| 摘要 |
PROBLEM TO BE SOLVED: To provide a crystal oscillator which controls the atmospheric temperature at which the crystal oscillator and an oscillation circuit are placed, with high accuracy and obtains an output frequency with high stability in OCXO.SOLUTION: When oscillation outputs of first and second crystal oscillators 10, 20 are defined as f1, f2, and oscillation frequencies of the oscillation outputs at a reference temperature are defined as f1r, f2r, {(f2-f1)/f1}-{(f2r-f1r)/f1r} is calculated by a frequency difference detection part 3. The resulted value is represented as a digital value of 34 bits to obtain a digital value corresponding to the temperature. Therefore the value is handled to be a temperature detection value, a difference between the value and a temperature setting value is supplied to a loop filter 61, a digital value from the loop filter is converted into a direct current voltage, and a heater 5 is controlled. |
