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The Bragg hypothesis provides a simplified representation of the complex real ripples that contribute to sea clutter returns. We propose to describe the microscopic profile of large-scale long waves by a set of sinusoidal ripples, which are assumed to be with the Bragg wavelength that satisfies the resonant condition, and travel along the local scattering lines of sight pointing towards and away from...
The wind fetch and water depth will greatly impact the ocean waves from the perspective of their shape and statistical characteristics. In this paper, special focus is given to the joint influence of wind fetch and water depth upon Doppler spectrum of dynamic nonlinear ocean surfaces. The study is based on the simulation of two-dimensional fetch- and depth-changed sea surfaces via nonlinear revised...
This paper introduces a methodology of synthetic aperture radar imaging by utilizing scattering coefficients of targets obtained from time-domain full-wave simulations. Compared with conventional point-reflector assumption in synthetic radar imaging as well as shooting and bouncing rays technology, such a method is able to achieve a higher resolution in range, and is especially useful in imaging complex...
This paper provides a theoretical model to analyze the performance of non-line-of-sight (NLOS) ultraviolet (UV) communication systems with multi-user interference (MUI). The model is developed on the basis of a multiple-scattering Monte Carlo (MC) model. The system geometry and algorithm flowchart are presented. Numerical simulations are conducted for an application scenario where both a transmitter...
Presented in this paper is an experimental research on the mobile sensor and communication system based on transmitting with ultraviolet in either line-of-sight or non-line-of-sight conditions. The performance of this type of communication system is shown on the experimental platform which is set up. It proves the feasibility of ultraviolet communication system.
Model of bistatic scattering strength of underwater object in the far field is set up by Kirchhoff approximation. Monostatic target strength (TS) of Generic BeTSSi-submarine versus azimuthal angles are calculated by the proposed method at 1 kHz, 4 kHz and 8 kHz, which agree well with the international well-known data, and the computational accuracy is enhanced with the increment of acoustic frequency,...
A Dark-Pulse Brillouin Optical Time Domain Analyzer (BOTDA) configuration has been proposed to prolong the total sensing length by measuring both Brillouin Gain and Loss effect along fiber. The detected Brillouin signal will be identified by subtracting the two sided band of the Optical Carrier Suppressed (OCS) Stokes light. Due to the innovated configuration, the distributed Brillouin sensor developed...
A fast Slope Summation Facet Model (SSFM) that derived from the original Bass and Fuks' two scale model (BFTSM) is proposed to describe the sea scattering including both the coherent and diffused incoherent features. This kind of facet implement can readily change the average line budget of sea return locally corresponding to the facet returns, so that it can be used to find the amplitude of each...
Microwave backscattering from two-dimensional wind-driven sea is investigated by using a refined composite surface model. In this composite model, a new choice of the cutoff wave number with wind-speed dependence and incident-frequency dependence is applied to separate the sea spectrum into large and small components in different sea states with increased accuracy. Meanwhile, a newly modified probability...
A bistatic Synthetic Aperture Radar (Bis-SAR) imagery simulation of an extended sea surface is presented which is based on a facet scattering model. A semi-deterministic approach is developed to calculate high frequency bistatic raw data from the model of large sea surface. An effective method of modified nonlinear chirp scaling (NLCS) algorithm is presented to handle a general case of bistatic raw...
Three-dimensional imaging of sonar has important application in the fields of precise navigation and target recognition. In the paper, we describe an efficient model to compute the backscattering sound of high-frequency from complex underwater target for simulating the 3D image based on sidescan sonar. The target we used is the Generic submarine model which was designed by German FWG workshop. The...
In the imaging algorithms of Inverse Synthetic Aperture Sonar (ISAS), Range-Doppler Algorithm (RDA) and Polar Formation Algorithm (PFA) can be only suitable for far-field imaging. For obtaining near-field imaging, Computed Tomography Algorithm (CTA) is introduced. Five point-targets in near-field at different locations are imaged with RDA, PFA and CTA, respectively. Imaging results show that five...
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