Abstract: A method and apparatus detects and filters pulse asymmetries in a read signal of a data storage device. A value indicative of the difference between the shape of a pulse from its first zero crossing to its peak and the shape of the pulse from its second zero crossing to its peak is determined. This value is minimized by adjusting at least one filter characteristic of a read signal filter.

Abstract: A magnetic medium comprises a magnetic disc having a read surface that has a plurality of tracks, at least some having servo sectors. The servo sectors comprise a plurality of magnetic irregularities, such as pits or regions of reduced magnetic coercivity, arranged in a servo pattern along the servo sector at a servo frequency. A magnetic pattern is recorded in the disc along the servo sector at a high carrier frequency. A process for manufacturing the servo pattern and for recovering servo data from the servo pattern are also described.

Abstract: A method and apparatus detects pulse asymmetries in a read signal of a data storage device. The read signal is rectified through multiplication with a rectification signal to produce a product signal. The product signal is integrated to produce integrands indicative of pulse asymmetry. In some embodiments of the present invention, the integrands are compared against a baseline value to determine a performance characteristic of a read head in the data storage device.

Abstract: An asynchronous demodulator and method is provided which determines a position error of a read head relative to a position on a medium in a storage device. The read head generates a read signal as the read head passes over a servo area on the medium. The demodulator generates a normal demodulating signal that is asynchronous with the read signal and a quadrature demodulating signal that is ninety degrees out of phase with the normal demodulating signal. The read signal is sampled to produce a series of digital read values which are multiplied by the normal demodulating signal and the quadrature demodulating signal to produce a plurality of normal and quadrature sample values. The demodulator produces the a position error magnitude and a position error direction based on the plurality of normal and quadrature sample values.

Abstract: A method of generating a position error estimate generates a phase field signal and a position error field signal. A set of operations is performed on the phase field signal and the same set of operations is performed on the position error field signal. The result obtained by performing the set of operations on the position error field signal is divided by the results obtained by performing the set of operations on the phase field signal. The result of the division is the position error estimate. In addition, a demodulation circuit is provided that utilizes field ratioing.

Abstract: A synchronous digital demodulator and method for demodulating a read signal including a user data waveform and a servo waveform which are generated by a read head as the read head passes over a user data area and a servo area, respectively, on a medium in a storage device. The user data waveform is converted to a series of digital user data values at a user data sample rate. The series of digital user data values are then applied to a user data detector circuit. The servo waveform is converted to a series of digital servo values at a servo sample rate, which is independent from the user data sample rate. The series of digital servo values are demodulated synchronously with the servo waveform to produce a position error value indicative of a position error of the read head relative to a location on the medium.

Abstract: A phase plane trajectory trough method and apparatus for fast settling of a data transducer for positioning a transducer head over a selected track on a disk surface are provided for use in a disk file. The disk file includes at least one disk mounted for rotation about an axis and the disk has at least one disk surface including a plurality of data tracks for storing data. An actuator moves the transducer head from one track location to another track location. A controller is coupled to the actuator for applying a gain control signal to control movement of the actuator. A phase plane trajectory trough function is defined for the disk file. Velocity and position states of the actuator are estimated and compared with the phase plane trajectory trough function for generating a base correction factor. The controller is responsive to both the estimated velocity and position states and the phase plane trajectory trough (PPTT) function for modifying the gain control signal.