Study On Acoustic Doppler Current Velocity Measurement Technology

Acoustic Doppler current velocity measurement technology plays an important role in the fields of flood hazard forecasting, water resource management and national defence. The principle of acoustic Doppler current velocity measurement system has been discussed in this thesis, including the acoustic Doppler effect, the selection of transmitting pulse waveform and the estimation of Doppler frequency shift. The complex self-correlation method for estimating average frequency of signal has been studied. In order to reduce the influence of noise on frequency estimation, the relationship between sampling frequency and estimation error is analyzed. Based on the system application and technical requirements, the whole current velocity measurement system has been designed in this thesis. The design ideas of the hardware circuits and the program flow as well as the scheme to resolve the key technique problems, together with some debugging results of system, have been given in detail. The single-chip computer MSP430F149 with ultra-low power consumption is used as the control and processing core of the system. Moreover, the DDS technique is introduced into the transmitting circuits and the quadrature demodulation circuits and a number of special integrated chips for automatic gain control, quadrature demodulation and low-pass filter are adopted in the receiving circuits, which makes the system more economic, more efficient and more accurate compared to the traditional analog system.