波束开角对多普勒测频结果的影响*

具有不同波束开角的声学多普勒测速设备未标定的测速结果存在偏差。基于水底椭圆散射模型研究了波束开角对声学多普勒测速结果的影响，对提高声学测速性能具有实际意义。水底椭圆散射模型下，足印上不同方位传播损失和散射强度存在差异，导致频谱不对称，测频结果偏小。利用不对称系数量化频谱不对称程度，若波束开角增大，方位不对称系数随之增大，测频偏差增大,推导了波束开角导致的测频偏差解析式。分析仿真和外场试验数据测频结果可知，不同多普勒频移下测频偏差和理论计算值相符，不同波束开角下实际测频偏差与理论公式计算的测频偏差均随波束开角增大而增大。

The influence of beam angle on Doppler frequency measurement result

The uncalibrated results of acoustic Doppler velocity measurement equipment with different beam angles are deviated.The influence of beam angle on the result of acoustic doppler velocimetry is studied ,in which underwater ellipse scattering model is adopted,and the conclusion is of practical significance to improve the performance of acoustic velocimetry measurement. When the ellipse scattering model is adopted, there are differences in propagation loss and scattering intensity from different directions,which result in asymmetric spectruman and small frequency measurement results. Using the asymmetry coefficient to quantify the degree of spectrum asymmetry, if the beam angle increases, the azimuth asymmetry coefficient increases, which leads to the growth of the frequency deviation.Besides,the expression of frequency measurement deviation caused by beam angle is derived. By analyzing the frequency measurement results of simulation and field test data, it can be seen that the frequency measurement deviation under different Doppler frequency shifts is consistent with the calculated value of the formula, and the actual frequency measurement deviation under different beam angles increases with the increasing beam angle.