Reproducing apparatus having an improved PLL circuit and related computer program

1. A reproducing apparatus comprising:

first means for reproducing a signal representative of digital information from a recording medium;

second means for sampling the signal reproduced by the first means in response to a clock signal to generate a sampling-resultant signal;

third means for deciding whether the sampling-resultant signal is in a continuous-wave interval where an inversion period of the sampling-resultant signal remains constant or in a random-wave interval where the inversion period of the sampling-resultant signal varies at random;

fourth means for extracting a first value of the sampling-resultant signal at a time point corresponding to every zero-cross timing, for controlling a polarity of the extracted first value in response to whether the sampling-resultant signal is rising or falling in value to generate a polarity-control-resultant value, and for generating a first phase error in response to the polarity-control-resultant value;

fifth means for repetitively extracting a second value of the sampling-resultant signal at a constant period corresponding to a normal inversion period occurring during the continuous-wave interval, for alternately changing a polarity of the extracted second value between positive and negative to generate a polarity-change-resultant value, and for generating a second phase error in response to the polarity-change-resultant value;

sixth means for selecting the first phase error generated by the fourth means when the third means decides that the sampling-resultant signal is in a random-wave interval, and for selecting the second phase error generated by the fifth means when the third means decides that the sampling-resultant signal is in a continuous-wave interval; and

seventh means for generating the clock signal in response to the phase error selected by the sixth means.

2. A reproducing apparatus comprising:

first means for reproducing a signal representative of digital information from a recording medium;

second means for sampling the signal reproduced by the first means in response to a clock signal to generate a sampling-resultant signal;

third means for deciding whether the sampling-resultant signal is in a specified-pattern repetition interval where an inversion period of the sampling-resultant signal changes in accordance with a repetition of a specified pattern or in a random-wave interval where the inversion period of the sampling-resultant signal varies at random;

fourth means for extracting a first value of the sampling-resultant signal at a time point corresponding to every zero-cross timing, for controlling a polarity of the extracted first value in response to whether the sampling-resultant signal is rising or falling in value to generate a first polarity-control-resultant value, and for generating a first phase error in response to the first polarity-control-resultant value;

fifth means for repetitively extracting a second value of the sampling-resultant signal at a period changing in accordance with the specified pattern, for controlling a polarity of the extracted second value in response to whether the extracted second value is in a value-rising time or a value-falling time to generate a second polarity-control-resultant value, and for generating a second phase error in response to the second polarity-control-resultant value;

sixth means for selecting the first phase error generated by the fourth means when the third means decides that the sampling-resultant signal is in a random-wave interval, and for selecting the second phase error generated by the fifth means when the third means decides that the sampling-resultant signal is in a specified-pattern repetition interval; and

seventh means for generating the clock signal in response to the phase error selected by the sixth means.

3. A reproducing apparatus as recited in claim 2 , wherein the third means comprises:

means for deciding whether or not a latest inversion period Y(l) of the sampling-resultant signal satisfies one of relations as follows:

Y ( i−J )−1 ≦Y ( i )≦ Y ( i−J )+1

Y ( i−J )−2 ≦Y ( i )≦ Y ( i−J )

Y ( i−J ) ≦Y ( i )+2

where J denotes a number of inversion period elements composing the specified pattern;

means for deciding whether or not the latest inversion period Y(i) consecutively satisfies one of the relations a prescribed number of times; and

means for deciding that the sampling-resultant signal is in a specified-pattern repetition interval when the latest inversion period Y(i) consecutively satisfies one of the relations the prescribed number of times.

4. A reproducing apparatus as recited in claim 2 , wherein the third means comprises:

means for deciding whether or not a latest inversion period Z(i+k) of the sampling-resultant signal satisfies one of relations as follows:

X ( k )−1 ≦Z ( i+k ) ≦X ( k )+1

X ( k )−2 ≦Z ( i+k ) ≦X ( k )

X ( k )≦ Z ( i+k ) ≦X ( k )+2

where X(k) denotes one among inversion period elements composing the specified pattern;

means for deciding whether or not the latest inversion period Z(i+k) consecutively satisfies one of the relations a prescribed number of times; and

means for deciding that the sampling-resultant signal is in a specified-pattern repetition interval when the latest inversion period Z(i+k) consecutively satisfies one of the relations the prescribed number of times.

5. A reproducing apparatus as recited in claim 2 , further comprising:

means for deciding whether or not a latest inversion period Y(i+1) and a second latest inversion period Y(i) of the sampling-resultant signal satisfy one of relations as follows:

Y ( i )•2 ≦Y ( i+ 1)

Y ( i )> Y ( i+ 1)•2;

where the character “•” denotes product; and

means for starting the decision about whether the sampling-resultant signal is in a specified-pattern repetition interval or a random-wave interval when it is decided that the latest inversion period Y(i+1) and the second latest inversion period Y(i) satisfy one of the relations.

6. A reproducing apparatus as recited in claim 2 , wherein the third means comprises:

means for measuring a time interval for which the sampling-resultant signal remains in a specified-pattern repetition interval; and

means for controlling the sixth means to select the first phase error when the measured time interval reaches a predetermined time value.

7. A reproducing apparatus as recited in claim 2 , wherein the specified pattern includes a succession of inversion periods as 5T•5T•3T•3T•2T•2T, where T denotes a bit period of the digital information.

8. A reproducing apparatus as recited in claim 2 , wherein the sixth means comprises means for selecting only the second phase error which corresponds to an inversion period longer than a prescribed period.

9. A reproducing apparatus as recited in claim 2 , further comprising:

eighth means for recovering the digital information from the sampling-resultant signal;

ninth means for deciding whether or not a sync signal regularly appears in the recovered digital information; and

tenth means for forcing the sixth means to select the first phase error when the ninth means decides that a sync signal regularly appears in the recovered digital information.

10. A reproducing apparatus comprising:

first means for reproducing a signal representative of digital information from a recording medium;

second means for sampling the signal reproduced by the first means in response to a clock signal to generate a sampling-resultant signal;

third means for subjecting the sampling-resultant signal to a re-sampling process and an interpolation process responsive to timing information to generate a re-sampling-resultant signal;

fourth means for deciding whether the re-sampling-resultant signal is in a specified-pattern repetition interval where an inversion period of the re-sampling-resultant signal changes in accordance with a repetition of a specified pattern or in a random-wave interval where the inversion period of the re-sampling-resultant signal varies at random;

fifth means for extracting a first value of the re-sampling-resultant signal at a time point corresponding to every zero-cross timing, for controlling a polarity of the extracted first value in response to whether the re-sampling-resultant signal is rising or falling in value to generate a first polarity-control-resultant value, and for generating a first phase error in response to the first polarity-control-resultant value;

sixth means for repetitively extracting a second value of the re-sampling-resultant signal at a period changing in accordance with the specified pattern, for controlling a polarity of the extracted second value in response to whether the extracted second value is in a value-rising time or a value-falling time to generate a second polarity-control-resultant value, and for generating a second phase error in response to the second polarity-control-resultant value;

seventh means for selecting the first phase error generated by the fifth means when the fourth means decides that the re-sampling-resultant signal is in a random-wave interval, and for selecting the second phase error generated by the sixth means when the fourth means decides that the re-sampling-resultant signal is in a specified-pattern repetition interval;

a loop filter for integrating the phase error selected by the seventh means to generate a phase-error integration result; and

eighth means for generating the timing information in response to the phase-error integration result generated by the loop filter.

11. A method of reproducing information from a recording medium, comprising the steps of:

reproducing a signal representative of digital information from the recording medium;

sampling the reproduced signal in response to a clock signal to generate a sampling-resultant signal;

deciding whether the sampling-resultant signal is in a continuous-wave interval where an inversion period of the sampling-resultant signal remains constant or in a random-wave interval where the inversion period of the sampling-resultant signal varies at random;

extracting a first value of the sampling-resultant signal at a time point corresponding to every zero-cross timing;

controlling a polarity of the extracted first value in response to whether the sampling-resultant signal is rising or falling in value to generate a polarity-control-resultant value;

generating a first phase error in response to the polarity-control-resultant value;

repetitively extracting a second value of the sampling-resultant signal at a constant period corresponding to a normal inversion period occurring during the continuous-wave interval;

alternately changing a polarity of the extracted second value between positive and negative to generate a polarity-change-resultant value;

generating a second phase error in response to the polarity-change-resultant value;

selecting the first phase error when it is decided that the sampling-resultant signal is in a random-wave interval, and selecting the second phase error when it is decided that the sampling-resultant signal is in a continuous-wave interval; and

generating the clock signal in response to the selected phase error.

12. A method of reproducing information from a recording medium, comprising the steps of:

reproducing a signal representative of digital information from the recording medium;

sampling the reproduced signal in response to a clock signal to generate a sampling-resultant signal;

deciding whether the sampling-resultant signal is in a specified-pattern repetition interval where an inversion period of the sampling-resultant signal changes in accordance with a repetition of a specified pattern or in a random-wave interval where the inversion period of the sampling-resultant signal varies at random;

extracting a first value of the sampling-resultant signal at a time point corresponding to every zero-cross timing;

controlling a polarity of the extracted first value in response to whether the sampling-resultant signal is rising or falling in value to generate a first polarity-control-resultant value;

generating a first phase error in response to the first polarity-control-resultant value;

repetitively extracting a second value of the sampling-resultant signal at a period changing in accordance with the specified pattern;

controlling a polarity of the extracted second value in response to whether the extracted second value is in a value-rising time or a value-falling time to generate a second polarity-control-resultant value;

generating a second phase error in response to the second polarity-control-resultant value;

selecting the first phase error when it is decided that the sampling-resultant signal is in a random-wave interval, and selecting the second phase error when it is decided that the sampling-resultant signal is in a specified-pattern repetition interval; and

generating the clock signal in response to the selected phase error.