PURPOSE: To suppress a sudden phase change in a time required for satellite communication by interrupting temperature compensation tentatively based on a temperature data or predicting the temperature data in a digital control type temperature compensation piezoelectric oscillator.

CONSTITUTION: The output digital code of a temperature detection circuit 1 is fed to a function generating circuit 2 through a control circuit 5. When a control input is at a high level, temperature compensation is implemented and when the control input is at a low level, a temperature data is stored. Thus, the temperature compensation is stopped tentatively. Moreover, as other embodiment, a control circuit 8, an arithmetic storage circuit 9 and a memory circuit 7 are added, a temperature is predicted by a high-degree approximation equation, and the temperature compensation is implemented by the predictive data. Consequently a period when the constant temperature is predicted is utilized. Satellite communication is implemented for the period.