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With the increasing demands of large maritime scene scattering prediction and also its high-resolution imaging simulation, the traditional two-scale scattering models, such as capillary wave modified facet scattering model (CWMFSM), appear to be inefficient and laborious when encountering scattering simulation of large maritime scene or long-time case. This paper proposes an effective and efficient approach, i.e. a statistical realisation of CWMFSM, for scattering simulation of space-time varying sea surface. Namely, this approach can give a fast and accurate simulation of large scene and long-time space-time varying sea surface scattering results using the memoryless non-linear transform method together with the statistic characteristics of results calculated by CWMFSM method. From the comparisons of texture feature, statistical characteristics and Doppler spectrum between the results derived from CWMFSM method and the statistical realisation, it is demonstrated that the proposed approach can give a pretty efficient simulation of space-time varying sea surface scattering with almost the same accuracy as the CWMFSM method itself. Similar with CWMFSM, the proposed approach can be applied to fields of sea surface scattering intensity distribution simulation, Doppler spectrum investigation of dynamic sea surface, composite scattering prediction of sea surface with multiple targets, SAR remote-sensing simulation of maritime scene, etc. [ABSTRACT FROM AUTHOR]

To simulate the multiple scattering effect of target in synthetic aperture radar (SAR) image, the hybrid method GO/PO method, which combines the geometrical optics (GO) and physical optics (PO), is employed to simulate the scattering field of target. For ray tracing is time-consuming, the Open Graphics Library (OpenGL) is usually employed to accelerate the process of ray tracing. Furthermore, the GO/PO method is improved for the simulation in low pixel situation. For the improved GO/PO method, the pixels are arranged corresponding to the rectangular wave beams one by one, and the GO/PO result is the sum of the contribution values of all the rectangular wave beams. To get high-resolution SAR image, the wideband echo signal is simulated which includes information of many electromagnetic (EM) waves with different frequencies. Finally, the improved GO/PO method is used to simulate the SAR image of targets above rough surface. And the effects of reflected rays and the size of pixel matrix on the SAR image are also discussed. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation of electromagnetic scattering from ship-generated internal wave wake and its underlying two-dimensional sea surfaces. The geometric modeling of internal wave wake and linear sea surfaces as well as nonlinear choppy wave model (CWM) sea surfaces are performed successively. Then, the normalized radar cross-section (NRCS) calculations are carried out using second-order small-slope approximation (SSA-2) in bistatic and monostatic configurations. To study the scattering characteristics of internal wave wakes that usually have a large coverage area, the calculations are performed in four successive regions. The results reflect that the scattering signals of four regions are distinguished from those of sea surface without wake; furthermore, the NRCSs for CWM sea surfaces with internal wave wakes are both larger than those of the linear sea surfaces with internal wave wakes in bistatic and monostatic configurations. [ABSTRACT FROM AUTHOR]

Doppler spectral signatures of sea echoes from two-dimensional (2-D) fetch- and depth-limited sea surfaces are investigated using the second-order small-slope approximation (SSA-II) model. For the description of 2-D nearshore sea surface, the revised choppy wave model (RCWM) is applied, which takes into account the wind fetch effect and water depth effect in nearshore marine environment. Comparisons of computed results in co-polarizations and cross polarization at various incident angles show that Doppler shift and spectral bandwidth can be greatly influenced by hydrodynamic modulation of waves in the large wind fetch and small water depth marine environment, which indicates that the hydrodynamic modulation induced by shoaling effect would be greatly enhanced in the situation of the nearshore shallow sea with a long wind fetch. The differences in variation trend between results in co-polarizations and cross polarization also reflect varying degrees of influence of aforementioned hydrodynamic modulation on different scattering mechanisms. [ABSTRACT FROM AUTHOR]

This paper deals with the effects of horizontal skewness on Doppler spectra. A.K. Fung et al. pointed out that the crests of the sea waves are tilted towards the wind direction, which is referred to as horizontal skewness. Although the nonlinear sea surface is more realistic than the linear one, it cannot embody the statistical front-back asymmetry of real sea waves due to the influence of the wind. Thus, the impact of horizontal skewness must be considered. The first-order modified Lagrange model for asymmetric ocean waves is combined with Monte Carlo method to produce the two-dimensional (2-D) time-varying skewed sea surfaces which are nonlinear and skewed simultaneously. Moreover, the second-order small-slope approximation method is used to calculate the scattering field and study the Doppler spectral characteristics from skewed sea surfaces. Horizontal skewness makes Doppler spectra broader in upwind case, but narrower in downwind case. In addition, the impact of horizontal skewness on Doppler spectra is dependent on wind direction and incident elevation angle. [ABSTRACT FROM PUBLISHER]