Readback Waveform Oversampling via Phase Offset Injection
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Solution Overview
Problem
Current disk drive technologies face challenges in accurately sampling and measuring readback waveforms from magnetic recording media, particularly in achieving sufficient oversampling to assess disk drive operation metrics effectively.
Innovation Solution
The method involves injecting multiple phase offsets into the read channel of a disk drive to oversample the readback waveform at a rate higher than the sampling rate, storing amplitudes in a buffer, and generating an oversampled waveform, which allows for improved resolution and measurement of disk drive operation metrics such as EWSNR, channel bit density, and thermal gradient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple phase offsets are injected to oversample the readback waveform, then measurement precision of disk drive operation metrics is improved, but device complexity and processing time increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing amplitude values for multiple phase offsets in lookup tables before actual measurement operations. This allows the system to quickly retrieve pre-computed values during operation, achieving high measurement precision for metrics like EWSNR and channel bit density without performing complex real-time calculations, thus reducing device complexity and processing time
Solution Approach 2:
The patent implements partial action by injecting a specific number of phase offsets (e.g., 5-10 offsets) that provides sufficient oversampling for accurate metric measurement without unnecessarily increasing complexity. This optimized number of phase offsets achieves the required measurement precision while avoiding excessive processing overhead, balancing accuracy with system complexity
2Measurement precision
If multiple phase offsets are injected to generate oversampled waveform, then measurement precision of disk drive operation metrics is improved, but time required for waveform generation increases
Solution Approach 1:
The patent uses preliminary action by pre-computing amplitude values for multiple phase offsets and storing them in lookup tables during initialization or calibration phases. During actual operation, the system simply retrieves these pre-computed values, achieving high measurement precision without the time cost of real-time complex calculations, thus significantly reducing the time required for waveform generation and metric measurement
Solution Approach 2:
The patent applies copying by creating multiple copies of the readback waveform at different phase offsets and storing their amplitude values in lookup tables. These copied waveforms are then used for metric measurements without requiring repeated physical readings, reducing the time required while maintaining measurement precision through the use of multiple phase-sampled copies
3Measurement precision
If sampling rate is increased to oversample the readback waveform, then measurement precision is improved, but productivity of data processing decreases
Solution Approach 1:
The patent implements partial action by using a moderate number of phase offsets (e.g., 5-10 offsets) that provides sufficient oversampling for accurate metric measurement without unnecessarily increasing data processing burden. This optimized approach achieves required measurement precision while avoiding excessive productivity loss, balancing accuracy with processing efficiency
Solution Approach 2:
The patent extracts only the essential amplitude values from the oversampled readback waveform at the specific phase offsets needed for metric calculation, rather than processing the entire high-rate waveform. This selective extraction of critical data points achieves measurement precision while significantly reducing the processing burden, thereby maintaining productivity
Data Source
AI summary
A read channel is configured to obtain an analog readback waveform from a magnetic recording medium of a disk drive at a sampling rate of one sample per one written bit. A buffer is coupled the read channel. Circuitry is configured to inject a plurality of different phase offsets into the read channel for each of a plurality of revolutions of the medium. The circuitry is also configured to store, in a buffer, an amplitude of the readback waveform for each of the different phase offsets. The circuitry is further configured to generate an oversampled readback waveform using the amplitudes stored in the buffer.