Dynamic magnetic information storage or retrieval – General recording or reproducing – Specifics of the amplifier
Reexamination Certificate
1998-12-28
2001-06-26
Neal, Regina Y. (Department: 2651)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Specifics of the amplifier
C360S046000
Reexamination Certificate
active
06252736
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to reducing crosstalk noise between a write element and a read element on a head of a drive. More particularly, this invention relates to a system that reduces the emission of magnetic pulses from the write head after a write operation is completed. Still more particularly, this invention relates to a system that gradually reduces the current applied to the write element after a write operation is completed to reduce the magnetic domains of the write element from emitting an electromagnetic pulse.
PROBLEM
A common method for storing data in computer systems is to write the data to a magnetic media such as a tape or a disk. Data is typically stored in the form of a binary string of ones and zeros. The ones and zeros are represented on the magnetic media by different magnetic orientations of material. For example, a one is represented by magnetic material oriented in a first direction and a zero is represented by magnetic material that is oriented in a second direction that is perpendicular to the first direction.
In a computer system, a drive reads and writes data to the magnetic media. The drive contains a head which performs read and write operations as the head passes over the media. In a write operation, a current is applied to a write element in the head. The current causes the magnet domain of the write element to go to a high energy state. The high energy magnetic domain emits a magnetic field that orients the magnetic material in the proper direction to represent the desired bit. When an opposite bit is desired, the direction of the current is reversed to change the magnetic domains of the write element which in turn changes the direction of the orientation of the magnetic material being passed over. Read operations are also performed by the head. In a read operation, the head is passed over the desired magnetic material while a read element detects the magnetic orientation of the material by detecting the magnetic field emitted by the material.
The proximity of the write element and read element in the head can lead to errors in read operations that are performed after a write operation. Errors are caused by a magnetic pulse that is emitted from the write element when the write operation is completed. The magnetic pulse is caused by the magnetic domains of the write element changing from a high energy state to a low energy state. The magnetic pulse is received by the read element and disrupts the detection of magnetic orientations of material in the media. The magnetic pulse from the write element that is received by the read element is known as crosstalk noise. There is a need in the art for a system that reduces crosstalk noise between read and write elements of a drive head.
SOLUTION
The above and other problems are solved and an advance in the art is made by the system for preventing crosstalk noise. The system for preventing crosstalk noise gradually reduces the current applied to a write element over a period of time after a write operation is completed. This allows the magnetic domains of the write element to be reduced gradually which prevents the write element from emitting a magnetic pulse and the read element does not detect any magnetic energy from the write element.
In a preferred embodiment of the system for preventing crosstalk noise, current is applied to the write element of a head in the following manner. Write circuitry generates a write current. The write current is then applied to step circuitry which sums the write current with a step current. The resulting current is then applied to the write element. After the last bit of data is written, the write circuitry continues to apply a current to the step circuitry. However, the step circuitry does not sum the write current and the step current. Instead, the write current alone is applied to the write element and the current applied to the write element is substantially weaker. This allows the magnetic domains of the write elements to change to an intermediate energy state before changing to a low energy state.
One manner by which the step circuitry can prevent the step current from being summed to the write current is by squelching the step current after the write operation is completed. Alternatively, the step current can be gradually reduced by a controller until no step current is being passed to the step circuitry. It is also possible to control the amount of the step current squelched over a period of time to gradually reduce the step current that is summed with the write current.
REFERENCES:
patent: 4970621 (1990-11-01), Gailbreath et al.
patent: 5168395 (1992-12-01), Klaassen et al.
patent: 5307214 (1994-04-01), Kawakami et al.
patent: 5910861 (1999-06-01), Ahn
Galanthay Theodore E.
Jorgenson Lisa K.
Kubida William J.
Neal Regina Y.
STMicroelectronics N.V.
LandOfFree
System for preventing crosstalk noise in a disk drive does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System for preventing crosstalk noise in a disk drive, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System for preventing crosstalk noise in a disk drive will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2449272