Mixed Frequency Servo Pattern for Positioning Accuracy

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Magnetic data storage media face challenges in maintaining accurate head positioning due to lack of redundancy in amplitude-based servo patterns, leading to errors from signal dropouts and complex servo write head configurations.

Innovation Solution

Implementing a servo frame with servo windows recorded at different frequencies in a checkerboard-like pattern, allowing for redundant positioning information without extending the servo frame length or sampling period, and using filters to generate position error signals from these frequencies.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If amplitude-based servo patterns are used for head positioning, then positioning functionality is provided, but positioning accuracy deteriorates due to signal dropouts and lack of redundancy

Engineering Contradiction:

Improvepositioning accuracyVSAvoidrobustness to signal dropouts

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies parameter changes by recording servo windows at two different frequencies (first frequency and second frequency) instead of a single frequency. This allows the servo system to detect positioning information through multiple frequency channels, providing redundancy that improves robustness against signal dropouts while maintaining positioning accuracy.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements copying by creating redundant positioning information through multiple servo windows at different frequencies. Each frequency provides a copy of the positioning data, and if one frequency experiences signal dropout, the other frequency provides the necessary positioning information, thereby improving reliability without sacrificing measurement precision.

Inventive Principle:

Principle #26Copying

2Measurement precision

If redundant positioning information is provided to minimize errors, then positioning accuracy improves, but servo frame length increases

Engineering Contradiction:

Improvepositioning accuracyVSAvoidservo frame length

Core Design Contradiction:

Measurement precisionVSLength of moving object

Solution Approach 1:

The patent applies periodic action by using different frequencies for the servo windows. The first servo windows are recorded at a first frequency and the second servo windows are recorded at a second frequency. This periodic variation in frequency allows redundant positioning information to be encoded within the same servo frame length, avoiding the need to extend the frame while maintaining positioning accuracy through multiple frequency channels.

Inventive Principle:

Principle #19Periodic action

3Measurement precision

If complex servo write head configurations are used to improve positioning, then positioning accuracy improves, but device complexity increases

Engineering Contradiction:

Improvepositioning accuracyVSAvoidservo write head configuration

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent resolves the contradiction by changing the frequency parameter of the recorded servo windows rather than complicating the write head configuration. By recording at two different frequencies, the system achieves improved positioning accuracy and redundancy without requiring complex multi-head configurations, thereby maintaining simplicity in the device while improving measurement precision.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances positioning accuracy by minimizing errors and improving signal-to-noise ratio, allowing for simpler servo write head configurations and robust data tracking.

Implementation Method 1

Magnetic data storage media includes a servo track and one or more data tracks. The servo track includes a plurality of servo frames that include a set of first servo windows recorded at a first frequency and a set of second servo windows recorded at a second frequency

Methodology Applied

Scientific EffectMagnetic signal detection: Magnetic Field

Implementation Method 2

Filters tuned to the first frequency and the second frequency generate a first frequency servo signal and a second frequency servo signal, respectively, from the mixed frequency servo signal

Methodology Applied

Scientific EffectFrequency filtering: Filter (electronic)

Data Source

PatentUS7379254B2Mixed frequency amplitude-based servo pattern

Publication Date: 2008.05.27 SONY GROUP CORP

AI summary

The invention is directed to a servo frame that includes servo windows written with different frequencies to provide redundant positioning information. The servo frame includes a set of first servo windows recorded at a first frequency and a set of second servo windows recorded at a second frequency arranged in a checkerboard-like pattern. The different frequencies of the servo windows allow the servo frame to achieve improved positioning information redundancy. A servo track may include a plurality of the servo frames described herein to accurately position data read/write heads adjacent corresponding data tracks. The redundancy built into each of the servo frames substantially minimizes errors in the positioning information.