Abstract: The present invention provides a phase-locked loop apparatus which extends a capture range in clock reproduction when digital data is reproduced and performs a high-speed and stable phase locking. A phase error is detected by a phase error detector 6 from a signal obtained by the sampling. Further, a frequency error is detected by a frequency error detector 8 on the basis of an inclination of a phase curve obtained by phase error information. A phase-locked loop circuit is controlled on the basis of these obtained phase error and frequency error.

Abstract: In a digital data reproduction apparatus for demodulating digital data from an optical recording medium, PRML (Partial Response Maximum Likelihood) signal processing effective to high-density recording/reproduction is carried out by using a half rate processing offset control means which performs data demodulation using half of the channel bit frequency, a half rate processing phase sync control means, a half rate processing adaptive equalization means, and a half rate processing maximum likelihood decoder, and the digital data recorded on the optical recording medium are reproduced while restoring signal components which are missing in the time direction, by linear interpolation or Nyquist interpolation. Therefore, digital data reproduction performance is improved, and power consumption is reduced.

Abstract: An optical disc playback apparatus that performs appropriate waveform equalization according to a difference in characteristics of reproduced signals between land parts and groove parts in an optical disc to which high-density recording is performed using a land/groove recording method. The optical disc playback apparatus includes a reproduction means 102, an A/D conversion circuit 103 for sampling a reproduced signal to be converted into a multi-bit digital signal, a filter 105 for subjecting the multi-bit digital signal to digital equalization, a filter coefficient learning means 106 for adaptively controlling filter coefficients for the filter 105 corresponding to the land part and the groove part to minimize an equalization error, and a switch signal generation means 107 for generating a signal for switching between land and groove, thereby changing the filter coefficient adaptively to the land or the groove.

Abstract: In a digital recorded data reproduction which applies PRML signal processing, it is an object to enhance a reproduction signal quality and a playability for an abnormal signal by an offset correction and a phase,-interpolation-type digital phase-locked loop.

Abstract: High-order partial response equalization is performed so that the equalization error of an input signal having non-linear distortions is minimized, thereby improving the characteristics of a reproduced signal.