PURPOSE: To correct the deviation of a carrier frequency from a normal value at every burst by utilizing a preamble part signal inserted to the loading part of each burst and applying an automatic closed loop frequency control for only the period of the preamble part in a multiphase PSK modulation wave.

CONSTITUTION: The output of a voltage comparator 11 goes to logic '1' for periods t1∼t2 corresponding to the sequence and the CR/BTR of a preamble. A frequency discriminator 5 generates a voltage proportional to a deviation F from a F3+B/2 to reduce a noise by a low pass filter 6. A sample/hold amplifier 7 acts like a conventional amplifier singly when the output of the voltage comparator 11 is logic '1'. Thus, the output of the low pass filter 6 is amplified and fed back to a variable voltage control oscillator 8, thereby resulting that the F2 is controlled so as to cancel the deviation F of the carrier frequency of burst from the normal value F1.