Modeling Of Electromagnetic Wave Propagation Research Articles

Four-dimensional Rotations in Coherent Optical Communications

To model electromagnetic wave propagation for coherent communications without polarization dependent losses, the unitary 2 ×2 Jones transfer matrix formalism is typically used. In this study, we propose an alternative formalism to describe such transformations based on rotations in four-dimensional (4d) Euclidean space. This formalism is usually more attractive from a communication theoretical perspective, since decisions and symbol errors can be related to geometric concepts such as Euclidean distances between points and decision boundaries. Since 4d rotations is a richer description than the conventional Jones calculus, having six rather than four degrees of freedom (DOF), we propose an extension of the Jones calculus to handle all six DOF. In addition, we show that the two extra DOF in the 4d description represents transformations that are nonphysical for propagating photons, since they does not obey the fundamental quantum mechanical boson commutation relations. Finally, we exemplify on how the nonphysical rotations can change the polarization-phase degeneracy of well-known constellations such as single-polarization QPSK, polarization-multiplexed (PM-)QPSK and polarization-switched (PS-) QPSK. For example, we show how PM-QPSK, which is well known to consist of four polarization states each having four-fold phase degeneracy, can be represented as eight states of polarizations, each with binary phase degeneracy.

A Precise Integration Method for Modeling GPR Wave Propagation in Layered Pavement Structure

Construction of electromagnetic wave propagation model in layered pavement structure is a key step in back analysis of ground penetrating radar (GPR) echo signal. The precise integration method (PIM) is a highly accurate, eff... | Find, read and cite all the research you need on Tech Science Press

Electromagnetic Field Computation for Power Transmission Lines Using Quasi-Static Sub-Gridding Finite-Difference Time-Domain Approach

A new approach to the modeling of electromagnetic wave propagation and penetration in and around electrically small objects is presented. The traveling electromagnetic wave from a source is simulated by the finite-difference time-domain solution of Maxwell's equations, and a sub-gridding technique is imposed at points of interest in order to observe the electromagnetic field at high resolution. The computational burden caused by the requirement for a large number of time steps has been ameliorated by implementing the state-of-the-art quasi-static approach. The method is demonstrated by finding the induced electromagnetic fields near a buried pipeline that runs parallel to 400-kV power transmission lines; results are presented and discussed.

Theoretical model for electromagnetic wave propagation in negative index material induced by cubic-quintic nonlinearities and third-order dispersion effects

We analyze the problem of characterization of electromagnetic (EM) wave that propagates in a negative index material (NIM) and compare to the behavior that observes in a positive index material (PIM), from the conventional technique of characterization of the pulse intensity profile. Firstly, we establish the nonlinear Schrodinger equation (NLSE) and use the Drude model to obtained the NLSE terms. Secondly, we apply the collective variables technique at each frequency range and show that the stability and the light pulse intensity are significantly depending on specific normalized frequencies. We determine the specific frequency range allowing a fear characterization of the intensity profile of light pulse when the frequency increases. We illustrate the effectiveness of this EM wave stabilization by applying the indicated frequency range. This conventional technique in NIM and PIM systems where the second-order dispersion, third-order dispersion, self phase modulation (SPM) and quintic effects originated from SPM called quintic phase modulation act to provoke strong perturbations.

Mathematical modeling of electromagnetic wave propagation in heterogeneous lossy coaxial cables with variable cross section

In this work, we focus on the time-domain simulation of the propagation of electromagnetic waves in non-homogeneous lossy coaxial cables. The full 3D Maxwell equations, that described the propagation of current and electric potential in such cables, are classically not tackled directly, but instead a 1D scalar model known as the telegraphist's model is used. We aim at justifying, by means of asymptotic analysis, a time-domain “homogenized” telegraphist's model. This model, which includes a nonlocal in time operator, is obtained via asymptotic analysis, for a lossy coaxial cable whose cross section is not homogeneous.

FDTD Modelling of Electromagnetic waves in Stratified Medium

A time domain numerical procedure is presented for a simulation of electromagnetic wave phenomena. The technique is an adaptation of the finite-difference time domain (FDTD) approach usually applied to model electromagnetic wave propagation. In this paper a simple 2D implementation of FDTD algorithm in mathematica environment is presented. Source implementation and the effect of conductivity on the incident field are investigated. Simple illustrations of propagation in a non-conducting, partial conducting and conducting medium are provided. For the computational space, Cartesian grids of fixed size were used as it makes grid generation to be relatively easy. The numerical data generated by the program code were sampled at various time steps from t0=1 to 90 along the computational space. The simulation results show the advancement of the pulse into the medium at various time stepping, shift in the peak of the amplitude was observed on the pulse for all the time steps. An attempt to further show the attenuation as the wave propagates into the stratified medium is made. The amplitude of the pulse falls sharply from 0.006 to 1x10-11 for t0=1 and t0=50. The results indicate the working of the model and it could be used to study the behavior of the wave as it does propagate across the medium.Keywords: Stratified Medium, Finite Difference Time Domain (FDTD), mathematica, Maxwell’s Equations, Electromagnetic Waves (EM)

Numerical modeling of electromagnetic wave propagation in a liquid crystal cell at oblique incidence

This paper presents a robust numerical method for the analysis of wave propagation in nematic liquid crystals. The structure is excited by a plane wave incident at an oblique angle with respect to the normal to the liquid–crystal cell. The underlined formulation is based on an eigenvalue problem which is solved analytically in order to obtain the governing field expressions inside a homogeneous, thin crystal layer. The liquid–crystal cell is comprised of N such layers. Enforcing the continuity of the tangential electric and magnetic fields at the interfaces formed by the various layers, a matrix system is generated. Solution of the linear system of equations results in the light intensity inside the liquid crystal, which is coupled to a non-linear differential equation for the director tilt angle. This equation is solved using either an explicit or implicit finite-difference scheme. An iteration process continues until convergence is reached for the coupled problem. The proposed numerical method was validated against published results that were generated by approximate analytical methods. Further simulations and studies were conducted emphasizing on the physics of the problem and related interesting phenomena.

SPECTRAL-DOMAIN FORMULATION OF PILLAR-TYPE PHOTONIC CRYSTAL WAVEGUIDE DEVICES OF INFINITE EXTENT

This paper presents a novel formulation for the modeling of electromagnetic wave propagation in pillar-type photonic crystal waveguide devices. The structure under consideration is formed in an infinitely extended pillar-type photonic crystal and the wave propagation is controlled by removing some cylinders from the original periodic structure. The structure is considered as cascade connections of straight waveguides, and the input/output properties of the devices are obtained using an analysis method of multilayer structure. Each layer includes periodic circular cylinder array with defects, and the transfer-matrix is obtained by using a spectral-domain approach based on the recursive transition-matrix algorithm with the lattice sums technique and the pseudo-periodic Fourier transform.

The First-Order Symplectic Euler Method for Simulation of GPR Wave Propagation in Pavement Structure

Construction of electromagnetic wave propagation model in layered pavement structure is a key problem for applying ground penetrating radar (GPR) to the road quality detection. A first-order explicit symplectic Euler method with Higdon absorbing boundary condition is presented to simulate GPR wave propagation in 2-D pavement structure. The incident wave is considered as line source and plane wave source, respectively. The total-field/scatter-field technique is used to simulate plane wave excitation. Numerical examples are provided to verify the accuracy and efficiency of the proposed algorithm. It can be observed that the symplectic Euler method achieves almost the same level of accuracy as the finite-difference time-domain scheme, while saving CPU time considerably.

Theoretical Study of Transmissivity of Electromagnetic Wave in Magnetorheological Fluids

The internal structure of magnetorheological fluid could change under external magnetic field, as well as its dielectric constant and magnetic conductance. A theoretical model of electromagnetic wave propagation in MRF was established and the basic formula of transmissivity was deduced. Theoretical simulation shows that the electromagnetic wave transmissivity decreases with the increasing of dielectric constant of magnetorheological fluid, and increases with the magnetic permeability. Theoretical analysis indicates that the change of its structure and dielectric magnetic properties of MR fluids is the main cause for the fact that the transmittance could be adjusted under external magnetic field.

Time-domain electromagnetic wave propagation analysis by edge-based smoothed point interpolation methods

In this work, smoothed meshfree methods are firstly applied to numerically analyze two-dimensional electromagnetic wave propagation models. A weakened weak formulation based on the edges of triangular cells obtained by a Delaunay triangulation is considered here, framing the so-called edge-based smoothed domains. The meshfree shape functions are computed by the Radial Point Interpolation Method (RPIM) considering two schemes for the shape function support domains, namely the T3- and the T6-scheme. These schemes are based on the above mentioned triangular cells and they consider fixed numbers of nodes for the support domains. A new procedure to compute the transient related matrices is discussed here, aiming to be more consistent with the edge-based smoothed point interpolation method. In this new procedure, finer local integration techniques are managed to be considered at lower computational costs, rendering more accurate and efficient techniques. At the end of the paper, numerical examples are presented, illustrating the effectiveness and potentialities of the proposed methodologies.

Analysis of ELF electromagnetic field pulses recorded by the Hylaty station coinciding with terrestrial gamma‐ray flashes

Terrestrial gamma‐ray flashes (TGFs) were registered the first time by the NASA's Compton Gamma Ray Observatory. The physical mechanism of TGF generation is not fully known, but there is a consensus among researchers that the radiation is produced by bremsstrahlung of relativistic electrons in the thunderstorm regions of the atmosphere. Therefore, TGFs have been linked to positive‐polarity intracloud lightning discharges, strong positive cloud‐to‐ground discharges or upward discharges from a thundercloud top. The currently operating Fermi Gamma‐ray Space Telescope is equipped with a Gamma‐ray Burst Monitor that can detect terrestrial gamma‐ray flashes. It opens up a new possibility to search for lightning discharges responsible for TGFs. Ground‐based lightning monitoring systems in the ELF, LF and VLF ranges can be used for that purpose. The ELF systems are especially useful, since they provide a large monitoring range of several thousand kilometers for strong atmospheric discharges (charge moments above several tens of C km). In this paper we have described the data analysis method for ELF electromagnetic field pulses and applied it to study our first examples of TGFs registered by Fermi GBM coinciding with ELF pulses recorded by the Hylaty ELF station located in the Carpathian Mountains in Poland. Using our ELF electromagnetic wave propagation model we have evaluated charge moments for the two registered events to be 320 and 110 C km and provided upper limits for the remaining events.

Modeling of Electromagnetic Wave Propagation with Tapered Transmission Line

Modeling of Electromagnetic Wave Propagation with Tapered Transmission Line

Modeling of Electromagnetic Wave Propagation with Tapered Transmission Line

Tapered transmission line was used for impedance matching, for high voltage pulse, and atmospheric medium is applied to characteristic equation of tapered transmission line and reflection coefficient so that nonlinear load and circuit modeling of atmospheric medium was simulated by electromagnetic transient program (EMTP). A characteristic of atmospheric medium and Time delay are decided by inductance and capacitance of tapered transmission line. For electromagnetic wave propagation modeling, in this paper, tapered transmission line is implemented. It is difficult to model tapered transmission line directly. Other transmission line that can be expressed by the circuit is used. So object of this paper is efficient modeling of tapered transmission line.

On elastic-electromagnetic mathematical equivalences

Elastic-electromagnetic mathematical equivalences, which here consist of recasting Maxwell′s equations and the constitutive relations for an electromagnetic medium into a form that is mathematically identical with that of the basic equations for elastic waves, are presented. These equivalences allow us, for example, to use a finite-difference modelling code developed for elastic wave propagation to model electromagnetic wave propagation. The reverse process, which consists of using a finite-difference modelling code developed for electromagnetic wave propagation to model elastic wave propagation, is valid only for particular forms of elastic wave equations, such as acoustic wave equations in a 2-D medium (i.e. an infinitely long line source in the cross-line direction and acoustic properties invariant in the cross-line direction).

Electromagnetic THz Radiation Modeling by DPSM

THz or T-ray imaging and spectroscopy are becoming increasingly popular nondestructive evaluation techniques for damage detection and characterization of materials. In order to understand the interaction between the T-ray electromagnetic waves and dielectric media a reliable model of electromagnetic wave propagation through dielectric materials must be developed. A recently developed semi-analytical method called the distributed point source method (DPSM) is extended to model electromagnetic wave propagation in THz range. Since T-ray signals generated by emitters or sources are close to Gaussian beams, the DPSM modeling is carried out for Gaussian beams generated by finite sized emitters. The DPSM generated results are compared with the analytical and experimental results. T-ray propagation in layered structures in absence of any anomaly and the interaction between the Gaussian beam and the spherical scatterer are also investigated.

Quantitative thermo-acoustics and related problems

Thermo-acoustic tomography is a hybrid medical imaging modality that aims to combine the good optical contrast observed in tissues with the good resolution properties of ultrasound. Thermo-acoustic imaging may be decomposed into two steps. The first step aims at reconstructing an amount of electromagnetic radiation absorbed by tissues from boundary measurements of ultrasound generated by the heating caused by these radiations. We assume that this first step has been performed. Quantitative thermo-acoustics then consists of reconstructing the conductivity coefficient in the equation modeling radiation from the now known absorbed radiation. This second step is the problem of interest in this paper. Mathematically, quantitative thermo-acoustics consists of reconstructing the conductivity in Maxwell's equations from available internal data that are linear in the conductivity and quadratic in the electric field. We consider several inverse problems of this type with applications in thermo-acoustics as well as in acousto-optics. In this framework, we obtain uniqueness and stability results under a smallness constraint on the conductivity. This smallness constraint is removed in the specific case of a scalar model for electromagnetic wave propagation for appropriate illuminations constructed by the method of complex geometric optics solutions.

Impedance technique for modeling electromagnetic wave propagation in anisotropic and gyrotropic media

A convenient and physically unambiguous interpretation of the invariant embedding technique is discussed in application to problems of electromagnetic wave propagation in complex media characterized by anisotropic and gyrotropic dielectric or magnetic response.

Impedansnyi metod resheniya zadach rasprostraneniya elektromagnitnykh voln v anizotropnykh i girotropnykh sredakh

Impedansnyi metod resheniya zadach rasprostraneniya elektromagnitnykh voln v anizotropnykh i girotropnykh sredakh

Complex Permittivity Measurements of Rainwater in the 0.5–26.5 GHz Frequency Range

Modeling electromagnetic wave propagation in rain requires knowledge of the complex permittivity of rainwater. In response, we measured the complex permittivity of rainwater in the 0.5-26.5 GHz frequency range using an Agilent Technologies 85070E Dielectric Probe Kit and an Agilent N5242A-400 Vector Network Analyzer. Rainwater samples were collected in Graz (Austria) and Kototabang (Indonesia). The results obtained were found to differ slightly from those of Ray's and Liebe's models. However, the difference in the complex permittivity of rainwater between the measurement and model results exhibits very small biases in the Mie extinction coefficients ( <; 0.01%).