Polarity encoded pattern for timing based servo
View Patent ↗Servo tracks for magnetic tape storage are written using two opposite polarities, rather than the one polarity normally used in servo tracks. Timing continues to be performed using only pattern members of like polarity, due to physical restraints, but the use of two polarities allows additional information to be encoded in the pattern more efficiently.
1. A media on which information can be magnetically recorded, said media comprising:
a magnetic material;
a plurality of servo tracks recorded on said magnetic material; and
a plurality of timing-based servo patterns written on respective ones of said plurality of servo tracks;
wherein said plurality of timing-based servo patterns contain two opposite polarities;
wherein each of said plurality of timing-based servo patterns contain a single polarity; and
wherein said opposite polarities in the plurality of timing-based servo patterns are used to determine which set of data tracks is being read.
2. The media of claim 1 , wherein each of said plurality of timing-based servo patterns are identical except for differences in polarity.
3. The media of claim 1 , wherein ones of said plurality of timing-based servo patterns contain said two opposite polarities.
4. The media of claim 1 , wherein each of said plurality of timing-based servo patterns contain said two opposite polarities.
5. The media of claim 1 , wherein each of said plurality of timing-based servo patterns contain said two opposite polarities and a first one of said servo patterns contains information encoded in a pattern of polarities that is an exact opposite of the pattern of polarities in a second servo pattern.
6. A method of recording a plurality of timing-based servo patterns on a magnetic media, comprising the steps of:
erasing said magnetic media; and
writing a plurality of polarized symbols to a plurality of servo tracks using two opposite polarities;
wherein each of said plurality of timing-based servo patterns is written with a single polarity; and
wherein said opposite polarities are used to determine which set of data tracks is being read.
7. The method of claim 6 , wherein identical timing-based servo patterns are written to each of said plurality of servo tracks except that polarities differ between ones of said plurality of servo tracks.
8. The method of claim 6 , wherein ones of said plurality of timing-based servo patterns are written with both of said two opposite polarities.
9. The method of claim 6 , wherein each of said plurality of timing-based servo patterns are written with both of said two opposite polarities.
10. The method of claim 6 , wherein each of said plurality of timing-based servo patterns are written with both of said two opposite polarities and a first one of said servo patterns is written with information encoded in a pattern of polarities that is an exact opposite of the pattern of polarities written in a second servo pattern.
11. The method of claim 6 , wherein said plurality of servo tracks are written simultaneously.
12. A method of recording servo patterns on a magnetic tape, comprising the steps of:
running a tape from a first reel, over a read/write head, and onto a second reel;
erasing said tape; and
writing a plurality of patterns on said tape with a given polarity to form first and second servo tracks, wherein said plurality of patterns comprise a first set of symbols having a first azimuthal inclination and a second set of symbols having a second azimuthal inclination that is different from said first azimuthal inclination;
wherein ones of said plurality of symbols are magnetized with a first polarity and ones of said plurality of symbols are magnetized with a second polarity that is opposite said first polarity;
wherein said first servo track is magnetized with a first polarity and said second servo track is magnetized with a second polarity; and
wherein said first and second polarities in said first and second servo tracks are used to determine which set of data tracks is being read.
13. The method of claim 12 , wherein said first servo track and said second servo track are each magnetized with both said first and said second polarity.
14. The method of claim 12 , wherein said first servo track and said second servo track are each magnetized with both said first and said second polarity and a first one of said servo patterns is written with information encoded in a pattern of polarities that is an exact opposite of the pattern of polarities written in a second servo pattern.
15. A method of operating a tape drive, comprising the steps of:
running a tape from a first reel, over a read/write head, and onto a second reel;
sensing a plurality of first symbols that are azimuthally inclined in a first direction and a plurality of second symbols that are azimuthally inclined in a second direction, wherein said plurality of symbols are carried in a plurality of servo tracks on said tape;
using ratios of distances between occurrences of said first and said second symbols to calculate corrections in the movement of a read/write head;
wherein ones of said plurality of first and second symbols are written in a first polarity and ones of said plurality of first and second symbols are written in an opposite polarity;
wherein ones of said plurality of servo tracks are each magnetized with one of said first and said second polarity; and
wherein said first and second polarities in said plurality of servo tracks are used to determine which set of data tracks is being read.
16. The method of claim 15 , wherein ones of said plurality of servo tracks are each magnetized with both said first and said second polarity.
17. The method of claim 15 , wherein each of said plurality of timing-based servo patterns contain said two opposite polarities and a first one of said servo patterns contains information encoded in a pattern of polarities that is an exact opposite of the pattern of polarities in a second servo pattern.