Conditions for phase-shift beamforming for broadband acoustic Doppler current profiler

In this paper, the error of the phase shifter in the broadband acoustic doppler current profiler (BBADCP) is analyzed, and the application conditions of phase-shift beamforming in BBADCP are summarized. The use of a phase shifter in BBADCP would cause "dislocation" in the time domain, uneven spectrum attenuation and energy dispersion. Through the analysis of these phenomena, variables that affect the output of the phase-shift array are as follows: center frequency, bandwidth, coding order, number of repetitions, and delay of adjacent elements. Then, the characteristics of phase-shift beamforming are analyzed from three aspects: beam direction and width, loss of array output SNR and frequency measurement error. The simulation results show that when the ratio of frequency to bandwidth is increased, the number of array elements is increased, and the array elements spacing is λ/2, the beam direction is accurate, the width is ideal, and the array output SNR loss is small. At same time, it is found that the normalized bandwidth should be reduced as much as possible to ensure the accuracy of the frequency measurement results under the condition of low SNR.