =09 List archives are viewable at: =20 =09 //www.freelists.org/archives/si-list or at our remote archives: =09 http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =20 =09 =09 =20 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =20 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu