| 摘要 |
PROBLEM TO BE SOLVED: To provide a frequency controller which enables quick frequency- locking with a PPL circuit to allow obtaining of a correct decoded data without depending on a shift of a threshold. SOLUTION: Cross detectors 111∼113 each have predetermined thresholds Th1-Th3 differing from each other set therefor and output a cross count each time a reproduction signal crosses the set thresholds. A coincidence signal is taken out of a comparator with the input cross count reaching the set value the earliest among the comparators 121∼123 and supplied to the cross detectors 111∼113 and a decremental counter 14 as reset pulse through an OR circuit 13 to reset them. When a zerocross count gives a fixed value, an error signal is outputted in the direction of correction depending on how much a bit clock count is shifted from the intrinsic value thereby enabling the control of frequency. |
