| 摘要 |
PROBLEM TO BE SOLVED: To obtain high stability for the output frequency in an OCXO, by controlling the atmospheric temperature of a quartz oscillator and an oscillation circuit with high accuracy.SOLUTION: When the oscillation outputs of first and second quartz oscillators 10, 20 are f1, f2, and the oscillation frequencies of the oscillation outputs at a reference temperature are f1r, f2r, respectively, a frequency difference detector 3 obtains a digital value by calculating {(f2-f1)/f1}-{(f2r-f1r)/f1r}. The calculation is performed by using PLL. An outside the detection range determination unit 5 determines whether or not the input value of the PLL is within a pull-in range of the PLL. If it is deviated from the pull-in range to the high temperature side, power supply to a heater circuit 5 is brought to zero, and the power supply is maximized if it is deviated to the low temperature side. |
