Disk Drive Read Sensor Down-Track Spacing Calibration
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Solution Overview
Problem
Existing disk drive technologies face challenges in accurately measuring and maintaining the down-track separation between read sensors, which affects signal processing and positioning accuracy due to manufacturing variances and real-time operating conditions.
Innovation Solution
The implementation of a method using time-stamps from multiple read sensors to measure down-track spacing, leveraging existing infrastructure within the read channel circuitry or as an independent component, to generate a calibration value representing the separation, enabling precise timing-alignment and improved signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If down-track spacing between read sensors is measured using traditional methods, then manufacturing precision can be maintained, but measurement precision deteriorates due to inability to detect real-time perturbations
Solution Approach 1:
The patent employs feedback by continuously monitoring the timing difference between sync mark detections from multiple read sensors and using this information to dynamically adjust timing alignment. The system measures the actual down-track spacing in real-time and feeds this information back to correct timing errors, thereby maintaining high measurement precision and reliability under varying operating conditions.
Solution Approach 2:
The patent changes the parameter being measured from static manufacturing dimensions to dynamic timing parameters. By measuring the time difference between sync mark detections and converting this to a timing offset, the system adapts to real-time perturbations in down-track spacing, improving both measurement precision and reliability.
2Device complexity
If timing-alignment is performed without accurate down-track spacing measurement, then device complexity is reduced, but signal-to-noise ratio deteriorates
Solution Approach 1:
The system performs self-service by using its own read sensors and existing sync mark structures to automatically measure down-track spacing and perform timing alignment. No external measurement equipment or complex additional hardware is required, keeping device complexity low while achieving high signal-to-noise ratio through accurate timing calibration.
Solution Approach 2:
The patent makes the read channel circuitry multi-functional by having it perform both its primary function of reading data and the additional function of measuring down-track spacing through sync mark detection. This universal use of existing infrastructure avoids adding complex dedicated measurement hardware while achieving precise timing alignment.
3Measurement precision
If multiple read sensors are used to improve signal-to-noise ratio, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent merges the measurement function with the existing read sensor array and sync mark detection infrastructure. By combining the timing information from multiple read sensors' sync mark detections, the system achieves high measurement precision without adding separate complex measurement devices, as the same sensors serve dual purposes.
Data Source
AI summary
A disk drive is disclosed comprising a disk comprising a track, wherein the track comprises a sync mark. The disk drive further comprises a head comprising a plurality of read sensors including a first read sensor, and a second read sensor separated from the first read sensor by a down-track spacing. A first time-stamp (TS1) is generated after detecting the sync mark using the first read sensor as the disk rotates, and a second time-stamp (TS2) is generated after detecting the sync mark using the second read sensor as the disk rotates. A calibration value representing the down-track spacing is generated based on the TS1 and the TS2.