Western Digital Technologies, Inc.

Finisar Corporation

Hui Li

Guoxiao Guo

Jie Yu

Wei Xi

Jianguo Zhou

Shuyu Cao

Wai Ee Wong

Jianyi Wang

Qing Wei Jia

Kun Ma

A data storage device is disclosed comprising a head actuated over a disk comprising a plurality of servo tracks defined by servo bursts. A number of burst correction values are generated by reading at least one of the servo bursts at a number of different radial locations across the disk. The burst correction values are filtered to generate filtered burst correction values, and the filtered burst correction values are downsampled to generate downsampled burst correction values. The downsampled burst correction values are written to the disk, and the head is servoed over the disk by reading the downsampled burst correction values from the disk.

Data storage device filtering burst correction values before downsampling the burst correction values

An embodiment of the invention includes a method of authenticating a second device connected to a first device. The method includes transmitting a first data string from the first device to the second device and receiving a second data string at the first device from the second device. The method also includes generating a third data string using an alteration key at the first device and comparing the third data string and either the first data string or the second data string. The method further includes authenticating the second device if the compared data strings match.

Protecting against counterfeit electronic devices

A data storage device is disclosed comprising a head actuated over a disk and a vibration detector configured to generate a vibration signal in response to a vibration affecting the data storage device. A timing loop is configured to generate a disk-locked clock substantially synchronized to a rotation frequency of the disk. An adaptation control signal is generated based on the vibration signal and an error signal of the timing loop. An adaptive filter is adapted based on the adaptation control signal, wherein the adaptive filter filters the vibration signal to generate feed-forward compensation values. The feed-forward compensation values are applied to the timing loop to compensate for the vibration.

Data storage device employing adaptive feed-forward control in timing loop to compensate for vibration

A disk drive is disclosed comprising a servo control system configured to control an actuator for actuating a head over a disk. Servo sectors are sampled at a servo sample frequency fto generate a position error signal PES(k) that is filtered with a compensator to generate a first control signal u(k). A first discrete-time sinusoid comprising a sinusoid frequency of f+&#x394;f is added to the first control signal u(k) to generate a second control signal u(k). The second control signal u(k) is applied to the actuator, and a frequency response of the actuator is determined at the frequency |&#x394;f|. The frequency response of the actuator is determined at the frequency f+&#x394;f based at least in part on the frequency response of the actuator at the frequency |&#x394;f| and a measured signal of the servo control system when applying the second control signal u(k) to the actuator.

Disk drive determining frequency response of actuator near servo sample frequency

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Singapore, Singapore

Hui Li