Research on pulse stretching of underwater bubbles echo signal of lidar

In the process of underwater lidar wake detection, the multipath effect leads to pulse stretching of the echo signal, which is a distinguishing feature to distinguish the wake echo signal. In order to explore the factors that affect the pulse stretching of the echo signal, this paper convolves the instantaneous echo energy of the bubbles at different distance layers with the transmitted pulse, and establishes a distance layer summation model(DLSM) of underwater bubbles. This paper analyzes the effect of bubble density on the backscattering coefficient of the bubbles and the pulse width of the echo signal, and introduces the attenuation length of the water and the multipath effect. The experimental results show that when the attenuation length increases from 1.2 to 2.0, the half-peak width of the echoes of the bubbles increases by 1.3ns. However, when the attenuation length increases from 1.5 to 2.2, the echo pulse width of the strong backscatter target decreases by 0.5ns. The thickness of the bubbles increases from 2cm to 5cm, the peak shifts by 0.4ns, and the echo pulse width increases by 0.6ns. The simulation model and experimental results provide an effective basis for distinguishing ship wakes and strong backscattering targets, and have an important role in improving wake detection and recognition capabilities.