Interference Cancellation for Narrow Track Pitch Disk Drives

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Solution Overview

Problem

In disk drives with narrow track pitches, off-track errors during data reading and writing can lead to incorrect data retrieval due to interference between adjacent tracks, which existing technologies struggle to effectively mitigate.

Innovation Solution

A controller is implemented with an interference canceller and Viterbi equalizer that uses auto-regressive and moving average models to estimate and cancel noise interference between adjacent tracks, improving signal quality by accounting for noise correlation and interference patterns across multiple read heads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the track pitch of the magnetic disk is narrowed to increase storage density, then the storage capacity is improved, but off-track errors during reading and writing increase due to interference between adjacent tracks

Engineering Contradiction:

Improvestorage capacityVSAvoiddata reading accuracy

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent converts the harmful interference between adjacent tracks into a useful signal by using the interference pattern itself to generate correction signals. The interference canceller utilizes the correlated noise and interference components from adjacent tracks to create cancellation signals that remove the harmful effects, thereby enabling higher storage density without sacrificing read accuracy

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces an interference canceller as an intermediary component between the read head and the data output. This canceller processes the raw read signals by estimating and removing interference components from adjacent tracks, acting as a mediator that separates the desired signal from the harmful interference to improve data reading reliability

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If the track pitch is narrowed to increase recording density, then the storage capacity is improved, but signal interference between adjacent tracks increases

Engineering Contradiction:

Improverecording densityVSAvoidsignal interference

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The patent transforms the harmful signal interference into a beneficial element by using the interference pattern from adjacent tracks to generate correction signals. The interference canceller estimates the interference components and uses them to create cancellation signals that eliminate the harmful effects, allowing narrow track pitches to be used without compromising signal quality

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent implements a feedback mechanism where the interference canceller continuously estimates interference components from adjacent tracks and feeds back correction signals to remove the interference. This closed-loop approach dynamically adjusts the cancellation signals based on the actual interference conditions, effectively suppressing signal interference while maintaining high recording density

Inventive Principle:

Principle #23Feedback

3Reliability

If off-track errors occur during reading from narrow track pitch disks, then data retrieval fails, but existing technologies cannot effectively mitigate the interference

Engineering Contradiction:

Improvedata retrieval correctnessVSAvoidinterference mitigation capability

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the signal processing into distinct functional components: an interference canceller that estimates and removes interference components, and a Viterbi equalizer that further processes the corrected signal. This segmentation allows each component to specialize in specific aspects of interference mitigation, achieving effective data retrieval without excessive overall complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an interference canceller as an intermediary processing stage between the read head and the final data output. This canceller acts as a mediator that specifically targets and removes interference components before the signal proceeds to further processing, enabling reliable data retrieval from narrow track pitch disks

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS9105277B1Controller, disk drive, and read processing method

Publication Date: 2015.08.11 KK TOSHIBA

AI summary

According to one embodiment, an equalizer is configured to obtain a noise included in a first correction signal by using a noise component of a first track and a noise interference component from a second track. The equalizer is configured to correct the first correction signal by using the obtained noise. The equalizer is configured to equalize the corrected first correction signal. The noise component of the first track is calculated based on a noise component of the first track at a first timing and a noise component of the first track at a second timing earlier than the first timing. The noise interference component from the second track is calculated based on a noise interference component from the second track at the first timing and a noise interference component from the second track at the second timing. The decoder is configured to decode the equalized first correction signal.