Jitter Stressor for CDR Timing Margin Measurement
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Solution Overview
Problem
Existing methods for measuring timing margin in clock and data recovery systems require duplicate hardware, which is inefficient and costly, especially in high-speed digital communication environments where bit error rates are sensitive to sampling accuracy.
Innovation Solution
A timing margin calculation system that introduces controlled jitter into the sampling clock to determine the system's ability to withstand phase offsets without additional hardware, using a jitter stressor to incrementally increase jitter until an unacceptable bit error rate is reached, allowing for the measurement of timing margin without duplicate data paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two separate data paths with duplicate hardware are used to measure timing margin, then measurement capability is improved, but device complexity and hardware cost increase
Solution Approach 1:
The patent creates a virtual copy of the data path by injecting jitter into the existing single data path. Instead of building physical duplicate hardware, the invention uses digital signal processing to simulate the effect of a second data path with phase offset, thereby achieving timing margin measurement capability without increasing hardware complexity.
Solution Approach 2:
The invention changes the parameter of the sampling clock by injecting controlled jitter with specific amplitude and frequency characteristics. This parameter modification allows the single data path to exhibit behavior equivalent to multiple data paths with different phase offsets, enabling timing margin measurement through parameter variation rather than structural duplication.
2Measurement precision
If jitter is injected into the sampling clock to measure timing margin, then measurement accuracy is improved, but bit error rate increases
Solution Approach 1:
The patent applies partial action by injecting jitter at levels sufficient to reveal timing margin characteristics but not excessive enough to cause unacceptable bit error rates. The jitter amplitude is carefully controlled to be just enough to stress the timing margin and reveal measurement information while maintaining system reliability within acceptable limits.
Solution Approach 2:
The invention uses feedback by continuously monitoring the bit error rate while jitter is injected. The jitter amplitude is adjusted based on the observed BER, allowing the system to find the optimal jitter level that provides sufficient timing margin characterization while maintaining acceptable reliability. The measurement process itself provides feedback to control the stressor intensity.
Data Source
AI summary
A method and a system for accurately calculating the timing margin in a clock and data recovery system (CDR) is provided that utilizes a singular path environment of hardware. The method entails adding an amount of jitter within the CDR to change the receiver phase. The amount of jitter is incrementally increased until a threshold level of bit errors occur. Based on the amount of jitter needed to cause the threshold level of bit errors, timing margin can be calculated.