| 摘要 |
PURPOSE:To realize a clock reproduction with higher performance than in the conventional practice by a simple circuit in the section having no change in a reproducing signal by comparing the same reproducing clocks with each other from a voltage control oscillator by a phase frequency comparator. CONSTITUTION:A changed point for the reproducing signal from 0 to 1 or from 1 to 0 is found out by a selection circuit 1, and when this changed point exists, the reproducing signal at this point is sent out unconditionally. In the case no changed point exists, on the other hand, the reproducing clock from the voltage control oscillator 4 is sent out by the selection circuit 1 and frequency-divided into n-divisions by a frequency divider 5. As the result, when the change exists in the reproducing signal, the reproducing clock and the signal to compare the original phase and frequency are compared in the phase frequency comparator 2, then an error voltage essentially required for the clock reproduction is produced. From thus obtained error voltage, an unnecessary high frequency variation is removed by a high band cut-off filter 3, and the followup ability for reproducing clock is improved by supplying the control voltage following the variation of reproducing signal to the voltage control oscillator 4. |
