Rigid and elastic acoustic scattering signal separation for underwater target

Abstract

Underwater target elastic acoustic scattering and other acoustic scattering components are aliasing together in the time and frequency domains, and the existing signal processing methods cannot recognize the elastic scattering features under the aliasing condition because of the resolution limitation. To address this problem, this study, which is based on the target echo highlight model, analyzes the characteristics of target acoustic scattering components when the transmitted signal is a linear frequency modulation pulse. The target acoustic scattering structure in the fractional Fourier transform (FRFT) domain is deduced theoretically. Then, filtering is used in the FRFT domain to separate the target elastic acoustic scattering components. In addition, noise suppression performance and filter resolution are discussed. The target rigid and elastic acoustic scattering components are separated. Experimental results show that filtering in the FRFT domain can separate the elastic scattering components from the target echoes. Moreover, separated elastic acoustic scattering components have consistent theoretical features, which lay the foundation for studying the elastic scattering characteristics further.

Sparse Reconstruction-Based Inverse Scattering Imaging in a Shallow Water Environment

“…It should be noticed that, when using SLIM, an implicit assumption is made that the frequency dispersion is neglectable. Here, for the 3-9 kHz bandwidth in use, according to (9), c l ranges from 1181 m/s to 1327 m/s. On the other hand, in two-dimensional free-field space, the cylindrical spread wave propagation causes a √ kR attenuation, which will reduce the impact of creeping waves' dispersion.…”

“…Moreover, when the object is placed near a horizontal surface, the acoustic color images are considered, and the ray-based model [3]- [5] , finite element model [6] , and threedimensional/hybrid models [7], [8] were developed to match their corresponding experimental configurations. The acoustic color image of the observed elastic waves can be generated by using fractional Fourier transform to separate each wave component [9] . After that, acoustic color images are also used for object classification and target identification [10], [11] because objects of different shapes or materials exhibit different scattering responses.…”

An Improved Velocity Estimation Method for Wideband Multi-Highlight Target Echoes in Active Sonar Systems

“…Different reflections have different time-space structures and are aliased in both the time and frequency domains [3]. Therefore, the whole echo can be viewed as equivalent to the summed superposition of the reflections from the multiple highlights, and the respective reflection from each highlight is determined by its spatial distribution and the material of the target [4], also including the information about the velocity, sound intensity and environment conditions, which form the theoretical basis to accomplish the estimation of an underwater target. The target velocity mentioned in this paper totally represents the radial velocity, which is along the line-of-sight of the receiving sonar.…”

Acoustic scattering theory without large-distance asymptotics

“…There are many researches on acoustic scattering, for example, acoustic waves scattering on different targets such as fluid spheroids [7] and finite rigid plates [8]. Underwater acoustic scattering is also an important issue, such as underwater acoustic scattering signal separation [9], acoustic scattering from underwater elastic objects [10], acoustic scattering by suspended flocculating sediments [11] and acoustic scattering in gassy soft marine sediments [12]. Other problems such as acoustic scattering-resonance [13], acoustic scattering reductions [14], acoustic scattering in nonuniform potential flows [15], designing the bilaminate acoustic cloak [16], control of acoustic absorptions [17], acoustic interaction forces [18], acoustic radiation forces [19], and scattering effects on an acoustic black hole [20] are also considered.…”