[SI-LIST] Re: anti-resonance point when use Embedded Capacitance Material
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: orphanou@xxxxxxxxxxxx
- Date: Fri, 10 May 2013 14:58:39 -0400
antonis
Sure radiating edges are a problem. Ever seen a cable routed adjacent to
the edge of a PCB in a chassis? Most radiation problems occur when
external antennas (cable shields, metal patches, package metal lead frames
and planes) couple resonances elsewhere.
On Fri, May 10, 2013 at 2:39 PM, Antonis Orphanou <orphanou@xxxxxxxxxxxx>wrote:
> Is edge fringing a real concern here? The dielectric to air interface is
> highly reflective after all .....
> The first order radiation mechanism is image currents from resonating
> planes (and patch antenna concepts as earlier mentioned).
> An ideal capacitor array is like an EM wall that splits the power plane
> into smaller sections hence shifting the radiated spectrum and resonance
> frequencies higher up in spectrum. Can a realistic capacitor and its
> inductance achieve that task? Judging from earlier responses that sounds
> impossible....
>
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Bradley Brim
> Sent: Friday, May 10, 2013 11:16 AM
> To: leeritchey@xxxxxxxxxxxxx; dennis.han@xxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: anti-resonance point when use Embedded Capacitance
> Material
>
> Hi Lee,
> Plane pair cavity resonances contribute to emissions. The earliest power
> integrity experts seem to have been EMC engineers concerned less with PDN
> noise at devices and more concerned with reducing emissions from the PDN.
> One can even view the operation of a microstrip patch antenna as a form of
> plane pair resonance and its sole purpose is to send/receive radiated
> emissions.
>
> To address a topic of the original inquiry ...
> Smaller plane separation implies less area of equivalent magnetic current
> at the plane pair edge, or equivalently less local fringing field volume,
> and therefore lower emissions for a given field strength. However, the
> smaller the plane separation the higher the Q of the cavity can be,
> implying a higher field strength at the plane pair edges.
>
> At frequencies where the sum of mounting inductance and ESL for the cap do
> not combine to make them exceedingly high impedance they will certainly
> affect plane resonances, whether or not placed in a uniform or grid
> pattern. EMC engineers typically guide for a uniform/grid placement with
> spacing based on a fraction of the wavelength in the cavity material at the
> highest frequency of concern. I observe PI experts with access to
> simulation tools approach the issue by visualizing PDN cavity resonances
> and placing caps near voltage/impedance maxima. This may not eliminate all
> resonances and can serve to shift the resonances to other frequencies. An
> iterative process of analyzing and cap placement is pursued. I've seen
> cases where this can yield as many or more caps than a uniform/grid
> placement. A procedure to consider simultaneous placement of all required
> "emicaps" (rather than the iterative process that does not reexamine
> selection/placement from previous iterations) can yield
> significantly fewer caps for the same level of emissions.
>
> Best regards,
> -Brad
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Lee
> Sent: Friday, May 10, 2013 9:16 AM
> To: dennis.han@xxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: anti-resonance point when use Embedded Capacitance
> Material
>
> I have seen no evidence that plane resonances contribute to EMI or that
> distributing capacitors evenly over a plane has much effect on resonances.
> I do this so that there is an even distribution of "ground" vias across the
> planes as has been recommended by Istvan.
>
> -----Original Message-----
> From: Dennis
> Sent: Friday, May 10, 2013 7:09 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: anti-resonance point when use Embedded Capacitance
> Material
>
> There are also free spreadsheet calculators from Altera, Xilinx, and Terry
> Fox & Associates. KEMET Spice can be used for that purpose to some extent.
>
> Dennis
>
> --- In si-list@xxxxxxxxxxxxxxx, Ken Wyatt <ken@...> wrote:
> >
> > Thanks Chas,
> > I remember those days...things have progressed greatly.
> >
> > Do you, or the group, know of affordable simulation S/W (Ansoft, maybe?)
> > that would simulate plane resonances? My limited budget won't support
> > multi-G$ S/W, unfortunately. That would be pretty cool to be able to
> > simulate that. I saw a recent demo of HyperLynx that was impressive.
> >
> > I know Istvan has several Excel calculators that will model PDN
> > impedances.
> >
> > You coming to the Denver symposium this year?
> >
> > Cheers, Ken
> > ___________________
> > Kenneth Wyatt
> > Wyatt Technical Services LLC
> > Woodland Park, CO
> > ken@...
> > Web Newsletter
> > Connect with me on LinkedIn!
> >
> > On May 9, 2013, at 2:22 PM, Grasso, Charles wrote:
> >
> > > Hello Ken,
> > >
> > > When faced with large areas of pwb that have little or no components,
> it
> > > used common practice for EMI guys to add lossy caps (the lossier the
> > > better)
> > > to the planes in a regular pattern to minimize the effects of plane
> > > resonance. With modern simulation tools, the resonant modes of the
> > > planes
> > > can be simulated and caps added (in just the right spot!) to reduce the
> > > effect.
> > >
> > > Chas
> > >
> > > -----Original Message-----
> > > From: si-list-bounce@... [mailto:si-list-bounce@...] On Behalf Of
> Istvan
> > > Novak
> > > Sent: Thursday, May 09, 2013 7:23 AM
> > > To: Ken Wyatt
> > > Cc: bruce@...; si-list@...
> > > Subject: [SI-LIST] Re: anti-resonance point when use Embedded
> > > Capacitance Material
> > >
> > > Ken,
> > > Bypass capacitors with more lossy dielectrics do help somewhat, but the
> > > dielectric loss shows up strongly in the ESR only at frequencies much
> > > lower than the series resonance frequency, where we usually dont need
> > > the higher ESR. Very lossy (and sloppy) dielectrics, such as Z5U and
> > > Y5V are good for cheap consumer electronics, but for professional
> > > circuits there are many drawbacks and it is not the best thing to use
> > > them. Ceramic capacitors with user-defined ESR are available from two
> > > of the major capacitor vendors, so they can be used when we need the
> > > highest performance and can afford the higher cost for these parts.
> > >
> > > Regards,
> > >
> > > Istvan Novak
> > > Oracle
> > >
> > >
> > >
> > >
> > > On 5/9/2013 9:00 AM, Ken Wyatt wrote:
> > >> Hi Group & Bruce,
> > >>
> > >> I'm kind of a "newby" when it comes to SI, but am reading Lee Richey's
> > >> books on the subject.
> > >>
> > >> One thing he recommends for PDN designs is the use of bypass
> > >> capacitors with a more lossy dielectric (higher ESR), such as X5R, Z5U
> > >> or Y5V, to dampen the anti-resonance. Would this be a reasonable thing
> > >> to try?
> > >>
> > >> Ken
> > >> ___________________
> > >> Kenneth Wyatt
> > >> Wyatt Technical Services LLC
> > >> Woodland Park, CO
> > >> ken@... <mailto:ken@...> Web
> > >> <http://www.emc-seminars.com> Newsletter
> > >> <http://emc-seminars.us1.list-manage.com/subscribe?u7f203d1f64dd89f
> > >> 06b0c3f5&id 0f29a904> Connect with me on LinkedIn
> > >> <http://www.linkedin.com/in/kennethwyatt>!
> > >>
> > >> On May 9, 2013, at 5:16 AM, Istvan Novak wrote:
> > >>
> > >>> Hi Bruce,
> > >>>
> > >>> The anti-resonance between the static capacitance of planes and
> > >>> inductance of bypass capacitors will always be present unless you
> > >>> either match the plane impedance with the ESRs of capacitors or
> > >>> overwhelm the antiresonance with MANY low-inductance bypass
> > >>> capacitors. The antiresonance is present with any laminate material,
> > >>> thin or thick.
> > >>> When you use thin laminates (Embedded Capacitance Material), the
> > >>> resonance magnitude and frequency both get lower with respect to a
> > >>> thicker laminate. First you have to determine whether the resonance
> > >>> causes a problem for power, signal integrity and EMI. If you dont
> > >>> excite the resonance, you dont need to care.
> > >>>
> > >>> Regards,
> > >>>
> > >>> Istvan Novak
> > >>> Oracle
> > >>>
> > >>>
> > >>>
> > >>>
> > >>> On 5/9/2013 2:26 AM, Bruce wrote:
> > >>>> Hi Expert
> > >>>>
> > >>>>
> > >>>> We use Embedded Capacitance Material for better PDN and less
> > >>>> capacitor component. According to PDN Simulation. We notice that is
> > >>>> an anti-resonance point between capacitor and Plane.
> > >>>>
> > >>>>
> > >>>>
> > >>>> We can find that when use Embedded Capacitance Material. There are
> > >>>> much better in most frequency but near anti-resonance point.
> > >>>>
> > >>>>
> > >>>>
> > >>>> In this case. We have to solution.
> > >>>>
> > >>>> 1. Try to reduce the anti-resonance point. We need many high
> > >>>> frequency
> > >>>> capacitor component. That is not good because we want to reduce the
> > >>>> number of capacitor component. Our purpose is reduce 70% number of
> > >>>> capacitor component.
> > >>>>
> > >>>> 2. Keep this anti-resonance point. That maybe have a risk if
> > >>>> there is
> > >>>> some noise by chance in this frequency
> > >>>>
> > >>>>
> > >>>>
> > >>>> How about your suggestion? Please let me know if my question is not
> > >>>> clear enough.
> > >>>>
> > >>>> Thanks
> > >>>>
> > >>>>
> > >>>>
> > >>>> Best Regards,
> > >>>>
> > >>>> Bruce Wu
>
>
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