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Hi Adam, I agree since eta_0 has such a great impact, we need to agree what it is. Resistor thermal noise (-174 dBm/Hz) is small. Less than a tenth of mV contribution to sigma_n. Other receiver noise seems more debatable. We use COM to determine how much noise the receiver should tolerate to reach say a 3 dB COM. So all the Rx noise is sort of included in the receiver interference tolerance test (RITT). It would seem that noise would need to be included in COM 3 dB budget. I believe the discussion originally (.3bj) was to budget for system noise. It started with sigma_r and subsequently moved to sigma_n and eta_0. Since we were talking about a budget for system noise Adee went back to his labs and reported typical LAN on motherboard system noise measurements which could only be seen outside the chips. What was missing was the PSD. So it boils down to: Is eta_0 1. System only noise
…Rich From: Adam Healey <adam.healey@xxxxxxxxxxxx> Hi Rich, I think there is some confusion about the intent of the eta_0 noise source. I think the confusion is due, in part, to a discrepancy shown on your slide 2. Slide 2 asserts that eta_0 is defined at the input to the Rx package. If this was the case, the noise spectrum should have been filtered by the Rx package and device termination models in addition to the noise filter and CTLE. Instead, as you show on slide 5, the noise is filtered only by the receiver noise filter and CTLE. This makes it look like it is intended to be an input-referred receiver noise source representing thermal noise and a noise figure allocation for the reference noise filter and CTLE. Perhaps it was assumed that the impact of the package and termination is negligible and as a result the intent shown on slide 2 and calculation agree. However, even if that is the case, clarity on the intention is important. If the noise source does not include receiver noise, and the reference receiver is noiseless, then the entirety of the noise in actual receiver implementations must fit in the 3 dB allocation set aside by the minimum COM (with other impairments). Some might assume that (at least part of) the receiver noise is included in eta_0 and therefore look at the 3 dB allowance differently. I think the presentation is good for starting the discussion and getting agreement on what eta_0 is really intended to represent. Thanks for sharing it. Thanks, --Adam On Wed, Feb 27, 2019 at 5:32 PM GMAIL Richard Mellit <richard.mellitz@xxxxxxxxx> wrote: Hi All, There have been number of discussions surrounding the system noise parameter, eta_0, in COM. Most recently in http://www.ieee802.org/3/ck/public/adhoc/feb27_19/wu_3ck_adhoc_01_022719.pdf. The attached is a copy of a brief history of the system noise parameter, eta_0, and an proposal to refine. Comments welcome and support would be much appreciated. Best Regards, Rich To unsubscribe from the STDS-802-3-100GEL list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-100GEL&A=1 To unsubscribe from the STDS-802-3-100GEL list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-100GEL&A=1 |