METHOD FOR INTERSYMBOL INTERFERENCE REMOVAL IN DATA RECOVERY
First Claim
1. A method for retrieving a signal corresponding to a distribution of magnetically polarized regions on a carrier of magnetically coated media by means of a magnetoresistive transducer coupled to a read channel circuit, the retrieved signal being free from intersymbol interference, the method comprising the steps of:
- (a). providing magnetoresistive transducer positioning means for positioning the magnetoresistive transducer to a user-selectable location over the carrier of magnetically coated media, said positioning means including drive means for producing a change in magnetic flux about the magnetoresistive transducer upon positioning thereof at said user-selectable location, said change in magnetic flux corresponding to the magnetically polarized regions on the carrier of magnetically coated media so as to produce a voltage at an output of the read channel circuit responsive thereto;
(b). constructing a spatial image of a response function of the magnetoresistive transducer by measuring said voltage signal at said output of the read channel circuit responsive to a known distribution of the magnetically polarized regions disposed on a first carrier of magnetically coated media;
(c). constructing a spatial image of raw read signal data by measuring said voltage signal at said output of said read channel circuit responsive to an unknown distribution of the magnetically polarized regions disposed on a second carrier of the magnetic media;
(d). constructing a spatial image of a distribution of virtual magnetic charge corresponding to said unknown distribution of the magnetically polarized regions on said second carrier of magnetically coated media by spatial deconvolution of said spatial image of said response function of the magnetoresistive transducer and said spatial image of said raw read signal data; and
(e). obtaining the retrieved intersymbol interference-free signal by spatially differentiating said spatial image of said distribution of virtual magnetic charge.
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Accused Products
Abstract
In recovering data originally written on a carrier of magnetic media after a catastrophic failure, data may be read without prior knowledge of the write channel by which the data was originally written and in the presence of intersymbol interference of the readback signal. This is accomplished by forming an image of the spatial response function of the magnetoresistive transducer used to recover the data and by forming an image of the raw data read from the carrier of magnetic media by the magnetoresistive transducer for which the response function has been characterized. An image of the distribution of virtual magnetic charge on the carrier of magnetic media is obtained through deconvolution of the image of the response function of the magnetoresistive transducer and the raw readback signal. The readback signal corresponding to the data originally written on the carrier of magnetic media is then recovered by spatial differentiation of the image of virtual magnetic charge. Further improvement in image quality of the resulting image is accomplished through a noise reduction technique such as by the application of an arctangent function to the data prior to differentiation.
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Citations
21 Claims
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1. A method for retrieving a signal corresponding to a distribution of magnetically polarized regions on a carrier of magnetically coated media by means of a magnetoresistive transducer coupled to a read channel circuit, the retrieved signal being free from intersymbol interference, the method comprising the steps of:
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(a). providing magnetoresistive transducer positioning means for positioning the magnetoresistive transducer to a user-selectable location over the carrier of magnetically coated media, said positioning means including drive means for producing a change in magnetic flux about the magnetoresistive transducer upon positioning thereof at said user-selectable location, said change in magnetic flux corresponding to the magnetically polarized regions on the carrier of magnetically coated media so as to produce a voltage at an output of the read channel circuit responsive thereto;
(b). constructing a spatial image of a response function of the magnetoresistive transducer by measuring said voltage signal at said output of the read channel circuit responsive to a known distribution of the magnetically polarized regions disposed on a first carrier of magnetically coated media;
(c). constructing a spatial image of raw read signal data by measuring said voltage signal at said output of said read channel circuit responsive to an unknown distribution of the magnetically polarized regions disposed on a second carrier of the magnetic media;
(d). constructing a spatial image of a distribution of virtual magnetic charge corresponding to said unknown distribution of the magnetically polarized regions on said second carrier of magnetically coated media by spatial deconvolution of said spatial image of said response function of the magnetoresistive transducer and said spatial image of said raw read signal data; and
(e). obtaining the retrieved intersymbol interference-free signal by spatially differentiating said spatial image of said distribution of virtual magnetic charge. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for retrieving previously written data from a magnetically coated disk by means of a magnetoresistive transducer coupled to a read channel circuit, the read channel producing at an output thereof a voltage signal corresponding to a change in magnetic polarity at the magnetoresistive transducer, the method comprising the steps of:
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providing positioning means for positioning the magnetoresistive transducer to a user-selectable location over the magnetically coated disk, said positioning means including a spindle motor for rotating the magnetically coated disk relative to said user-selectable location upon positioning the magnetoresistive transducer thereat so as to produce the change in magnetic polarity;
acquiring the voltage signal at the output of the read channel circuit responsive to a known pattern of magnetized regions on a magnetically coated disk in the rotation relative to said user-selectable location;
repeating the voltage signal acquiring step until a spatial image of a response function of the magnetoresistive transducer is formed;
acquiring the voltage signal at the output of the read channel circuit responsive to an unknown pattern of magnetized regions on a magnetically coated disk in the rotation relative to said user-selectable location;
repeating the voltage signal acquiring step until a spatial image of a raw read signal is formed;
providing signal processing means for recovering the signal corresponding to a distribution of magnetically polarized regions from said spatial image of said response function and said spatial image of said raw read signal, said signal processing means including storage means for storing executable program code and representations of said spatial image of said response function and said spatial image of said raw read signal, said executable code including the steps of;
calculating a frequency-domain representation of said response function image;
storing said frequency-domain representation of said response function image as a response function spatial frequency spectrum;
calculating a frequency-domain representation of said raw read signal image;
storing said frequency-domain representation of said raw read signal image as a read signal spatial frequency spectrum;
transforming into a virtual magnetic charge spatial image a scaled ratio of said read signal spatial frequency spectrum to said response function spatial frequency spectrum; and
differentiating said virtual magnetic charge spatial image to produce the previously written data. - View Dependent Claims (18, 19, 20, 21)
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Specification