| 摘要 |
PROBLEM TO BE SOLVED: To easily detect out-of-synchronism by reducing a required frequency lock time. SOLUTION: A voltage controlled crystal oscillation circuit (VCXO) 11 changes an oscillated frequency in response to a control voltage Vc via a filter 12 to generate a reference signal So. A phase detection circuit 15 detects a phase difference between the reference signal So and an intermediate frequency signal Si and provides an output of the detected phase difference as digital data Dp. A digital signal processor 14 corrects a control voltage Dc by making arithmetic operation based on the phase difference data Dp from the phase detection circuit 15. Furthermore, when the correction amount of the control voltage is not converged within an error within a prescribed time, an unlock alarm is sent. A D/A converter circuit 13 converts the control voltage Dc into an analog voltage, which is fed to the VCXO 11 as a control voltage Vc via the filter 12. |
