Study On ADCP Instantaneous Radial Velocity Measurement Technology

ADCP (Acoustic Doppler Current Profiler) is a kind of velocity sonar which works by using the acoustic Doppler principle. It is mainly used for remote sensing a wide range of current speed. ADCP plays an extremely important role in river test. The acoustic Doppler current measurement technology research based on ADCP has broad application prospects. And it promotes the development and mature of the signal processing, underwater acoustic transducer design, underwater acoustic physics, and other related science technologies. The main job in this article is to analyze several key technologies of ADCP and put forward the solution to the fuzzy speed problem. Specific content as follows:1. The key techniques of ADCP current measurement is introduced. The principle of Doppler current measurement and the four beam transducer of Janus structure configuration is introduced. The layered principle of Doppler Current technology is analyzed, including layered thickness, the selection of time window, the determination of receiving time, the contribution of scatterer inside the unit, etc.2. The Doppler frequency is estimated on the basis of the complex autocorrelation algorithm. The performance of narrowband and broadband current measurement is simulated. Narrow-band incoherent current measurement is mainly influenced by SNR, signal frequency, sampling frequency and pulse width. Narrow-band coherent current measurement is mainly influenced by SNR, signal frequency, pulse delay, and the number of pulse in one measurement cycle. Broadband current measurement is mainly influenced by SNR, signal frequency, unit thickness, code width and coding number.3. The "distance and velocity fuzzy" problem of the narrow-band coherent and broadband way is studied. Two methods of improving the problem are proposed, including by changing the pulse time delay and pulse frequency. The maximum radial velocity can be measured of Narrow-band coherent current measurement and broadband current measurement is improved. And simulations show good performance of the two methods.4. DSP algorithm of the broadband current measurement has been realized under the environment of SEED-DEC 138. The experimental results in similar to the result in MATLAB. It indicates that the system can satisfy the basic requirement of ADCP measurement.