Optical Sensor Timing Recovery for Bit Patterned Media
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Solution Overview
Problem
Bit patterned magnetic recording systems face challenges in timing recovery and synchronization due to the need for precise alignment of write heads with bit islands, leading to potential system failures and errors like cycle slips, insertion/deletion errors, and bit flips if synchronization is not achieved.
Innovation Solution
An apparatus and method utilizing an optical sensor to produce a bit pattern signal representing island locations, which is used to control the timing of write pulses applied to a write transducer, ensuring accurate magnetization of bit islands, and a timing recovery circuit to generate synchronization signals for precise positioning of read and write heads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If read-while-write synchronization is used for write synchronization, then write head alignment with bit islands is improved, but reader saturation and crosstalk occur
Solution Approach 1:
The patent separates the synchronization function from the data read function by introducing a dedicated optical sensor. This segmentation allows the optical sensor to handle synchronization tasks independently, preventing the magnetic read head from experiencing saturation and crosstalk while maintaining precise write head alignment with bit islands
Solution Approach 2:
The patent introduces an optical sensor as an intermediary device to detect bit island positions and provide synchronization signals. This intermediary approach eliminates the need for the magnetic read head to perform synchronization, thereby avoiding reader saturation and crosstalk while achieving precise positioning
2Measurement precision
If conventional magnetic sensors are used for timing recovery, then magnetic field sensing is achieved, but sensor saturation and crosstalk occur
Solution Approach 1:
The patent replaces the magnetic sensing mechanism with an optical sensing mechanism. The optical sensor detects bit island positions through optical interactions rather than magnetic field sensing, eliminating saturation and crosstalk issues inherent in magnetic sensors while maintaining high timing recovery precision
3Device complexity
If write head timing is not synchronized with bit island positions, then system complexity is reduced, but cycle slips and system failure occur
Solution Approach 1:
The patent implements a self-service synchronization mechanism where the optical sensor automatically detects bit island positions and generates timing signals that directly control the write head operation. This self-service approach ensures reliable synchronization without requiring complex external control systems, thereby maintaining system reliability while keeping the synchronization system relatively simple
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 precise synchronization of write heads with bit islands, reducing errors and ensuring reliable data storage by accurately controlling the timing of write pulses and positioning of heads relative to the bit patterned media.
Implementation Method 1
producing an error signal in response to light reflected from an island on the bit patterned data storage media
Implementation Method 2
The write head is controlled by a clock, which determines where the bit transitions occur... the write head needs to be aware of positions of the bit islands in order to precisely switch the write fields
Implementation Method 3
control the timing of write pulses applied to a write transducer to control a direction of magnetization of the bit islands
Data Source
AI summary
An apparatus includes a bit patterned magnetic storage media, a write transducer positioned adjacent to the bit patterned magnetic storage media, a write driver coupled to the write transducer to deliver write pulses to the write transducer, an optical sensor for producing a bit pattern signal, and a timing recovery circuit for producing a synchronization signal in response to the bit pattern signal, wherein the timing of the write pulses is adjusted in response to the synchronization signal.