Jitter Trigger Generation for Fast Data-Dependent Measurement
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Solution Overview
Problem
Current jitter measurement methods, particularly using sampling oscilloscopes, are inefficient as they acquire unnecessary data and slow down sampling speed due to sampling beyond transition periods, making it difficult to measure data-dependent jitter effectively, especially with longer pattern lengths.
Innovation Solution
A jitter measuring trigger generator that synchronizes the trigger pulse with the data signal, using a phase adjuster and adjustable frequency divider to ensure one sample per bit, and an interleaving unit to acquire data corresponding to the pattern length, allowing for high-speed sampling independent of pattern length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sampling oscilloscope is used to observe waveform in a broad band, then the waveform can be displayed, but unnecessary data is acquired and sampling speed decreases
Solution Approach 1:
The patent extracts only the necessary transition portion data from the broad band waveform signal. The trigger generator identifies and isolates transition portions (edges) of the data signal, sampling only during these critical moments rather than continuously sampling the entire waveform, thereby eliminating unnecessary data acquisition while maintaining measurement capability
Solution Approach 2:
The patent segments the continuous waveform observation into discrete transition portions. By dividing the waveform into individual transition events and sampling each separately, the system avoids the need to sample the entire broad band signal, improving sampling efficiency while capturing all necessary jitter information
2Measurement precision
If the trigger period is synchronized with the data pattern length to measure data dependent jitter, then DDJ measurement is enabled, but sampling speed becomes slow with longer pattern lengths
Solution Approach 1:
The patent performs preliminary identification of transition portions within the data pattern before completing the full pattern measurement. By detecting and marking transition points in advance, the system can efficiently sample only at these predetermined locations, avoiding the need to wait for the complete pattern cycle to begin sampling, thus maintaining high sampling speed even with long pattern lengths
Solution Approach 2:
The patent implements periodic sampling at transition portions rather than continuous sampling throughout the entire pattern. By sampling periodically only at the moments when transitions occur, the system achieves the necessary measurement precision for DDJ while dramatically reducing the overall sampling burden and maintaining high effective sampling speed
3Measurement precision
If multiple sample points are acquired to draw the waveform, then the waveform can be reconstructed, but data other than transition data is sampled making acquisition inefficient
Solution Approach 1:
The patent extracts only the essential transition portion data from the waveform signal. By using trigger-based sampling that activates only during transition events, the system obtains sufficient data points for jitter measurement without acquiring redundant non-transition data, thereby reducing data acquisition time while maintaining measurement accuracy
Data Source
AI summary
A phase adjuster 2a receives a trigger clock synchronized with a data signal to be measured as input, and controls the phase of the trigger clock such that the trigger period of samples of the data signal to be measured becomes one sample per bit. An adjustable frequency divider 2b has a frequency division ratio which is set such that a trigger pulse is generated at the fixed timing of the waveform pattern of the data signal to be measured. An interleaving unit 4d uses a discrete value which is in prime relation to the measured pattern length of the data signal to be measured, and acquires data for the number of samples corresponding to the measured pattern length from a sampler 3 by the trigger pulse from the adjustable frequency divider 2b.