Slider Fly Height Measurement Using Tone Patterns on Bit Patterned Media
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Solution Overview
Problem
Existing magnetic recording technologies face challenges in accurately determining the fly height of a slider relative to a bit patterned medium, which is crucial for efficient data writing and storage capacity utilization, as existing methods lack precise synchronization with the magnetic dots and often result in reduced storage capacity due to misalignment.
Innovation Solution
The method involves using pre-written timing synchronization fields with two different tone patterns or demodulating two odd harmonics of a mixed tone pattern to determine the fly height of the slider, allowing for precise synchronization and alignment with the magnetic dots, thereby enhancing data writing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fly height measurement methods are used, then the measurement process is simple, but the measurement precision is insufficient leading to misalignment with magnetic dots
Solution Approach 1:
The patent applies preliminary action by pre-writing timing synchronization fields containing known tone patterns (such as pseudorandom sequences or sinusoidal patterns) onto the bit patterned medium before data recording. These pre-written patterns serve as reference signals that enable precise fly height measurement through correlation analysis, eliminating the need for complex real-time calibration procedures while achieving sub-nanometer measurement precision
Solution Approach 2:
The patent introduces timing synchronization fields with known tone patterns as an intermediary element between the read/write head and the data fields. These intermediary patterns act as reference signals that facilitate precise fly height determination through correlation analysis, enabling accurate alignment with magnetic dots without requiring direct measurement of the head-to-medium spacing
2Productivity
If fly height determination is not accurate, then the measurement process is faster, but storage capacity utilization is reduced due to misalignment
Solution Approach 1:
The patent implements feedback by continuously measuring fly height using correlation analysis of read signals against known tone patterns in timing synchronization fields, and using this measurement information to adjust the head positioning and writing parameters. This closed-loop feedback mechanism ensures optimal alignment with magnetic dots, maximizing storage capacity utilization while maintaining measurement precision
Solution Approach 2:
The patent replaces mechanical measurement methods with signal processing-based correlation analysis. Instead of using mechanical sensors or physical gauges to determine fly height, the system uses electromagnetic signal correlation between read signals and known tone patterns, enabling non-contact, high-precision measurement that does not interfere with the magnetic recording process
3Productivity
If synchronization with magnetic dots is not achieved, then the writing process is simpler, but data writing efficiency is reduced
Solution Approach 1:
The patent applies preliminary action by pre-writing timing synchronization fields with known tone patterns at specific locations on the bit patterned medium before data recording begins. These pre-positioned reference patterns enable the system to achieve synchronization with magnetic dots through correlation analysis, eliminating the need for complex real-time alignment procedures during data writing
Solution Approach 2:
The patent implements feedback by using correlation analysis to compare read signals from timing synchronization fields against known tone patterns, determining fly height and alignment status, and using this information to adjust writing parameters and head positioning. This feedback mechanism ensures precise synchronization with magnetic dots, maximizing data writing efficiency
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 enables accurate fly height determination and synchronization, leading to improved storage capacity utilization and efficient data writing by ensuring that write operations are aligned with the magnetic dots, thereby optimizing the use of bit patterned media.
Implementation Method 1
a slider configured to magnetically interact with a magnetic bit pattern medium
Data Source
AI summary
A slider having a reader and a writer is moved relative to a magnetic bit pattern medium comprising magnetic dots arranged to include a plurality of pre-written servo sectors, data fields defined between servo sectors to which data can be written and erased, and pre-written timing synchronization fields interspersed within the data fields. In some approaches, two different tone patterns are read from one or more of the timing synchronization fields, and fly height of the slider is determined using the two different tone patterns. In other approaches, two odd harmonics are demodulated from a mixed tone pattern read from one or more of the timing synchronization fields, and fly height of the slider is determined using the two odd harmonics.