PURPOSE: To reduce the effect of fading, by splitting a signal in transmitted signal information format at a transmission side, changing a carrier frequency at each unit information, and changing an oscillated frequency of a local oscillator in correspondence to the transmission carrier frequency change at a receiving side.

CONSTITUTION: An information signal S1 is divided at a specific cycle by switch circuits 3, 4, inputted to transmission frequency converters 5, 6, superimposed on two radio waves comprising the carrier in frequencies fl1 and fl2 and radiated from an antenna 9. An antenna 10 of a receiving section receives two radio waves and the information signal superimposed on the two radio waves is detected continuously by switching the oscillating frequency of a receiving local oscillator 12 cyclically into the fl1 and fl2. A switching control circuit 13 is a circuit detecting the switching period and controlling the oscillating frequency of the local oscillator 12 in synchronization with the detection.