Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data clocking
Patent
1995-12-05
1998-03-10
Tran, Thang V.
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data clocking
360 7708, G11B 509
Patent
active
057268185
ABSTRACT:
A sampled amplitude read channel reads user data and embedded servo data stored on a magnetic medium by detecting digital data from a sequence of discrete time interpolated sample values. A write frequency synthesizer generates a write clock for writing digital data to the magnetic medium at a predetermined baud rate for a selected zone, and upon read back, a read frequency synthesizer generates a fixed sampling clock at a frequency slightly higher than the write frequency at the outer zone. A sampling device samples the analog read signal at this fixed sampling rate across the data zones and servo wedges to generate a sequence of discrete time channel samples that are not synchronized to the baud rate. Before sampling, an analog receive filter processes the read signal to attenuate aliasing noise without having to adjust its spectrum across data zones or servo wedges. A discrete time equalizing filter equalizes the channel samples according to a predetermined partial response (PR4, EPR4, EEPR4, etc.). An interpolating timing recovery circuit, responsive to the equalized channel samples, computes an interpolation interval .tau. and, in response thereto, generates interpolated sample values substantially synchronized to the baud rate. The timing recovery circuit also generates a synchronous data clock for clocking a discrete time sequence detector and pulse detector which detect the digital user and servo data from the interpolated sample values.
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Bliss William G.
Reed David E.
Cirrus Logic Inc.
Sheerin Howard H.
Shifrin Dan A.
Tran Thang V.
Wamsley Patrick
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