Synchronous read channel employing an expected sample value generator for acquiring a preamble
First Claim
1. A timing recovery circuit in a synchronous read channel utilized in reading data from a magnetic medium, said synchronous read channel detects digital data from a sequence of discrete time sample values Y(n) generated by sampling pulses in an analog signal from a magnetic read head positioned over the magnetic medium, said timing recovery circuit for adjusting the phase and frequency of a sampling clock signal relative to the phase and frequency of the pulse data, said timing recovery circuit comprises a phase detector circuit comprising:
- (a) a timing gradient circuit for generating a timing gradient value .increment.t(n) representing a minimum mean squared error between the discrete time sample values Y(n) and a corresponding a priori sequence of expected sample values X(n) corresponding to sample values of a known acquisition preamble; and
(b) an expected sample value generator for generating the a prior sequence of expected sample values X(n), wherein at least one of the expected sample values X(n) is generated independent from the discrete time sample values.
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Abstract
An improved timing recovery phase-locked loop in a partial response recording channel comprising a means for generating a frequency error and a means for generating a phase error represented by a timing gradient. The frequency error is not affected by a DC offset in the input reference signal and is less susciptible to noise due to an increase in sensitivity. A state machine for generating expected samples is used to generate the timing gradient, rather than estimated signal samples, which results in a shorter acquisition preamble. When tracking arbitrary user data, the timing gradient is smoothed to reduce variations in the gain of the loop.
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Citations
18 Claims
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1. A timing recovery circuit in a synchronous read channel utilized in reading data from a magnetic medium, said synchronous read channel detects digital data from a sequence of discrete time sample values Y(n) generated by sampling pulses in an analog signal from a magnetic read head positioned over the magnetic medium, said timing recovery circuit for adjusting the phase and frequency of a sampling clock signal relative to the phase and frequency of the pulse data, said timing recovery circuit comprises a phase detector circuit comprising:
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(a) a timing gradient circuit for generating a timing gradient value .increment.t(n) representing a minimum mean squared error between the discrete time sample values Y(n) and a corresponding a priori sequence of expected sample values X(n) corresponding to sample values of a known acquisition preamble; and (b) an expected sample value generator for generating the a prior sequence of expected sample values X(n), wherein at least one of the expected sample values X(n) is generated independent from the discrete time sample values. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A timing recovery method in a synchronous read channel utilized in reading data from a magnetic medium, said synchronous read channel detects digital data from a sequence of discrete time sample values Y(n) generated by sampling pulses in an analog signal from a magnetic read head positioned over the magnetic medium, said timing recovery method for adjusting the phase and frequency of a sampling clock signal relative to the phase and frequency of the pulse data, said timing recovery method comprising the steps of:
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(b) generating an a priori sequence of expected sample values X(n) corresponding to the discrete time sample values of a known acquisition preamble, wherein at least one of the expected sample values X(n) is generated independent from the discrete time sample values; and (a) generating a timing gradient value .increment.t(n) representing a minimum mean squared error between the discrete time sample values Y(n) and the corresponding a priori sequence of expected sample values X(n). - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification