Magnetic Reader Bias Current Linearization at High Field Strengths
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Solution Overview
Problem
Magnetic readers in hard disk drives exhibit non-linear responses to magnetic field strengths, particularly at high field strengths, limiting the useful range of field amplitudes and reducing signal-to-noise ratio (SNR) and areal density capability (ADC).
Innovation Solution
Varying the reader bias current to compensate for non-linearities, using non-linear circuit elements and pre-reading techniques to develop an anticipatory map, ensuring a linear response across a wider range of field strengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reader operates at high field strengths to increase signal amplitude, then the signal-to-noise ratio improves, but the reader response becomes non-linear
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the bias current based on the detected field strength. The bias current is increased at low field strengths and decreased at high field strengths to maintain linear response. This is achieved through a control system that modifies the operating parameters of the reader in real-time, allowing the system to operate linearly across a wider dynamic range and improve SNR without sacrificing linearity.
2Productivity
If the useful range of field amplitudes is expanded to increase areal density capability, then the storage capacity improves, but the reader non-linearity increases
Solution Approach 1:
The patent applies dynamics by transitioning from a static bias current to a dynamic bias current that adapts to the instantaneous field strength. The bias current is continuously adjusted based on the detected signal level, allowing the reader to maintain optimal linearity across varying field amplitudes. This dynamic adjustment enables the system to access a broader range of field strengths for higher areal density while preserving response linearity through real-time parameter optimization.
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
Enhances signal linearity, improves SNR, reduces bit error rate (BER), and increases areal density capability by maintaining reader linearity despite inherent non-linearities.
Implementation Method 1
a reader for reading a data track from a magnetic storage medium by detecting magnetic field strength
Data Source
AI summary
Disclosed are methods for linearizing the response of a non-linear magnetic reader, for example in the operation of a hard disk drive. Magnetic readers generally exhibit non-linearities in their response to an applied magnetic field, and those non-linearities may be particularly pronounced when the field strength is high. This deviation from linearity at larger field strengths can limit the useful range of field amplitudes. To expand the useful range of field amplitudes and thereby increase the available signal at the reader, the reader bias current may be varied in such a way to compensate for the natural non-linearity of the reader, thus making the reader output signal linear over a larger range of detected field strengths.