Dynamic magnetic information storage or retrieval – General processing of a digital signal – Address coding
Reexamination Certificate
2000-10-25
2002-06-11
Faber, Alan T. (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Address coding
C360S053000, C360S078140
Reexamination Certificate
active
06404577
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to improvements in mass data storage devices and methods, and more particularly to improvements in apparatuses and methods for trellis encoding, decoding, and detecting track identification indicia of a rotating disk using EPR4 data equalization.
2. Relevant Background
Mass data storage devices include tape drives, as well as well known hard disk drives that have one or more spinning magnetic disks or platters onto which data is recorded for storage and subsequent retrieval. Hard disk drives may be used in many applications, including personal computers, set top boxes, video and television applications, audio applications, or some mix thereof. Many applications are still being developed. Applications for hard disk drives are increasing in number, and are expected to further increase in the future. Mass data storage devices may also include optical disks in which the optical properties of a spinning disk are locally varied to provide a reflectivity gradient that can be detected by a laser transducer head, or the like. Optical disks may be used, for example, to contain data, music, or other information.
In the past, typically the track identification pulses are well separated from each other to enable them to be properly detected. However, there has been considerable recent pressure on disk drive manufacturers to increase the density of the data written to a disk to increase the capacity of the drive. Much effort has been directed to data detection techniques to increase the density of the data that can be contained on the disk. For example, maximum likelihood sequence detection (MLSD) and partial response (PR) filtering techniques have been developed that allow adjacent data pulses to at least partially overlap and still be properly detected. Moreover, EPR4 filtering techniques and Viterbi algorithms (VA's) have been developed that efficiently implement MLSD and enable the data to be written more closely. Specifically, EPR4 filtering shortens the response and, hence, the detection trellis. The VA efficiently implements MLSD.
However, to the best of my knowledge, others have not applied such EPR4 techniques to the detection of track identification information. Such EPR4 techniques are described in my copending patent application, application Ser. No. 09/660,174, filed Sep. 12, 2000, entitled METHOD AND APPARATUS FOR IDENTIFYING A TRACK OF A ROTATING DISK USING EPR4 DATA EQUALIZATION AND DETECTION TECHNIQUES, which is incorporated by reference herein. As a result, I believe that no efforts have been used to increase the signal to noise ratio by varying the parameters of the recorded track identification indicia, such as the minimum distance between adjacent track identification codewords. The minimum distance is the minimum distance among all pairs of the codewords in the codeset used.
There are various ways to measure the minimum distance between codewords. For example, a codeword is often thought of as a vector that is described by the values in the bit places, or coordinates, of the codeword. The distance between two codewords is then measured by the differences between the two codeword values. Typically, this distance is measured by a “Hamming distance”. The Hamming distance between two words is the number of coordinates in which the two words differ. The minimum distance is the minimum Hamming distance between all distinct pairs of code words in the code. Other distance measuring techniques exist, however. For instance, a Euclidean distance may be used. Euclidean distance is measured by the familiar square root of the sum of the squares of the difference values between the two vectors. Other techniques exist, as well.
When the codewords are received, they may be decoded by selecting the codeword from the codeset that is closest to the received value. The closest codeword is that which has the smallest distance from the received value.
SUMMARY OF THE INVENTION
Thus, in light of the above, it is an object of the invention to provide a track identification method in a mass data storage-device, in which the track identification indicia are selected such that the distance between any two indicia, or track identification codewords, has a distance larger than the minimum distance of the codeset from which they are selected.
It is another object of the invention to provide a track identification method in a mass data storage device, in which the track identification indicia are detected with a trellis-type detector in which the trellis paths have distances between any two paths that are larger than the minimum distance of the codeset from which the track identification indicia are selected.
It is another object of the invention to provide a mass data storage device, in which the track identification indicia are selected such that the distance between any two indicia has a distance larger than the minimum distance of the codeset from which they are selected, and are detected with a trellis-type detector in which the trellis paths have distances between any two paths that are larger than the minimum distance of the codeset from which the track identification indicia are selected.
It is still another object of the invention to provide a mass data storage device and method of operating same in which the immunity to noise is increased, improving the bit error rate (BER) to signal to noise ratio SNR.
These and other objects, features, and advantages will become apparent to those skilled in the art from the following detailed description when read in conjunction with the accompanying drawings and appended claims.
According to a broad aspect of the invention, a method is presented for making a mass data storage device. The method includes encoding track identification indicia onto a data storage medium of the mass data storage device with a code having a code distance greater than a minimum distance of a codeset containing the encoded track identification indicia. A detector is provided for detecting the track identification indicia for providing detected track identification indicia signals. A decoding trellis is provided in the detector for decoding the track identification indicia signals. The decoding trellis does not contain detection paths of the minimum distance and uses a data equalization technique having five target values (+2, +1, 0, −1 and −2), with pulses having non-zero values existing over three sample times, to identify a track of a rotating disk of the mass data storage device.
According to another broad aspect of the invention, a method is presented for operating a mass data storage device. The method includes detecting track identification indicia prerecorded on the disk and processing the detected track identification indicia using a data processing technique that does not contain detection paths of a minimum distance of a codeset containing the track identification indicia to identify a track of a rotating disk of the mass data storage device.
According to yet another broad aspect of the invention, a mass data storage device is presented. The Mass data storage device includes a rotating disk having a plurality of tracks encoded thereon adapted to be read by a transducer moveable in relationship thereto. A plurality of track identification indicia is recorded on the disk in respective association with the plurality of tracks. The track identification indicia are encoded with a code having a code distance greater than a minimum code distance of a codeset containing the track identification indicia.
REFERENCES:
patent: 6005727 (1999-12-01), Behrens et al.
patent: 6115198 (2000-09-01), Reed et al.
Conway et al., “A CMOS 260Mbps Read Channel with EPRML Performance”, VLSI Circuits Conference in Hawaii, Jun. 10, 1998.
Nagaraj, et al., “A Median Peak Detecting Analog Signal Processor for Hard Disk Drive Servo”, IEEE J. S-S Cir., vol. 30, No. 4, pp. 461-470 Apr. 1995.
Pai, et al., “A 160-MHz Analog Front-End IC for EPR-IV PRML Magnetic Storage Read Channels”, IEEE J. S-S Ci
Brady W. James
Faber Alan T.
Swayze, Jr. W. Daniel
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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