FREQUENCY CONTROL CIRCUIT

PURPOSE: To detect a center frequency of a reception signal whose frequency is deviated in a short time automatically. CONSTITUTION: A level detection means 15 divides a frequency band taking a maximum deviation of a frequency of a reception signal S1 into account into plural frequency bands, detects each power of the divided frequency bands, and a center frequency discrimination means 16 detects the division frequency band of a maximum power from each power. When a lock detection means 13 detects a fault of a demodulation signal S4 obtained by demodulating the reception signal S1, it is controlled that the sweep of the reception signal S1 conducted by a frequency control means 11 that mixes the frequency of the reception signal S1 with an oscillated frequency of an oscillator varied by a control signal S3 to convert the frequency is conducted in the detected band by the means 16. When the demodulation signal S4 is detected normal, the sweep in the means 11 is stopped and the control signal S3 used to control the oscillated frequency of the oscillator to be fixed is outputted from a means 14.