Design And Implementation Of Parametric Communication System Used In Shallow Water

Underwater acoustic communication technology has been an important research area of underwater acoustic engineering, marine engineering, the studies focused on how to overcome signal distortion caused by the effects of multipath and time-varying in shallow water channel, to descend the error rate, while increasing the communication speed. Parametric array technology has some features, such as narrow lowfrequency beamwidth, broadband, small scale, no sidelobe, which can be used well to overcome the Negative factors in underwater acoustic communica-tion in shallow water, to to achieve high rates of remote underwater acoustic communication by suppressing multipath effects and expanding the available bandwidth in low frequency.In this paper, a parametric underwater acoustic communication system, including the method of controling the phase of difference frequency sound wave and the program of OFDM modu-lating the primary frequency wave, has been designed and developed to achieve a hight data rate, a long range and directional transmission in shallow water. Parametric array’s sound field parameterse are simulated by the model of plane wave, the model of self-demodulation with plane wave conditions, and the broadband model considering absorption, diffraction. A para-metric array phase shift keying modulation method and the pool test result on phase controlling are given.The method on controlling peak to average power ratio, the design of boot frequency mode, the pretreatment methods of parametric array’s signal are discussed. Marine acoustic multi-path channel is modeled by the ray method. The effectiveness of shallow water acoustic communication system with parametric array are simulated with different hydrological condi-tions and typical marine seabed acoustic channel environment.The model and experimental results indicate that the design of the system has the prcati-cability to transmit data to a long distance directionally in shallow water with both the ability to reduce the error rate by overcoming multipath-induced problem, and the ablility of high data rate by broadening the frequency band. A image file has been tramitted in shallow water with depth of20m, and the OFDM with4PSK. is used. The system can achieve data rates of3.3kbps,5.lkbps when the bandwidth is6kHz and9kHz, with BER0.0058and0.0031.