| 摘要 |
PROBLEM TO BE SOLVED: To make measurable a jitter with high accuracy and over a wide range. SOLUTION: In an operating-range judgment circuit 23, an error signal Er which is outputted from a first low-pass filter 14 is judged to be outside an operating range when it exceeds a first voltage range±V1 corresponding to the linear operating range of a phase-frequency comparator 13. In addition, in a second low-pass filter 22, a DC component which is contained in the error signal is amplified to a voltage which is larger than a signal component in the frequency band of a jitter to be measured. In a synchronization judgment circuit 24, the output signal of the second low-pass filter 22 is judged to be outside a synchronization when it exceeds a second voltage range±V4 which is set to be wider than the linear operating range of the phase-frequency comparator 13.
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