Agilent Measurement Journal - Issue 5 - 2008 - (Page 42)

For increasing RJ values, measurement time goes up because more points are located on the slope of the bathtub curve. The sawtooth shape in this region is really an indication of the random variability of the measurement time. It entirely depends on how many points are located on the slope and where. The lower resolution setting hits fewer points on the slope, so the measurement completes earlier with decreasing resolution. From Tables 1 and 2, we see that an average measurement time of about 15 to 20 minutes is achieved, at 10 Gb/s and with a 1-ps delay-step resolution. Making the same measurement without using the bracketing approach and with 1-ps resolution generates a plot similar to that of Figure 5. It requires about 41.67 hours. The bracketing approach therefore reduces measurement times by a factor of about 40 (and as much as 100), depending on RJ and DJ values. Due to this direct measurement approach, accuracy of the results is independent of the TJ PDF. Consequently, the bracketing approach presents a signiﬁcant advantage over other methods based on oscilloscopes or time-interval analyzers, which fail if the jitter distribution doesn’t ﬁt the extrapolation model. References 1. Stephens, R. 2004. Analyzing Jitter at High Data Rate. IEEE Optical Communications, February 2004. 2. Jitter test methodology for Fibre Channel. ANSI X3.230-1994 Annex A, sub clause A.4.2. 3. Working draft, Fibre Channel–Methodologies for Jitter Speciﬁcation-MJSQ. 2003, Rev 10. National Committee for Information Technology Standardization (NCITS), 2003. 4. Papoulis, A. 1984. Probability, Random Variables, and Stochastic Processes. McGraw-Hill, New York. 5. Reed, J. 2000. Calculating Statistical Conﬁdence Levels for Error-Probability Estimates. Lightwave Magazine, April 2000: 110–114. 6. Jeruchim, M. C. Techniques for Estimating the Bit Error Rate in the Simulation of Digital Communication Systems, IEEE J. Select. Areas Commun., vol. SAC-2, no. 1, 1984: 153–170. 7. Macdonald, P.D.M. Foundations of Statistics - Conﬁdence Intervals for a Poisson Mean, available online at: www.math. mcmaster.ca/peter/s743/poissonalpha.html. 8. Mueller, M., Stephens, R., and McHugh, R. 2005. Total Jitter Measurement at Low Probability Levels, using Optimized BERT Scan Method. Designcon 2005, Worcester, Mass., September 19–21, 2005: TA-4. Conclusion BER measurement is critical to making an accurate peak-topeak total jitter measurement. A BERT can be used to make measurements with high conﬁdence levels, while the bracketing approach can be used to control the test time based on the required conﬁdence level in the measurement. Experimental data produced using this approach shows a 40x to 100x improvement in measurement time compared to a conservative bathtub measurement. For a TJ measurement that was done at the 10-12 BER level, with a conﬁdence level of better than 90 percent, typical test times are approximately 20 minutes at 10 Gb/s, and a little more than one hour at 2.5 Gb/s. 42 Agilent Measurement Journal http://www.math.mcmaster.ca/peter/s743/poissonalpha.html http://www.math.mcmaster.ca/peter/s743/poissonalpha.html

Table of Contents Feed for the Digital Edition of Agilent Measurement Journal - Issue 5 - 2008

Agilent Measurement Journal Issue 5 Finding a New Path when Assumptions Break Down Contents Testing MIPI D-PHY Protocols Oscilloscope Firmware Update DNA Replication Joining the LTE/SAE Trial Initiative Testing Proteins Praise for DC Power Analyzer Scripting Features for AMDS Testing Hybrid PCBA Systems Improving the Gene Expression System Workflow Turning a “Good Enough” Test Strategy into One That’s Reliable, Repeatable and Traceable Understanding the Effects of Limited-Bandwidth Channels on Digital Data Signals Introducing the 3GPP LTE Downlink Validating the 26 Validating the Physical and Protocol Layers in DDR Memory Interfaces Understanding Total Jitter Measurements of Low Probabilities Using Behavioral-Model Simulation to Accurately Predict First-Order PLL Performance Creating Synchronous High-Frequency Sampling across Multiple Digitizers Overcoming the Challenges of Testing FlexRay Networks Understanding Operating Life and Repeatability of Electromechanical Switches and their Effect on Total Cost of Ownership Implementing Micro and Nano LC/MS Techniques for High Sensitivity Lipidomics Analysis

Agilent Measurement Journal - Issue 5 - 2008

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