[SI-LIST] Dielectric constant measuring

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
> >>>>
> >>>>
> >>>>
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>
> -- 
> Steve Weir
> Teraspeed Consulting Group LLC 
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