| 摘要 |
PURPOSE:To prevent an erroneous decision on an out-of-phase state, by giving a greater difference between the out-of-phase state and a phase shift due to modulation. CONSTITUTION:A reference signal is shifted in phase by 180 degrees and then frequency-divided by a flip-flop 71. The output of the frequency divider is supplied to an exclusive OR circuit 64. The reference signal is frequency-divided by a frequency divider 73 to generate reset signals for flip-flops 71 and 72. Even when a comparison signal shifts in phase greatly owing to modulation, the flip- flops 71 and 72 output signals which have coincident initial state and the same logical level. Therefore, the exclusive OR circuit 64 sends out an output signal with a decreased duty ratio. When this output signal is made into a direct current, its level is extremely low, so a decision on phase locking is made. |
