| 摘要 |
PROBLEM TO BE SOLVED: To maintain prescribed stability even when a standard signal cannot be provided any more by synchronizing the frequency of an internal reference signal with the standard signal from the outside. SOLUTION: The oscillation output of a rubidium oscillator 11 having high frequency stability is inputted to a phase shifter 12 and is shifted in its phase by a phase shift quantity given by a phase shifter control circuit 13 so as to generate a reference frequency signal. The frequency of the reference frequency signal is divided by a frequency divider to the same frequency as that of a standard radio wave and in the phase shifter control circuit 13, a phase shift quantity corresponding to a phase difference is found and applied to the phase shifter 12 by comparing the phase with that of the frequency signal of the standard radio wave provided by a receiving antenna AT and a standard radio wave receiver RX. Further, in the phase shifter control circuit 13, a standard radio wave receiving state is monitored by synchronously detecting the frequency-divided signal and a standard radio wave receiving signal and in the case of out-of-synchronism, the phase shift quantity is fixed. Thus, the reference frequency in a free run state is stabilized. |
