Fault tolerant index patterns and decoding means
US4933786A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 21, 1988 |
| Grant date | Jun 12, 1990 |
| Priority date | — |
| Expiry date | Sep 21, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B27/3027
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A fault tolerant servo index scheme is described. The present invention provides a servo index pattern and detection method which can be utilized to any servo scheme, including, but not limited to, sector servo and dedicated surface servo. The servo pattern of the preferred embodiment of present invention is a twelve bit pattern chosen to limit the side lobes of an autocorrelation plot of the pattern with a template of the pattern. In this manner a greater number of errors can be tolerated while still permitting index identification. Initially, the entire servo pattern on a servo track is detected in sequence at the bit rate. Each twelve bit sequences of bits is compared to a template of the servo pattern and the number of bits whose position and value ("1" or "0") match the template are determined. Whenever a threshold level (less than the total number of bits in the pattern) of "hits" takes place it assumed that the index has been detected. By minimizing the magnitude of the side lobes of the correlation plot, the threshold can be set between somewhere between complete correlation and the side lobe number. The lower the side lobe, the greater the number of errors which can be tol…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.