Magnetic Disk Servo Demodulation Timing Adjustment
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Solution Overview
Problem
Magnetic disk devices face challenges in synchronizing read timing due to short servo sectors, leading to degraded demodulation quality and difficulty in determining radial timing deviations, especially when burst data is read in short servo sectors.
Innovation Solution
A magnetic disk device configuration with alternating normal and short servo sectors, where the second servo sector's demodulation timing is adjusted based on the first servo sector's demodulation timing, and the initial phase of the second servo sector's demodulation signal is corrected using the amplitude of the demodulation signal, improving the S/N ratio without causing dead zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If short servo sectors are used to increase storage capacity, then the storage density is improved, but the read timing synchronization deteriorates and demodulation quality degrades
Solution Approach 1:
The system performs preliminary actions by using normal servo sectors to calculate timing adjustment amounts and initial phase correction values before demodulating short servo sectors. The controller stores these correction parameters and applies them when processing short servo sectors, ensuring accurate timing synchronization and phase correction without requiring sufficient servo data within the short sectors themselves.
2Quantity of substance
If short servo sectors are used, then storage density is improved, but the ability to determine radial timing deviation deteriorates
Solution Approach 1:
The system uses normal servo sectors as intermediaries to establish timing references and calculate correction values. These normal sectors provide sufficient servo data to determine read timing characteristics, which are then applied as correction parameters for short servo sectors, enabling indirect detection of radial timing deviations despite the limited data in short sectors.
3Measurement precision
If read timing is adjusted for short servo sectors, then timing synchronization is improved, but initial phase errors are introduced requiring additional correction
Solution Approach 1:
The system implements feedback by using the known positions of servo address marks in normal servo sectors to calculate timing adjustment amounts. These timing adjustments are applied to short servo sectors, and the resulting initial phase deviations are measured and corrected using pre-calculated correction values, creating a closed-loop system that maintains accuracy while managing complexity.
Data Source
AI summary
According to one embodiment, a magnetic disk device includes a disk including two first servo sectors arranged side by side in a circumferential direction and a second servo sector located between the two first servo sectors, a head that writes data to the disk and reads data from the disk, and a controller that adjusts a second timing at which the second servo sector is demodulated based on a first timing at which the first servo sector is demodulated, and corrects a first initial phase of a first demodulation signal obtained by demodulating the second servo sector at the second timing, based on a first amplitude of the first demodulation signal.