Servo Demodulation Using Second Burst Data in Magnetic Disk Devices

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Solution Overview

Problem

In two-dimensional magnetic recording (TDMR) type magnetic disk devices, accurately positioning the head to read data is challenging due to varying cross-track separation caused by skew angles, which affects data writability and readability.

Innovation Solution

A magnetic disk device configuration that includes a disk with specific servo data structures and a controller that reads second burst data using multiple read heads without reading the first burst data, allowing for servo demodulation position calculation in a short servo mode, enabling improved head positioning and data writability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If burst data is not read in short servo mode to improve data format efficiency, then data writability region increases, but head positioning accuracy deteriorates due to varying skew angles

Engineering Contradiction:

Improvedata format efficiencyVSAvoidhead positioning accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent extracts only the necessary servo data (second burst data) from the servo sector while excluding unnecessary portions (first burst data, preamble, servo mark, gray code, post code). This selective extraction maintains head positioning accuracy by reading essential positioning information while improving data format efficiency by minimizing read operations.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent performs preliminary positioning using the second burst data before the write operation. The controller calculates the servo demodulation position based on the read second burst data, and uses this position information to adjust head positioning prior to writing data, ensuring accurate positioning even without reading complete servo data.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If complete servo data is read to ensure accurate head positioning, then head positioning accuracy is maintained, but data format efficiency decreases and writable region reduces

Engineering Contradiction:

Improvehead positioning accuracyVSAvoiddata format efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies partial action by reading only the minimum necessary servo data (second burst data) required for accurate head positioning, rather than reading complete servo data. This partial reading approach provides sufficient positioning information while maximizing data format efficiency and writable region.

Inventive Principle:

Principle #16Partial or excessive action

3Manufacturing precision

If cross track separation is adjusted for varying skew angles to improve positioning accuracy, then head positioning improves, but device complexity increases

Engineering Contradiction:

Improvehead positioning accuracyVSAvoidpositioning control complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent enables the system to self-correct positioning errors by reading the second burst data and automatically calculating the servo demodulation position. The controller uses this calculated position to self-adjust the head positioning, eliminating the need for complex external positioning control mechanisms while maintaining high positioning accuracy.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent implements feedback by reading the second burst data to calculate the actual servo demodulation position, then using this feedback information to adjust head positioning before data writing. This closed-loop feedback mechanism ensures accurate positioning while keeping device complexity manageable through software-based control.

Inventive Principle:

Principle #23Feedback

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 configuration enhances data writability and format efficiency by accurately positioning the head, even with varying skew angles, thereby improving data storage capabilities.

Implementation Method 1

a first read head and a second read head that read data from the disk

Methodology Applied

Scientific EffectMagnetic field detection: Magnetic Field

Data Source

PatentUS11475913B2Magnetic disk device and demodulation method for servo data

Publication Date: 2022.10.18 KK TOSHIBA

AI summary

According to one embodiment, a magnetic disk device includes a disk having first servo data including a first preamble, a first servo mark, a first gray code, first burst data, and second burst data written after the first burst data, a head including a write head that writes data to the disk and a first read head and a second read head that read data from the disk, and a controller that reads the second burst data using the first read head and the second read head and calculates a servo demodulation position when the first servo data is servo-read without reading the first burst data in a short servo mode in which the first preamble, the first servo mark, and the first gray code are not read.