Research On Key Technologies Of ADCP Based On 2MHz-ultrasonic Transducer

Basd on Doppler effect,The Acoustic Doppler Current Profiler(ADCP)can simultaneously measure the velocity of different water layers in the water profile.It can measure the velocity with high resolution,high precision,and portability,and is of great significance in the field of hydrological monitoring.The developed countries study ADCP in the early years,and they has a good technical foundation.So they have relatively mature ADCP development techniques now.However,due to the late research and weak technical foundation,the research on ADCP is still in the development stage in china.At present,there is no ADCP product with good performance produced by china.In the past few years,the author's laboratory has been conducting research on ADCP prototypes and continuously improving its performance.This paper has deeply studied several key technologies of ADCP.On the basis of theoretical analysis,combined with experiments,the performance of prototype is effectively improved.The specific work is as follows:1.This paper studies the ultrasonic emission technology.Due to the fast attenuation of ultrasonic waves when propagating in the water,ADCP measurement range is very small.The ultrasonic transmitting unit include NMOS and PMO for push-pull driving,with transformer boosting and impedance matching.The circuit achieves high power transmission.The ultrasonic transducer of the ADCP both transmits and receives,which results in a large blind zone.The paper analyzes the influence of transmit power on the blind zone and proposes a design idea that the transmit power is adjustable.2.The paper studies the signal reception technology.In view of the low SNR of ultrasonic echo signals,the paper uses various methods to suppress different noises,with designing LC circuit to filter out environmental noise and adding shielding to suppress EMI noise.While improving the SNR,the system also introduces automatic gain control(AGC)circuit to optimize the attenuation characteristics of the echo signal.The system uses a mixing circuit to reduce the sampling rate and data volume,which is beneficial for real-time processing of velocity information.3.The paper studies the software filtering technology and introduces a linear filter to improve the accuracy of ADCP.The paper introduces the design principle of Wiener filter and carries out simulation experiments.With Wiener filter being limited in ADCP,Kalman filtering is used and performance testing is performed.4.Based on the study of key technologies,this paper designs the prototype.It introduces the hardware design,software design and communication protocol design of the prototype.