The Design Of Underwater Acoustic Communication Transmitting System Based On OFDM

Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier parallel transmit technique. It has been a research hotspot in wireless communication field because of its remarkable anti-multipath performance and full bandwidth utilization in recent years. It belongs to multi-carriers modulating technology, and its most remarkable character is the high-speed transmitting ability as well as the excellent resistibility to interface of signal interval and decline of channel selectivity. However, OFDM for underwater communication is currently still in its infancy. Therefore, it must be of good theoretical and practical value to conduct research on acoustic communication based on OFDM. This paper takes this one as the background, have carried on studying of and designing a underwater acoustic communication transmitter based on the technology of OFDM transmitter.However, in the OFDM transmitter applications, the existence of high PAPR is the main disadvantage in the OFDM system. OFDM transmitter therefore requires linear amplifiers with wide dynamic range. Otherwise, the peak power enters into non-linear amplifiers range which results in aberrant signals, carriers' intermodulation interferer, radiation of out-of-band, destruct orthogonal and reducing performance of systems. In this paper, limiting technology is used to reduce the PAPR of OFDM system, and to carry out simulation through computer.Thesis is focused on the design of transmitter, the transmitter designed in this system is mainly composed of signal generator, power amplifier and matching networks. In this paper we bring the integrated digital audio power amplifier technology to the acoustic transmitter. In the design process based on the basic theory, combined with modern audio amplifier design methods and the experience of using TI's integrated chip, the paper bring forward a new scheme to design portable acoustic signal transmitter. The signal source and control part use DSP and CPLD, as key chips which make the system more stable and convenient for future upgrade. As the load impedance fluctuates with the frequency, the difficulty of matching technology is broadband matching.After pool experiments, the frequency of its 2-8kHz, when the signal which is transmitted doesn't distortion, the average level of sound source is close to 186dB. Therefore the transmitter designed to achieve the desired results...