Write Clock Phase Adjustment for Track Misregistration in Patterned Media Drives
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Solution Overview
Problem
Magnetic recording disk drives with patterned media face write errors due to write head track misregistration (TMR), as the write clock's phase needs to be synchronized with the position of data islands, but existing technologies fail to compensate effectively for the misalignment, leading to incorrect magnetization reversal.
Innovation Solution
A magnetic recording disk drive with a read head and write head on an air-bearing slider, where the read head detects position error signals to generate a position error signal (PES) used by the servo control system to maintain alignment, and the write clock's phase is adjusted using a lookup table or curve-fitting algorithm to compensate for TMR, ensuring the write field's magnetization reversal is synchronized with data island positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the write head is positioned on the track centerline, then the write field reversal is optimally synchronized with data islands, but the effective radial offset between read head and write head causes track misregistration (TMR) that leads to write errors
Solution Approach 1:
The write clock phase is made dynamically adjustable rather than fixed. The phase adjustment circuitry continuously adapts the write clock phase based on the detected PES value, allowing the system to compensate for TMR effects in real-time during operation.
Solution Approach 2:
The patent changes the parameter of write clock phase to compensate for track misregistration. By adjusting the phase of the write clock signal, the system compensates for the radial offset between read and write heads, ensuring optimal synchronization with data island positions.
2Reliability
If the write clock phase is fixed, then the system is simple to implement, but the fixed phase cannot compensate for track misregistration causing write errors
Solution Approach 1:
The system uses feedback from the position error signal (PES) detected by the read head to adjust the write clock phase. The phase adjustment circuitry receives the PES value and uses it to determine the appropriate phase correction, creating a closed-loop feedback system that compensates for TMR.
Solution Approach 2:
The patent uses a lookup table that stores pre-calculated phase adjustment values corresponding to different PES values. This allows the system to retrieve the appropriate phase correction without complex real-time calculations, reducing the computational complexity while maintaining effective compensation.
3Reliability
If phase adjustment using lookup table is implemented, then the phase compensation is accurate and easy to implement, but the lookup table requires storage space and initialization
Solution Approach 1:
The lookup table is pre-filled with phase adjustment values corresponding to different PES values during system initialization or manufacturing. This preliminary preparation allows the system to quickly retrieve appropriate phase corrections during operation without requiring complex real-time calculations or additional storage during data writing.
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 solution effectively compensates for write head misregistration, reducing write errors by synchronizing the write clock phase with the data island positions, thereby improving data accuracy and reliability in patterned-media magnetic recording disk drives.
Implementation Method 1
The write head produces a magnetic write field within a write 'bubble,' i.e., the region where the magnetic field has a strength sufficient to switch the magnetization of a data island
Implementation Method 2
As the disk rotates, the read head detects angularly spaced servo sectors and generates a position error signal (PES) which is used by the servo control system to maintain the read head on track
Implementation Method 3
As the disk rotates, the read head also detects angularly spaced synchronization marks, which are used to control the write clock so that magnetization reversal of the magnetic write field is synchronized with the position of the data islands beneath the write head
Data Source
AI summary
A patterned-media magnetic recording disk drive has compensation for write head track misregistration (TMR) from the track centerline. As the disk rotates, the read head detects angularly spaced servo sectors and generates a position error signal (PES) which is used by the servo control system to maintain the read head on track. As the disk rotates, the read head also detects angularly spaced synchronization marks, which are used to control the write clock so that magnetization reversal of the magnetic write field from the write head is synchronized with the position of the data islands. If there is TMR of the write head, there will be an effective shift of A(p in the timing of when the center of the data islands pass through the write field. The disk drive includes write clock phase adjustment circuitry that correlates the PES with Δφ to compensate for TMR of the write head.