Seagate Technology Incorporated

Magnetic Peripherals Inc.

Vladimir Kovner

Vadim B Minuhin

Srinivasan Surendran

Randall D Hampshire

Lisa Fredrickson

Otis L Funches

Steven V Holsinger

Robert A Bremmer

Dennis C Stone

Shafaollah Dahandeh

Dennis W Hogg

A method and apparatus are provided for identifying errors in a detected sequence of values generates the detected sequence of values from channel samples using a detector designed for a channel with a first channel response characteristic. The detected sequence of values is filtered using a filter that emulates a second channel response characteristic to produce a sequence of simulated second channel samples. The channel samples provided to the detector are also provided to a second filter which emulates a response characteristic equal to the second channel response characteristic divided by the first channel response characteristic. This produces a sequence of actual second channel samples. A sequence of difference values is then generated by subtracting each of the simulated second channel samples from a corresponding actual second channel sample. Using the sequence of difference values, at least one error is identified in the detected sequence of values.

Method and apparatus for identifying errors in a detected sequence of values

A phase detector for a timing control loop provided in a signal sampling system to control taking samples by a sampler of input signals provided to a signal sampling system to result in a signal sample sequence output using a slope estimator and an error determiner with a phase error estimator combiner. The combiner output is provided to a summer directly and through a delay element to form phase error estimates.

Phase detector estimator

A method for compensating for position and component induced variations in the acceleration and deceleration capabilities of a voice coil actuator in a disc drive, comprising the steps of dividing the discs radially into a plurality of zones, testing the acceleration and deceleration capability of the disc drive in each zone by performing specially controlled seeks in both inward and outward directions in each zone, comparing the result of these specially controlled seeks with a calculated nominal or desired result, and calculating a compensation factor for each zone which is applied by the servo system to all subsequent seek and track following operations.

Compensating for variations in torque capability of voice coil motors

An analog, adaptive generalized transversal equalizer for use in the filtering system of a disc drive PRML read channel, the transversal equalizer employing the use of non-ideal delay elements. The filtering system comprises the equalizer connected in series with an adaptive, analog prefilter. The prefilter is comprised of a plurality of serially connected, adaptive, analog filter stages having variable transfer functions determined by adaptive parameter signals received by the filter stages. The generalized transversal equalizer comprises a plurality of serially connected, adaptive, analog low pass filters, having taps on either side of each low pass filter, a plurality of multipliers that receive signals at the tap locations of the delay circuit, and a summing circuit that receives the outputs of the multipliers. The transfer functions of the delay circuit are continuously variable in relation to adaptive parameter signals received by the delay circuit and the coefficients of multiplication are variable in relation to the adaptation process.

Adaptive analog transversal equalizer

A disc drive system includes a plurality of subsystems. At least one of the subsystems includes a filter which is completely integrated using a synthetic integrated circuit element.

Fully integrated programmable filters for disc drive subsystems

An adaptive, analog filter system of a PRML [PARTIAL RESPONSE MAXIMUM LIKELIHOOD ] read channel of a disc drive comprising an adaptive, analog transversal equator connected in series with an adaptive, analog prefilter. The prefilter is comprised of a plurality of serially connected, adaptive, analog filter stages having variable transfer functions determined by adaptive parameter signals received by the filter stages. The transversal equalizer is comprised of a delay circuit, comprised of a plurality of serially connected, adaptive, analog sixth order low pass filters, that is tapped to either side of each low pass filter, a plurality of analog multipliers that receive signals at the tap locations of the delay circuit, and a summing circuit that receives the outputs of the multipliers. The transfer functions of the sixth order low pass filters are continuously variable in relation to adaptive parameter signals received by the low pass filters and the gains of the multipliers are continuously variable in relation to tap weights received by the multipliers.

Communication channel with adaptive analog transversal equalizer

Method and apparatus for controlling the timing of the sampling of signals and signal amplitude in a PRML read channel. A VCO generates a read clock and a clock generator connected to the VCO generates even and odd clock signals corresponding to even and odd cycles of operation of the VCO. Serially connected even sample and hold circuits respond to clock signals to store samples of the read channel signal taken during successive odd cycles and serially connected odd sample and hold circuits store samples taken during successive even cycles. Comparator circuits compare the samples taken in each cycle to reference signals and the comparisons are clocked through two stage, even and odd shift registers to provide estimates of the presence or absence of nonzero samples for each even and odd cycle. Even and odd time error generators connected to the sample and hold circuits and, via AND gates enabled during even and odd cycles respectively, to the shift registers, generate even and odd time error signals from the samples and estimates during even and odd cycles respectively. An adder transmits the even and odd time error signals to the VCO input. Even and odd gain error generators connected to the sample and hold circuits and the AND gates generate even and odd gain error signals transmitted to a variable gain amplifier in the read channel.

Timing and gain control circuit for a PRML read channel

A maximum likelihood detector for a disc drive in which data files are stored along tracks as a sequence of magnetically written data elements that give rise to a signal in the disc drive read chapel. The detector includes even and odd Viterbi decoders that determine the most likely even and odd subsequences of data elements from even and odd samples of the signal and a postcoder that generates the most likely sequence of bits of encoded user data from the subsequences. Each Viterbi decoder includes an analog adder and an analog subtracter for generating the sums and differences of each sample and a reference signal, a sample and hold circuit codected to the adder and subtracter to receive the sums and differences, a difference circuit that generates the difference between the contents of the sample and hold circuit and each sample, a comparator assembly that generates a two bit merge indicator signal from the output of the difference circuit and the reference signal, AND gates that transmit bits of the indicator signal to switches in the sample and hold circuit for entering the sum or difference of the sample and reference signal into the sample and hold circuit, a shift register having interstate decoders that transmit logical 1's in response to a specific nonzero bit of the merge indicator signal and an indicator bit while otherwise transmitting a logic value determined by the logic value received from a preceding stage of the shift register and a pointer for generating indicator bits for each sample for which the merge indicator signal is logical 00.

Maximum likelihood detector for a disc drive PRML read channel

A method and apparatus for increasing the amount of data capable of being stored in a magnetic storage device is disclosed. Basically, a magnetic characteristic of the disk to head interface is measured at several locations on the disk. The frequency for writing and reading the data is optimized in terms of the required resolution and the magnetic measurement. The read and write modes are then varied, based upon the optimized frequency, such that data is written on the disk at a frequency substantially equal to the optimized frequency and read from a disk having data recorded at the optimized frequency.

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Oklahoma City, OK, United States of America

Vladimir Kovner