Address Mark Detection Using EndOf2T Preamble Break
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Solution Overview
Problem
In hard disk drives, the magnetic recording head often mistakenly identifies a read preamble as a servo preamble, leading to impaired normal mode servo operations, especially when read and servo sectors are written at similar frequencies, causing false detection of servo address marks and prolonged search times.
Innovation Solution
A method and apparatus that utilize an EndOf2T detector to determine the end of a preamble, opening a window for detecting the servo address mark, and if not detected, restart the search mode to find the servo preamble, eliminating the need for external control and improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the magnetic recording head uses traditional search mode to locate servo preamble, then the system can recover timing and gain information, but the head may mistakenly identify read preamble as servo preamble causing false detection
Solution Approach 1:
The system uses feedback by monitoring whether an address mark is detected within the expected time window after preamble detection. If no address mark is found within the window duration, the system feeds back that the initial preamble detection was likely incorrect and restarts the search mode. This feedback mechanism resolves the contradiction by using the absence of expected subsequent signals to correct false detections.
Solution Approach 2:
The system performs preliminary action by establishing a detection window of specific duration based on address mark length before confirming servo preamble detection. This preliminary time-bound verification step allows the system to proactively identify and correct false detections before they lead to erroneous servo operations.
2Measurement precision
If the system extends the search window duration to improve address mark detection, then detection sensitivity increases, but the search time increases significantly
Solution Approach 1:
The system changes the parameter of window duration dynamically based on the known length of the address mark. By setting the window duration to match the expected address mark duration, the system optimizes detection sensitivity while minimizing unnecessary search time. This parameter optimization resolves the contradiction between detection sensitivity and search time.
3Device complexity
If the system continuously searches for servo preamble without restart capability, then search operations simplify, but false detections cause prolonged incorrect operations
Solution Approach 1:
The system implements self-service by automatically detecting false preamble identifications and restarting the search mode without external intervention. The detection logic monitors for the absence of expected address marks and autonomously triggers a new search, allowing the system to self-correct false detections while maintaining operational reliability.
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 significantly reduces false detection and miss rates of servo address marks, ensuring accurate servo operations by automatically restarting the search mode and positioning the detection window based on EndOf2T detector information, even when read and servo fields have similar frequencies.
Implementation Method 1
the preamble is detected by determining if energy associated with a 2T frequency is greater than energy associated with a non-2T frequency
Data Source
AI summary
A method and apparatus are disclosed for detecting an address mark in a data stream having a preamble followed by the address mark. The end of the preamble is detected in the data stream, which is then used to open a window to search for the address mark. If the address mark is not detected during the window, the search for the address mark is restarted. The window can have a duration based on a length of the address mark. The address mark can be, for example, a servo address mark following a servo preamble or a read address mark following a read preamble. The preamble can have a 2T pattern and the preamble can be detected by determining if energy associated with a 2T frequency is greater than energy associated with a non-2T frequency. The end of the preamble can be performed by an EndOf2T detector that detects a break in an expected bit pattern.