Constant Beamwidth Beamformer With Its Application In UUV Sonar

Unmanned underwater vehicle(UUV)is a popular underwater platform,and its operational capability depends on the sonar equipment installed on it.In other words,it is important to study sonar signal processing based on UUV platform.In this paper,we started from the problems which will occur during practical working,and mainly studied constant beamwidth beamforming,far-field and near-field interference suppression,robust adaptive beamforming and DEMON spectrum estimation.These are the main contents of this paper:Firstly,we analyzed several potential problems during UUV practical working,including signal spectrum distortion,far-field and near-field interference,steering vector mismatch problem.Secondly,in order to avoid the spectrum distortion caused by traditional beamformer,we studied several constant beamwidth FIR beamformer,and used second-order cone programming method to solve the corresponding convex optimization problem.Then we derived a pre-delay eliminated method to design the constant beamwidth FIR beamformer,which is convenient to engineering implementation.Then,on the one hand,to suppress the interference coming from far-field area,several different constant beamwidth beamforming algorithms have been studied.And based on interference-plus-noise matrix reconstruction,we obtained a constant beamwidth beamforming algorithm that could improve self-cancellation problem.On the other hand,a near-field interference suppression method has been proposed in this part.And the simulation results validated the above beamforming algorithms.Finally,we applied the above constant beamwidth beamformer to DEMON spectrum extraction.And the computer simulation results showed that the proposed algorithm has better performance in interference suppression and signal waveform estimation.