A system and method for modifying the carrier frequency of first and second signals associated with first and second sequences, respectively, of consecutive time intervals, comprises: first means determining two carrier frequencies respectively associated with each of the two signals based on one time interval or at least two consecutive and continuous time intervals, said time interval(s) belonging to a sequence of consecutive time intervals of known duration; and second means determining a first time interval or at least two first consecutive time intervals belonging to the first sequence, based on a second time interval belonging to the second sequence, by establishing a temporal correspondence between each end of said time interval of said second sequence and an interval of said first sequence including this end. The first means determines said carrier frequencies based on one time interval or at least two consecutive time intervals, belonging to said first sequence.