Abstract: A frequency-division multiplexer for carrying an OFDM signal on a large number of closely-spaced carriers receives the digital data at an input (12), applies coding such as convolutional coding (14), time interleaves (16) the signals, and assembles them frame-by-frame in a matrix (18). The data are converted to parallel form by a shift register (18), frequency interleaved (24), differentially encoded (26), and quadrature-phase-modulated (28) on several hundred or more closely-spaced carriers. A first inverse Fast Fourier Transform (FFT) circuit (30) transforms this information from the frequency domain into the time domain. Instead of being transmitted directly, the resultant signals are then amplitude-limited (42) and applied to an FFT (44) to reconvert them into the frequency domain. The phases of the wanted signals are then re-set, and the amplitudes of the signals near the edges of the band are reduced, in correction circuits (46).