Frequency-controlled circuit

A frequency-controlled circuit for automatically detecting a center frequency of a received signal whose frequency is shifted includes a frequency control unit for receiving the input signal and changing the frequency of the received signal into another frequency, a demodulating unit for demodulating a signal outputted from the frequency control unit, an incoming detecting unit for detecting whether a demodulated signal outputted from the demodulating unit is proper or improper and a level detecting unit for dividing a frequency band of the signal, obtained in the frequency control unit by adding a receive frequency band of the received signal to the center frequency of the received signal or subtracting the center frequency thereof from the receive frequency band thereof, into a plurality of narrower frequency bands and detecting respective power values of the divided frequency bands. A center-frequency determining unit detects the maximum value from the power values detected by the level detecting unit and outputs information about the divided frequency band having the detected maximum power value. A sweep/de-sweep control unit is provided, which allows the frequency control unit to sweep the received signal at a frequency bandwidth corresponding to the information about the divided frequency bands.