Oversampled Signal Equalizer Phase Diversity Detection
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Solution Overview
Problem
Conventional signal processing in disk-based storage devices faces challenges in achieving optimal detection performance due to limitations in sampling rates and phase dependencies, which affect timing and gain loops as well as decoding error rates.
Innovation Solution
The implementation of a multiple input, single output equalizer scheme that utilizes oversampled digital data signals with phase differences to improve equalization and filtering, combined with noise predictive filters and decoders like LDPC and Reed Solomon decoders, to enhance detection performance and reduce misequalization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-rate sampling is used, then device complexity is reduced, but detection precision and equalization performance deteriorate
Solution Approach 1:
The patent divides the single sampling stream into multiple parallel sampling streams with different phase offsets (e.g., 0°, 90°, 180°, 270°). Each stream is processed independently through separate equalizers and detectors, allowing the system to extract more information from the same signal bandwidth. This segmentation of the sampling process enables higher detection precision without requiring a higher overall sampling rate, thus avoiding proportional increases in device complexity.
Solution Approach 2:
The patent transitions from single-rate sampling to multi-rate oversampling by adding a time-phase dimension. Instead of simply increasing the sampling frequency, the system introduces multiple sampling phases at the same frequency, creating a multi-dimensional sampling space. This allows the equalizer to exploit phase diversity to improve detection precision while maintaining the same base sampling rate, thereby controlling device complexity.
2Reliability
If oversampled signals with multiple phases are processed, then detection performance is improved, but processing complexity increases
Solution Approach 1:
The patent merges the processing of multiple phase-offset sampling streams through a unified equalization and detection framework. The equalizer processes all phases simultaneously using combined training sequences, and the detector integrates information from all phases to make unified hard decisions. This merging approach improves detection performance by utilizing all phase information while avoiding the need for completely separate processing chains, thus controlling processing complexity.
Solution Approach 2:
The patent implements universal equalizer and detector structures that can process multiple sampling phases simultaneously. The equalizer uses a unified coefficient set that works across all phases, and the detector performs joint detection on all phase streams. This multi-functionality allows the system to achieve improved detection performance through phase diversity without requiring phase-specific processing components, thereby limiting the increase in processing complexity.
3Stability of the object's composition
If phase-dependent timing and gain loops are used, then loop convergence is achieved, but adaptability to different phases deteriorates
Solution Approach 1:
The patent implements dynamic equalizer coefficient adjustment that adapts to different sampling phases. The equalizer coefficients are initially trained using combined training sequences from all phases, then dynamically adjusted during operation to optimize performance for each phase while maintaining overall stability. This dynamic adaptation allows the timing and gain loops to converge for each phase independently while maintaining phase versatility.
Solution Approach 2:
The patent changes the equalizer parameters (coefficients) based on the sampling phase being processed. By training the equalizer on combined training sequences from all phases and then adjusting coefficients optimally for each phase, the system achieves both loop convergence and phase adaptability. The parameter changes enable the equalizer to optimize its response for each phase while maintaining stable operation across all phases.
Data Source
AI summary
An apparatus comprises read channel circuitry and signal processing circuitry associated with the read channel circuitry. The signal processing circuitry is configured to: equalize an oversampled digital data signal to determine an equalized digital data signal, filter the equalized digital data signal, determine a hard decision and reliability of the filtered digital data signal, and decode the filtered digital data signal based at least in part on the hard decision and reliability. The oversampled digital data signal comprises a first set of sampled digital data and a corresponding second set of sampled digital data, each of the samples in the first set of sampled digital data being offset from a corresponding one of the sample in the second set of sampled digital data by a phase difference.