PURPOSE: To remove distortion from a base band signal composed on a reception side by branching the base band signal on out-of-phase basis, and transmitting branched components through an in-use and a stand-by route which employ space diversity.

CONSTITUTION: A base band signal from a terminal 1 is branched by an opposite-phase hybrid into two out-of-phase signals, which are modulated by two different transmission frequencies through FM modulators 3a and 3b and mixer circuits 4a and 4b which mix signals of local oscillators 5a and 5b, thereby transmitting the resulting signal through a branching filter 7. On a reception side, a branching filter 11 separates two said transmitted signals of different frequencies, which are regenerated by the conventional receiver consisting of circuits 12a and 12b∼16a and 16b. An in-use transmission system A and a stand- by transmission system B have exactly the same constitution and generate the same secondary distortion, so that the base band regeneration output composed of two regenerated signals 25a and 25b through the opposite-phase hybrid 17 contains no secondary distortion.