Jitter measurement
A specialized structure measures clock-to-data jitter in an optical memory interface by averaging the result of two second-order estimates of zero crossing using measured signal values on either side of the zero crossing. In one embodiment, a first estimate uses two sample points before the zero crossing and one sample point after while the second estimate uses one sample point before the zero crossing and sample two points after. An existing clock associated with an internal analog-to-digital converter is used to evenly space the samples in time. To simplify the second-order estimate calculations, the three samples of the exemplary embodiment are give x values of −1, 0, and +1 respectively. Which of the two roots of the second-order estimates is used is based on the slope of the signal at the zero crossing.
Marvell International Ltd.
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Jingfeng Hongwei
Liu Song