| 摘要 |
PURPOSE:To detect the exact slip of a signal having frequency difference more than + or -25% to a reference frequency signal by providing a quadrant change detection circuit to divide the quadrant movement of an input signal and a quadrant detection circuit to detect a quadrant moving direction. CONSTITUTION:A quadrant change detecting circuit 6 samples the signal B1 (or B2) of a 0 deg. phase signal outputted from a PLL circuit 20 and the signal C1 (or C2) of a 90 deg. phase signal at the input rise of a reference frequency signal A(f) and successively compares the patterns of these signals with the pattern of a preceding sample. Thus, it is detected that the signal is slipped and whether the frequency difference is advanced or delayed, and rising sample signals D1 (or D2) and E1 (or E2) are outputted. When the skip of quadrant is detected, a quadrant detection circuit 7 detects whether it is skipped in an advancing direction or in a delaying direction. This detection signal and the sampled pattern are inputted to an exclusive OR circuit 8 and either advancement or delay is decided. |
