Phase synchronization circuit with units for setting sweep frequency and control voltage

摘要

Improved phase synchronization circuits shorten the length of the synchronization pull-in time. The phase synchronization circuit according to the first invention changes the free-running frequency of the voltage control oscillation means starting from one limit frequency of the sweep range when detecting a state of non-synchronization and performing a synchronization pull-in operation. The phase synchronization circuit according to the second invention changes the free-running frequency of the voltage control oscillation means starting to one limit frequency of the sweep range faster than a prescribed speed and then changes the free-running frequency of the voltage control oscillation means to the other limit frequency of the sweep range at the prescribed speed when detecting a state of non-synchronization and performing a synchronization pull-in operation.