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Uniform linear array is a kind of very important underwater acoustic detection equipment, it mainly divided into two kinds: rigid array and flexible array. Rigid array is the best means to obtain ideal detection result, but the layout and recovery is difficult. Flexible array is used more popular for its easy to operation, but the array shape is difficult to maintain. Shape distortion of the flexible...
Acoustic propagation in the ocean waveguide is characterized by mutual interference between the multiple ray paths connecting a source-receiver pair. In the Russian literature, these interference effects have been distilled mathematically into a single parameter, the so-called waveguide invariant defined as beta. The conventional wisdom is that the numerical value of beta is negative in deep water...
Ocean ambient noise mainly includes uncorrelated noise and correlated noise. The uncorrelated noise only affects the diagonal elements in the noise covariance matrix, and it can be suppressed by subtracting a value on the diagonal elements. Utilizing this feature, a high array-gain beamforming based on diagonal reducing is presented. Meanwhile, the robustness becomes poor. So, the array weight norm...
Matched-field processing (MFP) is an underwater acoustic signal processing method for passive source localization. It works by matching the measured field with the full-field solution for sound wave propagation in an oceanic waveguide. The popular Minimum Variance Distortionless Response (MV-DR) algorithm is known to be highly sensitive to environmental mismatch, which is one of the main obstacles...
Conventional beamforming is robust but suffers from fat beams and high level sidelobes. This paper applies the Lucy-Richardson algorithm to the conventional beam power (versus the complex beam output) similar to image de-blurring, and thus avoid the instability problem of common deconvolution algorithms. The deconvolved beam power yields narrow (high resolution) beams and low sidelobe levels. It is...
The purpose of this paper is to introduce a new beamforming method for sonar imaging, which is proposed based on the plane wave decomposition combine with back-propagation method and with transverse oscillations. This method was initially proposed for ultrasound Doppler imaging using transverse oscillations in linear geometry. The plane wave decomposition theory is used to decompose in different directions...
Superdirectivity is a very attractive option in array aperture constrained applications due to its high directivity and good angular discrimination. However, it is hardly applied in practice because of its extreme sensitivity to small random array errors. In this paper, we propose an online calibration method for superdirective arrays with gain-phase errors. Unlike the currently well-known robust...
An innovative technique for the synthesis of a nonuniform sonar array with as few elements as possible is proposed. This paper introduces a new method for linear array pattern synthesis based on continuous compressive sensing (CCS). Given a reference pattern subject to aperture constraints, the proposed approach allows the exact solution of the positions of sonar sensors, whose number is maximally...
In this paper, a compressed sensing based method for beamforming from a single snapshot of an acoustic array is proposed. Firstly, the observation model is presented and then the problem of direction of arrival of acoustic sources estimation is expressed as an optimization problem constrained by signal sparsity. Then a modified orthogonal matching pursuit algorithm is provided to solve this problem...
Beamforming has been used in wireless sensor networks (WSNs) to increase the communication range of sensor nodes. These works investigate the beamforming performance using the theory of random arrays, and aims to achieve maximum transmitting power. Since the relative positions of sensor nodes and frequency/spatial response are generally unknown, it's also referred to as blind beamforming. In this...
Bearing-time-record (BTR) is widely used in sonar signal processing as an important display formats which may benefit the subsequent processing. The general way to get a BTR display is to parallel the outputs of the beamformer along time axis. This paper proposes a method to generate the BTR display which uses the L1 norm regularization and the total variation (TV) regularization to enhance the point-based...
Performing reliable target detection in reverberation background is a critical problem demanding prompt solutions. Researching on the statistical characterization of reverberation envelope is significantly important for not only the CFAR detection, but also the environment detection and seafloor classification. Identified as a robust statistical model for shallow water reverberation envelope, K-distribution,...
Underwater acoustic (UWA) channels are characterized by spreading of received signals in space (angle of arrival) and delay. The spread is often limited to a small number of clusters. For combining signals spread in delay, equalizers are used. To separate space clusters, antenna arrays are used. In this paper, a receiver is investigated that exploits space-time clustering in UWA channels. The investigated...
The range resolution of an imaging sonar is difficult to be improved due to the restriction of the instantaneous bandwidth of the sonar system. To increase the range resolution of the imaging sonar, an imaging method with the use of the comb spectrum signal, which is composed of a set of continuous wave (CW) pulses with different center frequencies, is proposed. After the round-trip propagation these...
A formula is developed in this paper to calculate array gain when the plane-wave assumption is not applied. The formula is developped based on the assumption that the noise in the deep water is Gassian white and isotropic. The performance of a vertical linear is analyzed in the range-independent ocean, and also in a weak range-dependent ocean perturbed by random internal waves. Simulation results...
By taking advantage of the difference in spatial distribution between underwater sound source and ocean ambient noise, a detector based on bearing estimation variance is proposed. The time delay estimation method is adopted to estimate the bearing of the source, and the test statistics is deduced to evaluate the performance of the detector. The results show that its performance is far superior to...
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