Digital Signal Equalization via Jitter Removal
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Solution Overview
Problem
High-speed digital systems face challenges in accurately measuring and reducing Data Dependent Jitter (DDJ) in digital signals, which affects the correct determination of logical values due to the combined effects of timing and voltage jitter, making it difficult to isolate and mitigate DDJ using existing measurement techniques.
Innovation Solution
The method involves creating an Equalized Acquisition Record by adjusting the timing jitter by repositioning edges and correcting voltage jitter by adding a compensatory voltage waveform, using filtered time shifted interpolation and Finite Impulse Response Filters to attenuate discontinuities and improve the waveform quality, allowing for effective separation and reduction of DDJ.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing measurement techniques are used to measure jitter, then timing and voltage jitter can be measured, but Data Dependent Jitter cannot be isolated from other jitter types
Solution Approach 1:
The patent segments the jitter measurement process into distinct components: measuring total jitter, measuring periodic jitter, and calculating data dependent jitter as the residual. This segmentation allows DDJ to be isolated from other jitter types through mathematical decomposition, resolving the contradiction between measurement precision and detection difficulty.
Solution Approach 2:
The patent extracts DDJ from the combined jitter measurement by first removing periodic jitter components through correlation analysis with the data signal. This extraction process isolates DDJ as a separate measurable quantity, enabling precise measurement capability while overcoming the difficulty of detecting DDJ in the presence of other jitter types.
2Reliability
If jitter is measured in high-speed digital systems, then timing and voltage jitter information is obtained, but the combined effects make it difficult to reduce DDJ
Solution Approach 1:
The patent implements feedback by using the measured DDJ information to adjust the sampling timing and voltage thresholds for logical value determination. The DDJ calculation provides feedback that can be used to compensate for data dependent effects, improving reliability while managing complexity through targeted correction rather than complete system redesign.
Solution Approach 2:
The patent changes the measurement and correction parameters by adjusting sampling times based on DDJ calculations and modifying voltage threshold criteria. These parameter changes enable improved logical value determination accuracy while controlling device complexity through localized parameter adjustment rather than fundamental system changes.
3Manufacturing precision
If filtering and interpolation are applied to remove DDJ, then waveform quality is improved, but processing time and computational complexity increase
Solution Approach 1:
The patent applies partial filtering and interpolation only to the extent necessary to remove DDJ, rather than applying complete filtering to the entire waveform. This partial action approach improves waveform quality sufficiently for DDJ removal while minimizing processing time and computational complexity by avoiding excessive processing.
Solution Approach 2:
The patent optimizes processing time by changing the filtering parameters and interpolation methods based on the specific characteristics of the signal and the level of DDJ present. This parameter optimization allows sufficient waveform quality improvement through filtering while reducing unnecessary processing time through adaptive parameter selection.
Data Source
AI summary
Equalized Acquisition Record are prepared from Original Acquisition Records reflecting Total Jitter and from an existing description of DDJ. Removal of timing DDJ alters the locations of edges associated with data events. Voltage DDJ adjusts the asserted voltage in the central portion of a Unit Interval. One technique for equalizing timing jitter variably interpolates along the existing Original Acquisition Record to discover plausible new voltage values to assign to existing sample locations along the time axis. Another technique construes the desired amount of correction for each data event as an impulse that is applied to a Finite Impulse Response Filter whose output is a Voltage Correction Waveform having a smoothed voltage excursion. Time variant voltage values output from the Finite Impulse Response Filter are collected into a Voltage Correction Waveform Record having entry times found in the Original Acquisition Record. An entry by entry addition of these two Records produces the Equalized Acquisition Record.