This is in addition to Scott's answer. Here is how to distinguish the losses
from the resonances caused by the periodic variations of dielectric
properties or any other periodic discontinuities (meshed planes, periodic
cut-outs and so on) - the energy is mostly reflected in these cases and not
absorbed as in the case of the conductor and dielectric polarization losses.
Thus, when you see a resonance in the insertion loss, take a look at the
reflection loss. If the reflection shows the resonance - it is caused by the
periodic discontinuities, assuming no other discontinuities in the link.
See more at our "Material World..." tutorial at
http://www.simberian.com/TechnicalPresentations.php It also covers practical
algorithm for the conductor and dielectric model loss separation.
Best regards,
Yuriy
Yuriy Shlepnev, Ph.D.
President, Simberian Inc.
2629 Townsgate Rd., Suite #235, Westlake Village, CA 91361, USA
Office +1-702-876-2882; Fax +1-702-482-7903
Cell +1-206-409-2368; Virtual +1-408-627-7706
Skype: shlepnev
www.simberian.com
Simbeor - Accurate, Productive and Cost-Effective Electromagnetic Signal
Integrity Software
2010 and 2011 DesignVision Award Winner, 2015 Best In Design&Test Finalist
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Anto Kavungal Davis
Sent: Thursday, October 13, 2016 5:34 AM
To: Scott McMorrow
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Solving signal integrity problems at very high data
rates - EDN
Thank you Scott,
It is getting clear now.
Now that you have mentioned about "Dielectric losses are also not the
problem", I have a related doubt. I had some time back read (ref: section
6.3.4 of advanced signal integrity for highspeed digital designs by Stephen
hall and howard, 2009), that Dielectric resonances can exist at 30 GHz in
FR4 dielectrics (it was not mentioned for which material - could be for
cheaper ones). At what frequencies do you expect dielectric resonances? How
do we make sure that the losses are from metal only and not from dielectric
losses due to resonances? Is it measurable with VNA?
(Please note that I am only interested understanding the technical issues)
thanks, Anto
On Wed, Oct 12, 2016 at 9:09 AM Scott McMorrow <scott@xxxxxxxxxxxxx> wrote:
Key factor is length of the plated through hole. This is withoutstructure.
stub, and depends upon correct via design. Stubs dominate.
This does not mean that you will not see a lower impedance passing
through a via. Rather, the lengths of the discontinuities as a signal
passes through a via structure become distributed, because of the size vs.
wavelength of the signal. 12.5 GHz is the Nyquist frequency for a 25
Gbps signal. With an 80 ps period, a 100 mil long via that is only 15
ps long is seen to have all pad capacitance distributed across the
All of this is just to say that "vias ain't the problem", in ultra
high speed signalling. At least not until we get to 50 and 100 Gbps.
Dielectric losses are also not the problem. But metal losses are. We
need more copper surface area to go faster, and we are not going to
get that with traces on dense printed circuit boards.
Scott McMorrow
Technical Director SI/PI
16 Stormy Brook Rd
Falmouth, ME 04105
(401) 284-1827 Business
http://www.teraspeed.com
On Wed, Oct 12, 2016 at 8:47 AM, Anto Kavungal Davis
<antokdavis@xxxxxxxxx
wrote:
Hi,
I was going through Solving signal integrity problems at very high
data
rates - EDN, by
Lee Ritchey, Scott McMorrow & Kella Knack -October 04, 2016
Any papers/publications based on the following comment or with similar
results.
"What has been demonstrated by simulations as well as by laboratory
measurement is that when a signal travels the length of the plated
through
hole or via, the parasitic capacitance of the hole is distributed
along the
length of the hole, rendering it virtually invisible."
Thanks,
Anto
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