Key factor is length of the plated through hole. This is without 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 structure.
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
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
