System for reproducing data with increased accuracy by reducing difference between sampled and expected values

A data reproduction system which determines reproduced data based on comparison results of path metrics calculated in accordance with a Viterbi algorithm based on branch metrics calculated from expected values and a sampled value of a readout signal, the readout signal being obtained from a recording medium on which data is recorded in accordance with a recording signal of a partial response waveform, the expected values being determined by the partial response waveform, and the sampled value being obtained by sampling the readout signal at a predetermined frequency, said data reproduction system comprising:

• an expected value setting unit for variably setting the expected values used for a calculation of the branch metrics;
• and
• an offset detection unit which detects an offset included in the readout signal obtained steadily,
• wherein said expected value setting unit includes a second expected value calculation unit which calculates expected values to be set based on the offset detected in said offset detection unit.

A data reproduction system which determines reproduced data based on comparison results of path metrics calculated in accordance with a Viterbi algorithm based on branch metrics calculated from expected values and a sampled value of a readout signal, the readout signal being obtained from a recording medium on which data is recorded in accordance with a recording signal of a partial response waveform, the expected values being determined by the partial response waveform, and the sampled value being obtained by sampling the readout signal at a predetermined frequency, said data reproduction system comprising:

• an expected value setting unit for variably setting the expected values used for a calculation of the branch metrics;
• an initial offset setting unit which sets, as an initial offset, an offset included in the readout signal obtained immediately after a start of a reproduction of the data;
• an offset detection unit which detects an offset included in the readout signal obtained steadily;
• and
• a nonlinear component extraction unit which extracts a nonlinear torsion component included in the readout signal,
• wherein said expected value setting unit includes:
• a default expected value setting unit which sets default values of the expected values;
• and
• an expected value correction unit which corrects the default values of the expected values set in said default expected value setting unit, based on at least one of the initial offset set in said initial offset setting unit, the offset detected in offset detection unit, or the nonlinear torsion component extracted in said nonlinear component extraction unit.

A data reproduction system which determines reproduced data based on comparison results of path metrics calculated in accordance with a Viterbi algorithm based on branch metrics calculated from expected values and a sampled value of a readout signal, the readout signal being obtained from a recording medium on which data is recorded in accordance with a recording signal of a partial response waveform, the expected values being determined by the partial response waveform, and the sampled value being obtained by sampling the readout signal at a predetermined frequency, said data reproduction system comprising:

• an expected value setting unit for variably setting the expected values used for a calculation of the branch metrics;
• and
• an initial offset setting unit which sets, as an initial offset, an offset included in the readout signal obtained immediately after a start of a reproduction of the data,
• wherein said expected value setting unit includes a first expected value calculation unit which calculates expected values to be set based on the initial offset set in the initial offset setting unit.

A data reproduction system which determines reproduced data based on comparison results of path metrics calculated in accordance with a Viterbi algorithm based on branch metrics calculated from expected values and a sampled value of a readout signal, the readout signal being obtained from a recording medium on which data is recorded in accordance with a recording signal of a partial response waveform, the expected values being determined by the partial response waveform, and the sampled value being obtained by sampling the readout signal at a predetermined frequency, said data reproduction system comprising:

• an expected value setting unit for variably setting the expected values used for a calculation of the branch metrics;
• a phase error calculation unit which calculates a phase error based on differences between the sampled value and expected values used for a calculation of the branch metrics;
• and
• a synchronizing clock generation unit which generates a clock signal determining sampling timings of the readout signal based on the phase error obtained in said phase error calculation unit.

A data reproduction system which determines reproduced data based on comparison results of path metrics calculated in accordance with a Viterbi algorithm based on branch metrics calculated from expected values and a sampled value of a readout signal, the readout signal being obtained from a recording medium on which data is recorded in accordance with a recording signal of a partial response waveform, the expected values being determined by the partial response waveform, and the sampled value being obtained by sampling the readout signal at a predetermined frequency, said data reproduction system comprising:

• an expected value setting unit which sets the expected values used for a calculation of the branch metrics;
• a nonlinear portion detection unit which detects a nonlinear portion of the readout signal;
• a nonlinearity obtaining unit which obtains nonlinearities included in the readout signal when said nonlinear portion detection unit detects a given nonlinear portion of the readout signal;
• and
• an expected value adjustment unit which adjusts the expected values set in said expected value setting unit based on the nonlinearities calculated in said nonlinearity calculation unit.

A data reproduction system which determines reproduced data based on comparison results of path metrics calculated in accordance with a Viterbi algorithm based on branch metrics calculated from expected values and a sampled value of a readout signal, the readout signal being obtained from a recording medium on which data is recorded in accordance with a recording signal of a partial response waveform, the expected values being determined by the partial response waveform, and the sampled value being obtained by sampling the readout signal at a predetermined frequency, said data reproduction system comprising:

• an expected value setting unit which sets the expected values used for a calculation of the branch metrics;
• a nonlinear portion detection unit which detects a nonlinear portion of the readout signal;
• a first nonlinearity calculation unit which calculates, based on the sampled value of the readout signal, first nonlinearities of a given nonlinear portion of the readout signal when said nonlinear portion detection unit detects the given nonlinear portion;
• a second nonlinearity calculation unit which calculates, based on the sampled value of the readout signal, second nonlinearities at a sampling point next to the detected portion of the readout signal, the second nonlinearities being smaller than the first nonlinearities;
• and
• an expected value adjustment unit which adjusts, based on the first nonlinearities calculated in said first nonlinearity calculation unit, the expected values set in said expected value setting unit with respect to the sampled value sampled at the detected portion, and adjusts, based on the second nonlinearities calculated in said second nonlinearity calculation unit, the expected values set in said expected value setting unit with respect to a sampled value at the sampling point next to the detected portion of the readout signal.