Disk Device Servo Burst Pattern for Positioning
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Solution Overview
Problem
In disk devices, the short servo demodulation scheme faces challenges in accurately determining head position due to difficulties in distinguishing timing deviations from address deviations, leading to potential estimation errors and reduced data recording capacity.
Innovation Solution
The servo burst region is designed with a pattern that differentiates between down track and cross track deviations, using N- and Q-phases with altered magnetization patterns and duty ratios to accurately determine head position without additional patterns for timing deviation detection, thus enhancing the short servo demodulation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional patterns are added to detect timing deviation, then measurement precision improves, but device complexity increases
Solution Approach 1:
The existing servo patterns (N-phase and Q-phase burst patterns) are made to serve dual purposes: both addressing and timing deviation detection. By utilizing the existing pattern structure for both functions simultaneously, the patent eliminates the need for separate timing deviation detection patterns, thereby maintaining measurement precision while avoiding increased device complexity
Solution Approach 2:
The servo patterns are designed to self-differentiate between address deviations and timing deviations through their inherent structural characteristics. The N-phase and Q-phase patterns contain embedded features that automatically enable timing deviation detection without requiring external additional patterns, allowing the system to serve itself
2Measurement precision
If servo occupancy is increased to improve positioning accuracy, then measurement precision improves, but data recording capacity decreases
Solution Approach 1:
The servo patterns are designed to perform multiple functions within the same space: address identification, timing deviation detection, and head positioning. By making the existing servo patterns multi-functional, the patent achieves accurate head position determination without requiring additional dedicated space for timing deviation detection patterns, thereby preserving data recording capacity
Solution Approach 2:
The patent merges the timing deviation detection function with the existing address and positioning servo patterns. By combining multiple functions into unified servo patterns, the system achieves accurate head position determination while minimizing the space occupied by servo areas, thus maintaining high data recording capacity
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 configuration allows for accurate head position determination during short servo demodulation while maintaining high data recording capacity, preventing erroneous corrections and reducing servo occupancy.
Implementation Method 1
The servo area includes a burst region of an N-phase (null type) in which a magnetization polarity is reversed for every one of the servo tracks
Data Source
AI summary
According to one embodiment, in a disk device, a first pattern cut out from a burst region at a certain servo track by a first length and with a first start position, does not match a second pattern cut out from the burst region at an adjacent servo track by the first length and with an arbitrary second start position including first timing. The burst region at the servo tracks includes a first burst pattern including a first magnetized portion where a first value is recorded and a second magnetized portion where a second value reverse to the first value in polarity is recorded, the second magnetized portion being adjacent to the first magnetized portion in a down track direction. A width of the first magnetized portion in the down track direction and a width of the second magnetized portion in the down track direction are different from each other.