Analysis Of Electromagnetic Field Distribution Research Articles

Design of ultra-broadband absorption enhancement in plasmonic absorber by interaction resonance of multi-plasmon modes and Fabry-Perot mode

This paper shows a strategy to realize ultra-broadband absorption of multi-spectral coverage. A vertical cascaded plasmonic absorber constructed by multilayer helical metallic nanostructure wrapped in a pyramid-shaped dielectric jacket is presented and investigated by numerical simulations. By premeditated planning of the scale proportions of the spirals and the dimension size of the pyramid-shaped dielectric, more than 90% of absorption is realized in 189-3896 nm, an ultra-wide spectral range that basically covers the bands of near-ultraviolet, visible light, and near-infrared. The excitation mechanism of electromagnetic resonance and the formation process of light trapping are both included in the investigation through the analysis of electromagnetic field distribution. The localized surface plasmon mode in the metallic nano-spiral and the Fabry-Perot cavity mode with the gap plasmon resonance in the dielectric gap cooperatively make a significant contribution to reduce the reflection and form the ultra-broadband absorption. The simulation results show that the proposed absorber is basically insensitive to the incident angle and polarization angle, which basically keeps more than 90% absorption within the incident angle of ± 80 °. Such a specific implementation idea can also be applied to the terahertz region by modifying the geometrical size of the structure. This presented design implies new viability to develop the broadband photodetectors, solar cells, and thermal emitters.

Analysis of Electromagnetic Field Distribution Generated in an Semi-Anechoic Chamber in Aspect of RF Harvesters Testing

The results of work in the field of analysis of the distribution of electromagnetic fields generated by the antenna of an RFID reader operating in the UHF frequency band have been presented in this paper. The carried-out tests concern the efficiency of obtaining energy from the field of an electromagnetic RFID reader. To analyze the distribution of the electric field strength, the calculation procedures were elaborated on the basis of the developed mathematical dependencies in the MathCad program. The developed numerical procedures enable the synthesis of the electric field strength and power density distribution for a given antenna radiation pattern, for any suspension heights of the transmit and receive antennas and any mutual distance between them. In order to verify the correctness of calculations the test stands and measurements were made for a model antenna. The measurements were carried out in a semi-anechoic chamber.

Design and performance simulation of microcavity enhanced bilayer graphene infrared photodetector

Photodetectors based on bilayer graphene have raised great interest for its application in infrared and terahertz detection, because bilayer graphene performs well in optical and electrical area. However, weak light absorption of bilayer graphene limits the property of bilayer graphene photodetector. In this paper a design of microcavity enhanced infrared photodetector based on Bernal stacking bilayer graphene is presented. Quantum efficiency and responsivity of detector can be valid improved by confining light in the cavity. Theoretical analysis shows that microcavity length and reflectivity of reflectors are the key factors to influence the performance. When the microcavity length matches the operating wavelength, under the standing wave effect, the quantum efficiency can reach the maximum, while reflectivity becomes the key factor. To obtain a higher and more detailed reflectivity of reflectors, distributed bragger reflectors (DBRs) are chosen as reflectors of microcavity. Reflectivity is determined through the analysis of electromagnetic field distribution of membrane. The reflectivity of reflectors is calculated by transfer matrix. AlAs/Al0.1Ga0.9As and TiO2/SiO2 membranes are chosen as constituents of reflectors. The structure is confirmed through optimization, and the result is presented below: The microcavity length is 467.4 nm, 13/10 pairs of membranes constructs the top/bottom reflector and the bilayer graphene is located in the middle of microcavity. At a nominal operating wavelength of 1.55 μm, a widely used wavelength in laser range finder, the quantum efficiency can reach 99.33% and the responsivity can reach 1.24 A/W. The method provides a possible approach to fabricate high quantum efficiency bilayer graphene photodetector.

Fano-like resonance in large-area magnetic metamaterials fabricated by the nanoimprint technique

We experimentally and theoretically investigated the Fano-like resonance in large-area magnetic metasurfaces fabricated by nanoimprint lithography techniques based on elaborately designed Ag–SiN–Ag configuration. Asymmetric line shape is revealed in the reflection spectrum of magnetic metamaterials. The physical mechanism is elucidated through dispersion relation and electromagnetic field distribution analysis. Both the measured and calculated dispersion relation tell that there are magnetic resonance modes and surface lattices modes coexisting in magnetic metamaterials, their coupling leads to the asymmetric profile in the reflection spectrum. The calculated electromagnetic field distribution further consolidate the coupling phenomenon in the magnetic metamaterials. This work might significantly prompt the applications of metamaterials in sensing, lasing, and optical devices designing.

Assessment of SAR in human body model with the cochlear implant inside a railway vehicle

Abstract This article details simulation and analysis of electromagnetic field distribution within a railway vehicle, with special focus on distribution thereof in human body phantom with a cochlear implant. Research was carried out using modelling of electromagnetic fields based on the Finite Integration Method. Simulations were performed and analysed in cases where passengers were exposed to long-term radiofrequency field stemming from the use of mobile phones during railway transport. Results were evaluated based on the specific absorption rate (SAR) – the measure of electromagnetic energy absorption in the body (in watts per kilogram [W/kg]). Dual band (900 and 1800MHz) PIFA antennas were designed and employed as radio frequency sources. The homogeneous passenger model includes a cochlear implant and dielectric properties are set according to the evaluated frequency band. Results have shown that the calculated maximum values of SAR are higher than those established within the European maximum SAR limit and additionally, the obtained values are higher than values obtained in simulation in open space.

Performance analysis of the FDTD method applied to holographic volume gratings: Multi-core CPU versus GPU computing

The finite-difference time-domain method (FDTD) allows electromagnetic field distribution analysis as a function of time and space. The method is applied to analyze holographic volume gratings (HVGs) for the near-field distribution at optical wavelengths. Usually, this application requires the simulation of wide areas, which implies more memory and time processing. In this work, we propose a specific implementation of the FDTD method including several add-ons for a precise simulation of optical diffractive elements. Values in the near-field region are computed considering the illumination of the grating by means of a plane wave for different angles of incidence and including absorbing boundaries as well. We compare the results obtained by FDTD with those obtained using a matrix method (MM) applied to diffraction gratings. In addition, we have developed two optimized versions of the algorithm, for both CPU and GPU, in order to analyze the improvement of using the new NVIDIA Fermi GPU architecture versus highly tuned multi-core CPU as a function of the size simulation. In particular, the optimized CPU implementation takes advantage of the arithmetic and data transfer streaming SIMD (single instruction multiple data) extensions (SSE) included explicitly in the code and also of multi-threading by means of OpenMP directives. A good agreement between the results obtained using both FDTD and MM methods is obtained, thus validating our methodology. Moreover, the performance of the GPU is compared to the SSE+OpenMP CPU implementation, and it is quantitatively determined that a highly optimized CPU program can be competitive for a wider range of simulation sizes, whereas GPU computing becomes more powerful for large-scale simulations.

Theoretical analysis of electromagnetic field distribution and Cerenkov second harmonic generation conversion efficiency based on lithium niobate ion-implanted channel waveguide

Cerenkov type second harmonic generation (CSHG) is proposed in ion-implanted Z-cut lithium niobate (LiNbO3) channel waveguides. We have obtained exact analytical solutions for the field distribution and the power of second-harmonic waves. Conditions for attaining higher conversion efficiency are discussed on the basis of numerical calculations.

Design, implementation, and dosimetry analysis of an S‐band waveguide in vitro system for the exposure of cell culture samples to pulsed fields

The interaction between electromagnetic fields and biological media, particularly regarding very high power, short pulses as in radar signals, is not a fully understood phenomenon. In the past few years, many in vitro, cellular communications-oriented exposure studies have been carried out. This article presents a high-power waveguide exposure system capable of dealing with monochromatic, multicarrier or pulsed signals between 1.8 and 3.2 GHz (L- and S-band) with a pulse duration as low as 90 ns, minimum pulse repetition of 100 Hz, and maximum instantaneous power of 100 W. The setup is currently being used with a 2.2 GHz carrier modulated by 5 micros pulses with a 100 Hz repetition period and approximately 30 W of instantaneous power. After a worst-case temperature analysis, which does not account for conduction and convection thermal effects, the experiment's exposure is considered sub-thermal. Evaluation of the results through the specific absorption rate distribution is not considered sufficient enough in these cases. An electromagnetic field distribution analysis is needed. For monochromatic signals, the representation of the modulus of the electric and magnetic field components is proposed as a suitable method of assessment.

A quasi-analytical procedure for magnetic fields analysis in bounded domains via magnetization currents

In this paper a quasi-analytical procedure for the analysis of electromagnetic field distributions in bounded domains relating to linear materials is presented. The procedure allows the determination of analytical expressions far the magnetic fields by means of the superposition of analytical solutions relating to partially bounded domains i.e. half spaces or axially infinite geometries. The presence of ferromagnetic materials is taken into account by means of the determination of equivalent magnetization currents. The procedure can be used for the analysis of different geometries, and an application to the analysis of the induced voltage in a nondestructive testing system is shown. >

Equivalent network modeling of cylindrical systems with conductors in motion

Equivalent network models for the analysis of electromagnetic field distributions and forces in axisymmetric systems with linear ferromagnetic conductors in motion are presented. The infinite equivalent network model calculates the inductive parameters of the equivalent network by means of analytical expressions, obtained under the hypothesis of an infinite axial length of the system, in order to have a quick first evaluation of the system performance. The finite equivalent network model uses the magnetization vector and a magnetic scalar potential to take into account the actual finite axial length of the system in the evaluation of the inductive parameters of the equivalent network. The equivalent network model calculated results were compared with results obtained from an analytical model, and the models were then tested comparing calculated results with experimental data on a linear motor prototype.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis of electromagnetic field distribution in tunnels with partition walls

AbstractA method of formulation based on the boundary element method is provided for the electromagnetic field in a two‐dimensional impedance tunnel with partition walls excited by the fundamental mode. The impedance boundary condition used often for the analysis of the electromagnetic scattering problem from a lossy dielectric and of the wave propagation in a tunnel is based on the characteristic impedance for an infinitely thick medium. Since there is no provision on the transmitted wave behind the dielectric plate, this boundary condition cannot be applied directly if the dielectric plate used is thinner than the skin depth.This paper derives first a new boundary condition in which the values of the electromagnetic field in the region opposite to the wall surface are considered. In the case of a plane wave (TE wave) incidence on an infinitely wide than dielectric plate, the computed values by the boundary element method with the new boundary condition are compared with the rigorous solutions. It is found that the results agree with each other for both the reflection and transmission coefficients so that the impedance boundary condition introduced here can be used as the boundary condition for a thin dielectric plate. Further, assuming a tunnel with a thin partition wall, we carried out a microwave simulation experiment with a Bakelite plate so that the validity and usefulness of the present method are confirmed.

Analysis of electromagnetic field distribution in tunnels by the boundary-element method

An efficient numerical approach, based on the boundary element method, for the analysis of electromagnetic field distributions in twodimensional tunnels with discontinuities such as L-bends, T-junctions, and cross-junctions is described. The side walls of the tunnels are assumed to be lossy dielectric and the surface impedance approximation is used to determine the boundary condition on the side walls. A computer program has been developed for tunnels excited by a line current or a TE dominant mode. A comparison of the numerical results with the experimental results using microwave simulation shows a good agreement except in the vicinity of the inner wall of the output tunnel perpendicular to the excited tunnel.

Nonlinear analysis of field distribution in electric motor with periodicity conditions

Numerical analysis of electromagnetic field distribution in linear motion tubular electric motor has been performed with the aid of finite element method. Two Fortran programmes for the solution of DBBF and BF large linear symmetric equation systems have been developed for purposes of this analysis. A new iterative algorithm, taking into account iron nonlinearity and periodicity conditions, has been introduced. Final results of the analysis in the form of induction diagrammes and motor driving force and directly useful for motor designers.

High-Accuracy Wide-Range Measurement Method for Determination of Complex Permittivity in Reentrant Cavity: Part A --- Theoretical Analysis of the Method

New mathematical method for calculation of complex electric permittivity (epsilon) of a wide range of materials from the direct measured parameters of a reentrant cavity containing a sample of material is presented. Condition of resonance is drawn based on analysis of electromagnetic field distribution in the cavity with a sample. Accuracy of the obtained algorithm (convergences of series) and method of shortening iterative solution is discussed in detail.