Design Of Synchronous Measurement System For Distributed Seismic Wave Sensor Array

In the process of studying the characteristics and propagation law of underwater acoustic field,in addition to the traditional research on the propagation process of underwater acoustic,under the conditions of shallow sea propagation,deep-sea conditions conducive to acoustic wave propagation are not available.A considerable part of the energy of low-frequency and extremely low-frequency sound sources is equivalent to propagation attenuation in the undersea medium.The acoustic properties of sea bottom media have an important influence on the propagation of acoustic waves in sea water.Therefore,it is necessary to understand and analyze the acoustic propagation parameters and background noise of the shallow sea bottom.It will be helpful to study the law of Seismic wave propagation and improve the analysis accuracy of total acoustic field data.The distributed synchronous acquisition and measurement system is used as a test platform for collecting Marine low-frequency acoustic data,which is characterized by abundant data,accurate synchronization and high precision.Compared with asynchronous data,the collected data has more advantages for subsequent data processing and analysis.The main research direction of this paper is to design and develop a set of low-frequency distributed synchronous acquisition system of acoustic sensor array based on the acoustic propagation characteristics of the medium and low frequency propagated through the seabed medium.This paper discusses and designs a set of high precision distributed synchronous acquisition system for submarine low frequency ground sound.It is used to collect and store the Seismic wave signals in the shallow sea by nodes synchronously.The system is divided into two parts by function: The first part is a synchronization system based on rubidium clock and high precision crystal oscillator.This part is mainly composed of two units,The unit 1 is main deck clock unit,designed based on FE5680 A Rubidium atomic clock as the core master clock,can be tamed for a long time using PPS second pulses provided by a high-precision GPS receiver,as the clock reference in the whole system,PPS clock signals with high stability are provided to each acquisition node.Unit 2 is the clock unit of each child node.The child node unit is flexibly designed based on high-precision crystal oscillator(OCXO,TCXO).It makes use of PPS pulse clock signal under the main deck to conduct self-synchronous taming and provide standard acquisition clock signal.The second part is the acquisition unit.The board is composed of operational amplifier,AD converter,STM32 microcontroller,FPGA and memory card,which is responsible for the acquisition and storage of underwater acoustic signals.The board is equipped with a standard interface connected to the node clock unit to provide a synchronous clock.In addition,the whole system also includes wireless control components,GPS synchronous control unit,etc.,which can be combined flexibly to meet the requirements of different equipment,and facilitate the follow-up upgrade,maintenance and optimization.In the end,the paper carries out sufficient measurement experiments for the distributed synchronous acoustic sensor measurement system,and analyzes the experimental results.Each part of the measuring system works normally,the function is stable and reliable,and meets the requirements of the design index.