| 摘要 |
PURPOSE: To detect the timing point of demodulation in a short time by selecting two optimum couples of points for correction of a phase shift on the basis of a bit error estimation result and shifting one so that their correlation becomes equal. CONSTITUTION: The correlation detecting circuit 9 of a clock regenerating circuit 8 samples the levels of detection signals X and Y at plural extraction points which are previously sets in each symbol cycle. Then two adjacent extraction points are paired to detect the correlation between signals, and the signals X and Y are added by couples of extraction points and sent out to a correlation decision circuit 10. The circuit 10 compares correlation data stored in the circuit 9 to detect the couple of extraction points having the largest correlation and the following couple of extraction points. A bit error estimation part 11 estimates an error rate from the correlation value. On the basis of the estimation result, a switching part 12 selects the optimum couple of extraction points for correction of the phase shift and a phase shifting means 14 shifts the phase of the signal in a demodulation process to equalize the correlation. |
