Research On Wideband Beamforming And DOA Estimation In Underwater Acoustic Environment

Beamforming and direction of arrival estimation(DOA)is an important research content of array signal processing,especially in underwater target detection and parameter estimation.Wideband signals are more important than narrowband signals in carrying more abundant target information and strong anti-interference ability,so wideband beamforming and wideband DOA estimation are of great significance.Underwater acoustic signals are characterized by low frequency,wide frequency band,slow propagation speed,and complex and changeable marine environment,the wideband beamforming algorithm with constant beamwidth and the wideband DOA estimation algorithm based on the test of orthogonality of projected subspaces(TOPS)are studied.The main work of this paper is:1.The signal model of array signal processing is briefly summarized and the classical narrowband beamforming algorithm is analyzed,and the advantages and disadvantages of various algorithms are pointed out in combination with the simulation results.The difference between frequency domain implementation and time domain implementation of wideband beamforming is studied.The problem of constant beamwidth is analyzed,and the focusing transformation algorithm and the Bessel function algorithm are studied and simulated;2.According to the concept of response variation,the main lobe response at different frequencies of the broadband signal is approximated with the main lobe response at the reference frequency,and a simple constant beamwidth beamforming algorithm is proposed by combining the zero constraint and the sidelobe constraint.The effectiveness of the algorithm is verified by comparing with the simulation of the other two algorithms;3.Study on the subspace algorithm for wideband DOA estimation: incoherent signal subspace method(ISM)and coherent signal subspace method(CSM),analyzed two kinds of structure focusing matrix method of CSM algorithm;and the algorithms are simulated,analyzed the performance of the algorithm;4.The basic principle of TOPS algorithm is introduced,and an improved algorithm is proposed to suppress the false peak in the TOPS algorithm.Based on this,the method of pretreatment of beam space is proposed to further improve the algorithm,which can reduce the computation of the algorithm while suppressing the false peak in the range of the beam pointing.Finally,the simulation and experimental data processing results show that the proposed algorithm has better estimation performance.