Design and Implementation of a New Type of Acoustic Modem Analog Circuit

In view of the large volume, high power consumption and short communication distance of the traditional underwater acoustic modem, this study analyzed the key issues of relating the transmitting channel and the receiving channel in the overall design of the underwater acoustic modem. These issues include class-D power amplifier circuit design, dual resonant circuit impedance matching circuit design and receiving preprocessing circuit design. Subsequently, a class-D power amplifier circuit with small volume and high conversion efficiency, as well as a new combined bandpass filter design method and pro-gram-controlled automatic gain control(AGC) implementation method, was proposed. These methods were applied to the test prototype, and the prototype passed the pool test and the Danjiangkou reservoir communication test. The test results show that the sound source level of the prototype is improved by 10 dB, and its communication distance reaches to 4.8 km compared with the traditional prototype, which verifies the feasibility of the proposed scheme. This design may provide a reference for the development of underwater acoustic modem prototype.