Advanced Electromagnetics (E-Journal)
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Experimental study of EIT-Like phenomenon in a metamaterial plasma waveguide
No full textThis paper demonstrates the realization of the electromagnetically induced transparency (EIT)-like transmission in a metamaterial plasma waveguide with double side defects based on transmission lines. The waveguide with a single side defect works as a plasma resonator and the resonance wavelength is determined by the Fabry-Perot resonance of surface plasma. While in a waveguide with double side defects, a transmission peak appears between the two resonators frequencies because of the destructive interference between the resonance modes of the two resonators, which indicates a pronounced EIT phenomenon. The experiment results agree well with simulations in microwave frequencies
"Cut wires grating – single longitudinal wire" planar metastructure to achieve microwave magnetic resonance in a single wire
No full textHere we present metastructures containing cut-wire grating and a single longitudinal cut-wire orthogonal to grating’s wires. Experimental investigations at microwaves show these structures can provide strong magnetic resonant response of a single nonmagnetic cut-wire in dependence on configuration and sizes in the case when metastructures are oriented along the direction of wave propagation and cut-wires of grating are parallel to the electric field of a plane electromagnetic wave. It is suggested a concept of magnetic response based on antiparallel resonant currents excited by magnetic field of surface polaritons in many spatial LC-circuits created from cut-wire pairs of a grating and section of longitudinal cut-wire. Three separately observed resonant effects connected with grating, LC-circuits and with longitudinal cut-wire have been identified applying measurements in waveguides, cutoff waveguides and free space. To tune and mark resonance split cut-wires are loaded with varactor diodes
Curvilinear vector finite difference approach to the computation of waveguide modes
No full textWe describe here a Vector Finite Difference approach to the evaluation of waveguide eigenvalues and modes for rectangular, circular and elliptical waveguides. The FD is applied using a 2D cartesian, polar and elliptical grid in the waveguide section. A suitable Taylor expansion of the vector mode function allows to take exactly into account the boundary condition. To prevent the raising of spurious modes, our FD approximation results in a constrained eigenvalue problem, that we solve using a decomposition method. This approach has been evaluated comparing our results to the analytical modes of rectangular and circula rwaveguide, and to known data for the elliptic case
Combined FVTD/PSTD Schemes with Enhanced Spectral Accuracy for the Design of Large-Scale EMC Applications
No full textA generalized conformal time-domain method with adjustable spectral accuracy is introduced in this paper for the consistent analysis of large-scale electromagnetic compatibility problems. The novel 3-D hybrid schemes blend a stencil-optimized finite-volume time-domain and a multimodal Fourier-Chebyshev pseudo-spectral time-domain algorithm that split the overall space into smaller and flexible areas. A key asset is that both techniques are updated independently and interconnected by robust boundary conditions. Also, combining a family of spatial derivative approximators with controllable precision in general curvilinear coordinates, the proposed method launches a conformal field flux formulation to derive electromagnetic quantities in regions with fine details. For advanced grid reliability at dissimilar media interfaces, dispersion-reduced adaptive operators, which assign the proper weights to each spatial increment, are developed. So, the resulting discretization yields highly rigorous and computationally affordable simulations, devoid of lattice errors. Numerical results, addressing detailed comparisons of various realistic applications with reference or measurement data verify our methodology and reveal its significant applicability
A nonlinear model for AC induced corrosion
No full textThe modeling of corrosion poses particular difficulties. The understanding of corrosion as an electrochemical process has led to simple capacitive-resistive models that take into account the resistance of the electrolytic cell and the capacitive effect of the surface potential at the interface between conductors and the electrolyte. In some models nonlinear conduction effects have been added to account for more complex observed behavior. While these models are sufficient to describe the behavior in systems with cathodic protection, the behavior in the presence of induced AC currents from power lines and from RF sources cannot be accounted for and are insufficient to describe the effects observed in the field. Field observations have shown that a rectifying effect exists that affects the cathodic protection potential and this effect is responsible for corrosion in the presence of AC currents. The rectifying effects of the metal-corrosion interface are totally missing from current models. This work proposes a nonlinear model based on finite element analysis that takes into account the nonlinear behavior of the metal-oxide interface and promises to improve modeling by including the rectification effects at the interface
Surface impedance of BaFe2-xNixAs2 in the radio frequency range
No full textWe report measurements of the temperature dependence of the surface impedance in superconducting BaFe1.93Ni0.07As2 crystals using the radiofrequency reflection technique in the 5<T<30K temperature range. An LC resonant circuit with a phase sensitive detection was used at 92MHz. A measurement assembly with point contacts was used at 30MHz. The recent discovery of iron based arsenide superconductors BaFe2-xNixAs2 has attracted much interest. For a Ni doping level of 7% the superconducting phase transition is found around 20K. The temperature dependence of the superconducting penetration depth was determined
Propagation of ELF Radiation from RS-LC System and Red Sprites in Earth-Ionosphere Waveguide
No full textIn this paper, two different mechanisms return stroke-lateral corona (RS-LC) system and red sprites which excite Earth-ionosphere waveguide have been discussed. The electric and magnetic fields from RS-LC system and red spites in the Earth-ionosphere waveguide have been calculated. It has been found that red sprites contribute to the Schumann resonances (SR) greatly as compared to the RS-LC system
Calculations of near-field emissions in frequency-domain into time-dependent data with arbitrary wave form transient perturbations
No full textThis paper is devoted on the application of the computational method for calculating the transient electromagnetic (EM) near-field (NF) radiated by electronic structures from the frequency-dependent data for the arbitrary wave form perturbations i(t). The method proposed is based on the fast Fourier transform (FFT). The different steps illustrating the principle of the method is described. It is composed of three successive steps: the synchronization of the input excitation spectrum I(f) and the given frequency data H0(f), the convolution of the two inputs data and then, the determination of the time-domain emissions H(t). The feasibility of the method is verified with standard EM 3D simulations. In addition to this method, an extraction technique of the time-dependent z-transversal EM NF component Xz(t) from the frequency-dependent x- and y- longitudinal components Hx(f) and Hy(f) is also presented. This technique is based on the conjugation of the plane wave spectrum (PWS) transform and FFT. The feasibility of the method is verified with a set of dipole radiations. The method introduced in this paper is particularly useful for the investigation of time-domain emissions for EMC applications by considering transient EM interferences (EMIs)
On The Study of Development of X Band Metamaterial Radar Absorber
No full textA new development of metamaterial applications in radar absorbers for X band is introduced. Two modifications were suggested based on two different approaches which are a new called fan shaped resonator absorber and a modified high impedance metamaterial absorber. Both approaches introduce thin radar absorber (5.3% at centre frequency) with wide bandwidth and high absorption level. The theoretical concepts of each design are explained and validated using full wave simulation. Results illustrate that the new development can achieve wider bandwidth, multiple operating bands; the increase in bandwidth is up to 8 times the conventional one. Moreover, the reported absorbers have capability to operate with different polarizations
Reducing radar cross section by investigation electromagnetic materials
No full textDecreasing the Radar Cross Section (RCS) is investigated in electromagnetic materials, i.e. double-positive (DPS) , double-negative (DNG) , epsilon-negative (ENG) and mu-negative (MNG) materials. The interesting properties of these materials lead to a great flexibility in manufacturing structures with unusual electromagnetic characteristics. The valid conditions for achieving the transparency and gaining resonance for an electrically small cylinder are established, in this corresponding The effect of incidence direction on RCS inclusive of transparency and resonance conditions is also explored ,through computer simulations for an electrically small cylinder