On the radiation field from an electric dipole in an anisotropic and compressible plasma medium

The radiation fields from an electric dipole in a homogeneous, anisotropic, and compressible plasma are considered. Using the Fourier transform method, the problem is formulated in terms of three scalar functions, each of which satisfies the two-dimensional inhomogeneous wave equation. Asymptotic expressions of the radiation fields are obtained for the integrals by the saddle point method of integration.     

Dialectric spherioid in anisotropic medium under the influence of uniform field

An exact solution of the electrostatic problem of a dielectric prolate spheroid placed in a magnetoionic medium under the influence of uniform field is presented. This is a first step toward obtaining a quasi-static solution of the corresponding problem of planewave scattering.     

Electromagnetic field of a horizontal electric dipole buried in a medium covering one-dimensionally anisotropic medium

The electromagnetic fields of a horizontal electric dipole buried in a medium covering one-dimensionally anisotropic medium are studied. There are three media, one-dimensionally anisotropic medium covered with a dielectric under the air. The electromagnetic field components are complex because of the multiple reflections from the up and down boundaries. The electromagnetic field components between air and one-dimensionally anisotropic medium are given, the trapped surface waves and lateral waves along the dielectric-anisotropic medium boundary are computed. The results have some practical applications in the communication in sea or lake above one-dimensionally anisotropic earth or sediments.     

Far field radiation from an arbitrarily oriented Hertzian dipole in the presence of a layered anisotropic medium

Far field radiation from an arbitrarily oriented Hertzian dipole for two-layered uniaxially anisotropic medium with a tilted optic axis is treated analytically by using the dyadic Green's function of the problem when the dipole is placed over or embedded in a two-layered uniaxially anisotropic medium. The radiation fields are evaluated using the steepest descent method. Parameter studies including anisotropy, layer thickness and dipole location are performed to investigate the effects of changing different variables on the radiation fields. Results of this work can be applied in microstrip circuits and antennas.     

Two-dimensional surface-wave diffraction from an arbitrary source in an anisotropic medium

It is shown that, if a parabolic function approximates closely to the relevant wavenumber surface, the surface-wave diffraction pattern radiated from any source is related, by a simple scale factor, to that launched by the same source into an isotropic medium. The argument, based on resolution of the source into an orthogonal Gaussian?Hermite mode set, may find application both in integrated optics and in the design of acoustic-surface-wave matched filters.     

Efficient numerical solution of unbounded field problems

An efficient numerical method for solving certain unbounded field problems is presented. The method uses both the differential and integral formulations of the field problem and combines the particular advantages of each. The results obtained from an application of the method to a 2-dimensional exterior Laplacian problem are compared with those obtained by other methods.     

Waves along a cylindrical "Grid-like" antenna in an anisotropic compressible plasma

In an anisotropic compressible homogeneous plasma, the dispersion equation of waves along an infinitely long cylindrical "grid-like" antenna is obtained analytically. Numerical solutions of this equation show that an external static magnetic field has great influence upon the anomalously dispersive region of the dispersion relation around the plasma frequency.     

Effective constitutive parameters for anisotropic and compressible media

It is shown that the macroscopic electromagnetic properties of an anisotropic and compressible medium can be described by an effective permittivity tensor and an effective `compressivity tensor?. A new set of three governing equations can be written, which put the solution of electromagnetic problems in such a medium on a systematic basis. A new `pressure-displacement current? is also defined.     

Radiation from a uniformly moving distribution of electric charge in an anisotropic, compressible plasma

The radiation characteristics of a linear distribution of electric charge moving with a uniform velocity in a homogeneous electron plasma of infinite extent are investigated for the case in which a uniform static magnetic field is impressed externally throughout the medium. The linear distribution of charge and its direction of motion are assumed to be parallel and perpendicular, respectively, to the direction of the external magnetic field. Of the two possible modes of waves of small amplitude, namely, the modified electromagnetic mode and the modified electron plasma mode, the uniformly moving charge distribution excites the modified electron plasma mode. The emitted radiation has no frequencies less than the plasma frequency. For a particular value of the ratio of the gyrotropic to the plasma frequency of the electrons, the frequency and the angular spectrum of the emitted radiation are determined for two values of the velocity of the charge.     

A quasi-wave method for determination of a general solution to the complex maxwell equations in an inhomogeneous anisotropic absorbing medium

A formal general solution to the homogeneous Maxwell equations is obtained in the form of a matrix asymptotic series for the case of a quasi-plane-layered medium in which complex tensors \(\hat \varepsilon \) and \(\hat \mu \) arbitrarily depend on Cartesian coordinate zand slowly change in the planes z=const. A recurrent system of matrix first-order linear ordinary differential equations for the coefficients of this series is derived. In contrast to the method of geometric optics, this solution, even in the first approximation, takes into account the wave polarization and has a wider range of application.     

On waves in an anisotropic plasma imbedded in a moving dielectric medium

The governing equations for electromagnetic fields in an anisotropic plasma imbedded in a moving dielectric medium are obtained. Examination of the wave and dispersion equations yields information on the elliptically or linearly polarized waves which may exist when the external magnetic field is parallel or perpendicular to the direction of motion, respectively.     

Dyadic Green's function for magnetic current source in compressible anisotropic plasma

By making use of the recently formulated compressivity tensor for anisotropic and compressible media, the dyadic Green's function for a magnetic current source in such media is derived. A new dyadic operator is defined, which makes possible the expression of the Green's function in a concise form.     

Electromagnetic field radiated by a point source in an anisotropic layer

The field of a point electromagnetic source localized in a homogeneous anisotropic coating of a perfect conductor is constructed by the Fourier method. The field in the anisotropic layer can be interpreted as a sum of ordinary and extraordinary waves (Felsen and Marcuvitz, 1973). The asymptotics of the electromagnetic field in the far zone is studied. Far from the surface, the main contribution is due to the outgoing spherical wave and near the coating the field is represented as the sum of waveguide modes contributions. Specific asymptotics appear in a vicinity of critical directions across which the number of waveguide modes changes.     

Second-order magnetization precession in an anisotropic medium. Part 1: Uniaxial anisotropy

A second-order precession of the magnetization vector in a normally magnetized magnetic plate with a uniaxial anisotropy whose axis is tilted at an angle to the plate normal is considered. Under the conditions for the orientational transition, precession pattern of the forced oscillation in the form of a large ring filled, along the ring generator, with small rings is obtained. A relationship between the observed crowding and sparseness of small rings and the tilt of the anisotropy axis to the normal to the plate plane is established and explained on the basis of the potential-energy model. It is shown that the crowding and sparseness can be compensated by a constant transverse field. It has been found that the phenomenon is critically sensitive to the axis orientation and to the value of the anisotropy constant as well as to the strength of the constant field. It is indicated that the observed phenomena can be put to practical use.     

Electromagnetic radiation in drifting tellegen anisotropic medium

The electromagnetic waves in a homogeneous, drifting, general, linear, anisotropic Tellegen medium are evaluated in terms of the electric and magnetic current density sources. The fields are shown to be expressible in terms of the characteristic waves of the medium. The solution is in agreement with the particular cases for a nondrifting medium worked out originally by Bunkin.     

The field of a dipole enclosed in an elliptic anisotropic plasma cylinder

The boundary value problem for the field of an electric dipole enclosed in a thin elliptic anisotropic plasma cylinder with a vacuum cavity is considered. A solution to the problem is obtained and analyzed. The influence of a magnetic field and the cavity of variable size on the resonance electromagnetic field is studied in the case when the shape of the plasma cylinder’s cross section varies. The effect is compared to that observed in the case of a circular plasma cylinder.     

各向异性介质中的菲涅耳公式及应用

本文给出了在空气与各向异性介质分界面上反射光、折射光与入射光振幅间的关系及其在测定各向异性介质主折射率中的一个应用。     

Numerical solution of dipole radiation in a compressible plasma

The electric current and surface electron distributions for a dipole antenna in a compressible plasma are solved numerically. The results also include the input impedance and the upper limit of the driving voltage below which the small signal approximation is valid.     

阻抗球涂覆均匀等离子体电磁散射的解析解

均匀无源各向异性等离子体介质中的电磁场是第一、第二类各向异性等离子体球矢量波函数的线性叠加,在阻抗球表面满足阻抗边界条件、等离子体与自由空间表面满足电磁场切向连续的边界条件,可得出各向异性等离子体涂覆阻抗球在平面波入射情况下,均匀等离子体介质中电磁场用各向异性等离子体球矢量波函数表示的系数满足的矩阵方程,进而得出散射场由球矢量波函数展开的展开系数和雷达散射截面.数值计算的结果表明:当阻抗球的半径趋于0时,其结果和均匀各向异性等离子体球对平面波的电磁散射结果相同.最后还给出了一些数值计算的结果.     

Diffraction by an anisotropic dielectric half-plane: a uniformasymptotic PO solution

A uniform solution is proposed to, describe the diffraction by a penetrable anisotropic dielectric halfplane illuminated at normal incidence by an electromagnetic plane wave. Resorting to second-order boundary conditions on a sheet simulating a special type of anisotropic dielectric thin layer, a physical optics (PO) approximation for the induced electric and magnetic surface currents is derived. Then, a uniform asymptotic evaluation of the corresponding radiation integral provides the diffracted field in terms of the standard transition function relevant to the uniform theory of diffraction. The effectiveness of the solution is proved by many numerical tests