RE: [SI-LIST] : RF boards

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From: Degerstrom, Michael J. (degerstrom.michael@mayo.edu)
Date: Fri Apr 28 2000 - 13:52:15 PDT


Ron,

Isn't your statement that PCB dielectric losses dominate above
1 Ghz only relavent for your particular line length and line width? For
example, the few published comparisons of eye closure for various laminates
tend to base their measurement on .012" wide 12" long lines. My
experience is with .004" wide 2" long lines in FR-4. Simulations
with a .02 loss tangent and sqrt(freq) skin-effect losses predicted
12 Gb/s. I measured 5 Gb/s. I believe the extra loss is attributed
to surface roughness as I don't think a loss tangent of .06 at 5 Gb/s
is realistic.

By the way, with the lower loss laminates, how do
you know that the lower loss is mostly attributed to the lower
loss tangent? Couldn't the surface metal be smoother and/or of better
quality than the metal typically used on FR-4 laminates?

Mike

_______________________________________________________________
Mike Degerstrom Email: degerstrom.michael@mayo.edu
Mayo Clinic
200 1st Street SW
Gugg. Bldg. RM 1042A Phone: (507) 284-3292
Rochester, MN 55905 FAX: (507) 284-9171
WWW: http://www.mayo.edu/sppdg/sppdg_home_page.html
_______________________________________________________________

> -----Original Message-----
> From: Ron Miller [mailto:rmiller@Brocade.COM]
> Sent: Friday, April 28, 2000 3:12 PM
> To: 'si-list@silab.eng.sun.com'
> Subject: RE: [SI-LIST] : RF boards
>
>
> The dielectric loss tangent dominates high frequency losses
> at frequencys above 1 Ghz. Since most digital signals these
> days have edge rates which generate components much higher
> than 1 Ghz, the edges are distorted if you have lossy material.
>
> Roln MIller
>
> > -----Original Message-----
> > From: Sean Murray
> > Sent: Friday, April 28, 2000 10:31 AM
> > To: si-list@silab.eng.sun.com
> > Subject: RE: [SI-LIST] : RF boards
> > Importance: High
> >
> > Ron,
> > I do not see much of a difference between the nelco 4000 and
> > Getek. Is there some variable that I'm missing that plays a
> big part in
> > the performance at the RF levels other than the DK?
> >
> >
> >
> > > -----Original Message-----
> > > From: Ron Miller [mailto:rmiller@Brocade.COM]
> > > Sent: Friday, April 28, 2000 10:02 AM
> > > To: 'si-list@silab.eng.sun.com'
> > > Subject: RE: [SI-LIST] : RF boards
> > >
> > >
> > > Hi Sean
> > >
> > > I have done some work substituting Arlon 350(teflon with
> > > ceramic loading)
> > > for FR4 and have
> > > been able to double the bandwidth of previous generations.
> > > Going from FR4
> > > to Getek will
> > > not get you much, but if you go to Nelco 4000-13SI, you can
> > > expect a big
> > > improvement in
> > > the frequency dependent losses.
> > >
> > > Good luck
> > > Ron Miller
> > >
> > >
> > > > -----Original Message-----
> > > > From: Sean Murray
> > > > Sent: Friday, April 28, 2000 7:58 AM
> > > > To: 'si-list@silab.eng.sun.com'
> > > > Subject: [SI-LIST] : RF boards
> > > > Importance: High
> > > >
> > > > Anyone have any feelings on what subtle differences when
> > > fabricating a
> > > > board can do to an RF board. Such as going from FR-4 to
> > > Getek; 50/200
> > > > gold/nickle vs. 30/100 gold/nickle. Is there any books out
> > > there that
> > > > deal with strictly the layout of RF boards??
> > > >
> > > > Regards,
> > > > Sean Murray
> > > > Sales Manager
> > > >
> > > > M&M Specialties Inc.
> > > > 1236 W. Southern Ave. #106
> > > > Tempe, AZ. 85282-4518
> > > > Phone: (480) 858-0393 x105
> > > > Cell: (602) 684-7859
> > > > Fax: (480) 858-1882
> > > > Email: seandm@mmspec.com
> > > > WWW.mmspec.com
> > > >
> > > >
> > > >
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