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TP2 Waveform Capture

TP2 Waveform Capture

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TP2 Waveform Capture

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  1. TP2 Waveform Capture Pavel Zivny with input from Greg LeCheminant V1.0 10GMMF

  2. TOC • Proposal for the “TP2 – CR and Trigger method” • “Issues for jitter/noise analysis” • TP2 uncorrelated jitter/noise measurements V1.0 10GMMF

  3. TP2 - CR and Trigger methodProposal: • Record the single valued data pattern waveform (rather than the eye diagram) using a synchronizing timing reference obtained with a clock recovery unit having a characteristic as described in “802.3ae52.9.7 Transmitter optical waveform”*. If a sampling oscilloscope is used, the pattern waveform is acquired by means of triggering on divided recovered clock (the recovered clock is divided by the pattern length to produce a trigger edge occurring once per pattern repetition). • Only bits <x> through <y> of pattern <z> are analyzed. The bits are recognized by their position relative to the longest transition-less sequence in the pattern. In particular the bits are located <k> UIs after the sequence <?>. *See next page V1.0 10GMMF

  4. TP2 - CR and Trigger methodSupplementary info: CRU per 802.3ae From 802.3ae52.9.7 Transmitter optical waveform “A clock recovery unit (CRU) should be used to trigger the scope for mask measurements as shown in Figure 52-9. It should have a high-frequency corner bandwidth of less than or equal to 4 MHz and a slope of -20 dB/decade." V1.0 10GMMF

  5. Issues for jitter/noise analysis • Measured uncorrelated jitter and noise are assumed Gaussian or other high probability jitter. Low probability, high PkPk value jitter/noise escapes detection through RMS test. Mask test captures this, if there’d be no mask test this would need addressing in another way. • Pj, Pn are both bundled into R(andom) component That’s a pessimism. Comment from Xmitter designers desireable – is P ever a problem? • Always measure with the ORR on. Is there a consensus on this? V1.0 10GMMF

  6. Background InformationThree methods of Jitter/Noise Analysis • Analyze an LF square-wave +Simplest Measurement equipment setup − Signal far from natural − Dedicated pattern not useful for other measurements • Analyze Dedicated bit(s) within a Multi-use 348-bit Stress Pattern +Useful, near-natural pattern +Rj and Rn measurements simple & easily verifiable − Needs Trigger on Pattern (with e.g. a bit countdown trigger) − Needs a bit search (not implemented today) • Perform complete Jitter/Noise analysis (Rj and Rn,DDj and DDn) on the whole Pattern (e.g. the Multi-use 348-bit Stress Pattern) +Useful, near-natural pattern +Complete Jitter/Noise measured (rather than just one, possibly special, bit) − Needs Trigger on Pattern (with e.g. a bit countdown trigger) − Needs complete jitter/noise analysis package (single source, marginal availability today) Current choice V1.0 10GMMF