Western Digital Technologies, Inc.

Seagate Technology Incorporated

James P R McFadyen

Bernhard E Knigge

Michael L Mallary

Noureddine Kermiche

A disk drive is disclosed comprising a head actuated over a disk, wherein data is written to the disk comprising a first periodic pattern, a payload, and a second periodic pattern. The data is first read from the disk to generate a first read signal, and the first read signal is sampled asynchronously to generate first asynchronous signal samples. The first asynchronous signal samples representing the first periodic pattern are processed to measure a first phase, and the first asynchronous signal samples representing the second periodic pattern are processed to measure a second phase. A first phase error is generated based on a difference between the first phase and the second phase. The first asynchronous signal samples representing the payload are adjusted in response to the first phase error to generate first adjusted asynchronous signal samples.

Disk drive using preamble and postamble to adjust asynchronous signal samples of payload

A disk drive is disclosed comprising a head actuated over a disk. A test pattern is written to the disk and read from the disk to generate a read signal. The read signal is sampled to generate signal samples, the signal samples are filtered with an equalizer filter to generate a first output, and the test pattern is filtered with a target filter to generate a second output. An error signal is generated based on a difference between the first output and the second output. Coefficients of the target filter are adapted in response to the error signal, and after adapting the coefficients of the target filter, a sequence detector is configured based on the coefficients of the target filter.

Disk drive selecting target response based on identified response

A method of calculating a Head Media Separation (HMS) from a preamble of embedded servo sectors in a disk drive may include steps of reading the preamble, the read preamble being amplified by a variable gain amplifier (VGA) set at a predetermined gain; transforming samples of the read preamble into a first and a second frequency using a discrete time-to-frequency domain transform such as a Discrete Fourier Transform (DFT); calculating the ratio of the magnitude of the discrete time-to-frequency domain transform of the first frequency to the magnitude of the discrete time-to-frequency domain transform of the second frequency; determining the HMS from the calculated ratio, and enabling the predetermined gain to be updated in synchronism with the transforming step.

Calculation of head media separation (HMS) from servo preamble in a hard disk drive

A disk drive is disclosed comprising a plurality of disks having a plurality of disk surfaces. The disk drive further comprises a head actuated over each disk surface, and a spindle motor for rotating the disks. A first fly height measurement is generated for a first disk surface, and a second fly height measurement is generated for a second disk surface. A positive correlation is detected in the first and second fly height measurements.

Disk drive detecting positive correlation in fly height measurements

A disk drive is disclosed comprising a disk surface, and a head actuated over the disk surface. A first fly height measurement is generated for the head over the disk surface by measuring a first metric, and a second fly height measurement is generated for the head over the disk surface by measuring a second metric different from the first metric. The first fly height measurement is verified by detecting a positive correlation in the first and second fly height measurements.

Disk drive correlating different fly height measurements to verify disk warpage

A disk drive is disclosed comprising a disk having a plurality of tracks, and a head actuated over the disk. The disk drive further comprises control circuitry including a fly height actuator. A fly height map is measured for at least one track. A constant FHC signal applied to the fly height actuator is adjusted to decrease an average fly height of the head. After decreasing the average fly height of the head, a fluctuating fly height control (FHC) signal is applied to the fly height actuator to adjust a fly height of the head in response to the fly height map. When the head contacts the disk, an operating FHC signal is determined. The operating FHC signal is applied to the fly height actuator while executing at least one of a read and write operation.

Disk drive adjusting fly height when calibrating head/disk contact

A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of tracks. The disk drive further comprises a fly height actuator operable to adjust a fly height of the head. A fly height measurement (FHM) is generated for the head, and a fly height error (FHE) is generated as a difference between the FHM and a target fly height. A comb filter is used to generate fly height compensation values in response to the FHE, and a fly height control signal is generated in response to the FHE and the fly height compensation values, wherein the fly height control signal is applied to the fly height actuator.

Disk drive employing comb filter for repeatable fly height compensation

Disclosed is a disk drive that determines dynamic fly height (DFH) head non-linearity. A processor of the disk drive controls operations in the disk drive including: estimating a first and second set of head media spacing (HMS) actuation data for a DFH head at a first and second data frequency by commanding the application of power to the DFH head across a pre-defined power range; determining a first and second HMS value based upon the first and second sets of HMS actuation data; calculating a difference value between the first and second HMS values; determining whether the difference value exceeds a threshold.

Determining head non-linearity in a disk drive

A slider for use in a disk drive system with a read/write head that has a write coil as part of a write transducer. The write coil has a center tap thereon for connection to a conductor in addition to the connection of the ends of the write coil to two other conductors. This allows the write coil to be driven from opposite ends with opposite but equal currents in addition to the write currents that are used in write mode or alone in modes other than in write mode, such as just before write mode is entered. The current flowing in or out of the center tap then will be the sum of the currents flowing out or into the opposite ends of the write coil. In this manner, no magnetic fringing field is created since the currents/fields cancel each other out. Also, the power dissipation in the write coil during this time will be approximately the same as in write mode and a similar amount of pole tip protrusion should be produced thereby.

Growing community of inventors

Redwood City, CA, United States of America

James P R McFadyen