Design And Implementation Of Vertical Array Synchronous Acquisition System Of Hydrophone Based On GPS

In this paper,in the experimental research of underwater acoustic propagation characteristics analysis,the distance between multiple underwater acoustic signal acquisition arrays is long and there is no unified time reference,which will cause inaccurate acquisition data,data analysis is not convincing and other issues.In this case,a set of hydrophone vertical array data acquisition system with GPS time synchronization function is designed.The system has the acquisition time setting and synchronization function,which can be more convenient for underwater acoustic transmission test research work,with high accuracy and cost Low characteristics.This article analyzes the common synchronous timing methods,and then combines the actual working environment of the system,and finally selects the system synchronization scheme combining GPS synchronous timing and constant temperature crystal oscillator,and analyzes the source of the system error and verifies the feasibility of the system synchronization scheme.According to the system synchronization scheme and design indicators,the structure of the entire vertical array acquisition system is divided into a GPS synchronous terminal controller on the water and an underwater signal acquisition array.The GPS synchronous terminal controller mounted on the water buoy is used for system time calibration and acquisition control.The GPS synchronous terminal controller receives the GPS signal transmitted by the UM220 module.When the GPS signal positioning is valid,the GPS time is used to calibrate the local RTC clock,and the pps is used.The second pulse calibrates the constant temperature crystal oscillator,and uses the constant frequency crystal frequency division to generate a sampling reference signal with the same time base as the second pulse.This signal calibrates the temperature compensated crystal oscillator of the underwater acquisition array to ensure that the acquisition process of multiple systems is synchronized..When the GPS signal at sea is lost,the sampling reference signal generated by the high-precision constant-temperature crystal oscillator can still be consistent with the GPS second pulse within a certain time to ensure that the system's synchronous acquisition process is not affected by the environment.After the time synchronization of the GPS synchronous terminal controller is completed,the sampling reference signal,GPS time information and control instructions are packaged and transmitted to the underwater acquisition array through the RS485 interface,and the acquisition array is ordered to use the time information to calibrate the RTC clock.At the set acquisition time,the underwater acquisition array is triggered by the acquisition instruction of the GPS synchronous terminal controller and the sampling reference signal.Since each vertical array acquisition system uses GPS time as the time reference,it ensures the data acquisition process of each system With a unified time reference,the synchronous acquisition process is realized.Finally,the thesis conducted a test experiment on the vertical array acquisition system and analyzed the test results.The results show that the system design meets the index requirements.A sea trial experiment was also conducted in Qingdao.The test results show that the system has a stable working process,is easy to use,and can achieve synchronous acquisition tasks.