| 摘要 |
PURPOSE:To improve a data error due to variation such as a wow and a flutter by obtaining a clock corresponding to variation in time base from the playback signal of a cue track on the basis of a phase comparison. CONSTITUTION:The playback signal from the cue track is equalized by an analog waveform equalizer 31 and and then inputted to a level detector 41, which outputs a binary plus pulse signal. This is inputted to an NOR circuit 43 directly and through a delay circuit 42 to detect the 0-1 inversion position of the plus pulse signal. A variable clock from a voltage-controlled oscillator 60, on the other hand, is frequency-divided by N through a frequency divider 46 and inputted to clock terminals of FFs 44 and 45. The output of a circuit 43 is applied to the set terminal of the FF 44 and phase-compared with the frequency-divided clock of the variable clock, and the Q1 output of the FF 33 and the Q2 output of the FF2 are converted into a DC voltage through a differential active filter 50 and fed back to the frequency control terminal of the oscillator 60. The controlled variable clock is outputted and the clock period is corrected according to variation in the time base of the data. |
