US 7,679,853 B2 · Detection of signal disturbance in a partial response channel

Abstract

In one embodiment, irregular electronic disturbance signals in a partial-response read channel are detected by a disturbance detector using state metrics generated by maximum-likelihood sequence detector. For example, a thermal asperity (TA) detector detects the occurrence of TAs in the read channel of perpendicularly recorded magnetic media by using the state metrics generated by a Viterbi detector. Changes in state metrics (e.g., magnitudes of the branch metrics of the trellis diagram) used by the Viterbi detector are tracked. If the magnitude of the rise of the path metric increases above a set threshold, then a TA is detected. Alternatively, or additionally, the rate of change of the magnitude of the path metrics is tracked. If the rate of change within a set time window is above a specified threshold, then a TA is detected.

Claims20

Dependent claims

An apparatus for detecting electrical signal disturbances in a digital read channel, the apparatus comprising a disturbance detector adapted to:

receive values of a state metric from a sequence detector adapted to receive a signal of the digital read channel;
and
evaluate changes in the state metric values to determine whether an electrical signal disturbance occurred in the digital read channel, wherein:
the digital read channel is a partial-response read channel;
and
the disturbance detector is adapted to compare a calculated value based on the state metric values to a specified threshold to determine whether the electrical signal disturbance occurred.

3 more elements

Dependencies are inferred from the claim text.

Detection of signal disturbance in a partial response channel

Life of this patent

Detection of signal disturbance in a partial response channel

Life of this patent

Abstract

Claims20