Incoming Electromagnetic Wave Research Articles

Material parameters characterization for arbitrary N-sided regular polygonal invisible cloak

Arbitrary N-sided regular polygonal cylindrical cloaks are proposed and designed based on the coordinate transformation theory. First, the general expressions of constitutive tensors of the N-sided regular polygonal cylindrical cloaks are derived, then there are some full-wave simulations of the cloaks that are composed of inhomogeneous and anisotropic metamaterials, which will bend incoming electromagnetic waves and guide them to propagate around the inner region; such electromagnetic waves will return to their original propagation directions without distorting the waves outside the polygonal cloak. The results of full-wave simulations validate the general expressions of constitutive tensors of the N-sided regular polygonal cylindrical cloaks we derived.

Photoionization of the outer electrons in noble gas endohedral atoms

We suggest a prominent modification of the outer shell photoionization cross section in noble gas (NG) endohedral atoms NG@C n under the action of the electron shell of fullerene C n . This shell leads to two important effects: a strong enhancement of the cross section due to fullerene shell polarization under the action of the incoming electromagnetic wave and to prominent oscillation of this cross section due to the reflection of a photoelectron from the NG by the fullerene shell. Both factors lead to powerful maxima in the outer shell ionization cross sections of NG@C n , which we call giant endohedral resonances. The oscillator strength reaches a very large value in the atomic scale, 25. We consider atoms of all noble gases except He. The polarization of the fullerene shell is expressed in terms of the total photoabsorption cross section of the fullerene. The photoelectron reflection is taken into account in the framework of the so-called bubble potential, which is a spherical δ-type potential. It is assumed in the derivations that the NG is centrally located in the fullerene. It is also assumed, in accordance with the existing experimental data, that the fullerene radius R C is much larger than the atomic radius r A and the thickness ΔC of the fullerene shell. As was demonstrated recently, these assumptions allow us to represent the NG@C n photoionization cross section as a product of the NG cross section and two well-defined calculated factors.

Analytical design of conformally invisible cloaks for arbitrarily shaped objects

To design conformally invisible cloaks for arbitrarily shaped objects, we use the nonuniform rational B -spline (NURBS) to represent the geometrical modeling of the arbitrary object. Based on the method of optical transformation, analytical formulas of the permittivity and permeability tensors are proposed for arbitrarily shaped invisible cloaks. Such formulas can be easily implemented in the design of arbitrary cloaks. Full-wave simulations are given for heart-shaped invisible cloaks and perfectly electrical conducting (PEC) objects, in which we observe that the power-flow lines of incoming electromagnetic waves will be bent smoothly in the cloaks and will return to their original propagation directions after propagating around the object. We also show that the scattered field from the PEC object coated with the invisible cloak is much smaller than that from the PEC core. The application of NURBS in the design of arbitrary cloaks shows transformation optics to be a very general tool to interface with commercial softwares like 3D STUDIOMAX and MAYA.

Analytic characterization of a resonance surface in an experimental ECR setup

In this work we give a detailed description of some quantities related to the ECR phenomenon in a typical ion source. In particular, we describe the ECR surface area, the volume associated with the resonance space, and their dependence with respect to the frequency of the electromagnetic wave feeding the source. These are useful in the study of the experimental results observed in the ion sources with respect to the frequency of the incoming electromagnetic wave. Moreover, promising techniques for the increasing of the source performances consider the frequency tuning of the supplied electromagnetic wave, as well as the use of broadband microwave radiation for the apparatus feeding. The theoretical modelling used to describe these techniques by a statistical approach requires the efficiency of the ECR process and its dependence on frequency to be taken into account. In this context, the knowledge and formalization of the quantities described here can be very important.

Giant resonances of endohedral atoms

It is demonstrated for the first time that the effect of a fullerene shell on the photoionization of a “caged” atom in an endohedral can result in the formation of giant endohedral resonances or GER. This is illustrated by the concrete case of the Xe@C60 photoionization cross section that, at 17 eV, exhibits a powerful resonance with total oscillator strengths of about 25. The prominent modification of the 5p6 electron photoionization cross section of Xe@C60 takes place due to the strong fullerene shell polarization under the action of the incoming electromagnetic wave and the oscillation of this cross section due to the reflection of the photoelectron from Xe by the C60. These two factors transform the smoothly decreasing 5p6 cross section of Xe into a rather complex curve with a powerful maximum for Xe@C60, with the oscillator strength of it being equal to 25. We also present the results for the dipole angular anisotropy parameter that is strongly affected by the reflection of the photoelectron waves, but not modified by C60 polarization.

Arbitrarily elliptical–cylindrical invisible cloaking

Based on the idea of coordinate transformation (Pendry, Schurig and Smith 2006 Science 312 1780), arbitrarily elliptical–cylindrical cloaks are proposed and designed. The elliptical cloak, which is composed of inhomogeneous anisotropic metamaterials in an elliptical-shell region, will deflect incoming electromagnetic (EM) waves and guide them to propagate around the inner elliptical region. Such EM waves will return to their original propagation directions without distorting the waves outside the elliptical cloak. General formulations of the inhomogeneous and anisotropic permittivity and permeability tensors are derived for arbitrarily elliptical axis ratio k, which can also be used for the circular cloak when k = 1. Hence the elliptical cloaks can make a large range of objects invisible, from round objects (when k approaches 1) to long and thin objects (when k is either very large or very small). We also show that the material parameters in elliptical cloaking are singular at only two points, instead of on the whole inner circle for circular cloaking, which are much easier to be realized in actual applications. Full-wave simulations are given to validate the arbitrarily elliptical cloaking.

Planar Passive Electromagnetic Deflector for Millimeter-Wave Frequencies

A novel passive planar structure is proposed that is able to deflect an incoming electromagnetic (EM) wave into a desired direction. The direction of the outgoing EM wave is determined by the design of this deflector. The deflector can be used to extend coverage of a steerable source with limited scan capabilities. It consists of elements which alter the phase distribution of the incoming EM wave. It is called deflector, because it is designed primarily to deflect incoming EM waves, as opposed to focusing as in the case of the array lens. The design of a compact phase-shifting deflector element is given. Two deflectors have been designed and constructed. Measurements show good agreement with simulations.

STEREO/Waves Goniopolarimetry

The STEREO/Waves experiment is dedicated to the study of inner heliosphere radio emissions. This experiment is composed of a set of two identical receivers placed on each of the two STEREO spacecraft. The STEREO/Waves receivers have instantaneous Goniopolarimetric (GP) capabilities (also referred to as direction-finding capabilities). This means that it is possible to retrieve the direction of arrival of an incoming electromagnetic radio wave, its flux and its polarization. We review the state of the art of GP-capable radio receivers and available GP techniques. We then present the GP capabilities of the STEREO/Waves experiment. We finally show some GP results on solar Type III radio bursts, using data recorded with the Cassini/RPWS/HFR, which are very similar to the STEREO/Waves data.

Influence of an extended source on goniopolarimetry (or direction finding) with Cassini and Solar Terrestrial Relations Observatory radio receivers

In a recent paper, Cecconi and Zarka (2005) provided analytical goniopolarimetric inversions, which allow us to retrieve the direction of arrival of an incoming electromagnetic wave, its flux, and its polarization state, also referred as direction finding inversions, to be used with measurements acquired with a system of electric dipole antennas on a three‐axis stabilized spacecraft such as the Cassini/Radio and Plasma Wave Science/High Frequency Receiver or the Solar Terrestrial Relations Observatory/Waves receivers. In the present study, we establish the expressions of the measurements (autocorrelations and cross correlations) in the case of an extended source. We also analyze the effect of an extended source on the outputs of the analytical inversions presented in the former paper, which are supposing a point radio source. We show that for a source with an angular half width smaller than 5°, the induced biases are not significant.

The SVM-Based Smart Antenna for Estimation of the Directions of Arrival of Electromagnetic Waves

Microwave systems for object detection and imaging usually illuminate a given scene and measure the reflected signals. One of the most important tasks is a rapid and efficient detection of the angular positions of the scatterers present in the scene. This task can be accomplished by designing a smart antenna composed of multiple receiving elements, which is able to estimate the angles of incidence of the incoming electromagnetic waves. In this paper, a new efficient method based on a support vector regression is proposed for the detection of arriving electromagnetic waves scattered by objects located both in the far-field and near-field regions of the smart antenna. The effectiveness of the proposed approach is evaluated by means of several numerical simulations

Direction finding and antenna calibration through analytical inversion of radio measurements performed using a system of two or three electric dipole antennas on a three‐axis stabilized spacecraft

We present an analytical inversion method to achieve direction‐finding (DF) (i.e., retrieve the direction of arrival of an incoming electromagnetic wave, its flux, and its full polarization state) using radio measurements performed using a system of two or three electric dipole antennas on a three‐axis stabilized spacecraft. The Radio and Plasma Wave Science (RPWS) radio receiver on board Cassini includes such instantaneous DF capabilities, and so does the Solar Terrestrial Relations Observatory (STEREO) Waves radio receiver. We also present an analytical solution of the inverse problem which consists of calibrating the electric dipole orientations and effective lengths using a known radio source. Error sources (imperfect knowledge of antenna parameters, digitization errors, signal to noise ratio, etc.) and their propagation through the analytical inversion have been studied. The typical expected accuracy of our DF inversion is 1 dB [V2/Hz] for flux measurements, about 1–2° for source position and a few percent for degrees of polarization. For the antenna calibration procedure the expected accuracy is of the order of 2° on antenna direction and of 1% on antenna length. We define the data selection criteria to be used during both DF analysis and antenna calibration. We also discuss the limitations of the methods and the ways to improve their accuracy.

Field representation inside arbitrary linear optical media by single surface currents

Recently a novel method has been proposed for the calculation of the scattering of an incoming electromagnetic wave by an arbitrarily shaped photonic crystal. The method rests on the representation of an arbitrary electromagnetic field inside a volume V by a fictitious surface current distribution along the boundary of this volume which acts as a source for a point response tensor for the medium. The validity of such a representation is rigorously proven.

Influence of Sensor Location and Tank Size on Determination of Discharge Type Based on PD Electromagnetic Waves Propagation in GIS

The authors have studied diagnostic technique of gas insulated switchgear (GIS) using partial discharge (PD) induced electromagnetic wave measured by UHF sensors. So far, we have proposed to discriminate discharge type by introducing amplitude ratio Rp: the positive peak value Vp+ to the negative one Vp- of the first wave of incoming electromagnetic wave measured with UHF sensors. In this paper, we discuss electromagnetic wave radiated from simulated pulse and PD measured with disk-type UHF sensors and built-in sensors consisting of a metal ring embedded in epoxy spacer of GIS. The shape of electromagnetic wave measured by the built-in sensor was distorted and high frequency components attenuated through a spacer in comparison with signal measured with the UHF sensor. It was suggested that the spacer may play the role of a low pass filter. Moreover, we proposed to discriminate discharge type based on the first wave of electromagnetic wave measured with the built-in sensors. We also investigated frequency spectrum of propagating UHF signals in GIS with different tank size by finite difference time domain (FD-TD) method with focusing on the influence of higher-order modes.

Angular superposition method and its application in the concept of the antiradar missile homing head

In this paper the systems of classic passive radar detection of radar targets are analyzed and the requests of superposition of two very close radar targets are defined. Also, there are analyzed reference methods of superposition based on the angle determination of incoming electromagnetic waves by waves sampling and determination of signal power spectrum as a function of space frequency in the presence of angular noise (clutter). By sampling a number of footprints of signals and by the estimation of the space frequency and the co variation matrix of received useful signals and noise, it is possible to repeat accurately necessary information about the resolution of two close targets at the sensor of the antiradar missile homing head. After comparing required and gained parameters: accuracy of direction standard deviation of direction, accuracy of separation of two sources and probability of reliable separation, it is recommended in the paper to use a modified method of maximum entropy, as the best method for the separation of two angular very close targets that are seen by the homing head of the antiradar missile.

A new formalism for time-dependent electromagnetic scattering from a bounded obstacle

In this paper a time-dependent three-dimensional electromagnetic scattering problem is considered. Let R3 be the three-dimensional real Euclidean space filled with a medium of electric permittivity e, magnetic permeability μ and zero electric conductivity. The quantities e, μ are positive constants and there are no free charges in the space and the free current is taken to be zero. Let Ω⊂R3 be a bounded simply connected obstacle with a locally Lipschitz boundary ∂Ω, that is assumed to have a nonnegative constant boundary electromagnetic impedance. The limit cases of perfectly conducting and perfectly insulating obstacles are studied. An incoming electromagnetic wave packet that hits Ω is considered, and a method that solves the Maxwell equations to compute the corresponding electromagnetic field scattered by Ω as a superposition of time harmonic electromagnetic waves is proposed. These time-harmonic electromagnetic waves are the solutions of exterior boundary-value problems for the vector Helmholtz equation with the divergence-free condition and they are computed with an `operator expansion' method that generalizes the method presented by L. Fatone et al.[J. Math. Phys. 40 (1999) 4859–4887]. The method proposed here is computationally very efficient. In fact, it is highly parallelizable with respect to time and space variables. Several numerical experiments obtained with a parallel implementation of the method are shown. The numerical results obtained are discussed from a numerical and a physical point of view. The quantitative character of the numerical experiments shown is established. The website: http://www.econ.unian.it/recchioni/w4/ contains some animations relative to the numerical experiments.

Integral equations via saddle point problems for time-harmonic Maxwell's equations

We propose a new system of integral equations for the exterior time harmonic Maxwell's equation. This system is derived first from elementary manipulations of classical equations then by the minimization of a quadratic functional associated to incoming and outgoing electromagnetic waves. We analyze the inf–sup condition and various penalized problems related to this system. Then we prove that an iterative algorithm for the solution of the system of integral equations is convergent. Other numerical issues are also discussed.

Nonlinear interaction of electromagnetic pulses with an electron–positron plasma––a coupled NLS equation

Nonlinear interaction of strong electromagnetic pulse with an electron–positron plasma is analysed. A dispersion relation is deduced which can be used to analyse the parametric instabilities due to nonlinear coupling between high frequency and low frequency motions. It is shown that the electromagnetic wave envelope is governed by a coupled nonlinear Schrödinger equation which also possesses solitary wave like solutions. The dispersion relation turns out to be nonlinear being dependent on the incoming electromagnetic wave amplitude A → 0 . The growth or decay calculated as a function of this amplitude shows a saturation type behaviour for fixed temperature, whereas it goes to zero with temperature for a fixed value of the amplitude A → 0 . The amplitude of the nonlinear wave also exhibits a saturating behaviour with respect to A → 0 . So the nonlinear mode of propagation and interaction in an electron–positron plasma shows a remarkable feature quite distinct from the linear mode.

Large photonic band gap's in one-dimensional multilayer structures

A one-dimensional photonic lattice constructed from a material possessing a higher value of dielectric constant has been studied under the consideration of photonic band gap, filling fraction, and the competition of different transmission mechanism of the incoming electromagnetic waves. A special attention has been paid to the localized state introduced by the introduction of defect in our multilayer structure.

UHF法で測定された電磁波第一波の振幅比に基づくGIS絶縁異常の診断

UHF法で測定された電磁波第一波の振幅比に基づくGIS絶縁異常の診断

Explicit Matrix Formulation for the Analysis of Synthetic Linearly and Non Linearly Loaded Materials in Fdtd - Abstract

We present a new matrix differential equation formulation for the analysis of the response of linearly and non linearly loaded molecules to an incoming electromagnetic wave. The molecule is defined as an electrically small dipole or loop antenna connected to an electronic circuit called the load. Because we have a Maxwell FDTD code, we use a finite difference scheme to solve the differential equations, which greatly simplifies the problem. If the load is linear, a simple linear system of update equations can easily be derived from the system of differential equations describing the behavior of the load circuit. This approach leads to a natural choice for the intermediate unknowns in the use of the Auxiliary Differential Equation method, and gives a fully explicit matricial update equation. If the load contains one or more non linear devices, this method can be generalized and leads to the resolution of a system of non linear update equations with a simple Newton Raphson or Runge Kutta algorithm. Several numerical examples are shown, for dielectric molecules.