摘要:

A systematic formulation of constitutive relations for general field systems is explored, which takes into account the main material features. These are dispersion, inhomogeneity, which can be present in linear and nonlinear systems. There are two main difficulties associated with existing representations: Dispersion is usually referred to in the spectral domain, while inhomogeneity is obviously a spatiotemporal phenomenon; moreover, the existing representations involve spatiotemporally dependent integrals, and those suggest non-local interaction which raises relativistic causality issues. The present approach introduces new representations in terms of Volterra differential operators, which obviate these difficulties within the domain of their validity, allowing for spatiotemporal representation of both dispersion and inhomogeneity, in linear and nonlinear systems. Minkowski's methodology for representation of material properties in the presence of moving media is re-examined in view of the new constitutive relations, especially as regards Maxwell's equations of Electrodynamics.

ISSN:0920-5071    

DOI:10.1163/156939300X00626

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Full-wave electromagnetic interaction of two regular arrays of dipole scatterers is considered. To calculate the local field acting on a particle in the arrays a method analogous to the Lorenz-Lorentz approach is used. The contributions from distant and near scatterers are separately evaluated. The contribution from the near particles is determined by the direct summation of the dipole fields. Distant particles are replaced by a continuous distribution of dipole moments. The full-wave formulas representing the fields created by a continuous distribution sheet with a circular hole of a certain radius are obtained for the case when the observation point is located on the hole axis at an arbitrary distance from the hole center. Numerical examples illustrating the physical aspects of the obtained results are given. As application examples, the reflection from double arrays of magnetically polarizable particles are considered. This is relevant to the design of radar absorbing coverings based on thin layers of artificial magnetics. An explicit analytical solution for the reflection coefficient is given.

ISSN:0920-5071    

DOI:10.1163/156939300X00635

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Partially adaptive antennas are very attractive solution to enhance the desired signal and suppress interference, in communication and radar applications, at a minimum cost. A new design technique, based on the genetic algorithm, has been devised, in order to find the minimum number of controlled elements and their locations in a given linear array. The new technique has been used to steer a given number of nulls towards interfering signal directions and simultaneously reduce the number of controlled elements. The technique is demonstrated using 16-element uniform and Chebyshev arrays. The null steering method used in this work is element position perturbations. Results are given for one and four steered nulls. The results demonstrate the capability of the new technique to steer the array nulls while minimizing the number of controlled elements in the array.

ISSN:0920-5071    

DOI:10.1163/156939300X00644

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The method of multiple-scale perturbation method is developed in a new way to study the propagation of pulses through an optical fiber described by the perturbed Nonlinear Schrödinger's equation. We show that, by newly introducing a proper definition of the phase of the soliton for the first time, one can obtain the corrections to the pulse where the usual soliton perturbation approach fails. A comparison is made with results obtained by other methods in various other works as well as with numerical simulations.

ISSN:0920-5071    

DOI:10.1163/156939300X00653

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In this paper an asymptotic solution to the wave equation for a thin curved layer with periodically inhomogeneous permittivity is derived. The wave equation and field components are expanded in the thickness h of the layer. A propagator, i.e., an operator that maps the fields from one side of the surface to the other, is derived. This propagator is used to derive a higher order impedance boundary condition. The solution is expressed as an asymptotic expansion in the thickness h for a layer coated on a perfect electric conductor (PEC). The problem treated is two-dimensional and the TE case is considered. A couple of numerical examples are given with comparisons to solutions obtained by integral equation based techniques.

ISSN:0920-5071    

DOI:10.1163/156939300X00662

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A centered-inclined waveguide slot coupler has been modeled as a series-series ideal transformer since ever. Actually this equivalent circuit is not exact, but only approximate though, for resonant couplers, the approximation being usually very good. The approximation gets worse as the slot length moves away from resonance, and is completely useless for off-resonant slots, needed in shaped-beam slot arrays. In this paper, an in-depth discussion of the properties of such a slot coupler and of the admissible approximations allows to quantitatively set the limit of the "standard" model, and leads to suitable generalizations to non-resonant slots as well. The resulting equivalent circuits are compared against full-wave simulated data and result to be very accurate in a quite large frequency range.

ISSN:0920-5071    

DOI:10.1163/156939300X00671

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The class of self-dual linear bi-anisotropic media can be defined in three different ways. It consists of media which are invariant in a duality transformation, allow factorization of the second-order dyadic Helmholtz operator in terms of two first-order dyadic operators and allow decomposition of fields and sources in a way that is an extension of the Bohren decomposition for chiral media. It is shown that the Green dyadic can be solved in closed analytic form for any self-dual bi-anisotropic medium and its general expression is given in terms of the self-dual decomposition. This generalizes previous results where special cases of self-dual media were considered.

ISSN:0920-5071    

DOI:10.1163/156939300X00680

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939300X00699

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939300X00707

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor