Electromagnetic Field Propagation Research Articles

Characterization of Novel Chip Temperature-Sensing Device Using Mn-Substituted Li–Zn–Cu Ferrite

It has been very difficult to develop a miniaturized temperature sensor device using the conventional temperature-sensitive ferrites, such as Mn-Zn ferrite, which is due to difficulty of the high-frequency operation, because of their low natural resonance frequency (below 1 MHz) and low electrical resistivity (around 102-104 Omegamiddot cm). The authors have recently developed a polycrystalline Mn-substituted Li-Zn-Cu ferrite with a high natural resonance frequency beyond 10 MHz and high resistivity over 106 Omegamiddot cm, which exhibited strong temperature-dependent magnetic properties. It was considered that the transmission-line device using a new temperature-sensitive ferrite as an electromagnetic-field propagation substrate enables us to obtain a novel chip temperature-sensing micro device, because of the possibility of high-frequency operation due to a high resonance frequency and high resistivity of the new ferrite. We have simulated a quarter-wavelength resonator using the Mn-substituted Li-Zn-Cu ferrite substrate and its temperature-dependent properties. Since the quarter-wavelength transmission-line resonator includes distributed inductance and capacitance depending on the temperature-sensitive electromagnetic property of the ferrite substrate, this type of device operates as an integrated LC resonator-type temperature sensor. In this study, the integrated resonator-type temperature sensor using a spiral strip-line structure with the Mn-substituted Li-Zn-Cu ferrite substrate was fabricated, and its temperature-dependent characteristics were evaluated.

Propagation of light fields with radial or azimuthal polarization distribution at a transverse plane

In terms of the angular spectrum representation, general expressions are given to describe the free-space propagation of electromagnetic fields with radial or azimuthal polarization structure at a transverse plane. The transverse distributions of the radial, azimuthal and longitudinal components of these fields are also analysed. In particular, the on-axis behavior upon free propagation is studied. Furthermore, the special but important case of those fields that retain their polarization character (radial or azimuthal) under propagation is also considered. The analytical results are illustrated by application to some examples.

Dielectric permittivity superlattice formation

A dielectric medium consisting of roughly polarized molecules has been treated as a 3D disordered spin system (spin glass). Having in view the study of the statistical properties of this system on a micrometer scale and nanosecond time scale of a standing electromagnetic wave, a microscopic approach has been developed. Using the Birkhoff ergodic hypothesis, the initial 3D spin problem is reduced to two conditionally separate 1D problems along the external electromagnetic field propagation. The first problem describes a disordered N-particle quantum system with relaxation in the framework of a Langevin-Schrödinger (L-Sch)-type equation, while the second one describes a steric disordered spin-chain system. The statistical properties of both systems were investigated in detail. Based on these constructions, the coefficient of polarizability related to the collective orientational effects was calculated. The Clausius-Mossotti relation for the dielectric constant was generalized. Taking into account the generalized Clausius-Mossotti relation, a generalized equation for the dielectric permittivity function has been found. A simple formula was derived for the dielectric permittivity function in the X-ray frequency range, which can be larger than unity on the micrometer scale and nanosecond time scale.

A Coherent Model of Forest Propagation— Application to Detection and Localization of Targets Using the DORT Method

We study the propagation of electromagnetic fields in forest media in a frequency band between 100 and 300 MHz. We develop an exact coherent model in order to compute the electromagnetic field of a received wave after multiple scattering from the elements of the medium, in and outside the forest. We propose simplifications for the model of the forest and approximations for the electromagnetic method to reduce the computing time. We use and simulate a DORT based method to detect and locate a hidden target in the medium. We develop this method to adapt it to a real configuration and we apply it to measurements in anechoic chamber.

Dynamics of electromagnetic pulses with wide spectra in semiconductor superlattices

We considered the Maxwell equations for electromagnetic-field propagation in a solid with a one-dimensional semiconductor superlattice of quantum dots in the case where the spectral width of the electromagnetic pulse is sufficient to excite transitions between different minizones. A phenomenological equation was obtained in the form of the classical one-dimensional sine-Gordon equation with the perturbation caused by quantum transitions between the minizones. Quantum behavior of electrons was considered using the microscopic Hamiltonian, in the assumption that the pulse duration is small enough for the phonon effects to be neglected. The equation obtained was analyzed numerically, and cases where the adiabatic perturbation theory for the sine-Gordon equation can be used were found. Numerical solutions were obtained, and the domain where transitions between the minizones play a significant role in the electromagnetic-pulse dynamics was found.

A Method for Estimating the Probability of Lightning Causing a Methane Ignition in an Underground Mine

During the past decade, several methane/air explosions in abandoned or sealed areas of underground coal mines have been attributed to lightning. Previously published work by the authors showed, through computer simulations, that currents from lightning could propagate down steel-cased boreholes and ignite explosive methane/air mixtures. The presented work expands on the model and describes a methodology based on IEEE Standard 1410-2004 to estimate the probability of an ignition. The methodology provides a means to better estimate the likelihood that an ignition could occur underground and, more importantly, allows the calculation of what-if scenarios to investigate the effectiveness of engineering controls to reduce the hazard. The computer software used for calculating fields and potentials is also verified by comparing computed results with an independently developed theoretical model of electromagnetic field propagation through a conductive medium.

A lattice of electromagnetic solitons in a superlattice formed by a system of quantum dots

Considering the Maxwell equations for the electromagnetic-field propagation in a solid with a three-dimensional superlattice of quantum dots linked by strong tunneling along one axis, we obtained a phenomenological equation in the form of the classical 2+1-dimensional sine-Gordon equation. Electrons were considered classically in the formalism of the Boltzmann kinetic equation for the distribution function. Solutions were obtained as a soliton lattice for the vector potential of the electric field. These lattices emerge as a consequence of the coherent change of the classical distribution function and the electric field generated by tunneling electrons in a system of quantum wells.

4D Representation of Deep Ocean Controlled Source Electromagnetic Data

Deep ocean controlled source electromagnetic (CSEM) methods in oil and gas exploration have undergone rapid development in recent years. The CSEM transmitter generates coupled vector fields at low frequencies (less than 0.1 Hz) for a large number of transmitter receiver offsets on or close to the Ocean floor. Representation of the distribution and propagation of the transient electromagnetic fields within and below the ocean is of considerably importance to those people engaged in both pure research and the practical applications of electromagnetic methods.

Time-Domain Electromagnetic Fields Radiating Along the Horizontal Interface Between Vertically Uniaxial Half-Space Media

At the horizontal interface between vertically uniaxial half-space media, the propagation of electromagnetic fields is theoretically investigated for an interfacial impulse current source of infinitesimal size. For the electric field, the problem divides into the horizontal source and horizontal receiver (HH), vertical source and vertical receiver (VV), horizontal source and vertical receiver (HV), and vertical source and horizontal receiver (VH) cases. Employing the interface scheme of the Cagniard-style analysis, the solutions of the HH and VV cases are obtained in exact explicit forms. The solutions of the HV and VH cases cannot be expressed in integral-free forms, but the impulse components implicit in the integral solutions can be analytically extracted without the aid of the frequency-domain asymptotic techniques. Investigation is also made of the magnetic field and of the variation of waveforms when the receiver is taken a little off the interface. The uniaxial case is a generalization of the isotropic case, affording richer information of the wave physics

Magnetic response of split ring resonators at terahertz frequencies

AbstractWe investigate numerically the electric and the magnetic response of the split‐ring resonators (SRRs) for different electromagnetic (EM) field polarization and propagation directions. We have studied the current density J of circular and rectangular SRRs at THz frequencies. At low frequencies, J is confined to the edges of the SRRs, while at high frequencies J is all over the width of the wire. The diamagnetic response of the SRRs is also examined. Finally, the role of losses and the magnetic resonance frequency are studied as the size of the SRRs becomes less than 100 nm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

One-photon electrodynamics in optical fiber with fluorophore systems I One-photon correspondence principle for electromagnetic field propagation in matter

A system of coupled quantum harmonic oscillators (QHOs) whose Hamiltonian conserves photon number begets a one-photon correspondence principle (OPCoP), which allows solutions to the classical linear Maxwell equations for propagation in matter to be reinterpreted as a precise description of a one-photon state. We state, prove, and explore the OPCoP, whereby the vast extant body of linear, sourceless optical waveguide theory [Optical Waveguide Theory (Chapman & Hall, 1983)] can be applied to the exact analysis of one-photon propagation in optical fibers.

Nanoelectromechanical switches based on carbon nanotubes for microwave and millimeter waves

In this letter the authors analyze two configurations of nanoelectromechanical switches, which are working in the microwave and millimeter wave frequency ranges. Metallic nanotubes vertically or horizontally positioned on a propagating high frequency planar waveguide disable or enable the electromagnetic field propagation, whether they are actuated or not by a dc electric field of a few volts. Although the dimensions of metallic nanotubes are very small in comparison with the planar waveguide dimensions and the operating wavelengths, these switches are very efficient and agile.

3D animated visualization of EM diffusion for a frequency-domain helicopter EM system

The electromagnetic fields inside the earth are calculated by continuation downward of the electromagnetic (EM) solutions at the location of a frequency-domain helicopter electromagnetic (HEM) sensor. Models examined using the continuation approach include a layered isotropic and anisotropic earth. The finite-element approach is used to model 2D structures of a dipping contact or a dipping dike. By incorporating a time factor, we display the EM diffusion in the earth (change in direction and amplitude of the EM field through time) as 3D animated vectors or contours. The propagation of the EM smoke ring, influenced by the resistivity and structure of the earth, is apparent from the dynamic presentations. The current propagates downward and outward with time, becoming wider and more diffuse, and the phase varies with time, depth, and outward distance. The downward propagation of EM fields is slower in more conductive geology. In a layered isotropic earth, the current ring is symmetric with no vertical current flow for both vertical and horizontal dipole transmitters. In anisotropic or 2D structures; however, the current flow is significantly distorted resulting in vertical current flow and nonsymmetric smoke rings.

Lensless light focusing with the centric marine diatom Coscinodiscus walesii

In this work, we report on the light focusing ability exploited by the microshell of a marine organism: the Coscinodiscus wailesii diatom. A 100 microm spot size of a red laser beam is narrowed up to less than 10 microm at a distance of 104 microm after the transmission through the regular geometry of the diatom structure, which thus acts as a microlens. Numerical simulations of the electromagnetic field propagation show a good qualitative agreement with the experimental results. The focusing effect is due to the superposition of the waves scattered by the holes present on the surface of the diatom valve. Very interesting applications in micro-optic devices are feasible due to the morphological and biological characteristic of these unicellular organisms.

Collins’ integral for misaligned optical elements

The well known integral of Collins describes the propagation of electromagnetic fields through second-order optical elements, if the axis of the field propagation is aligned with respect to the axis of the optical element. It is shown that it holds for misaligned systems also, but an additional phase term ϕ appears, which depends on the shift and tilt vectors and on the 4 × 4 ABCD-matrix. Some examples are discussed.

A graphical user interface (GUI) for electromagnetic scattering from two- and three-dimensional canonical and non-canonical objects [EM Programmer's Notebook

Various numerical techniques have been developed for modeling electromagnetic-field propagation in conducting and dielectric media. The validity of these techniques is usually verified by comparison to the exact or asymptotic solutions of canonical or non-canonical problems of well-known solutions. This paper presents a software package designed as an educational and validation tool for the purpose of visualizing the physical phenomena of electromagnetic scattering from some canonical and non-canonical objects. The package is constructed to provide solutions for dielectric and conductive materials wherever appropriate, and it calculates and displays the near and far fields due to an excitation from a line source or a plane wave.

Electromagnetic plane wave scattering from building surfaces

PurposeTo provide a detailed investigation about methods commonly used for the computation of high‐frequency electromagnetic fields in the vicinity of obstacles that can reflect or diffract them. This is useful to create an elementary block that can be used to evaluate with a high accuracy the propagation of high‐frequency electromagnetic waves in real urban environment.Design/methodology/approachThe approach is based on a realistic application of the asymptotic theory of the uniform theory of diffraction. Therefore, the effect of material roughness and its electromagnetic properties on the reflection are taken into account.FindingsProvides information about the mechanisms involved in electromagnetic field propagation in urban environment, and the relative importance of each one.Research limitations/implicationsIn urban environment the buildings obviously have finite dimensions. The diffraction equations examined in the paper are strictly valid only in the case of infinite wedges; therefore, the behaviour of real building edges has not been taken rigorously into account.Practical implicationsA source of information for researchers interested in the development of a simulator for the electromagnetic propagation in urban environment.Originality/valueThis paper is aimed at providing to researchers, in a more comprehensive way, all information needed for the study of electromagnetic propagation in an environment containing many close scatterers.

On a model of electromagnetic field propagation in ferroelectric media

The Maxwell system in an anisotropic, inhomogeneous medium with non-linear memory effect produced by a Maxwell type system for the polarization is investigated under low regularity assumptions on data and domain. The particular form of memory in the system is motivated by a model for electromagnetic wave propagation in ferromagnetic materials suggested by Greenberg, MacCamy and Coffman [J.M. Greenberg, R.C. MacCamy, C.V. Coffman, On the long-time behavior of ferroelectric systems, Phys. D 134 (1999) 362–383]. To avoid unnecessary regularity requirements the problem is approached as a system of space–time operator equation in the framework of extrapolation spaces (Sobolev lattices), a theoretical framework developed in [R. Picard, Evolution equations as space–time operator equations, Math. Anal. Appl. 173 (2) (1993) 436–458; R. Picard, Evolution equations as operator equations in lattices of Hilbert spaces, Glasnik Mat. 35 (2000) 111–136]. A solution theory for a large class of ferromagnetic materials confined to an arbitrary open set (with suitably generalized boundary conditions) is obtained.

SOLUTION OF PRIDE'S EQUATIONS THROUGH POTENTIALS

In 1994, S. Pride offered a system of equations describing interdependent propagation of acoustic and electromagnetic (EM) fields in porous media saturated by a fluid electrolyte (electrokinetic effect). We proved that the displacement vectors of frame and of pore fluid can be represented as a linear combinations of gradients of two scalar potentials and rotors of two vector potentials provided the coefficients of Pride's equations are independent of spatial coordinates. Each of these potentials satisfies Helmholtz equation with appropriate complex velocity. This representation underlies the computer code created by us for exploring borehole acoustics logging problems in axial-symmetric radially layered medium. Noteworthy, layers can be of any of the following types: uniform porous medium saturated by fluid electrolyte, uniform nonporous elastic medium, compressible nonviscous fluid or compressible viscous fluid. Results of numerical experiments are presented and discussed. The most important of them is that the back influence on acoustic disturbance of EM field excited by this disturbance is negligibly small in usually used frequency band and for realistic formation parameters. The mechanism of generation and propagation of different types of EM waves during acoustic logging is discussed as well.

Nonlinear field dynamics of electromagnetic pulses in plasmas

Abstract In the present analysis we study the self-consistent propagation of nonlinear electromagnetic fields in a one dimensional relativistic electron–ion plasma. Using techniques of nonlinear dynamics we address several issues of current interest showing how a series of Hamiltonian bifurcations affects characteristics of localized pulses. Connections between these bifurcated solutions and results of earlier analysis are made.