Head Position Detection Using Phase Angle Correction
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Solution Overview
Problem
Conventional area demodulation methods face challenges in smoothly connecting demodulation signals at track boundaries due to gain differences, leading to discontinuous position signals.
Innovation Solution
A storage device and control circuit that include an area demodulator and head position demodulator, which demodulate first and second demodulation signals with a 90° phase difference, and use a function correction module to correct the arctangent function, ensuring position linearity by generating a correction function conversion table based on probability density measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional area demodulation is used to detect head position, then position detection capability is provided, but discontinuity occurs at track boundaries due to gain differences in demodulation signals
Solution Approach 1:
The patent changes the parameter used for position detection from the length of the vector (which causes discontinuity at track boundaries) to the phase angle of the vector. This parameter transformation allows continuous and smooth position signals across track boundaries while maintaining detection accuracy.
Solution Approach 2:
The patent introduces a phase angle as an intermediary parameter to represent head position. Instead of directly using the vector length which has discontinuous characteristics at track boundaries, the phase angle serves as a mediator that provides continuous position information across all tracks.
2Manufacturing precision
If phase demodulation is used to achieve linear head position detection, then position linearity is improved, but track boundary information is lost
Solution Approach 1:
The patent merges the advantages of both phase demodulation and area demodulation by using the phase angle from area demodulation. This combined approach achieves the linearity of phase demodulation while preserving the track boundary information inherent in area demodulation patterns.
Solution Approach 2:
The patent transforms the position representation from vector length to phase angle, which maintains the linear characteristics needed for accurate position detection while preserving the ability to identify track boundaries through the periodic nature of the phase angle changes.
Data Source
AI summary
According to one embodiment, a storage device includes an area demodulator and a head position demodulator. The area demodulator demodulates a first demodulation signal and a second demodulation signal having a phase difference of 90° from a read signal by a head of an area demodulation pattern recorded on a medium. The head position demodulator receives the first demodulation signal and the second demodulation signal, and outputs a phase angle indicating a direction of a vector formed in a phase plane by the first demodulation signal and the second demodulation signal as a head position signal.