A serial-parallel converter 102 of a transmitter apparatus receives an input of a signal to be transmitted and serial-parallel-converts this to output m (m≧2) number of intermediate signals. A unitary matrix modulator 103 modulates the output m number of intermediate signals into a unitary matrix of m rows and m columns whose components other than diagonal components are 0 and outputs the obtained matrix. A splitter 111 supplies the respective diagonal components of the output matrix to the input channels of an inverse Fourier transform unit 112 as input signals. The inverse Fourier transform unit 112 outputs m number of inverse-Fourier-transformed signals obtained by performing inverse Fourier transform of the supplied input signals. A parallel-serial converter 113 parallel-serial-converts the output m number of inverse-Fourier-transformed signals to output one transmission signal. A transmission unit 114 transmits the output transmission signal. The difference between the frequency of any two channels of the inverse Fourier transform unit 112 is equal to or larger than a predetermined coherent bandwidth.