Magnetic Disk Servo Sector Phase Deviation Correction
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Solution Overview
Problem
Magnetic disk devices face challenges in synchronizing read timing and degrading demodulation quality due to shorter servo sectors, where burst data is read with difficulty, and determining radial deviations are complicated by inverted phase patterns.
Innovation Solution
A magnetic disk device configuration with alternating normal and short servo sectors, where the short servo sectors include an additional pattern with a different frequency and phase, allowing for correction of servo demodulation positions based on phase deviations, thereby improving demodulation accuracy and increasing recording area efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If short servo sectors are used to increase recording area efficiency, then the recording area for user data increases, but the read timing synchronization deteriorates and demodulation quality degrades
Solution Approach 1:
The servo sector is segmented into distinct functional regions: a first region containing burst data for radial position detection, and a second region containing additional patterns for timing synchronization and demodulation correction. This segmentation allows the short servo sector to maintain sufficient functional components despite reduced overall length, thereby preserving demodulation quality while increasing recording area efficiency.
2Area of stationary object
If short servo sectors are used to increase recording area efficiency, then the recording area for user data increases, but the read timing synchronization deteriorates
Solution Approach 1:
Additional patterns are introduced as intermediary elements between the burst data and the servo mark in short servo sectors. These additional patterns serve as mediators that provide reference signals for timing synchronization, enabling the system to maintain accurate read timing despite the reduced sector length that characterizes high-density recording formats.
3Measurement precision
If burst data phase is inverted by 180° in radial direction to encode position information, then the radial position detection capability improves, but the determination of read timing deviation becomes difficult
Solution Approach 1:
The additional patterns are designed to serve multiple functions simultaneously: they provide reference signals for timing synchronization, enable detection of read timing deviations, and assist in demodulation correction. This multi-functionality allows the system to maintain accurate timing detection despite the phase inversion of burst data used for radial position encoding.
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a disk including two first servo sectors and at least a second servo sector, a head, and a controller, wherein the first servo sector includes burst data and a first data pattern written before the circumferential direction of the burst data, the second servo sector includes the burst data, the first data pattern, and a second data pattern written after the circumferential direction of the burst data, a first frequency of the first data pattern is different from a second frequency of the second data pattern, and a first length of the first data pattern is different from a second length of the second data pattern.