Abstract: A transmitter device comprises a transmission antenna with at least one transducer and one signal generation unit for generating an acoustic communication signal to be transmitted to a receiver device including hidden information, wherein the signal generation unit is configured to previously record an original acoustic signal, the signal generation unit capable of generating the communication signal to be transmitted by adding, to an initial signal x(t) derived from the original signal, an auxiliary signal previously multiplied by at least one symbol, the symbol having a phase and/or an amplitude carrying the hidden information and the auxiliary signal calculated from the initial signal by a chosen transformation operator which depends on a steganographic key.

Abstract: This invention concerns the field of passive sonar systems simultaneously processing several linear antennas. This invention includes a method to eliminate ghost sources for a passive sonar having at least two linear antennas A and B, the method including: An initial acquisition step during which the signal received is measured at different moments ti, and for each antenna, the Doppler frequency f of the signal received is determined, as well as the potential values of the azimuth ? of the source; A second step of determining the potential values of the source performed by use of the measured azimuth ? frequency f values; A third step of eliminating ambiguity and rejecting ghost sources during which it is determined, for which of the potential sources, the speed and frequency values will satisfy, for each moment ti, the measurement equations linking the frequency of the signal received to the frequency f0 emitted by the source, at the source speed and position.

Abstract: This invention concerns the field of passive sonar systems simultaneously processing several linear antennas. This invention includes a method to eliminate ghost sources for a passive sonar having at least two linear antennas A and B, the method including: An initial acquisition step during which the signal received is measured at different moments ti, and for each antenna, the Doppler frequency f of the signal received is determined, as well as the potential values of the azimuth ? of the source; A second step of determining the potential values of the source performed by use of the measured azimuth ? frequency f values; A third step of eliminating ambiguity and rejecting ghost sources during which it is determined, for which of the potential sources, the speed and frequency values will satisfy, for each moment ti, the measurement equations linking the frequency of the signal received to the frequency f0 emitted by the source, at the source speed and position.