Research On Selection Technique Of Vertical Beam Pitch Angle For Sonar Array

Because of the heterogeneity of the sea water,sound velocity varies with depth,the sound line is a curve.The bending of voice line and the reflection of sea surface cause most of the sound line is not horizontal to reach the receiving sonar.At present most sonar only focus on the horizontal beam forming and search target only in horizontal direction.For the sonar such as vertical linear array or cylindrical array,the vertical direction of them has a certain beam width.When the incident angle of the sound beam exceeds the beam width of the array,the performance of the sonar will degrade.By adjusting the pitch angle of the sonar array in the vertical direction,it is possible to avoid the decrease of the array gain due to the incident angle of the sound line deviates from the horizontal direction,so that the actual performance of the sonar is closer to the theoretical value,improve the detection distance,the detection range or the detection reliability,optimize the performance of sonar and increase the detection capabilities.In this paper,based on a cylindrical array which is one of commonly used sonar array shapes,we have analyzed the influence of acoustic incident angle on the performance of sonar detection,depending on the characteristics of sonar gain changing with acoustic incident angle,the variation law of sound incident angles in signal field calculated by underwater acoustic propagation model based on ray acoustics,and the vertical directivity of interfacial noise and its spatial correlation.According to the commonly used signal detection method of active sonar and passive sonar,the beam pitch angle optimization scheme of sonar array in its vertical direction is proposed.Simulation is carried out under several typical channels,and the optimization effect of sonar detection performance after adjusting the pitch angle is analyzed.In the deep sea channel,when the sonar to play the best performance,so that it can detect the sound image area,by adjusting the sonar pitch angle,can eliminate the detection blind spots due to sound lines incident non-horizontally,and can greatly improve the sonar detection area.But the pitch angle adjustment range is large,fixed beam direction can't cover all areas at the same time.When the sonar can not detect the sound image area even though it performs best,adjusting the pitch angle does not make sense.In the shallow channel,for the shallow gradient and the sub-gradient channel,only when the sonar working depth is greater than the target depth,the sonar pitch angle optimization effect is obvious;for the surface channel,only sonar work depth is less than the target Depth,the pitch angle optimization effect is obvious;for the uniform shallow channel,the pitch angle optimization is of little significance.By adjusting the vertical beam pitch angle of the sonar array,you can use the sound image area to increase the detection range.