Patterned Media Write Clock Synchronization
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Solution Overview
Problem
Magnetic recording disk drives with patterned media require an accurate write-clock signal to precisely write data to isolated data blocks, as the magnetic transitions are restricted to predetermined locations, necessitating precise synchronization of the write head with the passing data islands.
Innovation Solution
A system and method for accurately clocking write data using timing marks that are equally angularly spaced across data tracks, with a timing mark detection circuitry and write clock control logic to synchronize the write clock with the data blocks, incorporating a state estimator and phase-locked loop for frequency and phase adjustments, and error recovery mechanisms to ensure accurate data writing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If patterned media with isolated data blocks is used to increase data density, then storage capacity is improved, but precise synchronization of write clock with data blocks becomes necessary
Solution Approach 1:
The patent applies preliminary action by pre-patterning the media with isolated data blocks and pre-positioning timing marks at known angular intervals before the writing process. The write clock is pre-synchronized by detecting these timing marks in advance, allowing the system to prepare the correct clock phase and frequency before actual data writing begins, thus ensuring precise alignment with the patterned data blocks.
Solution Approach 2:
The patent implements feedback by using timing marks detected during disk rotation to continuously monitor and adjust the write clock's frequency and phase. The system measures the actual angular position of timing marks, compares it with the ideal position, and generates error signals that feed back to the phase-locked loop to correct any drift, ensuring the write clock remains precisely synchronized with the passing data blocks throughout operation.
2Measurement precision
If timing marks are added to synchronize write clock, then write accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the timing mark detection function with the existing servo system by utilizing the same read head and servo infrastructure already present in the disk drive. The timing marks are integrated into the existing track structure, and the detection circuitry is combined with the servo control electronics, thereby achieving precise write synchronization without adding completely separate systems and minimizing overall device complexity.
Solution Approach 2:
The patent introduces timing marks as intermediary reference elements that mediate between the mechanical rotation of the disk and the electronic write clock. These timing marks serve as a physical intermediary that translates rotational position into detectable signals, which then control the write clock through a phase-locked loop, providing a reliable coupling mechanism between the mechanical and electronic domains without requiring direct complex interaction.
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
The solution ensures accurate and synchronized writing to patterned media data blocks, enhancing data density and reliability by precisely controlling the write clock to match the passing data islands, thereby improving data integrity and storage capacity.
Implementation Method 1
a magnetic recording disk drive with patterned media, wherein each data bit is stored in a magnetically isolated block or island on the disk
Implementation Method 2
the magnetization directions are parallel to or in the plane of the recording layer, or perpendicular magnetic recording disks, wherein the magnetization directions are perpendicular to or out-of-the-plane of the recording layer
Data Source
AI summary
A system and method accurately clocks write data to the discrete data blocks in a patterned media disk drive. The precise time intervals between successive timing marks in the data tracks are measured by a timing mark detector that counts the integer number of write clock cycles between successive timing marks and the fractional part of a write clock cycle by detecting the phase difference between a timing mark and a reference signal. The resulting timing error is output to a write clock compensator. The write clock is capable of generating equally spaced primary phases and phases intermediate the primary phases. The compensator includes a phase rotator that controls which write clock phase is selected for output. The value in a phase register of the compensator is used to control the phase rotator to advance or retard the write clock phase, and thus to adjust its frequency and phase so as to be synchronized for writing to the data blocks.