Apparatus and method for spectrum analysis-based serial data jitter measurement
AssigneeTektronix, Inc.
InventorsBenjamin A. Ward, Kan Tan, Mark L. Guenther
Life of this patent
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Abstract
A jitter separation apparatus and method, based on spectrum analysis, separates deterministic jitter and random jitter using their spectral properties. Deterministic jitter is periodic and nature and exhibits a spectrum of impulses, whereas random jitter exhibits a broad, flat spectrum. A time domain histogram and a frequency domain histogram of the signal are investigated to obtain jitter components.
Claims13
A method for decomposing Total Jitter of a data signal into its component parts of Deterministic Jitter and Random Jitter for measurement of said Deterministic Jitter and Random Jitter, comprising the steps of:
- measuring Total Jitter;
- performing Spectral Separation of Deterministic Jitter and Random Jitter;
- performing further spectral separation of Deterministic Jitter into Periodic Jitter and its components Duty Cycle Jitter, and ISI;
- performing an inverse FFT on spectrum impulses of said Deterministic Jitter and its components to obtain a histogram of said Deterministic jitter and histograms of its components;
- performing further separation of Duty Cycle and ISI components using separate histograms or statistics for positive and negative edges;
- measuring Peak-Peak statistics on all Deterministic Jitter components;
- using Random Jitter spectral power to estimate true Random Jitter distribution;
- convolving the estimated Random Jitter distribution with a Histogram of Deterministic Jitter-only data to form a histogram of said convolution;
- and
- using said histogram of said convolution to generate a bathtub error curve to estimate bit error rate.
A method in an oscilloscope without an arming system for measuring Deterministic Jitter (DJ) and Random Jitter (RJ) in a serial data sequence having a periodically repeating pattern and a known length, comprising the steps of:
- a) measuring a time interval error (TIE) of said serial data signal;
- b) employing interpolation to estimate data points at locations in said signal where no transitions occur;
- c) performing a Fast Fourier Transform (FFT) using a first windowing function on said TIE to obtain a spectrum of total jitter (TJ);
- d) employing a sliding window;
- e) finding impulses in said spectrum of total jitter;
- f) generating a frequency domain histogram on a portion of said total jitter spectrum within said sliding window;
- g) estimating the amount of said RJ component from said frequency domain histogram of said total jitter spectrum;
- and
- h) calculating an amount of said DJ component from impulses in said frequency domain histogram.
A method in an oscilloscope without an arming system for measuring Deterministic Jitter (DJ) and Random Jitter (RJ) in a serial data sequence having a periodically repeating pattern and a known length, comprising the steps of:
- a) measuring a time interval error (TIE) of said serial data signal;
- b) employing interpolation to estimate data points at locations in said signal where no transitions occur;
- c) performing a Fast Fourier Transform (FFT) on said TIE to obtain a spectrum of total jitter (TJ);
- and
- d) separating spectral peaks.
Dependencies are inferred from the claim text.