Presumably you are measuring microstrip. The dielectric constant you computed includes signal traveling in the air above the microstrip. You are getting a composite measurement of air and laminate, and that is why the answer is less than that of the laminate alone. Orin On Tue, 23 Oct 2007 11:38:46 -0700 (PDT) ma mu <sitaskina@xxxxxxxxx> writes: > Hi , > > I am trying to measure the dielectric constant value of our ckt > at 100mhz -3 Ghz in our lab. I have measured it but the value is too > low 2.5 ( expectiing value is between 3.2 to 3.5) . > > I have used Iconnect software to measure the transient time for an > electromagnetc pulse to travel the length of my transmission line. > > and the formula I have used is following: > td=measured data > l=length of the transmission line > Vc= velocity of light. > > Er= (Vc*Vc*td*td)(l*l) > > the TDR I have used has 35 ps rise time . > > > please let me know why I did get this low value. or you could > recommend me to find a way to get Er value. I will appreciate your > help. > > > Ma > > Steve, > > Thanks for the plug! Sometimes the best solutions are the easiest! > > Lee > > > > [Original Message] > > From: steve weir > > To: > > Cc: QU Perry > ; si-list > > > Date: 9/15/2007 12:10:47 PM > > Subject: Re: [SI-LIST] Re: fiber-weave effect alive and well? > > > > In the shameless plug for someone else dept: Lee's book "Right the > > > First Time Volume 2" does do a nice job of demonstrating the > difference > > between various weaves including some good cross-section > > microphotographs and TDR plots. I think it is worth the price of > the > > book for that information alone. > > > > Steve > > Lee Ritchey wrote: > > > The link to the Circuitree web site requires each person to > register and > > > obtain a password. > > > > > > It is true that the thinner weaves are the problem. > > > > > > I cover these weaves and results in Chapter 5 of Volume 2 of my > book. > > > There are photos showing what the weaves look like compared to a > 3.5 > mil > > > trace. Also show what vias do to very fast signals. > > > > > > Lee Ritchey > > > > > > > > > > > >> [Original Message] > > >> From: QU Perry > > > >> To: si-list > > >> Date: 9/14/2007 12:25:54 PM > > >> Subject: [SI-LIST] Re: fiber-weave effect alive and well? > > >> > > >> 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. > > >>>> To: > > >>>> 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 =3D20 > > >>>> > > >>>> To see where no one notices the contrast of white on white is > = > > >>>> > > >> an=3D20=20 > > >> > > >>>> indispensable virtue of infinite potential. > > >>>> > > >>>> =3D20 > > >>>> > > >>>> > > >>>> > > >>>> > ------------------------------------------------------------------ > > >>>> To unsubscribe from si-list: > > >>>> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the=20 > > >>>> > > >>> 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: =3D20 > > >>>> //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 > > >>>> =3D20 > > >>>> > > >>> =20 > > >>> =20 > > >>> > ------------------------------------------------------------------ > > >>> To unsubscribe from si-list: > > >>> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the > Subject field > > >>> =20 > > >>> or to administer your membership from a web page, go to: > > >>> //www.freelists.org/webpage/si-list > > >>> =20 > > >>> For help: > > >>> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > >>> =20 > > >>> =20 > > >>> List technical documents are available at: > > >>> http://www.si-list.net > > >>> =20 > > >>> List archives are viewable at: =3D20 > > >>> //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 > > >>> =3D20 > > >>> > ------------------------------------------------------------------ > > >>> To unsubscribe from si-list: > > >>> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the > Subject field > > >>> =20 > > >>> or to administer your membership from a web page, go to: > > >>> //www.freelists.org/webpage/si-list > > >>> =20 > > >>> For help: > > >>> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > >>> =20 > > >>> =20 > > >>> List technical documents are available at: > > >>> http://www.si-list.net > > >>> =20 > > >>> 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 > > >>> =20 > > >>> =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 > > >> > > >> > > > > > > > > > > ------------------------------------------------------------------ > > > 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 > > > > > > > > > > > > > > > > > > > > > -- > > Steve Weir > > Teraspeed Consulting Group LLC > > 121 North River Drive > > Narragansett, RI 02882 > > > > California office > > (408) 884-3985 Business > > (707) 780-1951 Fax > > > > Main office > > (401) 284-1827 Business > > (401) 284-1840 Fax > > > > Oregon office > > (503) 430-1065 Business > > (503) 430-1285 Fax > > > > http://www.teraspeed.com > > This e-mail contains proprietary and confidential intellectual > property > of Teraspeed Consulting Group LLC > > > ------------------------------------------------------------------------- --- > -------------------------- > > Teraspeed(R) is the registered service mark of Teraspeed > Consulting Group > LLC > > > ------------------------------------------------------------------ > 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 > > > > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com > > ------------------------------------------------------------------ > 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 > > > > ------------------------------------------------------------------ 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