Sampled servo code format and system for a disc drive
US4823212A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 26, 1986 |
| Grant date | Apr 18, 1989 |
| Priority date | — |
| Expiry date | Nov 26, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2220/20
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The system and method for normalizing the amplitude of servo code derived signals in a disc drive, includes an improved embedded servo code format of separate magnetic dibit fields, recorded in half track steps. One magnetic dibit field is an automatic gain control field in which the magnetic head sees the same amount of magnetic dibit regardless of its position with respect to the track. A fast settling AGC loop responding to signals from the AGC field, produces a gain adjust signal while the magnetic head is still in the AGC field, which is used to normalize the amplitude of all following servo code and data code signals in that sector. The cycle of automatic gain control is repeated for each track in each sector. A sector mark following the AGC field has a magnetic dibit pattern which is fault tolerant. It is transduced in three parts to minimize error in its detection and identification and provides a timing reference for servo signals which follow. A defect dibit is recorded if the following servo gap is found to be defective during manufacture so that the next servo gap may be ignored. A track position servo code field provides signals for track following.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.