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Science Forum Index » Electronics - Basics Forum » Electrical gigabit transmission ?
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| Joel Kolstad |
 Posted: Tue Jan 30, 2007 11:00 pm |
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"Wes Felter" <wesley@felter.org> wrote in message
news:45bff261$0$9000$4c368faf@roadrunner.com...
Quote: Don't forget parallel copper. The cheapest version of 10GigE is CX4 and will
probably remain so. 100GigE could be 12 lanes of 10GHz over copper, although
people might not put up with the huge connectors.
Many of them would, I imagine... that's ~25 pins, right? -- which even in a
high-density D-sub is "game port" (traditional DB-15) sized, and denser
connectors (such as the newer parallel printer port connector) are readily
available.
I'm sure I'm not the only one who remembers some the truly enormous SCSI
connectors in years past.
Or 60 pin IDCs! |
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| Jan Vorbrüggen |
| Posted: Wed Jan 31, 2007 3:32 am |
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Quote: I'm sure I'm not the only one who remembers some the truly enormous SCSI
connectors in years past.
SCSI connectors "truly enormous"? Surely not! Take a Massbus connector instead!
Jan |
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| jasen |
| Posted: Wed Jan 31, 2007 3:51 am |
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On 2007-01-30, Joel Kolstad <JKolstad71HatesSpam@yahoo.com> wrote:
Quote: "Joseph H Allen" <jhallen@TheWorld.com> wrote in message
news:epoiig$d2v$1@pcls6.std.com...
OK so which technology is going to be cheaper for 100 G ethernet: fiber with
its expensive optical transceivers or all-electrical flexible waveguide?
I'd wager there's a better chance that optical transceivers will become dirt
cheap before flexible waveguides do.
a flexible waveguide of the size required is little more than coaxial cable
without the inner conductor.
OTOH monomode fibre-optic cable is a waveguide too,...
Bye.
Jasen |
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| Paul Keinanen |
| Posted: Wed Jan 31, 2007 4:51 am |
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On Tue, 30 Jan 2007 11:19:36 +0100, "Michael Weiss"
<maerchenprinz@arcor.de> wrote:
Quote: Hi all,
I wonder what is curently state-of-the art in serial high-speed transmission
and what are the prevailing data rates? I know about some SerDes in the
gigabit-per-second range but I cannot imagine if 10 Gbps are really a
challenge or the applied method or if it's 1 Gbps (or something in
between)...?
From the RF design point of view, one should remember that the power
is no longer transmitted with the conductors, but instead propagates
as a field between the conductor and ground plane (or between
conductors in a balanced system). Thus, the dielectric losses of the
PCB or coaxial cable insulation materials will be important, so
ordinary glass fiber boards and PE insulated cables may be
inappropriate at higher frequencies and more expensive materials may
have to be used.
Paul |
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| Nick Maclaren |
| Posted: Wed Jan 31, 2007 6:19 am |
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In article <12s01ibq6bijg1b@corp.supernews.com>,
"Joel Kolstad" <JKolstad71HatesSpam@yahoo.com> writes:
|> "Wes Felter" <wesley@felter.org> wrote in message
|> news:45bff261$0$9000$4c368faf@roadrunner.com...
|>
|> > Don't forget parallel copper. The cheapest version of 10GigE is CX4 and will
|> > probably remain so. 100GigE could be 12 lanes of 10GHz over copper, although
|> > people might not put up with the huge connectors.
|>
|> Many of them would, I imagine... that's ~25 pins, right? -- which even in a
|> high-density D-sub is "game port" (traditional DB-15) sized, and denser
|> connectors (such as the newer parallel printer port connector) are readily
|> available.
|>
|> I'm sure I'm not the only one who remembers some the truly enormous SCSI
|> connectors in years past.
|>
|> Or 60 pin IDCs!
You ain't seen nothing yet, folks!
Regards,
Nick Maclaren. |
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| Joel Kolstad |
| Posted: Wed Jan 31, 2007 12:43 pm |
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"Jan Vorbrüggen" <jvorbrueggen@not-mediasec.de> wrote in message
news:52auu8F1n1fnaU1@mid.individual.net...
Quote: SCSI connectors "truly enormous"? Surely not! Take a Massbus connector
instead!
Hmm... (Googles for Massbus connector imagine, finds it)... yeah, you're
right, that is worse! |
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| Erik Magnuson |
| Posted: Thu Feb 01, 2007 2:29 am |
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Paul Keinanen wrote:
Quote: On Tue, 30 Jan 2007 11:19:36 +0100, "Michael Weiss"
maerchenprinz@arcor.de> wrote:
Hi all,
I wonder what is curently state-of-the art in serial high-speed transmission
and what are the prevailing data rates? I know about some SerDes in the
gigabit-per-second range but I cannot imagine if 10 Gbps are really a
challenge or the applied method or if it's 1 Gbps (or something in
between)...?
From the RF design point of view, one should remember that the power
is no longer transmitted with the conductors, but instead propagates
as a field between the conductor and ground plane (or between
conductors in a balanced system). Thus, the dielectric losses of the
PCB or coaxial cable insulation materials will be important, so
ordinary glass fiber boards and PE insulated cables may be
inappropriate at higher frequencies and more expensive materials may
have to be used.
PE is still a pretty good dielectric in the GHz range, but FR-4
substrate starts hurting by the time you gets to a GHz (Del Cecchi made
similar rude noises about FR-4 as well - wonder what he would think of
PVC...). The microwave guys have had a lot of experience with PCB
performance in the GHz range - dielectric loss will have a much worse
effect on a stripline filter than it will on a digital signal.
- Erik |
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| Del Cecchi |
| Posted: Thu Feb 01, 2007 9:59 pm |
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Erik Magnuson wrote:
Quote: Paul Keinanen wrote:
On Tue, 30 Jan 2007 11:19:36 +0100, "Michael Weiss"
maerchenprinz@arcor.de> wrote:
Hi all,
I wonder what is curently state-of-the art in serial high-speed
transmission and what are the prevailing data rates? I know about
some SerDes in the gigabit-per-second range but I cannot imagine if
10 Gbps are really a challenge or the applied method or if it's 1
Gbps (or something in between)...?
From the RF design point of view, one should remember that the power
is no longer transmitted with the conductors, but instead propagates
as a field between the conductor and ground plane (or between
conductors in a balanced system). Thus, the dielectric losses of the
PCB or coaxial cable insulation materials will be important, so
ordinary glass fiber boards and PE insulated cables may be
inappropriate at higher frequencies and more expensive materials may
have to be used.
PE is still a pretty good dielectric in the GHz range, but FR-4
substrate starts hurting by the time you gets to a GHz (Del Cecchi made
similar rude noises about FR-4 as well - wonder what he would think of
PVC...). The microwave guys have had a lot of experience with PCB
performance in the GHz range - dielectric loss will have a much worse
effect on a stripline filter than it will on a digital signal.
- Erik
the non teflon stuff isn't too bad if it is nice and foamed. UHF TV
does ok.
--
Del Cecchi
"This post is my own and doesn’t necessarily represent IBM’s positions,
strategies or opinions.” |
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| Erik Magnuson |
| Posted: Thu Feb 01, 2007 11:33 pm |
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Guest
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Del Cecchi wrote:
Quote: Erik Magnuson wrote:
Paul Keinanen wrote:
From the RF design point of view, one should remember that the power
is no longer transmitted with the conductors, but instead propagates
as a field between the conductor and ground plane (or between
conductors in a balanced system). Thus, the dielectric losses of the
PCB or coaxial cable insulation materials will be important, so
ordinary glass fiber boards and PE insulated cables may be
inappropriate at higher frequencies and more expensive materials may
have to be used.
PE is still a pretty good dielectric in the GHz range, but FR-4
substrate starts hurting by the time you gets to a GHz (Del Cecchi
made similar rude noises about FR-4 as well - wonder what he would
think of PVC...). The microwave guys have had a lot of experience with
PCB performance in the GHz range - dielectric loss will have a much
worse effect on a stripline filter than it will on a digital signal.
- Erik
the non teflon stuff isn't too bad if it is nice and foamed. UHF TV
does ok.
AFAIK, the foaming is more to increase inner conductor size and thus
reducing copper losses, than to reduce dielectric losses. I've seen
solid PE cable spec'ed to operate at 10 GHz (e.g. RG-223). Besides,
polytetrafluoroethylene (PTFE aka Teflon) is basically polyethylene with
the hydrogen replaced by fluorine - there may be subtle effects due to
the fluorine being much heavier than hydrogen, but there isn't anything
that would give PTFE a large advantage over PE (other than PTFE doesn't
soften when soldered).
Big problem with Coax much above 10 GHz is that it needs to be small
(0.5 inch Heliax is the largest that will work at 10 GHz per Andrew
catalog) to suppress non-TEM modes and the small size plus skin effect
send attenuation through the roof.
I knew someone at Lockheed Martin who worked on a modulator capable of
working at 100 GHz - an impressive accomplishment - but wondered how it
would have been possible to send a 100 GHz signal more than a few mm via
copper.
- Erik |
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| Rob Warnock |
| Posted: Mon Feb 12, 2007 1:08 am |
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Guest
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Del Cecchi <delcecchiofthenorth@gmail.com> wrote:
+---------------
| QAM and other modulation schemes have been proposed but never really
| caught on. ... QAM only halves the baud or symbol rate compared to
| the data rate by encoding 2 bits per baud.
+---------------
True, QAM is seldom used in baseband copper, though note that GbE
uses PAM-5 (2 b/Baud + some slight coding). Where QAM *has* been
really pushed is in CATV RF nets, where QAM-64 (6 b/Baud) and
QAM-256 (8 b/Baud) are fairly common.
Of course, now that the RF nets (including RF-over-fiber) are being
displaced by digital fiber... ;-}
-Rob
-----
Rob Warnock <rpw3@rpw3.org>
627 26th Avenue <URL:http://rpw3.org/>
San Mateo, CA 94403 (650)572-2607 |
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| Rob Warnock |
| Posted: Mon Feb 12, 2007 1:14 am |
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Tim McCaffrey <timcaffrey@aol.com> wrote:
+---------------
| The fastest signaling over copper that I'm (being a software guy, and not
| involved in bleeding edge hardware development) aware of (in production)
| is 3Gig SAS/SATA cables. I'm not sure what the "baud" of the protocol is.
+---------------
10GCBASE-CX4 runs each of its four pairs at 3.125 GBaud
(2.5 Gb/s net after 4b/5b coding [or is it 8b/10b?]).
+---------------
| Perhaps Infiniband is faster?
+---------------
Original Infiniband was only 2.5 GBaud/lane (2.0 Gb/s/lane net after
8b/10b coding), but DDR is readily available and QDR is "coming"(?).
-Rob
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Rob Warnock <rpw3@rpw3.org>
627 26th Avenue <URL:http://rpw3.org/>
San Mateo, CA 94403 (650)572-2607 |
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