PURPOSE: To extract a reference phase pulse in which no phase fluctuation component nor jitter is applied.

CONSTITUTION: Two outputs of a bipolar/unipolar conversion circuit 1 connected to an input terminal 10 are respectively connected to a pattern detection circuit 17 via retiming circuits 13, 14 and also to an OR gate 15. The output of the OR gate 15 is connected to a timing extract circuit 16. The timing extract circuit 16 is connected to the retiming circuits 13, 14, the pattern detection circuit 17 and a window generating circuit 18. The pattern detection circuit 17 is connected to the window generating circuit 18 and the output of the window generating circuit 18 and the output of the OR gate 15 are connected to an AND gate 19, the output of the AND gate 19 is connected to an output terminal 20.