Research On Class D Power Amplifier For Underwater Acoustic Communication System

In this thesis, the technological research is based on engineering application background of underwater acoustic communication system .We design the Class D power amplifier which is based on ?-? modulation technology. Compared with the traditional analog power amplifier, the Class D power amplifier has a higher efficiency, which means the equipment has smaller power loss and lower heat dissipation. Compared with traditional PWM modulation of digital power amplifiers,the signal modulation technique in this thesis is based on ?-? modulation, which means the output signal has less harmonic interference. These two advantages allow the underwater acoustic communication device to have a smaller volume structure and a higher energy transmission power.In this thesis, the Class D power amplifier based on the ?-? modulation technology mainly has two parts: ?-? signal modulation section (digital part) and the power amplifier section (analog part). In the signal modulation section, there are two key points of over-sampling technology and noise shaping technology. Oversampling uses the method of multi-level realization, during which the design of interpolation filter also has carried out structural optimization. The noise shaping technology is implemented by a sigma-delta modulator, which is actually a closed-loop control system. The modulator model and the zero pole of the system are optimized. The modulator eventually outputs high-speed 1-bit data stream and the signal-to-noise ratio of output is about 110 dB. The analog section is embodied as a power amplification function and the signal is reduced to initial signal by low-pass filtering.The thesis introduces the key technology of class D power amplifier based on ?-? modulation technology and its concrete realization process in detail. Not only the signal modulation part has carried on the simulation in Simulink environment, but also we achieve full-bridge structure of the power output stage in hardware. And the deadtime is set up by VHDL accurately. In the long run, both the modulator part and the design of deadtime can be completed through the FPGA chip and related programming language , which reflects the advantages of high integration and conveniently to be improved. Combined with the optimization of the interpolation filter, modulator NTF zero position,complementary signal's deadtime and other aspects of the optimal design, the final design of Class D power amplifier meets the requirements of underwater acoustic communication system .In summary, this paper elaborates the principle and implementation process of Class D power amplifier based on E-A modulation technology from three aspects:theory, software and hardware. It verifies the feasibility of the scheme and achieves the expected design goal.