Propagation theory for bi-static long-range bottom reverberation in shallow water waveguide

Underwater reverberation is a main limitation of the sonar performance and thereby the reverberation level estimation becomes crucial. In this study, based on the Lambert law and ray theory, a model for predicting 3D bistatic reverberation performance by interface scattering at linear sound speed profile is established and then verified through the underwater explosion experiments. The Influences of source and receiver positions, and relative sound speed gradient on reverberation performance are further investigated. The results indicate that: (1) the proposed model can predict the shortrange mean reverberation level effectively, with the deviation 2-4 dB and describe the whole reverberation level distribution in some details; (2) at the early reverberation phase, the interference effects between the interface scattering sounds are considerable and a dominating interface exists; the counterbalance between the losses by scattering, spreading and medium absorption results in the local high-intensity zones close to corresponding interfaces, respectively; (3) as the sound source moves towards some interface, associated local high-intensity zone gradually expands, while the other one shrinks; if the sound speed approaches are constant, an extra local high-intensity zone will appear between the previous two but with a lower magnitude.

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A three-dimensional bistatic reverberation model of underwater explosion by interface scattering at variable sound speeds

Guo

Liu

Sheng

et al. 2018

Journal of Low Frequency Noise, Vibration and Active Control

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Design of multistatic sonar space-time code detection signal and time reversal copy-correlation detection technology

Sheng¹,

Jia²,

Ling³

et al. 2014

Acta Phys. Sin.

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A space-time code (STC) detection signal is designed for multistatic sonar to distinguish the multiple access echoes in the shallow water, and a time reversal (TR) copy-correlation detection method is presented for solving the problem of multi-path sub-channel differences when the vertical array is oblique. STC detection signal has a good orthogonality through modulating with pseudo-random signals, can distinguish multiple access target echoes while combating with sub-channel attenuation. The vertical array affected by current is oblique, its multi-path sub-channel differences causing signals from different sub-channels can not focus on the receiving end, so the array gain decreases. Meanwhile, it causes resolution to decline and the error rate of signal judgment to rise. Channel training signal is designed to estimate the sub-channel multipath environment, and the best matched detection signal for sub-channel differences is got through virtual time reversal mirror (VTRM) with the estimated channels and the received signal being detected by TR copy-correlation. Simulation results of tristatic sonar (two transmitters and one receiver) show that the SPC detection signal and TR copy-correlation can meet the requirements of multistatic sonar detection and distinguish the multiple access echoes in low SIR and complex channel environment. The best matched detection signal is got through VTRM (virtual time reversal mirror) with the estimated channels, and the received signal is detected by TR copy-correlation. Simulation results of tristatic sonar (two transmitters and one receiver) show that the STC detection signal and TR copy-correlation can meet the requirements of multistatic sonar detection and distinguish the multiple access echoes in low SIR environment.

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Optimizations for robust low sidelobe beamforming of bistatic multiple-input multiple-output virtual array

Cong¹,

Sun²,

Zhang³

et al. 2014

Acta Phys. Sin.

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Two-dimensional estimation for direction of arrival and direction of departure is required in the target location of bistatic multiple-input multiple-output (MIMO) system. In view of the huge calculation of array covariance matrix processing and the sensitivity to the array manifold mismatch, a beam optimization algorithm which can resist array manifold mismatch is proposed based on the virtual array of bistatic MIMO. Optimization for beam pattern through the second-order cone programming is used in the algorithm. The waveform diversity technology and location of bistatic system are combined. The relationship between direction of arrival at and direction of departure from the ellipse locating line is used to convert the two-dimensional synthesis direction vector into one-dimensional virtual array manifold. It is proved that the beam pattern of virtual array manifold transformed in bistatic MIMO can be equivalent to the combination of the beam pattern of transmitting array mapping on the receiving array angle domain and the beam pattern of receiving array. The algorithm can not only control the side lobe and null the beam pattern but also improve the ability to resist array manifold mismatch. The validity of the method is verified by the computer simulation of the optimized beam pattern and spectrum.

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Propagation theory for bi-static long-range bottom reverberation in shallow water waveguide

Cited by 3 publications

References 16 publications

A three-dimensional bistatic reverberation model of underwater explosion by interface scattering at variable sound speeds

A three-dimensional bistatic reverberation model of underwater explosion by interface scattering at variable sound speeds

Design of multistatic sonar space-time code detection signal and time reversal copy-correlation detection technology

Optimizations for robust low sidelobe beamforming of bistatic multiple-input multiple-output virtual array

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