Horizontal-Longitudinal Spatial Correlation of Acoustic Field with Deep Receiver in the Direct Zone in Deep Water

The horizontal-longitudinal correlation of acoustic field for the receiver near the bottom is analyzed by using nu- merical modeling. An approximate analytical solution of horizontal-longitudinal correlation coefficient is derived based on the ray method. Combining the characteristic of Lloyd＇s mirror interference pattern, the variability of acoustic field and its effect on horizontal-longitudinal spatial correlation are discussed. The theoretical pre- diction agrees well with the numerical results. Experimental results confirm the validity of analytical solution. Finally, the applicability of the analytical solution is summarized. The conclusion is beneficial for the design of bottom-moored array and the estimation of integral time for moving source localization.

Rejection of Direct Blast Interference Based on Signal Phase-Matching Array Processing

In bistaic acoustic testing, there will be strong direct blast interference. An algorithm based on signal phase-matching array processing that rejects direct blast interference in bistatic acoustic testing has been studied, through which the object scattering signal is accurately extracted. Characteristics of bistatic acoustic testing and signal phase matching processing principle are fully integrated in this algorithm. Firstly, the direct blast interference is calculated from the receiving signal based on three subarrays signal phase matching processing. Secondly, the direct blast is rejected by subtraction from the receiving signal. In this way the limitations of the high signal to noise ratio that signal phase matching processing required for direct calculating the object scattering signal can be avoided. Simulation and sea trial results show that, when the ratio of signal to interference is greater than -20 dB, this algorithm of direct blast interference rejection based phase matching signal processing can accurately extract the object scattering signal.

On fast estimation of direction of arrival for underwater acoustic target based on sparse Bayesian learning

The Direction of Arrival （DOA） estimation methods for underwater acoustic target using Temporally Multiple Sparse Bayesian Learning （TMSBL） as the reconstructing algorithm have the disadvantage of slow computing speed. To solve this problem, a fast underwater acoustic target direction of arrival estimation was proposed. Analyzing the model characteristics of block-sparse Bayesian learning framework for DOA estimation, an algorithm was proposed to obtain the value of core hyper-parameter through MacKay＇s fixed-point method to estimate the DOA. By this process, it will spend less time for computation and provide more superior recovery performance than TMSBL algorithm. Simulation results verified the feasibility and effectiveness of the proposed algorithm.