Read/Write Channel Timing Acquisition via Adjacent Track Pattern Differentiation
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Solution Overview
Problem
In hard disk drives, increased track density leads to inter track interference (ITI) due to adjacent tracks' preambles interfering with the ability to detect the target track's preamble, causing signal amplitude decrease and phase shift, which affects timing recovery and storage capacity.
Innovation Solution
Encoding preambles of adjacent tracks with different timing recovery patterns, allowing the read channel to distinguish and filter out ITI by using known or expected periods and frequencies of the target track's preamble, thereby enhancing timing acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If track density is increased to increase storage capacity, then storage capacity is improved, but inter track interference increases causing preamble detection difficulty
Solution Approach 1:
The patent applies local quality by assigning different timing recovery patterns to preambles on different tracks. Specifically, even tracks use one timing recovery pattern while odd tracks use a different pattern, allowing the read channel to locally distinguish between adjacent tracks through pattern recognition rather than physical separation
Solution Approach 2:
The patent changes the temporal parameters of the preamble signals by using different timing recovery patterns (different frequencies or phases) for adjacent tracks. This parameter differentiation allows the read channel to filter out interference from adjacent tracks while maintaining high track density
2Ease of manufacture
If adjacent tracks use the same timing recovery pattern, then manufacturing is simpler, but timing acquisition becomes unreliable due to interference
Solution Approach 1:
The patent segments the timing recovery patterns into distinct groups for different tracks. By dividing tracks into even and odd categories with different patterns, the system maintains manufacturing simplicity while ensuring reliable timing acquisition through pattern differentiation
Solution Approach 2:
Instead of using the same pattern for all tracks (which would be simpler), the patent inverts the approach by deliberately using different patterns for adjacent tracks. This inversion resolves the reliability issue while maintaining encoding simplicity through the systematic even/odd pattern assignment
3Measurement precision
If filtering is applied to remove inter track interference, then timing recovery accuracy is improved, but signal processing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring the read channel with knowledge of which timing recovery pattern should be present on the target track. This preliminary information allows the system to selectively filter interference before timing acquisition, reducing the need for complex post-processing
Data Source
AI summary
A read/write channel module including a sampling module configured to sample a read signal corresponding to data stored on a disk. A first preamble is encoded with a first timing recovery pattern on a first track of the disk. The first timing recovery pattern includes a first pattern that changes every x bits. A second preamble is encoded with a second timing recovery pattern on a second track of the disk adjacent to the first track. The second timing recovery pattern includes a second pattern that changes every y bits. A data processing module is configured to process the read signal to remove inter track interference from the read signal based on a difference between the first timing recovery pattern and the second timing recovery pattern.