[SI-LIST] Re: Thesis (Eliminating package resonances due to standing waves)

Thanks very much for taking the time to read the presentation, and the
encouragement. Although the presentation can be looked through for an
idea about the approach, some slides lack enough information to be
interpreted in detail without explanation. I hope to write a paper about
this in the near future.
To answer some of the questions.

Mr. Grasso,

  1. Actually the ?screen? (the term we gave the floating metal) is the
    62.5 mils thick copper layer. We used FR4 dielectric in the gaps of
    the screen only to try and get close to reality when the screen is
    used with FR4 dielectric. We used a 62.5 mil thick screen to only
    compare its effect with a 62.5 mils thick FR4 piece which is a
    commonly available bare FR4 insulator. 

  2. Yes, the screen is not connected to either plane. We tried shorting
    the screen to the ground plane in simulations and we observed that it
    had the same effect in terms of the resonance positions. 

Mr. Anderson,

    3.  The screen is used to cause resonances due to standing waves, but
at frequencies much higher than any 

frequency of interest on the board. We can literally choose the first
resonant frequency for any given board, by

incorporating a screen with appropriate dimensions (dimension of the
opening in the metal grid) and a

dielectric with low dielectric constant. In our last experiment we didn?t
fill the gaps in the screen with

anything so we created a situation of a dielectric constant of unity,
which increased the velocity of propagation

of the wave and hence the first resonant frequency. I am not completely
sure what other resonances could be

caused due to the screen on a real board with active circuitry. There
could be some LC resonances due to the

capacitance and inductances caused by the screen.

Mr. Weir,

Thanks again for your detailed message. I think you summarized the
technique pretty perfectly. I however

        would like to mention that the spacing between the planes need
not be increased just to accommodate the

        screen. The thickness of the screen layer really does not matter
as long as it is insulated with a thin dielectric

(about 5 mils) from the power and ground planes.

Yes, I would agree that this setup in its current form, is not
economically Feasible. We had to buy the screen for 65$ (just the one
piece).  There will also have to be more a few more steps in the
manufacturing process.

Thanks again for taking the time to go through the presentation and your
comments. I hope to discuss this in more detail with some of you offline.


Regards,

Vijay

  ----- Original Message -----
  From: "steve weir"
  To: ray.anderson@xxxxxxxxxx, Charles.Grasso@xxxxxxxxxxxx,
  vijayis@xxxxxxxx, si-list@xxxxxxxxxxxxx
  Subject: [SI-LIST] Re: Thesis (Eliminating package resonances due to
  standing waves)
  Date: Mon, 27 Jun 2005 10:27:19 -0700

  >
  > Ray, I think that you see that up around 6GHz. The thesis as I
  understood
  > it was not to eliminate resonance per-se, but to move it up in
  frequency to
  > a region where there is little excitation energy. I think it was a
  good
  > Master's project, but don't see much practical value.
  >
  > Regards,
  >
  > Steve.
  > At 10:18 AM 6/27/2005 -0700, Ray Anderson wrote:
  > > And a 3rd question: IF the 'screen' isn't at RF ground, might it
  not
  > > have some interesting resonances of it's own at frequencies
  removed from
  > > the plane resonance frequencies where it might radiate?
  > >
  > > -Ray
  > >
  > > Raymond Anderson
  > > Senior Signal Integrity Staff Engineer
  > > Product Technology Department
  > > Advanced Package R&D
  > > Xilinx Inc.
  > >
  > >
  > >
  > > -----Original Message-----
  > > From: si-list-bounce@xxxxxxxxxxxxx
  [mailto:si-list-bounce@xxxxxxxxxxxxx]
  > > On Behalf Of Grasso, Charles
  > > Sent: Monday, June 27, 2005 10:08 AM
  > > To: 'vijayis@xxxxxxxx'; 'si-list@xxxxxxxxxxxxx'
  > > Subject: [SI-LIST] Re: Thesis (Eliminating package resonances due
  to
  > > standing waves)
  > >
  > > Congratulations on a nice presentation.=20
  > > First a question: As I understand it, your technique
  > > is to add a 40mils thick piece of copper in a "screen"
  > > inbetween the planes.?
  > > OK a second question (!) - I assume that the screen is NOT
  > > connected to either of the planes.?
  > >
  > > Best Regards
  > > Charles Grasso
  > > Senior Compliance Engineer
  > > Echostar Communications Corp.
  > > Tel: 303-706-5467
  > > Fax: 303-799-6222
  > > Cell: 303-204-2974
  > > Pager/Short Message: 3032042974@xxxxxxxx
  > > Email: charles.grasso@xxxxxxxxxxxx; =20
  > > Email Alternate: chasgrasso@xxxxxxxx
  > > =20
  > >
  > >
  > > -----Original Message-----
  > > From: si-list-bounce@xxxxxxxxxxxxx
  [mailto:si-list-bounce@xxxxxxxxxxxxx]
  > > On
  > > Behalf Of Vijay B
  > > Sent: Friday, June 24, 2005 5:15 PM
  > > To: si-list@xxxxxxxxxxxxx
  > > Subject: [SI-LIST] Thesis (Eliminating package resonances due to
  > > standing
  > > waves)
  > >
  > >
  > > Hello,
  > > I recently graduated with an M.S in EE from State University of
  New
  > > York at
  > > Binghamton. My thesis was in eliminating package resonances due
  to
  > > standing
  > > waves formed due to propagation and reflection of radial waves in
  > > between
  > > power and ground planes. I would like to share the presentation
  with the
  > > list.
  > >
  > > We incorporated a metal screen in between the power
  > > and
  > > ground planes of a board to act as a distributed capacitor
  arrangement.
  > > We
  > > used Speed2000 to model the setup and we confirmed simulations
  with
  > > measurements on a hardware model using a vector network analyzer.
  We
  > > concluded that with this approach we can eliminate all resonances
  due to
  > > standing waves upto 10 GHz (may be even higher) on a 4"X5" board
  by
  > > incorporating a screen of appropouriate dimension and a
  dielectric with
  > > low
  > > dielectric constant. If anyone is interested in the topic please
  go to
  > > http://bingweb.binghamton.edu/~bj95053/ and open the file "Thesis
  > > Presentation". It is a power point file. If you have any
  questions or
  > > comments on this I would be happy to hear from you.
  > >
  > > Thanks.
  > >
  > > Regards,
  > >
  > > Vijay
  > >
  > > --=20
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