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Data detection apparatus

  • US 5,666,341 A
  • Filed: 09/13/1996
  • Issued: 09/09/1997
  • Est. Priority Date: 09/18/1995
  • Status: Expired due to Term
First Claim
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1. An apparatus for reproducing digital information which is subjected to modulation recording with a discrete record length, comprising:

  • a digitizing section for digitizing a reproduced signal at a predetermined level so as to output a digital signal;

    an oscillator for outputting a clock signal having a frequency proportional to an input signal;

    a phase comparing section for comparing the digital signal with the clock signal so as to output a first difference signal indicating a difference in phase between the digital signal and the clock signal;

    a specified pattern width detecting section for detecting a time interval of a specified pattern included in the digital signal so as to output first information indicating either a reproduced period or a reproduced frequency;

    an oscillating period detecting section for detecting a period of the clock signal so as to output second information indicating either an oscillating period or an oscillating frequency of the oscillator;

    a period comparing section for comparing the first information with the second information so as to output a second difference signal indicating a difference between the first information and the second information;

    an operating section for performing an operation in accordance with the first difference signal and the second difference signal; and

    a filter for limiting a frequency band of the output from the operating section so as to output a resultant signal as an input signal for oscillator;

    wherein the apparatus has;

    a phase lock loop operating so that the clock signal is phase-locked with an edge of the digital signal by the oscillator, the phase comparing section, the operating section and the filter; and

    a frequency loop operating so that a clock period and reproducing period become almost identical to each other by the oscillator, the specified pattern width detecting section, the oscillating period detecting section, the period comparing section, the operating section and the filter.

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