Asymmetric Cross-Track Profiles for Intertrack Interference Attenuation
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Solution Overview
Problem
Current data storage devices face challenges in minimizing intertrack interference (ITI) during read operations, particularly when data tracks are shingle written, as existing servo systems struggle to effectively attenuate interference from adjacent tracks.
Innovation Solution
The implementation of asymmetric cross-track profiles with larger amplitude undershoots positioned towards the inner diameter of the disk surface for both top and bottom heads, which are fabricated to mirror each other, helps attenuate ITI by effectively canceling positive and negative amplitude areas, thereby reducing interference from shingled data tracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If data tracks are shingle written to increase storage capacity, then storage density is improved, but intertrack interference increases
Solution Approach 1:
The patent applies asymmetry by configuring the cross-track profile to be asymmetric rather than symmetric. The larger amplitude undershoot is positioned on one side of the track centerline while the smaller amplitude undershoot is on the other side. This asymmetric configuration is specifically designed to match the asymmetric interference pattern generated by shingled tracks, where interference from adjacent tracks is not uniform across the track width. By positioning the larger undershoot toward the direction of greater interference, the patent effectively cancels out more of the harmful interference signal, thereby reducing overall intertrack interference while preserving storage capacity benefits from shingled writing.
Solution Approach 2:
The patent applies local quality by making the cross-track profile properties location-dependent. Specifically, the undershoot amplitudes are not uniform across the track but are distributed asymmetrically with different magnitudes at different lateral positions. The larger amplitude undershoot is concentrated in the region where interference from shingled adjacent tracks is most problematic, while the smaller amplitude undershoot is in the region with less interference. This localized optimization of the read signal profile allows for targeted cancellation of interference in the most affected regions without unnecessarily affecting other areas.
2Ease of manufacture
If symmetric cross-track profiles are used, then manufacturing is simplified, but intertrack interference attenuation is insufficient
Solution Approach 1:
The patent deliberately introduces asymmetry into the cross-track profile to resolve this contradiction. Instead of using a symmetric profile that would be easier to manufacture but provides insufficient interference attenuation, the patent employs an asymmetric profile with unequal undershoot amplitudes. This asymmetric design is specifically tailored to counteract the asymmetric interference pattern produced by shingled track writing. The manufacturing complexity increase is justified by the significant improvement in interference cancellation performance, particularly in high-density shingled configurations where interference attenuation is critical.
Solution Approach 2:
The patent applies parameter changes by modifying the amplitude distribution parameters of the cross-track profile. Specifically, the undershoot amplitudes are adjusted to be unequal, with one undershoot having a larger amplitude than the other. The ratio and positioning of these undershoot amplitudes are optimized parameters that can be tuned during head fabrication or through signal processing to achieve the desired interference cancellation performance. This parameter optimization allows the system to achieve superior ITI attenuation while maintaining reasonable manufacturing feasibility through controlled variations in read element characteristics or signal weighting.
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 significantly reduces intertrack interference, enhancing read accuracy and capacity by optimizing the radial density and skew angle of data tracks, particularly in butterfly pattern writings, and is achieved through the configuration of free-layer bias directions in magnetoresistive read elements.
Implementation Method 1
configuration of free-layer bias directions in magnetoresistive read elements
Data Source
AI summary
A data storage device is disclosed wherein when a first head is over a top disk surface, a first undershoot of a first cross-track profile is closer to an inner diameter of a disk and a second undershoot of the first cross-track profile is closer to an outer diameter of the disk. When a second head is over a bottom disk surface, a second undershoot of a second cross-track profile is closer to the inner diameter of the disk and a first undershoot of the second cross-track profile is closer to the outer diameter of the disk.