NIST collaborates on study of adaptive characterization of jitter noise in sampled high-speed signals.
Researchers at NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. have developed an adaptive functional data analysis method to characterize random timing errors in high-speed sampled signals measured by sampling oscilloscopes. On average, jitter A flicker or fluctuation in a transmission signal or display image. The term is used in several ways, but it always refers to some offset of time and space from the norm. For example, in a network transmission, jitter would be a bit arriving either ahead or behind a standard clock cycle noise blurs a measured signal and reduces its power in the spectral domain. However, given an estimate of the standard deviation In statistics, the average amount a number varies from the average number in a series of numbers.
(statistics) standard deviation - (SD) A measure of the range of values in a set of numbers. of the jitter noise, one can correct the measured power spectrum. This correction dramatically reduces prediction error and is essential for characterizing the impulse response function of high-speed sources and detectors in optical fiber communications systems at high frequencies (up to 50 GHz).
To estimate the standard deviation of jitter noise, many (hundreds to thousands) jittered signals are measured. Researchers first align the signals based on estimates of time translation errors, determined from a cross-correlation analysis of all possible pairs of signals. Based on the time-varying sample variance of the aligned signals and estimated derivatives of the noise-free signal at each time sample, they estimate the standard deviation of the jitter noise. Since there is no analytic model for the noise-free signal, the derivative is estimated using a regression spline In computer graphics, a smooth curve that runs through a series of given points. The term is often used to refer to any curve, because long before computers, a spline was a flat, pliable strip of wood or metal that was bent into a desired shape for drawing curves on paper. See Bezier and B-spline. model for the signal. Due, in part, to the non-linear nature of the estimation procedure, the initial estimate of the standard deviation of the jitter noise is biased. A computationally intensive Monte Carlo resampling scheme called the parametric bootstrap See boot.
(operating system, compiler) bootstrap - To load and initialise the operating system on a computer. Normally abbreviated to "boot". From the curious expression "to pull oneself up by one's bootstraps", one of the legendary feats of Baron von Munchhausen. is used to estimate this bias. Based on the bootstrap estimate of bias, the jitter standard deviation estimate is adaptively corrected.
The results of this study will appear in an upcoming edition of the IEEE (Institute of Electrical and Electronics Engineers, New York, www.ieee.org) A membership organization that includes engineers, scientists and students in electronics and allied fields. Transactions on Instrumentation and Measurement.
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