Patent ID: 8497740

Claim:
A reference signal oscillator comprising: a high stability oscillator; a metastable oscillator which is inferior in a frequency stability of a long term compared with said high stability oscillator but is superior in a frequency stability of a short term shorter than the long term compared with said high stability oscillator and which constitutes a redundant configuration to said high stability oscillator; an abnormality detector detecting an abnormality of said high stability oscillator; a frequency calculating section which performs a calculation of A·f 1 +(1−A)·f 2 and outputs a calculation result as an output frequency of an oscillating device, when an output frequency of said high stability oscillator and an output frequency of said metastable oscillator are f 1 and f 2 , respectively, and a ratio of weighting of said high stability oscillator is A (0≦A≦1); a weighting setting section which sets a correspondence between an elapsed time since a time point at which the abnormality of said high stability oscillator is detected by said abnormality detector and a value of the A, wherein the value of the A increases from 0 to 1 in stages along with the elapsed time a first phase synchronization section synchronizing a phase of an output signal of said high stability oscillator with a phase of an output signal of said metastable oscillator; a second phase synchronization section synchronizing the phase of the output signal of said metastable oscillator with the phase of the output signal of said high stability oscillator while said metastable oscillator is on standby; and a control section which outputs a control signal to drive said metastable oscillator independently when the abnormality of said high stability oscillator is detected, and to once synchronize the phase of the output signal of said high stability oscillator with the phase of the output signal of said metastable oscillator and thereafter drive said high stability oscillator independently when the abnormality of said high stability oscillator is solved.