Read Transducer Position Error Correction for High-Density Storage
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Solution Overview
Problem
As areal density in hard disk drives increases, existing read transducers face challenges in reading back data from narrower tracks due to decreased signal-to-noise ratio and cross-track interference, particularly in technologies like heat-assisted magnetic recording (HAMR), bit-patterned recording (BPM), and shingled recording, which require more sophisticated decoding and relaxed constraints on transducer width and erase bands.
Innovation Solution
The use of multiple read transducers co-located on a slider allows for simultaneous reading of adjacent tracks, employing two-dimensional decoding algorithms and servo patterns to correct position errors and improve data rate, while also utilizing redundant data for error correction and track ID identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If areal density is increased, then storage capacity is improved, but track pitch is reduced making data reading more challenging
Solution Approach 1:
The patent divides the reading function into multiple independent read transducers (first read transducer and second read transducer) that can simultaneously read adjacent tracks. This segmentation allows each transducer to focus on a narrower track while maintaining adequate signal strength, resolving the contradiction between increased areal density and reading capability.
Solution Approach 2:
The patent transitions from reading a single track at a time to simultaneously reading multiple adjacent tracks in the cross-track dimension. By utilizing multiple read transducers positioned at different cross-track locations, the system can read multiple tracks concurrently, effectively increasing the data rate and compensating for the reduced track pitch.
2Quantity of substance
If track pitch is reduced, then areal density is improved, but signal-to-noise ratio decreases
Solution Approach 1:
The patent combines the output signals from multiple read transducers through a signal combiner. By merging the signals from the first and second read transducers, the system achieves signal integration that improves the overall signal-to-noise ratio, allowing reliable reading despite the reduced track pitch and weaker individual signals.
Solution Approach 2:
The patent uses multiple read transducers to create redundant copies of the data reading function. Each transducer reads the same or adjacent tracks, providing redundant signal paths that can be combined to improve signal quality and error correction capability.
3Quantity of substance
If track pitch is reduced, then areal density is improved, but cross-track interference increases
Solution Approach 1:
The patent employs feedback mechanisms where the position error signals from multiple read transducers are processed to determine and correct tracking position errors. This feedback loop allows the system to compensate for cross-track interference by continuously adjusting the read head position based on the combined information from multiple transducers.
Solution Approach 2:
The patent introduces position error correction as an intermediary process between the raw signal reading and final data recovery. By using position error signals and correction algorithms, the system mediates the effect of cross-track interference, separating the desired signal from the interference through computational processing.
4Productivity
If multiple read transducers are used, then data reading capability is improved, but device complexity increases
Solution Approach 1:
The patent designs the multiple read transducers to perform multiple functions: they simultaneously read user data from adjacent tracks, generate position error signals for tracking correction, and provide redundant data for error correction. This multi-functionality justifies the increased device complexity by extracting multiple benefits from the additional transducers.
Solution Approach 2:
The system uses the signals from the multiple read transducers to automatically correct its own tracking errors and improve its own reading capability. The position error signals generated by the transducers are fed back to adjust the read head position, allowing the system to self-correct without external intervention.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy and efficiency of track positioning and data reading, reducing errors and maintaining manufacturing yields by leveraging the correlation between signals from multiple read transducers, even in high-density storage environments.
Implementation Method 1
reading first and second user data signals of respective first and second tracks of a disk via first and second read transducers
Data Source
AI summary
First and second user data signals of respective first and second tracks are simultaneously read from a disk via first and second read transducers co-located on a slider. A position error of the first and second read transducers is corrected based on the first and second user data signals.