Equations for wave propagation in an inhomogeneous compressible plasma

Equations for wave propagation in an inhomogeneous warm plasma are given, which emphasise the separation into quasi-electromagnetic and quasidynamical constituents. The equations are similar to those encountered in ionospheric coupling between ordinary and extraordinary modes.     

Radiation through an inhomogeneous plasma covering a ground plane

Electromagnetic radiation from a slot-excited ground plane covered by a plasma layer with exponentially decreasing electron density is considered. It is found that the far-field radiation pattern is simply related to that found for the case where the layer is absent.     

Transient response of an inhomogeneous MOS transmission line

Analytical solutions for charge transport in inhomogeneous MOS transmission lines are obtained. The line is assumed to have an initial exponential doping profile. An exact solution is obtained for the case of a constant charge being injected into the structure. An approximate solution is obtained for the case of a fixed voltage being applied at one end of the structure.     

Scattering cross-section of an inhomogeneous plasma cylinder

Scattering of em waves by the plasma cylinder is of significance in radar target detection, plasma diagnosis, etc. This paper discusses the general method tocalculate the scattering cross-section of em waves from a plasma cylinder which is radially inhomogeneous and infinitely long. Numerical results are also provided for several plasma density profiles. The effect of the electron density distribution on the scattering cross-section is investigated.     

Time domain analysis of transient propagation in inhomogeneous magnetized plasma using Z-transforms

The electromagnetic propagation through an inhomogeneous magnetized plasma slab is studied using the Z-transform formulation of the Finite-Difference Time-Domain（FDTD） method. The direction of electromagnetic propagation is parallel to the biasing magnetic filed. To validate the Z-transform algorithm, the reflection and transmission coefficients for the right-hand circularly polarized wave of the homogeneous magnetized plasma slab are computed by means of discrete Fourier transform. The comparison between the reflection and transmission coefficients of the homogeneous plasma slab and analytical values indicates that Z-transform algorithm is very accurate. When the plasma frequency varies according to the square root and parabolic relations, the reflection and transmission coefficients of the inhomogeneous magnetized plasma slab are computed.     

Electromagnetic scattering by an exponentially inhomogeneous plasma sphere

The mathematical analysis of electromagnetic wave scattering by radially inhomogeneous spherical objects is treated. Numerical integration of the differential equations for the separated radial wave functions has been carried out for the case of a plasma with an exponential electron density gradient, Parametric calculations of bistatic scattering have given many interesting results. The range of validity of the Born approximation has been demonstrated by comparing it with computed results.     

Harmonic generation by an electromagnetic wave in an inhomogeneous isotropic plasma

The generation of harmonic waves by a plane electromagnetic wave normally incident on a collision-free plasma with a linear density profile is considered. The solution for the primary wave in the plasma region is first obtained, and nonlinear polarization currents for the higher harmonics are expressed in terms of the lower harmonic fields by a perturbation method. The analysis shows that the plasma excites a longitudinally oscillating second harmonic electric field which is totally confined inside the plasma and has a singularity. The third harmonic wave excited in the plasma, however, radiates back into free space, although the effect is negligibly small in a quasi-homogeneous limit. The amplitude of this radiated field oscillates as a function ofomega^{3}, and the electron density gradient has little effect on it.     

Pulsed beam propagation in inhomogeneous medium

Pulsed beams (PB) are localized space-time wavepackets that propagate along ray trajectories. This paper deals with general PB solutions in inhomogeneous medium. We derive an approximate form of the time-dependent wave equation (termed the wavepacket equation), valid within a moving space-time window that brackets the wavepacket, and then construct its exact PB solutions. This is done first in a free-space and latter on in a general smoothly varying medium where the propagation trajectories are curved. We also determine the reflection and transmission laws at curved interfaces. These new PBs are related to the so called complex source pulsed beams which are exact solutions in free-space, but they have more general form that admits wavepacket astigmatism and medium inhomogeneity. Since they maintain their wavepacket structure throughout the propagation process they are identified as eigen-wavepacket solutions of the time dependent wave equation     

Surface waves of an inhomogeneous plasma layer in a waveguide

Surface waves of a smoothly inhomogeneous plasma layer in a waveguide are investigated. The complex frequency spectra and structures of the surface wave field are determined analytically and numerically. It is shown that various types of surface waves exist. It is established that the surface waves of a plasma layer with sharp boundaries change and even disappear when the boundaries are smeared.     

Electromagnetic scattering by an inhomogeneous plasma anisotropic sphere of multilayers

Electromagnetic scattering by an inhomogeneous plasma anisotropic sphere is formulated and obtained, where the inhomogeneous plasma anisotropic sphere is divided into (s-1) homogeneous anisotropic spherical layers. The electromagnetic fields in the inner spherical multilayers and outer free space of the inhomogeneous plasma anisotropic spherical structure can be expanded in terms of the spherical vector wave functions in plasma anisotropic medium and in isotropic medium, respectively. By applying the continuous boundary conditions of electromagnetic fields on the spherical interfaces of the (s-1)-layered homogeneous anisotropic plasma medium, the unknown expansion coefficients of fields in the multilayered plasma spherical structure are obtained, and then the electromagnetic field distributions are calculated. Numerical results for the very general inhomogeneous plasma dielectric material sphere are given and the data in a special case are obtained using the present method and the method of moments accelerated with the conjugate-gradient fast-Fourier-transform approach and compared to each other to verify the correctness and applicability of the present analysis.     

Wave propagation in transversely inhomogeneous dielectric waveguide

Guided mode propagation in inhomogeneous dielectric waveguides is calculated by a series expansion method which is particularly useful for analysing single-mode dielectric waveguides. As an example we estimate the error in the phase constant of waveguides whose dielectric constant profile is not necessarily near-parabolic.     

Wave propagation in transversely inhomogeneous dielectric waveguide

The problem of guided mode propagation in inhomogeneous dielectric waveguides is solved by a Cheby?shev-like economised power-series approach. The formulation involved is shown to be quite simple. Numerical examples using a `P?schl-Teller? medium demonstrate the accuracy of this approach.     

Electromagnetic-wave propagation along radially inhomogeneous dielectric cylinders

The results of a computational method for determining the propagation characteristics of a radially inhomogeneous dielectric cylinder are presented. A continuous variation in permittivity is represented by means of a staircase function, and the corresponding propagation problem for a cylindrically stratified dielectric is solved using a digital computer. For refractive-index profiles commonly used in optical waveguides, the propagation coefficient differs negligibly from the asymptotic value when the number of layers is equal to five.     

Scattering by an infinite cylinder coated with an inhomogeneous and anisotropic plasma sheath

The problem of the interaction of an incidentHwave with an infinite conducting cylinder coated with an inhomogeneous and anisotropic plasma sheath is treated analytically. Numerical results for the farfield pattern of the scattered field as well as the backscattering cross sections are presented for various interesting ranges of the parameters involved. Detailed discussion of the effects of the impressed static magnetic field, the sheath thickness, and the density and profile of the plasma sheath on the scattered wave is also presented. A parabolic electron density profile is assumed.     

High-frequency scattering from a conducting cylinder with an inhomogeneous plasma sheath

The high-frequency backscattering characteristics of an infinite conducting cylinder enveloped in a radially inhomogeneous plasma sheath are studied in detail. When the permittivity of the sheath has a general power-law dependence,epsilon(rho) = epsilon(rho_{0}) (rho/rho_{0})^{p}, whererho_{0}is the outer radius of the sheath andpis any real numberneq -2, the wave function in the plasma is expressible in terms of Bessel functions of a fractional order. The slowly convergent series form of the backscattering coefficient is first recast into an integral by means of the Watson transformation, which is then asymptotically evaluated by the method of stationary phase. The mathematical result is conveniently interpreted in terms of geometrical optics by identifying the contributions due to the central ray and the trapped "interrupted" and "uninterrupted" rays. In contrast to the rather unpredictable and violent backscattering coefficient variations with frequency when a conducting cylinder is clad in a homogeneous plasma sleeve, the change in the coefficient for the same cylinder enveloped in a plasma sheath with a power-law radial inhomogeneity is much more smooth and, in most cases, the approximate locations of the maximums and minimums can be predicted. Numerical results showing the dependence of the backscattering coefficient on the type of power-law inhomogeneity, sheath thickness, and permittivity level are presented in graphical form.     

利用辛几何理论求解电磁波在非均匀媒质中的传播

提出了一种基于辛几何的高频近似的新方法，并用此方法求解了电磁波在一非均匀媒质中的传播问题。通过辛空间上的坐标变换，使电磁波传播中的焦散问题转化为非焦散的问题，并结合几何光学的方法，求得了包括焦散区在内的高频近似解。解决了几何光学法无法在焦散区求解的问题，还可以推广到二维及三维的情况。     

Time-domain analysis of propagation in inhomogeneous anisotropiclossy slabs

An equivalent-transmission-line-circuit (ETLC) model is developed to discuss the transient propagation problem of a plane wave in inhomogeneous, anisotropic, and transversely lossy slabs. This model is based on the analogy between the field equations and the coupled transmission line equations. By establishing the analogy, suitable lumped-circuit models are proposed to treat the equivalent transmission lines, which may then be solved by the circuit simulation program. In this study, the accuracy and convergence of the lumped-circuit models are examined. The ETLC model is then applied to discuss the propagation problem in anisotropic graphite/epoxy laminates with numerical results presented to show the transient responses due to the electromagnetic pulse and Gaussian pulse