Phase modulated servo system
US4549232A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 27, 1983 |
| Grant date | Oct 22, 1985 |
| Priority date | — |
| Expiry date | Jun 27, 2003 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B21/106
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
In parallel track data storage systems, such as disk files, servo information is recorded using a plurality of constant frequency fields each having a phase shift between tracks. Servo information is thus encoded in the phase of the servo pattern instead of the amplitude of the servo signal lobes. Multiple phase shifts per track are used to make the signal constantly varying with transducer head displacement. Phase is measured modulo 360.degree. such that the phase of a given field will go through 360.degree. every M tracks. By using several fields having different values of M, coarse, medium and fine position resolution can be obtained with the same servo pattern and demodulation scheme. Further, using two fields, one field may be split and positioned at either side of the other field to provide a common center for both fields and eliminate error conditions due to factors such as speed variation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.