[BP] Partial analysis of simulation results
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|--------------------------------------------------------------------|
| Charles Moore
| Avago Technologies
| Image Solutions Division
| charles.moore@avagotech.com
| (970) 288-4561
|--------------------------------------------------------------------|
guys,
I suggested 3 crosstalk models for simulation. I selected them to
demonstrate differing spectral content of crosstalk. Joe Abler has
simulated them. Here is an excerpt of his result plus my calculations
of couple of measures of crosstalk:
crosstalk model EYE with ICR Power
31mUI DCD margin ratio
Molex/1m_OUTBOUND_FEXT/sj5k5g4h4_SPARS.s4p 34mUI 4.57dB 27.94dB
Tyco/Case5/Case5DS1310N2D13L6.s4p 168mUI 1.79dB 33.94dB
Intel/peters_01_0605_T1_next5.s4p 183mUI 15.26dB 33.69dB
No crosstalk 185mUI infinite infinite
ICR margin is the margin by which the channel would pass ICR spec if this
crosstalk model were combined with the Thru channel joe used (Agilent ITTC23).
Power ratio is the signal power divided by crosstalk power, done by in
a way similar to the one suggested by Rich Mellitz. I describe the method
a bit more in the appendix.
The sj5kg4h4 model nearly fails with 31mUI DCD and little or no self
interference. Joe says that he considers it to have failed.
The Case5_N2 model and the T1_next5 models both pass with some margin
for additional self interference and possibly DCD.
ICR margin would not very useful in determining whether there is too much
crosstalk. The Case5D_N2 model works approximately as well as the
T1_next5 model but has more than 13dB worse ICR margin, and it is almost
3dB worse in ICR margin than the sj5kg4h4 model but has significantly
better performance.
On the other hand, the 2 passing cases have nearly equal power ratios and
the failing case is 6dB worse.
So i suggest that we use power ratio to specify crosstalk and use a value
of 33dB as the minimum.
charles
Appendix:
if
xtalk = crosstalk attenuation in dB = IL
atten = thru attenuation in dB = PSXT
sinc = sin(pi*fTt0)/(pi*f*T0)
T0 = 1/(signaling speed)
define:
channelGain=integ(2*t0*sinc**2*(10**(-atten/10)))
XtalkGain=integ(2*t0*sinc**2*(10**(-xtalk/10)))
Power ratio=10*log10(channelGain/XtalkGain)