Disk Drive Servo Sector Radial Reference Pattern
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Solution Overview
Problem
Existing disk drives face challenges in accurately controlling the fly height of the head during write and read operations, which affects data recovery due to limitations in synchronizing and demodulating servo bursts and measuring head positioning.
Innovation Solution
Incorporating a periodic reference pattern in each servo sector at a different frequency than the preamble, allowing for independent measurement of fly height and demodulation of servo bursts, and using control circuitry to generate position error signals and adjust gain settings for precise head positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a periodic reference pattern is recorded in each servo sector at a frequency different from the preamble, then fly height measurement and servo burst demodulation can be performed independently with improved accuracy, but the disk structure and servo sector composition become more complex
Solution Approach 1:
The servo sector is segmented into distinct functional components: preamble, periodic reference pattern, and servo bursts. Each component operates at a different frequency and serves a specific function. The periodic reference pattern is positioned between the preamble and servo bursts, creating clear temporal and functional separation that enables independent processing of fly height measurement and servo demodulation without interference.
2Adaptability or versatility
If the periodic reference pattern is used for both servo burst demodulation and fly height measurement, then system versatility is improved, but the reliability of each function may be compromised due to potential interference
Solution Approach 1:
The periodic reference pattern is recorded at a specific frequency that differs from both the preamble frequency and the servo burst frequency. This periodic structure with distinct frequency characteristics enables the system to reliably distinguish between different functions. The control circuitry exploits these frequency differences to separately process fly height measurement and servo demodulation, ensuring reliable execution of each function despite the shared medium.
3Measurement precision
If the head positioning accuracy is improved through precise fly height control, then data recovery accuracy is improved, but the device complexity increases due to additional control mechanisms
Solution Approach 1:
The periodic reference pattern embedded in the servo sector serves dual purposes: it enables fly height measurement and provides reference information for servo burst demodulation. This self-service approach allows the same structural element to support multiple functions, reducing the need for additional separate control mechanisms while maintaining high head positioning accuracy through precise fly height control.
Data Source
AI summary
A disk drive is disclosed comprising a disk comprising a plurality of data tracks defined by servo sectors. Each servo sector comprises a periodic preamble recorded at a first frequency, servo data, a periodic reference pattern recorded at a second frequency different from the first frequency, and at least one servo burst. A servo sector is processed by processing the periodic preamble to extract the servo data, demodulating the servo burst in response to the periodic reference pattern, generating a position error signal based on the extracted servo data and the demodulated servo burst, and measuring a fly height of the head based on the periodic reference pattern.