Write Pulse Pairing for Asymmetry-Corrected Read Signals
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Solution Overview
Problem
Current read signal linearization techniques, such as Magnetoresistive Asymmetry Compensation (MRAC) and pulse pairing, are inadequate for highly asymmetrical read elements, introducing excess noise and failing to correct higher-order distortions, especially time-varying distortions like read-head misalignment.
Innovation Solution
A method involving a write precompensation circuit that shifts the rising and falling edges of pulses in the write signal by a select magnitude in opposite directions, combined with an MRAC block tuned to correct specific distortion signatures, effectively linearizes the read signal by introducing a non-linear characteristic that combines with the read element's non-linearities to generate correctable distortion signatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If second order signal subtraction technique (MRAC) is used to linearize the read signal, then second order non-linearities are removed, but higher order distortion terms remain and excess noise is introduced
Solution Approach 1:
The patent applies write precompensation that introduces carefully selected timing shifts before data is written to the media. This preliminary action predistorts the write signal in a controlled manner so that when the asymmetrical read element reads the data, the combined distortion produces a signal with reduced higher order terms that can be more effectively processed by subsequent linearization circuitry.
Solution Approach 2:
The patent deliberately introduces asymmetric timing shifts to rising and falling edges of write pulses through the write precompensation circuitry. This controlled asymmetry in the write signal compensates for the asymmetry in the read element, transforming the distortion characteristics to reduce higher order terms in the read signal.
2Manufacturing precision
If multi-parameter optimization is applied to pulse pairing technique, then linearization performance improves, but configuration time and hardware requirements increase significantly
Solution Approach 1:
The patent implements a simplified pulse pairing technique that applies only the essential timing shifts needed to address the most significant distortion components. Rather than performing exhaustive multi-parameter optimization, the invention applies a reduced set of precompensation parameters that provide sufficient linearization performance while dramatically reducing configuration time and hardware complexity.
3Manufacturing precision
If traditional pulse pairing is used to correct read signal asymmetry, then some non-linear characteristics are canceled, but time-varying distortions such as read-head misalignment cannot be corrected
Solution Approach 1:
The patent employs dynamic write precompensation that can adapt to time-varying conditions. The precompensation parameters are designed to accommodate variations in read-head alignment and other time-dependent distortions, allowing the system to maintain linearization performance even when operating conditions change during normal operation.
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 distortion in the read signal, improving signal-to-noise ratio and linearization efficiency, even for highly asymmetrical read elements, by leveraging the MRAC block's effectiveness in removing second-order non-linearities and controlling higher-order terms.
Implementation Method 1
transmitting a write signal through a write precompensation circuit that shifts rising edges and falling edges of pulses in the write signal by a select magnitude and in opposite directions
Implementation Method 2
transmitting the read signal through a magnetoresistive asymmetry compensation (MRAC) block, where the MRAC block is tuned to correct second-order non-linearities characterized by a particular set of distortion signatures in the signal
Implementation Method 3
A read element interprets encoded data bits on a magnetic media by detecting magnetic flux emitted from those data bits and translating the flux read into an output voltage
Data Source
AI summary
A method for reducing noise in a read signal due attributable to read element asymmetry provides for transmitting a write signal through a write precompensation circuit that shifts rising edges and falling edges of each of pulse in the write signal by a select magnitude and in opposite directions. After the write signal is encoded on a media, a corresponding read signal is read, with a read element, from the media. The method further provides for transmitting the read signal through a magnetoresistive asymmetry compensation (MRAC) block that is tuned to correct second-order non-linearities characterized by a particular set of distortion signatures. The select magnitude of the waveform shift applied by the write precompensation circuit introduces a non-linear signal characteristic that combines with non-linear signal characteristics introduced by the read element to generate one of the particular distortion signatures that is correctable by the MRAC block.