| 摘要 |
PROBLEM TO BE SOLVED: To provide a phase comparator which is capable of accurately comparing two signals with each other on phase and frequency, even if the signals vary in a duty ratio, when two signals are compared with each other for their phase and frequency. SOLUTION: A VCO 121 is controlled, so as to oscillate clock signals whose frequency is synchronized with that of wobbling signals. A rise comparator 111 compares the sub-harmonic clock signals of the clock signals oscillated by the VCO 121 with the wobbling signals, and signals corresponding to the above comparison result are outputted from a charging pump 112, while a fall comparator 113 compares the trailing edge of the subharmonic clock signal with that of the wobbling signal pulse, and signals, corresponding to the above comparison result, are outputted from a charging pump 114. The signals outputted from the charging pumps 112 and 114 are smoothed into DC voltage signals by a low-pass filter 120, the DC voltage signals are applied to the VCO 121. |
