Multi-Viterbi Read Channel Decoding for DC Noise Reduction

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Solution Overview

Problem

Perpendicular magnetic recording (PMR) technologies face performance limitations in handling time-variant noise, such as DC noise, due to the long latency of the baseline loop in traditional read channel detection architectures, which affects the reliability of data decoding in hard disk drives.

Innovation Solution

A multi-Viterbi detector architecture is introduced, where a first Viterbi detector generates preliminary decision signals with a shorter depth and a second Viterbi detector generates final decision signals with a longer depth, combined with a filter bank and feedback loops to reduce DC noise without compromising timing loop and automatic gain control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single Viterbi detector with long path memory is used to ensure reliable final decisions, then data decoding reliability is improved, but the latency increases and timing loop tracking capability deteriorates

Engineering Contradiction:

Improvedata decoding reliabilityVSAvoidViterbi path memory latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent divides the Viterbi detection function into two separate detectors: a first Viterbi detector that produces preliminary decisions with shorter path memory for fast tracking, and a second Viterbi detector that produces final decisions with longer path memory for high reliability. This segmentation allows each detector to be optimized for its specific function, resolving the contradiction between latency and reliability.

Inventive Principle:

Principle #1Segmentation

2Stability of the object's composition

If the Viterbi early depth is increased to reduce errors in preliminary decisions, then timing loop and AGC loop stability is improved, but the ability to track fast-varying timing and gain errors deteriorates

Engineering Contradiction:

Improvetiming loop and AGC loop stabilityVSAvoidtracking capability for fast-varying errors

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The patent segments the detection function so that the first Viterbi detector with optimized early depth handles the stability requirement for timing and AGC loops, while the second Viterbi detector handles the final high-reliability decisions. This allows the system to maintain both stability and tracking capability simultaneously.

Inventive Principle:

Principle #1Segmentation

3Device complexity

If a traditional single Viterbi detector architecture is used, then device complexity is low, but performance in handling time-variant noise such as DC noise deteriorates

Engineering Contradiction:

Improvedetector architecture complexityVSAvoidnoise cancellation performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent introduces a segmented multi-Viterbi detector architecture where the first detector handles preliminary detection and the second detector refines the final decisions. This segmentation enables better handling of time-variant noise like DC noise through the collaborative operation of the two detectors, accepting increased complexity as necessary for improved noise performance.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS8090059B1Multi-viterbi receive channel decoder

Publication Date: 2012.01.03 MARVELL ASIA PTE LTD

AI summary

A detector includes Viterbi detectors. A first Viterbi detector generates a preliminary decision signal. A second Viterbi detector generates a final decision signal based on an input data signal and the preliminary decision signal. The second Viterbi detector is arranged in series with the first Viterbi detector.