Band insertion and precancellation technique for simultaneous communications of analog frequency-modulated and digitally modulated signals

In a system for simulcasting digitally modulated and analog FM signals over the same FM frequency band, the effect of the analog FM signal on the digitally modulated signal in the simulcast is calculated and canceled from the latter signal before its transmission. As a result, the digital transmission is free from interference from the analog FM signal. Moreover, the digital transmission is achieved by adaptively inserting a time varying number of carriers modulated by digital data into the FM band. The carriers are selected frame by frame to control their interference with the analog FM signal. In accordance with the invention, the carriers are selected in a predetermined order, and in a preferred embodiment grouped contiguously with one another in the FM band. As a result, the rate of control information required to identify the inserted carriers to a receiver is advantageously low.