THE ELECTROMAGNETIC SCATTERING OF A RADIALLY INHOMOGENEOUS DIELECTRIC CYLINDER

A new method is demonstrated for solving the electromagnetic scattering problemof a radially inhomogeneous lossless or lossy dielectric cylinder by Fourier series expansion.Com-pared with other methods,the method is simpler in numerical calculation and can be used forsolving scattering problems of a cylinder due to an arbitrary incident electromagnetic beam.     

VIRTUAL-RAY METHOD AND ITS APPLICATION IN THE PLANE WAVE SCATTERING BY AN IMPEDANCE WEDGE

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).     

NUMERICAL ANALYSIS OF TWO-DIMENSIONAL MULTI-OBJECT SCATTERING SYSTEMS WITH ARBITRARY STRUCTURE

A general analysis approach to multi-object(M-object)scattering systems of ar-bitrary structure is presented.Through the system scattering equation(SSE),the M-objectproblems are first transformed into a series of single-object(S-object)problems and then arethey solved,one-object by one-object,to determine the unknown coefficients of SSE.Finally theSSE is solved to yield the global solutions of original M-object problems.As to the solution ofS-object problems concerned,we use the global numerical boundary condition(GNBC)basedfinite element method(FEM)for complex scatterers,or the moment method(MM)for conduct-ing scatterers.For clarity we will confine ourself in two-dimensional(2-D)cases,and show somecalculation examples of M-object scattering systems for demonstration.     

Computer aided measurement of the electromagnetic parameter for the microwave absorbing materials

The electromagnetic parameters of microwave absorbing materials are important criteria when appraising the properties of absorbents. For reconstruction of parameters which belongs to the inverse scattering problem, the test data in requirement of traditional impedance method are "just enough" and not "redundant" to comprehensively evaluate the electromagnetic properties of materials. A novel optimization approach involving multiple impedance measurements is introduced in this paper to implement automatic measurement for electromagnetic parameters on microwave slot-line. Some results for standard samples and microwave absorbing materials are given.     

WAVELET ALGORITHM FOR INTEGRAL OPERATOR EQUATION AND ITS APPLICATIONS TO ELECTROMAGNETIC PROBLEMS

A brief summary of the basic theory of wavelet is proposed. The properties of wavelet function are discussed. The possible applications of wavelet to electromagnetics are given. Examples show that the wavelet method is feasible and effective for solving electromagnetic problems.     

NEW APPROACH TO ELECTROMAGNETIC SCATTERING FROM A CONDUCTIVE DISC-RING STRUCTURE

A one-dimensional modified integral equation for electromagnetic scattering from a metallic concentric disc-ring structure is derived by using Fourier expansion and separating the contribution of charge density from conventional EFIE. In the case of normal incidence, the derived equation is very simple and easy to be solved numerically regardless of the electric dimension of the structure. The comparison between the data of RCS of a disc by using this method and analytical method shows the effectiveness of this approach. Numerical results are also given for current distributions and the scattered fields for a disc-ring structure.     

FINITE DIFFERENCE METHOD FOR ELECTROMAGNETIC SCATTERING FROM PERFECTLY CONDUCTING CYLINDER

A numerical method of solving electromagnetic wave scattering problem is described.Radiation boundary condition(RBC)is applied to confine EM scattering problem in unboundedregion into problem in finite region.Combined with RBC and scatterer surface boundary condi-tion,Helmholtz equation in the finite region is solved numerically by the finite difference method.Thus the distribution of induced surface current on conducting cylinder and near field can beobtained.Computational results for both polarizations for circular,elliptic and square cylindersare presented.These results are in excellent agreement with those obtained by the eigenfunctionexpansion method or moment method and much better then the results of OSRC method.     

High resolution parametric modelling for two-dimensional radar target using prony algorithm

On the conditions of low-resolution radar, a parametric model for two-dimensional radar target is described here according to the theory of electromagnetic scattering and the geometrical theory of diffraction. A high resolution estimation algorithm to extract the model parameters is also developed by building the relation of the scattering model and Prony model. The analysis of Cramer-Rao bound and simulation show that the method here has better statistical performance. The simulated analysis also indicates that the accurate extraction of the diffraction coefficient of scattering center is restricted by signal to noise ratio, radar center frequency and radar bandwidth.     

The Fast Electromagnetic Analysis and RCS Reducing of Two Dimensional Complex Targets

Radar scattering characteristic of the aircraft is an important factor for its survivability. Wings are one of the important scattering sources on the aircraft. In order to reduce their RCS, the intense and powerful electromagnetic analysis is needed. For reducing the complexity, the wings can be viewed as a two dimensional large electric objects consisting of both conductors and inhomogeneous dielectrics. In this dissertation, we aim at a precision and efficiency method for numerical computing of two dimension objects. Moded wings and the RCS of the wings can be calculated in turn. The RCS results of different wing are compared and examined,     

The Fast Electromagnetic Analysis and RCS Reducing of Two Dimensional Complex Targets

Radar scattering characteristic of the aircraft is an important factor for its survivability. Wings are one of the important scattering sources on the aircraft. In order to reduce their RCS, the intense and powerful electromagnetic analysis is needed. For reducing the complexity, the wings can be viewed as a two dimensional large electric objects consisting of both conductors and inhomogeneous dielectrics. In this dissertation, we aim at a precision and efficiency method for numerical computing of two dimension objects. Moded wings and the RCS of the wings can be calculated in turn. The RCS results of different wing are compared and examined, and the stealth technology of wing is found out. Scattering mechanism are explained, which can give strong predictive power for stealth technology of aircraft.     

THE RELATIONSHIP BETWEEN THE EM ENERGY ABSORPTION OF HUMAN BODY AND THE INCIDENT DIRECTION AND POLARIZATION OF PLANE WAVE

The problems of EM energy absorption of human body irradiated by plane wave arediscussed by the Finite-Difference Time-Domain(FD-TD)method.The local Specific AbsorptionRates(SARs),the whole-body average SARs and the layer average SARs for the inhomogeneousblock model of human body with different incident direction and different polarization of theincident waves are calculated.The results show that the appearance of maximum EM energyabsorption is not always at the situation of the front incidence and the local SARs are moreimportant for the interaction of the EM fields with human body.All results provide more infor-mation about the electromagnetic dosimetry for human body.     

THE INVERSE ELECTROMAGNETIC SCATTERING OF INHOMOGENEOUS DIELECTRIC THIN TUBES

By using the method of Fourier series expansion, the inverse electromagnetic scattering problemof a 2- dimensional lossy dielectric body, of which the cross section is a narrow annulus, is studied. Theanalytic expressions of the electric parameters of a dielectric body are given in terms of the outsidesca,ttering field, and the simulative results are satisfactory.     

Progress of Expert Systems in Electromagnetic Engineering

It is urgent to solve various problems in electromagnetic （EM） engineering under the increasingly complicated environment. Some expert systems （ES） come into being just to keep up with the demand for solving these problems. Combined with the analysis of development orES technology and the development trend of EM engineering software in recent years, the application orES technology in EM engineering is discussed, and especially the progress of complete ES in electromagnetic compatible （EMC） is introduced.     

Overview： Electromagnetic Scattering from Ocean Surface

Understanding the sea surface scattering process is very important in the development of models to detect the target above or under the surface. In this paper, both the analytical and the numerical methods applied in sea surface scattering are summarized. Some important problems concerned in this field are discussed. For numerical study, edge effect brings artificial nonrealistic scattering and therefore must be suppressed. Different edge treatment methods are compared in this paper. Scattering of breaking wave surface at very low grazing angle always needs more attentions than other scattering problems. Some numerical results show the existence of the special phenomena at very low grazing angle, for example, the ＂sea spikes＂ and the Doppler splitting.     

Characteristic Mode Analysis: Application to Electromagnetic Radiation,Scattering, and Coupling Problems

Recent years, the theory of characteristic modes has emerged as a powerful analysis technique in antenna engineering, providing a means to reveal the natural resonant properties of objects and providing a variety of modal parameters. Based on these modal parameters, advanced techniques have been developed based on the theory of characteristic modes to address a wide range of electromagnetic radiation, scattering, and coupling problems. This review provides an overview of some of the latest chara...     

SOLVING THE PROPAGATION OF ELECTROMAGNETIC WAVE IN A SIMPLE TWO—DIMENSI8ONAL INHOMOGENEOUS MEDIUM BASED ON SYMPLECTIC GEOMETRICAL THEORY

A new symplectic geometrical high-frequency approximation method for solving the propagation of electromagnetic wave in the two-dimensional inhomogeneous medium is used in this paper. The propagating caustic problem of electromagnetic wave is translated into non-caustic problem by the coordinate transform on the symplectic space. The high-frequency approximation solution that includes the caustic region is obtained with the method combining with the geometrical optics. The drawback that the solution in the caustic region can not be obtained with geometrical optics is overcome by this method. The results coincide well with that of finite element method.     

A NEW METHOD FOR SOLVING DYADIC GREEN''''S FUNCTION OF ELECTROMAGNETIC FIELD

A new method for solving electromagnetic field boundary value problem is given.Byusing this method,the boundary value problem of the vector wave equation can be transformedinto the independent boundary value problem of scalar wave equations and the two additionalvector differential operations.All the dyadic Green's functions got by eigenfunction expansionof the dyadic Green's function can be got by this method easily and some of the dyadic Green'sfunctions for complex systems which are very difficult to get by the ordinary method have beengot by this new method.The dyadic Green's function for a dielectric loaded cavity is one of thegiven examples.     

BIBO Stability of Continuous Time Systems

In this paper, the problems of the stability analysis and BIBO stabilization for the switched systems are considered. Applying a stabilizing local state feedback to each subsystem, the sufficient conditions of the asymptotically stable and BIBO stabilization for the switched systems are obtained by means of the method of Lyapunov function and the method of inequality analysis.     

Error improvement of temporal discretization in TDFEM for electromagnetic analysis

Integral method is employed in this paper to alleviate the error accumulation of differential equation discretization about time variant t in Time Domain Finite Element Method （TDFEM） for electromagnetic simulation. The error growth and the stability condition of the presented method and classical central difference scheme are analyzed. The electromagnetic responses of 2D lossless cavities are investigated with TDFEM; high accuracy is validated with numerical results presented.