Study And Design Of Underwater Acoustic Communication Transmitter Based On ?? Modulation Technique

Underwater acoustic sonar transmitter is an important part of the active sonar system.The performances of sonar transmitter have major impact on the entire sonar system. ??modulation technique because of its advantages of high output signal to noise ratio, low harmonic distortion, and convenience to demodulation has been applied in the field of radio such as in data converters. The background of this paper is the application of underwater acoustic communication institute. And the purpose is introducing this modulation technique into the field of underwater acoustic engineering practice to achieve a desired performance.The paper starts from the principle of ?? modulation and demodulation, and simulates the relevant factors in the process. In accordance with the indicator of sonar system, an underwater acoustic communication transmitter based on ?? modulation was designed and implemented. The paper is based on second-order single-loop ?? modulation technology, and focuses on the impact of technical parameters in the key techniques such as over-sampling,noise shaping, and digital filtering. Equivalent parameter models of a low-pass filter and an acoustic transducer are established. Simulation results showed the feasibility of the ??modulation method in underwater acoustic transmitter applications. And by comparison with the conventional PWM and zero-crossing comparator modulation scheme, it showed the advantage of ?? modulation. Meanwhile, by comparing the performance of analog and FPGA circuits, the results that FPGA achieved a better performance is given.This article discusses the implementation method of ?? modulation based on FPGA digital circuits, and the transmitter. A second-order EA modulation hardware circuit is achieved by Cyclone II series chip, and a underwater acoustic communication transmitter hardware circuit is designed based on Class D power amplifier. Eventually, the combined circuit realized the underwater acoustic communication transmitter based on ?? modulation,and its performance meets the design requirement.