Nystrm method is a new method for solving electromagnetic scattering problems. This paper gives the detailed description on high-order Nystrm method used for the electric field integral equation of electromagnetic sca...Nystrm method is a new method for solving electromagnetic scattering problems. This paper gives the detailed description on high-order Nystrm method used for the electric field integral equation of electromagnetic scattering problems. The numerical solutions of two examples are correct compared with Method Of Moment(MOM).展开更多
According to the equivalence principles, high frequency approximation and boundary conditions, a method has been developed to deal with the EM scattering by a rectangular conducting flat plate coated with uniaxial ani...According to the equivalence principles, high frequency approximation and boundary conditions, a method has been developed to deal with the EM scattering by a rectangular conducting flat plate coated with uniaxial anisotropic radar absorbing material (RAM). The simple and effective method is available to the system of RCS prediction in which the large complex targets modeled by facets and wedges. Numerical results show some properties of EM scattering by conducting plate coated with thin uniaxial anisotropic RAM.展开更多
The TM-polarized electromagnetic scattering problem of a two-dimensional inho-mogeneous structure buried in lossy stratified media is presented. Analysis work consists of two parts mainly, derivation of the Green’s f...The TM-polarized electromagnetic scattering problem of a two-dimensional inho-mogeneous structure buried in lossy stratified media is presented. Analysis work consists of two parts mainly, derivation of the Green’s function of a filament buried in lossy stratified media and constitution of the electric field integral equation of the equivalent current caused by the differences between the inhomogeneities and the stratified media. Based on these works, illustrative numerical results are given to model inhomogeneous underground tubes in lossy stratified media, and to describe the scattering field affected by different factors such as permittivity distribution, dimension, and buried depth of the inhomogeneities and so on.展开更多
It is of both the theoretical and practical importance to reduce the storage andCPU time of moment methods by utilizing the geometrical and physical features of the scatterer.An unified approach based on the group the...It is of both the theoretical and practical importance to reduce the storage andCPU time of moment methods by utilizing the geometrical and physical features of the scatterer.An unified approach based on the group theory is presented to deal with the EM scattering fromsymmetric and anti-symmetric structures.展开更多
In this paper, Laplace transform method is used to solve the problem of wave scattering from the rough surface. The rough surface is described by y=ζ (x, z) . First, we make Laplace transform to y variable, th...In this paper, Laplace transform method is used to solve the problem of wave scattering from the rough surface. The rough surface is described by y=ζ (x, z) . First, we make Laplace transform to y variable, then do the Fourier transform to x and z variables. In the k space, we can obtain the solution of the problem of wave scattering by simple algebraic operation. Finally, the Laplace inverse transform is performed by complex variable method and Fourier inverse transform by stationary phase method.展开更多
The volume-surface integral equation(VSIE) ,the surface integral equation(SIE) and the volume integral equation(VIE) of EM scattering problem are converted into linear equations with the method of moment,then the prec...The volume-surface integral equation(VSIE) ,the surface integral equation(SIE) and the volume integral equation(VIE) of EM scattering problem are converted into linear equations with the method of moment,then the precorrected-FFT method is used to solve the linear equations.To overcome the drawback of conventional stencil topology,two kinds of improved stencil topology,stencil topology B and stencil topology C,are presented,and the construction and actual performance of the three kinds of stencil topology are compared.Numerical results show that good agreement is observed between the P-FFT solutions combined with each of the three kinds of stencil topology and the standard solutions.Stencil B can significantly reduce the number of near-zone precorrections.Stencil C potentially holds for parallel multilevel P-FFT since grid overlapping never occurs between any stencils.展开更多
In this paper, we study electromagnetic (EM) wave scattering problem by many small impedance bodies. A numerical method for solving this problem is presented. The problem is solved under the physical assumptions ka??1...In this paper, we study electromagnetic (EM) wave scattering problem by many small impedance bodies. A numerical method for solving this problem is presented. The problem is solved under the physical assumptions ka??1, where a is the characteristic size of the bodies and k is the wave number. This problem is solved asymptotically and numerical experiments are provided to illustrate the idea of the method. Error estimate for the asymptotic solution is also discussed.展开更多
The regular and smooth objects are always studied in conventional geometry. But very rough and irregular objects which have self-similarity, the fractal structure, are efficiently solved by fractal geometry. The self-...The regular and smooth objects are always studied in conventional geometry. But very rough and irregular objects which have self-similarity, the fractal structure, are efficiently solved by fractal geometry. The self-similarity is that the local configuration is similar to the whole configuration. In other words, for each resolution scalar, the form of the curves is similar. Fractal structure exists widely in nature. In this note, band-limited fractal functions展开更多
A new approach to the EM scattering problem of an inhomogeneous lossy dielectric body is pro-posed.It is shown that the entire interior electric field distribution can be obtained from the measured exteri-or field dis...A new approach to the EM scattering problem of an inhomogeneous lossy dielectric body is pro-posed.It is shown that the entire interior electric field distribution can be obtained from the measured exteri-or field distribution by simple recurrence relations.Detailed derivations of these recurrence relations for thefield distribution inside the scattering body are presented,and the results obtained by computer simulationsare given.展开更多
As a marked extension of the traditional MoM-PO （method of moment-physical optics） hybrid method, a new hybridization of PO, SBR, and MoM （MoM-SBR/PO） is presented to calculate the multireflection contribution in ...As a marked extension of the traditional MoM-PO （method of moment-physical optics） hybrid method, a new hybridization of PO, SBR, and MoM （MoM-SBR/PO） is presented to calculate the multireflection contribution in the PO region efficiently by introducing the method of SBR based on RDN notion, which avoids the time-consuming iterative procedure and the choice of proper Green＇s function. As compared with the traditional MoM-PO hybrid method, the calculation efficiency of the proposed method is greatly improved, and its validity is verified by numerical results.展开更多
A breaking wave can exert a great influence on the electromagnetic（EM） scattering result from sea surfaces. In this paper, the process of small-scale wave breaking is simulated by the commercial computational fluid ...A breaking wave can exert a great influence on the electromagnetic（EM） scattering result from sea surfaces. In this paper, the process of small-scale wave breaking is simulated by the commercial computational fluid dynamics（CFD）software FLUENT, and the backscattering radar cross section（RCS） of the turbulence structure after breaking is calculated with the method of moments. The scattering results can reflect the turbulent intensities of the wave profiles and can indicate high polarization ratios at moderate incident angles, which should be attributed to the incoherent backscatter from surface disturbance of turbulence structure. Compared with the wave profile before breaking, the turbulence structure has no obvious geometrical characteristic of a plunging breaker, and no sea spikes are present at large incident angles either.In summary, the study of EM scattering from turbulence structure can provide a basis to explain the anomalies of EM scattering from sea surfaces and help us understand the scattering mechanism about the breaking wave more completely.展开更多
A RCS prediction system named SCTE (Scattering from Complex Target and Environment) for calculating high-frequency electromagnetic scattering from complex target within complex environment is presented. The scattering...A RCS prediction system named SCTE (Scattering from Complex Target and Environment) for calculating high-frequency electromagnetic scattering from complex target within complex environment is presented. The scattering body is described by Computer-Aided-Design (CAD) representations in which the complex body is modeled as NURBS (Non-Uniform Rational B-spline) surfaces. The complex environment (rough surface of sea or ground) is also carefully considered by using fractal function. Scattering fields are calculated by using physical optics and the equivalent currents methods. There is a good agreement between the present results and that from measurements which demonstrates the accuracy of this system.展开更多
The solution of scattering problem of buried complex bodies needs to not only consider the scattering from the complex bodies, but also apply the boundary conditions in two different types of coordinate systems. This ...The solution of scattering problem of buried complex bodies needs to not only consider the scattering from the complex bodies, but also apply the boundary conditions in two different types of coordinate systems. This paper applies the conversion technique of vector wave functions combined with the three-dimensional unimoment method to effectively solve this type of complex electromagnetic problem. Using the conversion relations between the cylindrical and spherical vector wave functions, two types of boundary-value problems are conveniently jointed. Both the vector wave function expansion and the multipole expansion belong to eigen function expansion methods and have the same convergence rate. But the former is more rigorous in theory and needs to calculate only two types of eigen components while the latter needs to calculate four types.展开更多
The virtual-ray method for treating HF electromagnetic scattering problems is derived from the plane wave of free space, and using this the plane wave scattering by an impedance wedge is studied. In the solution proce...The virtual-ray method for treating HF electromagnetic scattering problems is derived from the plane wave of free space, and using this the plane wave scattering by an impedance wedge is studied. In the solution process a novel concept of generalized circle is introduced so that the complete amplitude function is obtained. And a reasonable physical interpretation for the term W2, which was neglected previously, is given. The calculated results agree well with those of the analytical solution obtained by G.D. Maliuzhinets(1958).展开更多
An iterative physical optics（IPO） model is proposed to solve extra large scale electric electromagnetic（EM） scattering from randomly rough surfaces. In order to accelerate the convergence of the IPO model, the for...An iterative physical optics（IPO） model is proposed to solve extra large scale electric electromagnetic（EM） scattering from randomly rough surfaces. In order to accelerate the convergence of the IPO model, the forward-backward methodology and its modification with underrelaxation iteration are developed to simulate the rough surface scattering; the local iteration methodology and the fast far field approximation（Fa FFA） in the matrix-vector product are proposed to reduce greatly the computational complexity. These techniques make Monte Carlo simulations possible. Thus, the average Doppler spectra of backscattered signals obtained from the simulations are compared for different incident angles and sea states. In particular, the simulations show a broadening of the Doppler spectra for a more complicated sea state at a low grazing angle（LGA）.展开更多
基金Supported by the National Natural Science Fbundation of China(No.60371003)
文摘Nystrm method is a new method for solving electromagnetic scattering problems. This paper gives the detailed description on high-order Nystrm method used for the electric field integral equation of electromagnetic scattering problems. The numerical solutions of two examples are correct compared with Method Of Moment(MOM).
文摘According to the equivalence principles, high frequency approximation and boundary conditions, a method has been developed to deal with the EM scattering by a rectangular conducting flat plate coated with uniaxial anisotropic radar absorbing material (RAM). The simple and effective method is available to the system of RCS prediction in which the large complex targets modeled by facets and wedges. Numerical results show some properties of EM scattering by conducting plate coated with thin uniaxial anisotropic RAM.
基金Supported by the National Natural Science Foundation of China
文摘The TM-polarized electromagnetic scattering problem of a two-dimensional inho-mogeneous structure buried in lossy stratified media is presented. Analysis work consists of two parts mainly, derivation of the Green’s function of a filament buried in lossy stratified media and constitution of the electric field integral equation of the equivalent current caused by the differences between the inhomogeneities and the stratified media. Based on these works, illustrative numerical results are given to model inhomogeneous underground tubes in lossy stratified media, and to describe the scattering field affected by different factors such as permittivity distribution, dimension, and buried depth of the inhomogeneities and so on.
文摘It is of both the theoretical and practical importance to reduce the storage andCPU time of moment methods by utilizing the geometrical and physical features of the scatterer.An unified approach based on the group theory is presented to deal with the EM scattering fromsymmetric and anti-symmetric structures.
文摘In this paper, Laplace transform method is used to solve the problem of wave scattering from the rough surface. The rough surface is described by y=ζ (x, z) . First, we make Laplace transform to y variable, then do the Fourier transform to x and z variables. In the k space, we can obtain the solution of the problem of wave scattering by simple algebraic operation. Finally, the Laplace inverse transform is performed by complex variable method and Fourier inverse transform by stationary phase method.
文摘The volume-surface integral equation(VSIE) ,the surface integral equation(SIE) and the volume integral equation(VIE) of EM scattering problem are converted into linear equations with the method of moment,then the precorrected-FFT method is used to solve the linear equations.To overcome the drawback of conventional stencil topology,two kinds of improved stencil topology,stencil topology B and stencil topology C,are presented,and the construction and actual performance of the three kinds of stencil topology are compared.Numerical results show that good agreement is observed between the P-FFT solutions combined with each of the three kinds of stencil topology and the standard solutions.Stencil B can significantly reduce the number of near-zone precorrections.Stencil C potentially holds for parallel multilevel P-FFT since grid overlapping never occurs between any stencils.
文摘In this paper, we study electromagnetic (EM) wave scattering problem by many small impedance bodies. A numerical method for solving this problem is presented. The problem is solved under the physical assumptions ka??1, where a is the characteristic size of the bodies and k is the wave number. This problem is solved asymptotically and numerical experiments are provided to illustrate the idea of the method. Error estimate for the asymptotic solution is also discussed.
文摘The regular and smooth objects are always studied in conventional geometry. But very rough and irregular objects which have self-similarity, the fractal structure, are efficiently solved by fractal geometry. The self-similarity is that the local configuration is similar to the whole configuration. In other words, for each resolution scalar, the form of the curves is similar. Fractal structure exists widely in nature. In this note, band-limited fractal functions
文摘A new approach to the EM scattering problem of an inhomogeneous lossy dielectric body is pro-posed.It is shown that the entire interior electric field distribution can be obtained from the measured exteri-or field distribution by simple recurrence relations.Detailed derivations of these recurrence relations for thefield distribution inside the scattering body are presented,and the results obtained by computer simulationsare given.
文摘As a marked extension of the traditional MoM-PO （method of moment-physical optics） hybrid method, a new hybridization of PO, SBR, and MoM （MoM-SBR/PO） is presented to calculate the multireflection contribution in the PO region efficiently by introducing the method of SBR based on RDN notion, which avoids the time-consuming iterative procedure and the choice of proper Green＇s function. As compared with the traditional MoM-PO hybrid method, the calculation efficiency of the proposed method is greatly improved, and its validity is verified by numerical results.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61372004 and 41306188)the Fundamental Research Funds for the Central Universities,China(Grant No.K 5051207015)the Foundation of the Science and Technology on Electromagnetic Scattering Laboratory,China(Grant No.HX0113071414)
文摘A breaking wave can exert a great influence on the electromagnetic（EM） scattering result from sea surfaces. In this paper, the process of small-scale wave breaking is simulated by the commercial computational fluid dynamics（CFD）software FLUENT, and the backscattering radar cross section（RCS） of the turbulence structure after breaking is calculated with the method of moments. The scattering results can reflect the turbulent intensities of the wave profiles and can indicate high polarization ratios at moderate incident angles, which should be attributed to the incoherent backscatter from surface disturbance of turbulence structure. Compared with the wave profile before breaking, the turbulence structure has no obvious geometrical characteristic of a plunging breaker, and no sea spikes are present at large incident angles either.In summary, the study of EM scattering from turbulence structure can provide a basis to explain the anomalies of EM scattering from sea surfaces and help us understand the scattering mechanism about the breaking wave more completely.
文摘A RCS prediction system named SCTE (Scattering from Complex Target and Environment) for calculating high-frequency electromagnetic scattering from complex target within complex environment is presented. The scattering body is described by Computer-Aided-Design (CAD) representations in which the complex body is modeled as NURBS (Non-Uniform Rational B-spline) surfaces. The complex environment (rough surface of sea or ground) is also carefully considered by using fractal function. Scattering fields are calculated by using physical optics and the equivalent currents methods. There is a good agreement between the present results and that from measurements which demonstrates the accuracy of this system.
文摘The solution of scattering problem of buried complex bodies needs to not only consider the scattering from the complex bodies, but also apply the boundary conditions in two different types of coordinate systems. This paper applies the conversion technique of vector wave functions combined with the three-dimensional unimoment method to effectively solve this type of complex electromagnetic problem. Using the conversion relations between the cylindrical and spherical vector wave functions, two types of boundary-value problems are conveniently jointed. Both the vector wave function expansion and the multipole expansion belong to eigen function expansion methods and have the same convergence rate. But the former is more rigorous in theory and needs to calculate only two types of eigen components while the latter needs to calculate four types.
基金Supported by the National Natural Science Foundation of China
文摘The virtual-ray method for treating HF electromagnetic scattering problems is derived from the plane wave of free space, and using this the plane wave scattering by an impedance wedge is studied. In the solution process a novel concept of generalized circle is introduced so that the complete amplitude function is obtained. And a reasonable physical interpretation for the term W2, which was neglected previously, is given. The calculated results agree well with those of the analytical solution obtained by G.D. Maliuzhinets(1958).
基金supported by the National Natural Science Foundation of China(61372033)
文摘An iterative physical optics（IPO） model is proposed to solve extra large scale electric electromagnetic（EM） scattering from randomly rough surfaces. In order to accelerate the convergence of the IPO model, the forward-backward methodology and its modification with underrelaxation iteration are developed to simulate the rough surface scattering; the local iteration methodology and the fast far field approximation（Fa FFA） in the matrix-vector product are proposed to reduce greatly the computational complexity. These techniques make Monte Carlo simulations possible. Thus, the average Doppler spectra of backscattered signals obtained from the simulations are compared for different incident angles and sea states. In particular, the simulations show a broadening of the Doppler spectra for a more complicated sea state at a low grazing angle（LGA）.
