Disk Drive Biasing Sync Pattern Extended Sync Mark
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Solution Overview
Problem
Corrupted servo sync marks on disk drives can render servo or data sectors difficult or impossible to recover, leading to degraded performance of the servo system, as existing designs often ignore corrupted servo sectors to maintain simplicity.
Innovation Solution
The implementation of control circuitry that correlates a detected data sequence with a target sync mark and target data, biasing the correlation to detect sector sync marks, using XNOR circuits and scaling coefficients to enhance sync mark detection, allowing for accurate positioning even with corrupted sync marks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simple sync mark detection method is used, then the device complexity is reduced, but the reliability of sync mark detection deteriorates when sync marks are corrupted
Solution Approach 1:
The patent applies preliminary action by performing correlation between the read signal and expected sync mark patterns before making a detection decision. The correlation values are calculated in advance for multiple possible sync mark positions, allowing the system to identify the most likely sync mark location even when corruption is present. This pre-computation of correlation metrics enables robust detection without requiring complex post-processing.
Solution Approach 2:
The patent implements feedback by using the correlation results to adjust and refine sync mark detection. The system calculates correlation values and uses this feedback information to determine the optimal sync mark position, potentially iterating or comparing multiple correlation results to confirm detection. This feedback mechanism allows the system to distinguish true sync marks from random patterns even when corruption occurs.
2Productivity
If corrupted servo sectors are ignored to maintain simplicity, then the device complexity is reduced, but the productivity of the servo system deteriorates
Solution Approach 1:
The patent converts the harmful effect of corrupted sync marks into a beneficial detection mechanism. By using correlation analysis, the system can actually detect sync marks even when they are corrupted, transforming what was previously a failure condition into a detectable signal. The corruption patterns themselves become part of the correlation calculation, allowing the system to identify and recover from errors rather than simply ignoring them.
Solution Approach 2:
The patent applies parameter changes by modifying the detection threshold and correlation criteria to accommodate corrupted sync marks. Instead of requiring exact pattern matching, the system adjusts the correlation parameters to allow for certain levels of corruption while still reliably detecting sync marks. This parameter adjustment enables the system to maintain productivity by recovering from errors rather than discarding corrupted sectors.
Data Source
AI summary
A disk drive is disclosed comprising a disk including a plurality of sectors each comprising a sector sync mark pattern and sector data preceding and following the sector sync mark pattern, and a head actuated over the disk for generating a read signal. A data sequence is detected from the read signal, and the data sequence is correlated with an extended sync mark comprising a target sync mark pattern and target data. The correlation of the target sync mark pattern with the data sequence is biased relative to the correlation of the target data with the data sequence.