US 5,862,161 A · Sampled amplitude read channel with simplified sequence detector matched to partial erasure

Abstract

This invention provides apparatus for reliably and efficiently reading data from a magnetic storage medium under the condition that adjacent magnetization regions are partially erased. A simplified nonlinear description of a read signal resulting from such partially erased magnetization regions is used to derive a state machine model of the read signal. The state machine model implicitly defines a sequence detector for demodulating recorded data from received samples. For a PR4 signal, the state machine has ten states; for an EPR4 signal, the state machine has eighteen states; and for an EEPR4 signal, the state machine has twenty-six states. The PR4 machine is further simplified using squaring and state sharing to provide state machine models with six and four states.

Claims16

Dependent claims

A sampled amplitude read channel for reading digital data from a magnetic storage medium, comprising:

(a) a sampling device for sampling an analog read signal from a read head positioned over the storage medium to generate a sequence of discrete time sample values;
and
(b) a sequence detector for demodulating the digital data from the discrete time samples wherein:
(a) the sequence detector compensates for a reduction in amplitude of a primary pulse in the analog read signal caused by adjacent secondary pulses in the analog read signal;
and
(b) the sequence detector operates according to a code constraint which increases a minimum distance error event of the sequence detector.

3 more elements

Dependencies are inferred from the claim text.

Sampled amplitude read channel with simplified sequence detector matched to partial erasure

Life of this patent

Sampled amplitude read channel with simplified sequence detector matched to partial erasure

Life of this patent

Abstract

Claims16