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Study On The Algorithm Of Broadband Signal Beamforming

Posted on:2016-01-18Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y BiFull Text:PDF
GTID:1222330509454699Subject:Underwater Acoustics
Abstract/Summary:PDF Full Text Request
Broadband signal beamforming is one of the main research directions in underwater acoustic signal processing, but broadband acoustic signal processing is much more complex than that of the narrowband. In this dissertation, the broadband beamforming algorithms by focus transform are studied, and the validation of the algorithms are proved through the simulation and experimental results. The main contributions are described as follows:1. The classical narrowband signal beamforming algorithms are studied. The method of calculating the actual and theoretical array manifold vectors of the common arrays are given. Based on this, a method of calculating the actual manifold vector is described in detail and is used to validate the proposed algorithms in this dissertation.2. Two factors which are deciding the effects of broadband focus beamforming algorithms are studied: one is the focus matrix, the other is the focus frequency. The methods for determining the optimal focus matrix and the best focus frequency are given. Various focus algorithms are presented based on the different methods of calculating the focus matrix. In this paper, the effectiveness of the best focus frequency is validated by simulation and pool experiments for the first time. Both the simulation and pool experiments show that: the broadband focus beamforming algorithms which are obtained at the optimal focus frequency have a better performance than which are obtained at other focus frequency.3. The second-order cone broadband focus beamforming algorithm based on the best focus frequency is proposed. Firstly, the second-order cone programming(SOCP) method and the software which solving the second-order cone programming-Se Du Mi are introduced, the transform process from the optimization problem to the SOCP problem is described. Secondly, the common SOCP beamforming algorithms are introduced, the method of determining the best focus frequency is introduced to the second-order cone broadband focus beamforming algorithm, and thus a second-order cone broadband focus beamforming algorithm which is based on the best focus frequency is proposed. The simulation and pool experiments show that: the proposed SOCP broadband focus beamforming algorithm which based on the optimal focus frequency has a narrower main lobe and lower side lobe in the beam pattern, it is because the proposed method combine the effectiveness of the optimal focus frequency andthe SOCP narrowband beamforming algorithms.4. An optimized broadband focus beamforming algorithm is proposed by incorporating the broadband focus beamforming with robust Capon beamforming(RCB) algorithm. Firstly, the basic theory of the ellipsoid is introduced, and then the principle of the RCB algorithm is described on the basis of the uncertainty ellipsoid constraints and the covariance estimation. Finally, the superiority of RCB algorithm is reflected by comparing with minimum variance distortionless response(MVDR) narrowband beamforming algorithm in the simulation experiments. Since the closer to the real steering vector can received by RCB algorithm, the broadband focus beamforming algorithm can be combined with RCB algorithm to correct the focus matrix. Thus, an optimized broadband focus beamforming algorithm which combines the broadband beamforming with RCB algorithm is proposed by considering the best focus frequency. The simulation and pool experiments show that: a narrower main lobe is obtained when the best focus frequency of the focus matrix is corrected by the RCB algorithm, it also can keep the main lobe constant and make the side lobe lower.5. A dual optimized broadband beamforming algorithm is proposed. Firstly, the RCB algorithm is used to correct the focus matrix, then the broadband signals are focused on the best focus frequency by the corrected focus matrix, lastly, the narrowband signals are beamformed by the SOCP algorithm. The simulation, pool experiments and lake experiments show that: the dual optimized broadband beamforming algorithm make full use of the advantages of the RCB algorithm, the optimal focus frequency and the SOCP algorithm. By using the dual optimized broadband beamforming algorithm, the best broadband focus beam pattern is obtained in this paper.
Keywords/Search Tags:Broadband beamforming, Focus transform, The focus matrix, The focus frequency, Second-order cone programming, RCB algorithm
PDF Full Text Request
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