adam, et al,
I can't argue with points 1-3, those issues need fixing.
Point 4 is really an invitation do discussion and i will take it:
Clearly rich intended that this or something else very similar "is the
way to go"
or he would not have presented the slides. I for one would like to go
this way at
least in the sense that i want to see crosstalk should be measured as a
power (or
energy) integral and a ratio of crosstalk to some measure of signal.
I do not see the crosstalk integral as very contoversial, clean up
rich's, or use one
from healey_c1_0505, or even one from one of my presentations, they all
will give
close to the same result.
The signal part is harder. A few suggestions, starting with the more
difficult but
most accurate and working to easier:
1. Simulate (with suitable Tx equalization) pattern1= 11111000 and pattern2=
11110111, through the channel. Look at difference between the 2
patterns at the Rx end, and find the positive peak of (response1-response2).
This is the difference between the response to a 1 and to a 0 (with maximum
precursor interference) and is what the Rx needs to discriminate, regardless
of how it does the discrimination. Call this difference (scaled by the input
amplitude) the signal gain.
2 Simulate a pulse going through the channel and call the peak of the
output
the signal gain.
3. Integrate sinc(f/10.3125 GHz)/10.3125 GHz * |Sdd21| (which will give an
upper bound on 2.) and call it signal gain.
4. Evaluate -A(f) at some fixed frequency and call it signal gain.
These are all amplitude rather than power numbers so either the signal
gain will have
to be squared or the square root taken of the crosstalk power.
charles
Healey, Adam B (Adam) wrote:
> One more thing, from the practical standpoint, data is measured from
> fmin to fmax (nominally 50 to 15000 MHz). Do you propose extrapolation
> to DC or to simply ignore missing data points between DC and fmin
> (assume they are zero?).
>
> -----Original Message-----
> *From:* Healey, Adam B (Adam)
> *Sent:* Wednesday, January 18, 2006 4:10 PM
> *To:* 'Mellitz, Richard'; charles.moore@avagotech.com
> *Cc:* Spagna, Fulvio; Radhakrishnan, Prakash K
> *Subject:* RE: signal to noise enery
>
> Rich et al.,
> I have looked at the proposed signal-energy calculations and I
> have following questions/comments...
> 1. You have taken the square-root of the energy terms but then
> converted them to decibels with a factor of 10. I think you need
> to pick one or the other (e.g. 20*log10( sqrt( E_sig/E_xtk ) ) or
> 10*log10( E_sig/E_xtlk ).
> 2. Maybe I'm too much of a mathematician for my own good, but I am
> troubled by the use of a "PDF" in the frequency-domain integral. I
> think you are really looking for the power spectral density (PSD)
> which already has the appropriate units and does not need to be
> squared. For that matter, you really want to square the
> _magnitude_ of s21, and that is not clearly shown. You may also
> clarify the limits on your integrals and you can dispose of the
> 1/(2*pi) if you just elect to integrate over f rather than omega,
> 3. What PSD do you intend to use? Will it be a basic sinc( )
> function or will you add roll-off to represent transmit and
> receiver bandlimiting. What amplitude will you assume?
> 4. I don't see anything in these slides indicating that "this is
> way to go". Please note that this methodology is basically an
> extension of what I proposed in May (refer to
> http://ieee802.org/3/ap/public/channel_adhoc/healey_c1_0505.pdf).
> You are essentially proposing that we also integrate the signal
> energy and consider the ratio, rather than just examine the
> crosstalk in isolation. What does this ratiometric view add in
> terms of value, and how does it relate the expected equalization
> capability and noise enhancement properties of actual devices?
> Thanks,
> -Adam
>
> -----Original Message-----
> *From:* Mellitz, Richard [mailto:richard.mellitz@intel.com]
> *Sent:* Thursday, January 12, 2006 9:24 AM
> *To:* Mellitz, Richard; charles.moore@avagotech.com
> *Cc:* Healey, Adam B (Adam); Spagna, Fulvio; Radhakrishnan,
> Prakash K
> *Subject:* RE: signal to noise enery
>
> Put pdf inside of integral.
>
> … R
>
> ------------------------------------------------------------------------
>
> *From:* Mellitz, Richard
> *Sent:* Thursday, January 12, 2006 9:11 AM
> *To:* 'charles.moore@avagotech.com'
> *Cc:* 'Healey, Adam B (Adam)'; Spagna, Fulvio; Radhakrishnan,
> Prakash K
> *Subject:* signal to noise enery
>
> Here’s a quick set of slides that suggest energy may be the
> way to go. I think this is the gist of where we were going
> last night. We will need data for all the channel to support
> this for the Feb meeting.
>
> …Rich
>
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| Charles Moore
| Avago Technologies
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