Abstract: A method and apparatus for providing matched differential MR biasing and pre-amplification. Tightly matched and well centered low-level MR bias voltage is provided directly to the sensing element for controlled input-impedance differential pre-amplification without common-mode voltage level control with loops.

Abstract: A method and apparatus for providing matched differential MR biasing and pre-amplification. Tightly matched and well centered low-level MR bias voltage is provided directly to the sensing element for controlled input-impedance differential pre-amplification without common-mode voltage level control with loops.

Abstract: A magneto-resistive (M-R) head has a read element with a servo sensing width as wide as a data track width and a data sensing width of less than one data track width. The two read sensing widths are achieved by using a single read element having a center electrical contact from the M-R read element that effectively reduces the sensing width of the read element. In a first embodiment, the servo sensing width comprises a first portion of the read element and the data sensing width comprises a second, smaller portion of the read element. In a second embodiment, the servo sensing width comprises the entire read element width and the data sensing width comprises a portion thereof. In yet another embodiment, abutting read elements are constructed to enable separate optimization of each sensing width. The wide servo sensing width permits use of a wide servo pattern having servo bursts as wide as a data track width.

Abstract: A multi-track density direct access storage device is disclosed. In accordance with a preferred embodiment of the present invention, a direct access storage device for data storage within a data processing system comprises a housing, a rotatable spindle, at least one disk, and several heads. The disk is fixedly mounted to the rotatable spindle, and the rotatable spindle is rotated by a motor within the housing. A first disk surface of the disk has a first track density and a second disk surface of the disk has a second track density; wherein the second track density is preferably greater than the first track density. Each of the several heads contains a transducer to read and write information from and to the disk during the disk rotation.

Abstract: A digital servo system for a disk drive provides servo information signal demodulation. The system includes a digital demodulator including a burst signal accumulator that accumulates terms according to respective burst timing intervals to produce a digital, quadrature position error signal (PES). The demodulator also can include a dibit burst filter with synchronous dibit sampling preferably implemented as a Hilbert Transform filter. Alternatively, the demodulator does not include a filter and a squarer and, instead, the squarer comprises a sum-and-squarer that sums the squares of odd and even digitized samples. In another embodiment, the system employs a digital demodulator having a digital squarer that removes any phase component of the digitized servo information signal and includes a burst signal accumulator that accumulates the squared terms according to respective burst timing intervals to produce the PES. The demodulator may include a filter comprising a harmonic notch filter.

Abstract: A multi-track density direct access storage device is disclosed. In accordance with a preferred embodiment of the present invention, a direct access storage device for data storage within a data processing system comprises a housing, a rotatable spindle, at least one disk, and several heads. The disk is fixedly mounted to the rotatable spindle, and the rotatable spindle is rotated by a motor within the housing. A first disk surface of the disk has a first track density and a second disk surface of the disk has a second track density; wherein the second track density is preferably greater than the first track density. Each of the several heads contains a transducer to read and write information from and to the disk during the disk rotation.

Abstract: Servo pattern bursts are recorded with two frequencies that are detected using heterodyne detection with oscillators at the same frequency as the respective recorded frequencies. The two frequencies are selected to be orthogonal so the sensed servo pattern of one frequency is zero when detected with the detecting circuitry of the other frequency. The servo pattern bursts of the two frequencies are placed close together on the disk so they are sensed simultaneously so that, with orthogonality processing, a PES signal from a three phase pattern is sufficient to provide a robust linear signal, thereby eliminating one of the bursts from a quadrature pattern and reducing the disk surface area needed in each track for the servo pattern by 25% or more.

Abstract: An apparatus, system and method are described for generating a continuous and linear position signal generated from stitched position error signal (PES) components, for use by a servo control system in positioning a transducer with respect to a storage surface. Continuity is achieved by providing a normalization stage in the servo control loop for correcting discontinuities at the stitch points with minimal impact to the PES zero-crossing points. According to a first preferred embodiment normalization is applied using an algorithm determined by the width of the read transducer. According to a second preferred embodiment, normalization is selectively applied near the stitch points of the PES components, but is not applied at their zero-crossing points. In another preferred embodiment, a first normalization algorithm is applied near the stitch points, and a second normalization algorithm is applied at the zero-crossing points.

Abstract: A digital servo control system for a disk drive provides asynchronous servo information signal demodulation. The system includes a digital demodulator having a digital squarer that removes any phase component of the digitized servo information signal and includes a burst signal accumulator that accumulates the squared terms according to respective burst timing intervals to produce a digital, quadrature position error signal (PES). The demodulator also can include a filter comprising a harmonic notch filter preferably implemented as a Hilbert Transform filter. Alternatively, the demodulator does not include a filter and squarer and, instead, the squarer comprises a sum-and-squarer that sums the squares of odd and even digitized samples. A split burst servo pattern for the servo control system is comprised of half-width transitions that can be written in a single pass of a recording head and therefore has no phase misalignment between adjacent flux patterns.

Abstract: A digital servo control system for a disk drive provides asynchronous servo information signal demodulation. The system includes a digital demodulator having a digital squarer that removes any phase component of the digitized servo information signal and includes a burst signal accumulator that accumulates the squared terms according to respective burst timing intervals to produce a digital, quadrature position error signal (PES). The demodulator also can include a filter comprising a harmonic notch filter preferably implemented as a Hilbert Transform filter. Alternatively, the demodulator does not include a filter and squarer and, instead, the squarer comprises a sum-and-squarer that sums the squares of odd and even digitized samples. A split burst servo pattern for the servo control system is comprised of half-width transitions that can be written in a single pass of a recording head and therefore has no phase misalignment between adjacent flux patterns.

Abstract: A servo system accurately detects and processes signals from servo patterns encoded on magnetic storage disks using weighted accumulation, for use in precisely positioning read/write heads with respect to tracks of data contained on the disks. After servo patterns are sensed by reading them from a disk, the resultant servo signals are processed by weighted accumulation circuitry to provide a position signal, which may be decoded to ascertain the positioning error of the read/write head and to apply any corrections that might be needed. In one embodiment, an amplitude position signal is generated by multiplying the servo signal by complementary quadrature weighting signals, then squaring each quadrature output signal, summing them, and taking the square root of the summed signal.