J. Phys. IV France 02 (1992) C1-989-C1-992
TRANSMISSION ULTRASONORE D'INFORMATIONS NUMÉRISÉES DANS L'EAUM. ATASSI, P. BENARD, G. MAZE and J. RIPOCHE
Laboratoire d'Acoustique Ultrasonore et d'Electronique, L.A.U.E. U.R.A. C.N.R.S. 1373, Université le Havre, Place Robert Schuman, F-76610 Le Havre, France
This paper describes an acoustic communication system that allows to transmit and to receive high-rate digital data (100 kbauds) with a directive ultrasonic beam through water. To solve the communication problem in water, the data logical levels are modulated in two opposite phases of the carrier "BPSK. To distinguish which of the two phases is the reference, the information is coded using the "DPSK" method. At the reception, the carrier is restored from the received signal to avoid the problem of Doppler effect during the transmission in water and, after an appropriate processing, the logical restored signal is then decoded using the "DEPSK" method to cancel the ambiguity of phase. To test the sensibility of system to the parasite echos, an experimental set up has been used. The emitted beam is separated in two parts, by two plane reflectors. The difference in phase and the relative amplitude are adjustable.
© EDP Sciences 1992