Selective Oversampled ADC in Read Channels for Digital Equalization
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Solution Overview
Problem
Conventional magnetic recording read channels face challenges in designing analog circuits that meet demanding performance specifications due to increasing process technology and data rates, leading to noise and intersymbol interference issues, necessitating improved signal processing techniques that transfer burden from the analog to the digital domain.
Innovation Solution
The implementation of selective oversampled analog to digital conversion in read channels, allowing for partial equalization and filtering processes to be performed in the digital domain, with the option to bypass analog or digital filtering based on channel conditions, enabling improved signal-to-noise ratio and error rate performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If analog circuits are designed to meet demanding performance specifications at smaller process technology and higher data rates, then signal processing capability is improved, but circuit complexity and noise susceptibility increase
Solution Approach 1:
The patent replaces analog signal processing circuits with digital signal processing circuits. Specifically, continuous-time filters and equalizers in the analog domain are substituted with discrete-time filters and equalizers in the digital domain, thereby eliminating the complexity and noise susceptibility associated with high-performance analog circuits while maintaining or improving signal processing capability
Solution Approach 2:
The patent changes the operating parameters of the system by introducing oversampling, where the sampling rate is increased beyond the Nyquist rate. This parameter change allows digital filters to achieve the same signal processing performance with reduced complexity, as the oversampled signals contain redundant information that simplifies filter design and reduces the order of filters needed
2Reliability
If oversampled analog to digital conversion is implemented, then digital signal processing capability is improved, but analog filtering requirements change
Solution Approach 1:
The patent applies partial filtering in the analog domain before oversampled A/D conversion. Instead of implementing complete anti-aliasing and equalization filters in the analog domain, only basic anti-aliasing filtering is performed, with the remaining filtering and equalization functions transferred to the digital domain. This partial action approach reduces analog filter complexity while achieving the desired signal-to-noise ratio through subsequent digital processing
Data Source
AI summary
Methods and apparatus are provided for processing a signal in a read channel using a selective oversampled analog to digital conversion. The disclosed selective oversampled analog to digital conversion simplifies the analog design by transferring at least a portion of the equalization and/or filtering processes to the digital domain. An analog input signal in a read channel is converted to a digital signal to generate one or more digital samples corresponding to the analog input signal for a given bit interval. The analog input signal is selectively filtered in an analog domain in a first mode and the digital samples are selectively filtered in a digital domain in a second mode. A data detection algorithm is applied to the digital samples to obtain a detected output. The selection of the first mode and the second mode can be, for example, based on channel conditions. The analog to digital conversion can be performed at a baud rate in the first mode and at an oversampled rate in the second mode.