Design And Implementation Of Miniature Underwater Acoustic Modem

With the exploration and development of marine resources,the global marine industry has developed rapidly.Representative industries include aquaculture,underwater Internet of Things,and diving tourism.There is a huge demand for underwater communication networks.However,the underwater channel environment is complex,and its limited channel bandwidth,random time-varying space-time frequency conversion and channel multipath interference characteristics have always restricted the development of underwater acoustic communication.In order to meet the market demand of underwater acoustic communication in the low-end field,this paper designs and implements a low-cost,high-quality acoustic modem with appropriate performance.Based on the theoretical model of underwater communication,this paper determines several system indicators and parameters,and designs a set of Convolutional Code-Block Interleaving-Frequency Hopping-MFSK(CCBIFH-MFSK)underwater communication schemes based on it,and studies and implements several key technologies of underwater communication.Using a low-cost,low-power embedded microcontroller(MCU)STM32F767 as the core processor of the acoustic modem,making the most of the processor's resources,the channel convolution coding and interleaving,spreading,and Modulation and other key technologies,and hardware implementation of PWM modulation class D amplifier.At the receiving end,key technologies such as real-time accurate signal acquisition,channel decoding,deinterleaving,despreading,and demodulation are implemented,as well as hardware implementation of the amplification filter circuit.At the end of this article,a system test was conducted.The parameters of the acoustic modem are tested,and the results are consistent with the theoretical values of the design.The sound source level was tested with a standard hydrophone in the pool.The sound source level is about 140dB at a center frequency of 40kHz,and the theoretical propagation distance is estimated to be about 1.5km.The communication performance test is divided into two parts:simulation test and field test.In the simulation test,the bit error rate of the system is basically consistent with the theoretical value.In the field test,we used multiple sets of acoustic modems to form a communication system.Reservoir test results show that when the communication distance is 200m-300m,the signal-to-noise ratio is about 20dB,and the bit error rate is 0.15%.After many tests,such as pools and reservoirs,the test results prove that our acoustic modem works normally,with low power consumption,good performance,and high reliability.