A spread spectrum modulator converts input sequences composed of digital symbols into n.gtoreq.2 spread-spectrum sequences. The spread spectrum modulator can generate spreading code and can combine the spreading code with the input sequences to produce the n spread spectrum sequences for transmission from n respective antennas of a radio transmitter. Each spread spectrum sequence corresponds to a sum of at least two contributions mutually shifted by a time substantially less than the duration of a symbol, each contribution being the product of a version of one of the n input sequences times the spreading code.