The coherent and incoherent scattering are composed in the backscattering characteristics of arbitrarily shaped dielectric object with rough surface both in laser and THz bands. If the radius of curvature at any point of the surface is much greater than the incident wavelength which is also longer than the surface height fluctuation and RMS of surface slope, the Kirchhoff approximation and Physical optics method, as well as the stationary phase evaluation are invited here to deduce the analytical expression of coherent backscattering cross section of rough dielectric object. Basically, the coherent cross section can be viewed as the combination of the RCS of corresponding smooth and perfectly conducting object, the Fresnel reflection coefficient of dielectric surface and the characteristic function of rough surface. Thus, the scattering expression of rough conducting object, smooth dielectric object and the rough dielectric object can be logically obtained. Using the tangent plane approximation, the surface of the object is divided into a series of patches, and then the incoherent component is achieved by integrating over the illuminated area combined with the covering function. Based on the Physical optics approximation and GPU parallel computing, the coherent scattering component of smooth conducting object, the incoherent component of rough object and its corresponding backscattering cross section can be easily computed. In this paper, we numerically simulate the backscattering characteristics in laser and THz bands of rough dielectric sphere and other complex rough dielectric targets respectively, meanwhile, we also analysis the influence of dielectric coefficient and roughness concentration on the results of the backscattering cross section.
Scattering characteristics of space target in the visible spectrum, which can be used in target detection, target identification, and space docking, is calculated in this paper. Algorithm of scattering characteristics of space target is introduced. In the algorithm, space target is divided into thousands of triangle facets. In order to obtain scattering characteristics of the target, calculation of each facet will be needed. For each facet, calculation will be executed in the spectrum of 400-760 nanometers at intervals of 1 nanometer. Thousands of facets and hundreds of bands of each facet will cause huge calculation, thus the calculation will be very time-consuming. Taking into account the high parallelism of the algorithm, Graphic Processing Units (GPUs) are used to accelerate the algorithm. The acceleration reaches 300 times speedup on single Femi-generation NVDIA GTX 590 as compared to the single-thread CPU version of code on Intel(R) Xeon(R) CPU E5-2620. And a speedup of 412x can be reached when a Kepler-generation NVDIA K20c is used.
The problem of electromagnetic waves scattering at rough boundaries is of practical interest and has been addressed many times in different papers. Theories for investigation of rough surface scattering primarily two kinds of methods: numerical method and approximate method. As the classic analytical methods cannot calculate the electromagnetic scattering characteristics at Low Grazing Angle (LGA) accurately, in this paper, a novel method is presented by utilizing the Radar Cross Section (RCS) of the low grazing two-dimensional sea surface based on the triangles-based Physical Optics (PO) method. Firstly, the Monte Carlo method is applied to simulate the two-dimension rough sea surface in different wind speeds based on the PM sea spectrum. Then, the sea surface is generally meshed by 1/8~1/10 length of the incident wave. Secondly, the complex permittivity of the sea surface is calculated by two-Debye method and compared with the experiment. The physical optical is used to calculate the backscattering coefficient of the random rough sea surface. Considering the problem of low grazing, it is especially sampled more densely between the scattering angles 70°~90°. Then the self-shadow and inter-shadow of the sea surface at low grazing angle is taken into account, the Z-BUFFER method is used to judgment of the shadow effect. The numerical result is compared with the FEKO and good agreement is obtained. As the frequency increasing, the sea surface will have more triangles to be calculated, it will take more time. Finally, we propose a novel graphic processing unit (GPU)-accelerated decoding system. The result is 68.96 faster than its CPU counterpart.
The scattering characteristic of complex target from terrestrial and celestial background radiation has been widely used in such engineering fields as remote sensing, feature extraction, tracking and recognition of target thus having been an attractive field for many scientists for decades. In our method, the model of target is constructed using 3DMAX and the surface is divided into triangle facets firstly. Bidirectional Reflectance Distribution Function (BRDF) is introduced and MODTRAN is applied to calculate background radiation for a given time at a given place. Finally the scattering of each facet is added up to get the scattering of the target. As the background radiance comes in all directions and in a wide spectrum and the complex target always consists of thousands of facets, in general it takes hours to complete the calculation. Consequently this limits its use in the real time applications. Recent years have seen the continual development of multi-core CPU. As a result parallel programming on multi-cores has been more and more popular. In this paper, the openMP, Intel CILK ++, Intel Threading Building Blocks (TBB) are used separately to leverage the processing power of multi-cores processors. Our experiments are conducted on a DELL desktop based on an Intel I7- 2600K CPU running at 3.40 GHz with 8 cores and 16.0 GB RAM. The Intel Composer 2013 is employed to build the program. Also in OpenMP implementation, gcc is used. The results demonstrate that highest speedups for three parallel models are 5.06X, 5.02X, 5.15X respectively.