Hewlett-packard Company

Charles B Gamble

Lawrence A Hansen

Ralph F Simmons, Jr

Michael Clinton Allyn

Uri Rogers

Asynchronous sampling digital detection (ASDD) methods and apparatus are described. In one embodiment, noise-corrupted information is received and comprises a plurality of information-carrying events which encode binary information which is desired to be retrieved. A plurality of values are extracted from the noise-corrupted information-carrying events which are representative of the encoded binary information. An amount of noise corruption carried by one of these plurality of values is estimated by considering an amount of noise corruption carried by another of the plurality of values. Responsive to the estimation of the noise corruption, the one value is then modified. In another embodiment, noise-corrupted information is received comprising a plurality of information-carrying events which encode binary information which is desired to be retrieved. A plurality of values from the noise-corrupted information-carrying events are determined which are representative of the encoded binary information. A set of conditions is defined which are a function of the plurality of values, and which have value-dependent outcomes. For a given determined value of the plurality of values, a value-dependent outcome is imposed to produce at least two intermediate noise-adjusted values. Using the two intermediate noise-adjusted values, a noise-reduced output value for the given determined value is selected.

Asynchronous sampling digital detection (ASDD) methods and apparatus

A data recording system includes media such as a magnetic disk or tape, a read/write head assembly, and a circuit that provides a write signal having edge placement equalization. The circuit responds to a binary serial data signal such as a run length limited signal of the type (1,x) and provides a write signal having data transitions corresponding to one of the two binary data values, the absence of a transition corresponding to the other data value. In addition, the write signal is provided with a pair of equalization transitions during periods of no data transitions. A first data transition is shifted away from the last provided equalization transition by a predetermined offset. A second data transition, provided immediately after the first data transition, may be shifted toward the last provided equalization transition. Timing of the data transitions is derived from a clock used to provide the equalization transitions.

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Boise, ID, United States of America

Charles B Gamble