回波信号限幅对声学多普勒测速偏差的影响

声学多普勒测速设备常采用复协方差算法测量多普勒频移，当回波信号出现限幅时会产生频移测量偏差，进而导致测速偏差。文章基于复协方差算法分析了回波信号限幅引起多普勒测速偏差问题的原因，得出限幅后频移测量偏差随真实频移变化而呈现正弦振荡变化的规律，分别使用窄带和宽带发射信号完成回波限幅仿真计算。基于声学多普勒测速仿真器和海上试验完成了对声学多普勒测速设备回波限幅数据的采集，仿真和试验数据结果与理论分析结果一致。

The influence of echo amplitude limiting on acoustic Doppler velocimetric bias

Acoustic Doppler velocimetric equipment often uses complex covariance algorithm to measure Doppler frequency shift. When the echo amplitude is limited, the frequency shift measurement bias occurs, which leads to velocimetric bias. Based on the complex covariance algorithm, the causes of Doppler velocimetric bias due to echo amplitude limiting are analyzed, and the rule that the frequency shift measurement bias for the amplitude limited echo signal changes with the real frequency shift is revealed, which appears as a change in a sinusoidal oscillation. The simulations of echo amplitude limiting for narrowband and wideband transmitting signals are performed respectively. By the acoustic Doppler velocimetric simulator and the sea trial, the amplitude limited and unlimited echo data of the acoustic Doppler velocimetric equipment are acquired, and the simulation and test results are consistent with the theoretical analysis.