Patterned Servo Fields with Zigzag Magnetization for Head Positioning
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Solution Overview
Problem
Patterned-media magnetic recording disks with nondata servo islands of alternating polarity are needed to achieve optimal signal-to-noise ratio (SNR) while forming an improved servo pattern that is easily demodulable into a position error signal (PES) for precise head positioning.
Innovation Solution
The implementation of pre-patterned nondata servo sectors with alternating polarity magnetization in a zigzag pattern across data tracks, utilizing at least two pairs of fields (A-B and C-D) with specific phase differences to generate main and substitute PES signals for accurate head positioning, and optionally incorporating synchronization patterns for reduced noise and increased data storage capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If all servo islands are magnetized in the same direction during manufacturing, then the disk can be easily formatted and manufactured, but the signal-to-noise ratio is reduced because half of the available signal amplitude is sacrificed
Solution Approach 1:
Instead of magnetizing all servo islands in the same direction during manufacturing, the patent inverts the approach by magnetizing adjacent servo islands in alternating directions (up and down). This inversion allows the system to achieve optimal signal amplitude while maintaining ease of manufacturing through a modified formatting process that detects and corrects the alternating polarity pattern.
2Reliability
If conventional quadrature servo pattern is used with alternating polarity, then the signal-to-noise ratio is improved, but the servo pattern becomes more complex and harder to demodulate
Solution Approach 1:
The patent segments the servo pattern into distinct fields (first field with islands at track centerlines, second field with islands at midlines between tracks) and uses a zigzag pattern within each field. This segmentation allows the system to maintain alternating polarity for optimal SNR while creating a more regular, easier-to-demodulate structure through the systematic arrangement of islands in specific geometric patterns.
3Measurement precision
If more servo islands are added to improve positioning precision, then the position error signal accuracy improves, but the disk space available for data storage is reduced
Solution Approach 1:
The patent applies local quality by placing servo islands at specific critical locations (track centerlines and midlines between tracks) rather than uniformly distributing them. This strategic placement provides the necessary positioning information at key reference points while minimizing the total number of islands required, thereby preserving maximum disk space for data storage.
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 enhances the signal-to-noise ratio and simplifies demodulation of the PES signal, allowing for more precise head positioning and increased data storage efficiency by optimizing the use of disk space with improved servo pattern design.
Implementation Method 1
Each field contains generally radially directed magnetized stripes, with each stripe comprising a plurality of islands forming a zigzag pattern. The stripes have alternating polarity of magnetizations in the along-the-track direction.
Data Source
AI summary
A magnetic recording disk drive uses a disk having pre-patterned servo sectors extending generally radially across the data tracks. The servo sectors include at least two position error signal (PES) bursts or fields. The phases of the PES fields in the servo readback signal are demodulated to generate a PES to control the disk drive actuator for positioning the read/write heads. Each field contains generally radially directed magnetized stripes, with each stripe comprising a plurality of islands forming a zigzag pattern. The stripes have alternating polarity of magnetizations in the along-the-track direction. In one implementation there are four fields: a first pair of fields A and B wherein the zigzag pattern of the radial stripes in field A is the mirror image about a radial line of the zigzag pattern of the radial stripes in field B, and a second like pair of fields C and D, but wherein the radial stripes in fields C and D are shifted radially by one-half the island radial height from the radial stripes in fields A and B.