Sreen,
A 9.5 ENOB ADC in combination with a 2nd order 300 MHz LPF would be
required for the 833 MHz system to operate over CAT6 100 m IL.
Note, that this requirement is only mandatory for the severely
band-limited signal for which the aperture and slew rate limitations
should not be an issue. This would considerably ease up the ADC
implementation.
At shorter channels the signal BW would go up, but the ENOB requirement
would not be as stringent as for 100m. So, a degradation in ADC resolution
to 7-8 bit my well prove sufficient. A relatively straightforward study
should clear this.
Regards,
Albert
Sreen Raghavan wrote:
I have to disagree with your analysis. In HDD read channels, you are trying
to detect a 2-level signal (binary). Due to partial response channel
shaping, the slicer initially slices the equalizer output to 11-levels, when
further get reduced to a 2-level decision by ISI- sequence detector.
In PAM-10 modulation, we are trying to decode between 11 transmitted symbols
as opposed to 2. The uncoded SNR needed goes up by 6 dB for every doubling
of transmitted symbols, which means that you need an additional 14 dB of
detection SNR for decoding PAM-10 signals.
In addition, HDD read channels do not suffer form 50 dB of channel
attenuation, or need echo cancellation, both of which further increase the
requirements of the ADC needed.
Sreen Raghavan
Vativ Technologies
-----Original Message-----
From: owner-stds-802-3-10gbt@majordomo.ieee.org
[mailto:owner-stds-802-3-10gbt@majordomo.ieee.org] On Behalf Of
sugawara@necelam.com
Sent: Tuesday, July 29, 2003 7:43 PM
To: stds-802-3-10gbt@ieee.org
Subject: [10GBASE-T] RE: PAR and 5 critters
Hello, everyone,
I believe it is not easy but doable job to realize 10G base-T analog
frontend based on my previous experiences.
In ISSCC '97,'99, and '01, we demonstrated this kind of technology
for HDD readchannel devices. The '01 paper described 2.5years ago;
700MHz, 11 level detection (equivalent to 11PAM) by ADC with
sample & hold,
compensating channel responses by combined 7th order analog filter
and 8tap digital filter,
connected to a Viter Bi detection,
using 0.18um BiCMOS.
This is an old technology.
Now 90nm process is available and 65nm and beyond will be popular
in 2006 when 10G Base-T will be standardized.
In the time, even CMOS can be designed at much higher speed
operation.
We can use over sampling technology to earn more effective bits, at
least. We can use analog cancellation mentioned by Dr. Spencer in
July plenary, as well as frequency response compensation above.
These are some design options.
At this time, do we need more investigation for analog frontend ?
Mitsutoshi SUGAWARA
NEC Electronics America Inc.
Director Analog Engineering
Sreen,
Over the course of last four IEEE 10GBASE-T SG meetings plus
the CFI (Nov. 2002) and through several presentations I have
highlighted the difficulty of realizing a stand alone CMOS ADC
with ~1GS/s and ENOB=11 bits. I have also pointed out the
problem of jitter-limited ENOB that is a result of integrating
four such ADCs along with large number of digital gates on the
same chip.
I have also offered some alternative solutions that involve
implementing part of the signal processing in analog. The
following three bullets are borrowed from Prof. Richard Spencer's
July presentation:
*A mostly digital (DSP) solution will severely tax the sate-of-
the-art ADC capabilities
*The AFE could include significant equalization to reduce burden
on the ADC and back end DSP
*The AFE might also include some echo cancellation and/or NEXT
cancellation
http://www.ieee802.org/3/10GBT/public/jul03/spencer_1_0703.pdf
I agree with you that traditional AFE + DSP approach, in this case,
runs into trouble however, alternative approaches do exist. Some
of these approaches have been successfully applied to high data-rate
read channels.
Regards,
Joseph N. Babanezhad
Plato Labs.
-----Original Message-----
From: "Sreen Raghavan" <sreen-raghavan@vativ.com>
To: "'Kardontchik, Jaime'" <jaime@integration.com>, <stds-802-3-
10gbt@ieee.org>
Date: Tue, 29 Jul 2003 15:35:04 -0700
Subject: RE: [10GBASE-T] PAR and 5 critters
I understand there is a huge difference between implementing a 7-bit
precision ADC and an 11-bit precision ADC.
Sreen Raghavan
-----Original Message-----
From: owner-stds-802-3-10gbt@majordomo.ieee.org
[mailto:owner-stds-802-3-10gbt@majordomo.ieee.org] On Behalf Of
Kardontchik,
Jaime
Sent: Tuesday, July 29, 2003 2:53 PM
To: stds-802-3-10gbt@ieee.org
Subject: RE: [10GBASE-T] PAR and 5 critters
Yeah, the analog target specs look reasonable ...
For comparison, in my previous life (company) I did some
system simulations (and actual design) and came to the
conclusion that one could run 10 Gbps over cat-7 STP to
a distance of about 25 meters with a 7-bit effective ADC
at 625 Mbaud (PAM-5 modulation). At least, the 7-bit
effective ADC was achievable ...
Jaime E. Kardontchik, PhD
Integration
Mountain View, CA 94041
-----Original Message-----
From: Sreen Raghavan [mailto:sreen-raghavan@vativ.com]
Sent: Tuesday, July 29, 2003 1:58 PM
To: 'DOVE,DANIEL J (HP-Roseville,ex1)'; sreen@vativ.com; 'Alan
Flatman';
Kardontchik, Jaime
Cc: '[unknown]'; 'Sterling Vaden'
Subject: RE: [10GBASE-T] PAR and 5 critters
Dan:
We are really referring to the theory (Shannon Capacity) when we say
10Gbps
cannot be achieved over CAT-5e or CAT-6 cabling. Theory shows that
10Gbps
can be achieved over CAT-7 cabling. Practical issues to accomplish
10Gbps
over CAT-7 cabling include (assuming PAM-10 modulation):
1. Building an 11-bit effective ADC at 833 MBaud,
2. Performing large number (x8 relative to 1000BaseT) of DSP
calculations at
833MHz,
3. DDFSE critical path to be implemented in 1.2 ns
4. Building a linear transmit driver with an 833MGz bandwidth & 40 dB
SNR
The above list by no means is exhaustive, but shows the implementation
issues that need to be considered.
Sreen
-----Original Message-----
From: DOVE,DANIEL J (HP-Roseville,ex1) [mailto:dan.dove@hp.com]
Sent: Tuesday, July 29, 2003 1:09 PM
To: 'sreen@vativ.com'; 'Alan Flatman'; 'Kardontchik, Jaime'
Cc: '[unknown]'; 'Sterling Vaden'
Subject: RE: [10GBASE-T] PAR and 5 critters
Hi Sreen,
One thing that occurs to me on this point is the difference between
theory and application. Specifically, how many process actions have to
take place within a baud time to close the loops on the DSP and what
process geometry would be required to make that timing closure?
I know that with 1000BASE-T, the theory was rock solid long before the
processes to implement it were reliable.
Dan
HP ProCurve
-----Original Message-----
From: Sreen Raghavan [mailto:sreen-raghavan@vativ.com]
Sent: Tuesday, July 29, 2003 11:52 AM
To: 'Alan Flatman'; 'Kardontchik, Jaime'
Cc: '[unknown]'; 'Sterling Vaden'
Subject: RE: [10GBASE-T] PAR and 5 critters
Just to clarify, Vativ, Broadcom & Marvell presented capacity
calculations
at the Portsmouth meeting and showed that worst-case CAT-7
(Class F) cabling
had sufficient channel capacity to achieve 10Gbps throughput
at 100 meter
distance. The reason for "may be possible" statement in the
conclusions was
that the 3 PHY vendors felt that more work needed to be done
on practical
implementation issues before the conclusion could be altered to a
more
definitive statement.
In addition, we proved conclusively that there was NOT
sufficient channel
capacity on existing CAT-5e (Class D), or CAT-6 (Class E)
cables to achieve
10 Gbps throughput.
Sreen Raghavan
Vativ Technologies
-----Original Message-----
From: owner-stds-802-3-10gbt@majordomo.ieee.org
[mailto:owner-stds-802-3-10gbt@majordomo.ieee.org] On Behalf
Of Alan Flatman
Sent: Tuesday, July 29, 2003 9:51 AM
To: Kardontchik, Jaime
Cc: [unknown]; Sterling Vaden
Subject: RE: [10GBASE-T] PAR and 5 critters
Message text written by "Kardontchik, Jaime"
Was any reason given why it would not run on Class F ? Was it for
technical reasons or for marketing reasons ?<
The 3-PHY vendor presentation made in Portsmouth (sallaway_1_0503)
calculated 49.36 Gbit/s capacity using unscaled Cat 7/Class F
cabling. This
figure was reduced to 37.71 Gbit/s with worst case limits. Overall, I
thought that this was a refreshingly realistic presentation and I
interpreted the summary statement "Capacity calculations with
measured data
indicate 10 Gigabit data transmission over 100m Cat 7 may be
possible"
(slide 16, bullet 3) as overly cautious engineering judgement.
So, what has changed since the May interim? Not the laws of physics!
Best regards,
Alan Flatman
Principal Consultant
LAN Technologies
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