Patterned Media PES Servo Segments for Local Track Position
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Solution Overview
Problem
Conventional servo systems for patterned media face challenges in accurately determining local track position due to incompatibility between asymmetric low-order Gray code bits and self-assembled features, necessitating alternative methods for providing local track location information.
Innovation Solution
The implementation of patterned magnetic media with servo sectors featuring two PES offset segments that deviate from the track centerline in opposite directions, with systematically varied lengths to generate a unique servo signal pattern for each track group, allowing the servo system to use these signals for local track position identification, similar to low-order Gray code bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If asymmetric low-order Gray code bits are used to encode local track position, then local track location information is provided, but the fabrication process becomes incompatible with self-assembled features
Solution Approach 1:
The patent extracts the local track position information function from the asymmetric low-order Gray code bits and relocates it to the PES servo bursts. By removing the asymmetric encoding requirement and using only symmetric amplitude modulation in the PES bursts, the solution eliminates the conflict with self-assembly fabrication while preserving the local track position information capability
Solution Approach 2:
The patent changes the encoding parameter from asymmetric presence/absence of Gray code bits to symmetric amplitude modulation of PES burst signals. The local track position is encoded by varying the amplitude of symmetric PES bursts in different zones, which is compatible with self-assembly fabrication processes that produce symmetric patterns
2Measurement precision
If conventional quad-burst PES patterns are used, then position error signal is provided, but local track position identification capability is lost
Solution Approach 1:
The patent merges the position error signal function and the local track position identification function into a single PES burst pattern. By encoding both the head's fractional track position (through amplitude variations) and the local track ID (through zone assignments) in the same symmetric burst structure, the solution eliminates the need for separate Gray code bits while providing both measurement capabilities
Solution Approach 2:
The PES burst pattern is designed to serve multiple functions simultaneously: providing the position error signal for head centering, encoding the local track position through amplitude modulation, and identifying the track zone through systematic amplitude variations across different radial zones. This multi-functional design eliminates the need for separate asymmetric Gray code fields
Data Source
AI summary
Patterned magnetic media are described in which the servo sectors include at least two PES offset segments that can be used for the position error signal (PES) and identification of local track position. The two PES offset segments deviate from the track centerline in opposite directions. The lengths of the offset PES offset segments are systematically varied in a repeating pattern to provide a unique servo signal pattern for each track in a local group of adjacent tracks. The locally unique servo sector pattern allows the servo system to use the pattern of the signals generated from the offset and non-offset segments to determine the local track position, which is similar to information provided by the low order Gray code bits in prior art designs. Therefore, the number of bits in the track ID code can be reduced.