HAMR Read-Channel Harmonic Sensor for Laser-Induced Phase Errors
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Solution Overview
Problem
Existing data storage devices using heat-assisted magnetic recording (HAMR) face challenges in efficiently measuring phase errors due to laser mode hops and down track thermal gradients, which impact performance and reliability, and current methods require significant computational resources and time.
Innovation Solution
Implementing a harmonic sensor in the read channel to directly measure phase errors by analyzing amplitude data from a tone pattern written on the storage medium, allowing for efficient detection of thermal write operating conditions such as mode hops and down track thermal gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If post-processing read signals in software for spectral analysis is used, then phase error measurement can be performed, but processing time and computational power requirements increase significantly
Solution Approach 1:
The patent replaces software-based post-processing with a dedicated hardware harmonic sensor circuit that performs spectral analysis in the analog domain. The circuit includes a harmonic sensor that directly measures phase errors by analyzing the amplitude of tone patterns at specific frequencies, eliminating the need for time-consuming digital signal processing while maintaining measurement precision.
Solution Approach 2:
The patent introduces a harmonic sensor as an intermediary component between the read channel and the control system. This sensor circuit acts as a mediator that extracts phase error information from the read signal through hardware-based spectral analysis, providing real-time measurements without requiring extensive computational resources from the main processor.
2Measurement precision
If post-processing read signals in software for spectral analysis is used, then phase error measurement can be performed, but processing power requirements increase significantly
Solution Approach 1:
The patent replaces complex software-based spectral analysis algorithms with a dedicated hardware circuit that performs the same function through analog signal processing. The harmonic sensor circuit uses fixed-frequency oscillators and amplitude measurement circuits to directly determine phase errors, significantly reducing the computational burden on the main processor while maintaining measurement accuracy.
Solution Approach 2:
The patent implements a self-contained harmonic sensor circuit that autonomously performs spectral analysis without requiring continuous intervention from the main processor. The circuit includes integrated oscillators, amplifiers, and amplitude measurement components that work independently to extract phase error information, reducing the overall computational complexity of the system.
3Productivity
If hardware harmonic sensor is used in read channel, then computational requirements are simplified and real-time detection is enabled, but device complexity increases due to additional hardware components
Solution Approach 1:
The patent designs the harmonic sensor circuit to serve multiple functions within the read channel. The same circuit architecture used for phase error measurement also supports tone pattern generation, frequency analysis, and thermal gradient detection. This multi-functionality justifies the added hardware complexity by eliminating the need for separate dedicated circuits for each function.
Solution Approach 2:
The patent merges the harmonic sensor functionality with existing components in the read channel. The circuit integrates oscillators, amplifiers, and amplitude measurement functions into a unified block that works cooperatively with the existing read element and control circuitry. This integration approach minimizes the impact of added hardware complexity while achieving real-time detection capability.
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 simplifies computational requirements and provides real-time detection of phase errors, enabling improved management of operating conditions and enhancing the performance and reliability of HAMR data storage devices.
Implementation Method 1
Heat assisted magnetic recording (HAMR) is a more recent development that improves the quality of written data by heating the disk surface with a laser during write operations in order to decrease the coercivity of the magnetic medium
Implementation Method 2
acquire, using a harmonic sensor in a read channel configured to receive a read signal from the head, amplitude data from the tone pattern and corresponding to differences between a target frequency of the tone pattern and a read frequency from the read signal
Data Source
AI summary
Example systems, data storage devices, and methods for using a harmonic sensor in the read channel of a data storage device to determine phase error are described. The data storage device includes a storage medium with data tracks and a head that can be positioned for reading and writing those tracks. A tone pattern may be written to a data track and a read signal from the tone pattern may subsequently be processed through the harmonic sensor to acquire amplitude data corresponding differences between a target frequency of the tone pattern and a read frequency from the read signal. The amplitude data may be processed to determine phase error values that correspond to an operating condition during writing, such as mode hops and/or down track thermal gradients related to operation of a laser during heat assisted magnetic recording.