| 摘要 |
PURPOSE:To suppress a noise, and to facilitate a recovery to a locked state, by constituting a loop filter of two stages in case of a locked state, and constituting the loop filter of one stage in case of an unlocked state. CONSTITUTION:When a phase locking circuit is in a locked state, a lock detector 10 detects the locked state and opens a switch 7. As a result, a first loop filter 4 and a second loop filter 6 are connected in a longitudinal train, the capacity for suppressing an unnecessary frequency component such as an input noise, etc., increases, and a noise appearing in an output terminal 5 becomes small. Also, in case of an unlocked state, the lock detector 10 detects it and closes the switch 7. As a result, an output of the first loop filter 4 is directly inputted to a voltage control oscillator 2, a capture range is widened, and a return to the locked state is facilitated. |
