Underwater Two-dimensional DOA Estimation Under Variance Acoustic Velocity Environment

Underwater direction of arrival(DOA)estimation is an important research field in array signal processing,which is widely used in marine exploration,underwater sonar system.DOA estimation algorithms use the wave path-difference between the received signals to estimate the azimuth information of the spatial signals,and the wave path-difference is related to the propagation velocity of the acoustic wave.The accuracy of the used wave velocity will directly affect the accuracy of the wave path-difference.So the accuracy of the wave velocity has a great impact on the accuracy of DOA estimation.Underwater environments such as rivers and oceans are extremely complex,and the velocities of acoustic waves in different times or at different locations are different and varied.Wave velocity inaccuracies often lead to inaccurate DOA estimation.So it is necessary to eliminate the influence of wave velocity on the accuracy of underwater DOA estimation.Therefore,a velocity-independent DOA estimation algorithm is proposed in this paper,especially for underwater two-dimensional(2D)DOA estimation.The details are summarized as follows:1.The common array and mathematical model of one-dimensional(1D)and 2D DOA estimation are briefly introduced.The mathematical model of coherent signal and the performance index of DOA estimation are introduced.2.The principle of 1D and 2D DOA estimation based on ESPRIT algorithms are introduced.The influence of inaccurate on the 2D ESPRIT algorithm is analyzed,and simulation experiments are given.3.Aiming at the variable velocity environment,an improved 2D ESPRIT algorithm based on a double L-shaped array is proposed,which makes full use of the stereo geometry of the double L-shaped array to eliminate the effect of the wave velocity factor on the DOA estimation performance.At the same time,a simplified parameter matching method is given.In the variable velocity environment,simulation experiments show that the proposed algorithm improves the performance more superior.4.The conventional spatial smooth 2D ESPRIT algorithm can solve the coherent signal interference well.For the variable velocity environment,the spatial smoothing-improved 2D ESPRIT algorithm is proposed,which can solve both coherent signal and the variable velocity environment.Finally,the proposed algorithm is verified by simulation experiments.