External Electromagnetic Wave Research Articles

Hadronic vacuum polarization and muong−2from magnetic susceptibilities on the lattice

We present and test a new method to compute the hadronic vacuum polarization function in lattice simulations. This can then be used, e.g., to determine the leading hadronic contribution to the anomalous magnetic moment of the muon. The method is based on computing susceptibilities with respect to external electromagnetic plane wave fields and allows for a precision determination of both the connected and the disconnected contributions to the vacuum polarization. We demonstrate that the statistical errors obtained with our method are much smaller than those quoted in previous lattice studies, primarily due to a very effective suppression of the errors of the disconnected terms. These turn out to vanish within small errors, enabling us to quote an upper limit. We also comment on the accuracy of the vacuum polarization function determined from present experimental R-ratio data.

Reciprocity principle-based model for shielding effectiveness prediction of a rectangular cavity with a covered aperture**Project supported by the National Natural Science Foundation of China (Grant No. 51307055) and in part by the State Grid Corporation of China (Grant No. No. SGRI-WD-71-12-009).

According to the reciprocity principle, we propose an efficient model to compute the shielding effectiveness of a rectangular cavity with apertures covered by conductive sheet against an external incident electromagnetic wave. This problem is converted into another problem of solving the electromagnetic field leakage from the cavity when the cavity is excited by an electric dipole placed within it. By the combination of the unperturbed cavity field and the transfer impedance of the sheet, the tangential electric field distribution on the outer surface of the sheet is obtained. Then, the field distribution is regarded as an equivalent surface magnetic current source responsible for the leakage field. The validation of this model is verified by a comparison with the circuital model and the full-wave simulations. This time-saving model can deal with arbitrary aperture shape, various wave propagation and polarization directions, and the near-field effect.

Realizing Tunable Inverse and Normal Doppler Shifts in Reconfigurable RF Metamaterials

The Doppler effect has well-established applications in astronomy, medicine, radar and metrology. Recently, a number of experimental demonstrations of the inverse Doppler effect have begun to appear. However, the inverse Doppler effect has never been observed on an electronically reconfigurable system with an external electromagnetic wave source at radio frequencies (RF) in experiment. Here we demonstrate an experimental observation of the inverse Doppler shift on an electronically reconfigurable RF metamaterial structure, which can exhibit anomalous dispersion, normal dispersion or a stop band, depending on an applied bias voltage. Either inverse or normal Doppler shift is realized by injecting an external RF signal into the electronically reconfigurable metamaterial, on which an electronically controllable moving reflective boundary is formed. The effective velocity of this boundary and the resulting frequency shift can be tuned over a wide range by a digital switching circuit. This work is expected to open up possibilities in applying the inverse Doppler effect in wireless communications, radar and satellite navigation.

Contribution of Electromagnetic Perturbation to the Transient Response of an Electronic Circuit Exposed to a High Multi-MeV X-Ray Flux

The contribution of the electromagnetic field to the electric response of a circuit exposed to high x-ray flux is quantified based on a novel approach which combines both experimental and numerical tools. First, we describe the method used to quantify the ionizing and electromagnetic stress induced by the x-ray beam in free space as well as on the target circuit. Next we show the perturbation resulting from the x-ray irradiation of an analog circuit. Also, we present the effect of an electromagnetic plane wave on the electric response of the circuit. Based on the comparison of experimental results, we demonstrate that electromagnetic fields coupling resulting from photoelectrons produced by the x-ray/circuit interaction is similar to the coupling induced by an external electromagnetic plane wave.

A thorough investigation into active and passive shielding methods for nano-VLSI interconnects against EMI and crosstalk

In this study two main shielding methodologies, active and passive, are comprehensively investigated for crosstalk and EMI alleviation. Electromagnetic coupling is a major concern for digital system wiring. It can cause logic fault, consume power and make signal integrity problem for neighbor wires. Active and passive shielding is employed to enclose partially some important wires like CLOCK network. Passive shield, which is a line connected to POWER rail or the GROUND, can enforce extra delay to the concerned wire. Rather, active shield is used to gain both guarding effect and reduction in time delay based on Miller's effect capacitance reduction. With area constraint for both silicon and metal, we have optimized which methodology should be chosen for best achievable performance. With simple analytic steps, the accuracy is verified and a design approach is introduced to choose the best. In addition, the immunity of the active and passive shield is studied against external electromagnetic wave. The result concludes that the passive shield show a better resistance in front of electromagnetic coupling, for both near pairing (crosstalk) and distant coupling (incident electromagnetic wave); in addition, active shielding method has better characteristic for timing issues.

FDTD for Hydrodynamic Electron Fluid Maxwell Equations

In this work, we develop a numerical method for solving the three dimensional hydrodynamic electron fluid Maxwell equations that describe the electron gas dynamics driven by an external electromagnetic wave excitation. Our numerical approach is based on the Finite-Difference Time-Domain (FDTD) method for solving the Maxwell’s equations and an explicit central finite difference method for solving the hydrodynamic electron fluid equations containing both electron density and current equations. Numerical results show good agreement with the experiment of studying the second-harmonic generation (SHG) from metallic split-ring resonator (SRR).

Magnetic-field-driven surface electromagnetic states in the graphene-antiferromagnetic photonic crystal system

The surface electromagnetic states (SEMSs) on graphene, which has a linear carrier dispersion law and is placed in an antiferromagnetic photonic crystal, are theoretically studied in the terahertz frequency range. The unit cell of such a crystal consists of layers of a nonmagnetic insulator and a uniaxial antiferromagnet, the easy axis of which is parallel to the crystal layers. A dc magnetic field is parallel to the easy axis of the antiferromagnet. An expression that relates the SEMS frequencies to the structure parameters is obtained. The problem of SEMS excitation by an external TE-polarized electromagnetic wave is solved, and the dependences of the transmission coefficient on the dc magnetic field and the carrier concentration are constructed. These dependences are shown to differ substantially from the case of a conventional two-dimensional electron gas with a quadratic electron dispersion law. Thus, the positions of the transmission coefficient peaks related to resonance SEMS excitation can be used to determine the character of carrier dispersion law in a two-dimensional electron gas.

An analysis of electromagnetic interference on RF circuits based on electromagnetic topology

ABSTRACTIn this article, we propose a method of analysis of the intentional electromagnetic interference (IEMI) in radio frequency circuits that are directly exposed to an external electromagnetic wave, using electromagnetic topology (EMT). EMT solves IEMI problems, by a fast and efficient transformation of the main penetrating channels of the external electromagnetic wave in the target, into general equivalent transmission lines. To handle nonlinear devices, we combined EMT with the harmonic balance method, by applying the least square method to the experimental data of the devices. To verify the proposed method, we applied it to microstrip line circuits with passive loads, a dipole antenna, and a low noise amplifier, and compared the results with the experimental ones. The two results were in good agreement. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2784–2789, 2014

Second-harmonic generation by a graphene nanoparticle

We study the second-harmonic generation by a spherical dielectric nanoparticle covered by graphene. We demonstrate that a strong nonlinear response is caused by an induced surface current in the graphene nanoparticle illuminated by an external electromagnetic wave. We obtain analytical expressions for the field multipoles characterizing the second-harmonic radiation and analyze the dependence of intensity and directivity of the nonlinear scattering on the frequency and structure of the electromagnetic field, revealing the asymmetric radiation patterns due to constructive multipole interference for the resonantly enhanced second-harmonic generation.

The gain in the plane wiggler with inhomogeneous magnetic field

We calculate the gain in a plane wiggler (undulator) with inhomogeneous magnetic field and in the external electromagnetic wave. The electromagnetic field-induced corrections to electron trajectories are found. The linear (field-independent) gain is calculated using these corrections to complex motion of electrons, which was described in previous paper, without electromagnetic field. This complex motion arises because of magnetic field inhomogeneity. It is shown that the account of inhomogeneity of the magnetic field leads to appearance of additional peaks in the gain of usual wiggler with uniform magnetic field.

Decision tree structure based classification of EEG signals recorded during two dimensional cursor movement imagery

Input signals of an EEG based brain computer interface (BCI) system are naturally non-stationary, have poor signal to noise ratio, depend on physical or mental tasks and are contaminated with various artifacts such as external electromagnetic waves, electromyogram and electrooculogram. All these disadvantages have motivated researchers to substantially improve speed and accuracy of all components of the communication system between brain and a BCI output device. In this study, a fast and accurate decision tree structure based classification method was proposed for classifying EEG data to up/down/right/left computer cursor movement imagery EEG data. The data sets were acquired from three healthy human subjects in age group of between 24 and 29 years old in two sessions on different days. The proposed decision tree structure based method was successfully applied to the present data sets and achieved 55.92%, 57.90% and 82.24% classification accuracy rate on the test data of three subjects. The results indicated that the proposed method provided 12.25% improvement over the best results of the most closely related studies although the EEG signals were collected on two different sessions with about 1 week interval. The proposed method required only a training set of the subject and automatically generated specific DTS for each new subject by determining the most appropriate feature set and classifier for each node. Additionally, with further developments of feature extraction and/or classification algorithms, any existing node can be easily replaced with new one without breaking the whole DTS. This attribute makes the proposed method flexible.

Carpet anti-cloak based on transformation optics

We propose a scheme for carpet anti-cloak based on the transformation optics. An anti-cloak layer is designed, which can make the external electromagnetic waves break the carpet cloak shielding. The external electromagnetic waves can be detected under the carpet cloak, while not affecting the role of carpet cloak of stealth. The Jacobian transformation tensor is calculated by numerically solving the Laplace equations with proper boundary condition. Thus, it is possible to design the anti-cloak layer of irregular shape. The simulation results demonstrate the feasibilities and flexibilities of the structure. Design details and full-wave simulation results are provided.

TRANSIENT ANALYSIS OF A RECTANGULAR CAVITY CONTAINING AN INTERIOR SCATTERER USING TD-EFIE WITH WEIGHTED LAGUERRE POLYNOMIALS AS TEMPORAL BASIS FUNCTIONS

Novel 2-D Time Domain Electric Field Integral Equations (TD-EFIE) are established in order to predict transient response of a wire enclosed within a rectangular cavity. The wire and cavity are excited by an external incident transient electromagnetic wave through a slot in the cavity wall. The formulation of the TD-EFIE is based on equivalence principle and boundary conditions taking account the effect of reflection from cavity walls. The equations are efficiently solved by Method of Moments. The transient unknown coefficients of the electric current at the wire and magnetic current at the slot are approximated using a set of orthonormal temporal basis functions derived from Laguerre Polynomials. The analysis demonstration is presented to prove that the novel TD-EFIE combined to MoM is able to solve this critical problem. No late-time instability is encountered.

A Minimized Invisibility Complementary Cloak With a Composite Shape

Based on the transformation optics and the concept of complementary media, this letter develops a minimized external invisibility cloak. The proposed cloak composed of a circular sector and two triangle sectors makes this invisible device with a smaller size compared to the complementary cylinder cloak. With the complementary media, the target object to be hidden can be placed at the outside of the cloak, and thus the target object can receive the external electromagnetic waves. Full-wave simulation results demonstrate that the proposed complementary invisibility cloak has a good performance for cloaking multiple target objects and simultaneously generating the illusion images.

Resonant mode behavior of lumped-resistor-loaded electric-inductive-capacitive resonator and its absorber application

This paper presents investigations into the resonant mode behavior of a lumped-resistor-loaded electric-inductive-capacitive (ELC) resonator, which is illuminated with a parallel polarization external electromagnetic wave. An ELC resonator exhibits a negative effective permittivity for both parallel and perpendicular polarizations. In contrast to a common ELC resonator, the lumped-resistor-loaded ELC resonator exhibits a switchable resonant mode behavior, thereby revealing a negative effective permeability. In addition, this resonator exhibits a low quality factor owing to the loaded lumped resistors. A metamaterial absorber, which consists of a lumped-resistor-loaded ELC resonator and a cut-wire strip, is designed to confirm the effectiveness of the resonator.

Design of invisibility anti-cloak for two-dimensional arbitrary geometries

In this paper, we derive the material parameter formulae for designing an electromagnetic invisibility anti-cloak of two-dimensional arbitrary geometry, which is conformal with the cloaked object. Different shapes of electromagnetic invisibility anti-cloaks are proposed to verify the correctness and effectiveness of the proposed formulae. The simulation results show that the invisibility anti-cloak can break cloak shielding and make the external electromagnetic waves into the cloak. This is not only to realize the transfer of information, but will not affect the role of cloak of stealth.

Modelling dielectric-constant values of concrete: an aid to shielding effectiveness prediction and ground-penetrating radar wave technique interpretation

A number of efficient and diverse mathematical methods have been used to model electromagnetic wave propagation. Each of these methods possesses a set of key elements which eases its understanding. However, the modelling of the propagation in concrete becomes impossible without modelling its electrical properties. In addition to experimental measurements; material theoretical and empirical models can be useful to investigate the behaviour of concrete's electrical properties with respect to frequency, moisture content (MC) or other factors. These models can be used in different fields of civil engineering such as (1) electromagnetic compatibility which predicts the shielding effectiveness (SE) of a concrete structure against external electromagnetic waves and (2) in non-destructive testing to predict the radar wave reflected on a concrete slab. This paper presents a comparison between the Jonscher model and the Debye models which is suitable to represent the dielectric properties of concrete, although dielectric and conduction losses are taken into consideration in these models. The Jonscher model gives values of permittivity, SE and radar wave reflected in a very good agreement with those given by experimental measurements and this for different MCs. Compared with other models, the Jonscher model is very effective and is the most appropriate to represent the electric properties of concrete.

경량전철용 유도급전 시스템의 전자파 분석 연구

Traction motors for driving and power conversion devices using semiconductor switch are equipped with a transportation systems such as an electrical railway system. Power conversion devices have the possibility of malfunction by external electromagnetic waves. As a result, these could affect the safe operation of the railway. Moreover, the electromagnetic waves above safe limits will be harmful to the passengers inside the railway vehicles or anyone working around the rail-track. For this reason, the importance and need about the reliability check and complement of electromagnetic waves generated from the IPT(Inductive Power Transfer) system have been suggested for the safe application of the IPT system to the railway system. In this study, prediction for the electromagnetic wave properties was conducted through FEM(Finite Element Method) analysis of 5kW-class IPT system design model. Next, the 5kW IPT system prototype was made and then the small-scaled railway vehicle was made to mount the IPT system and the energy management system. Finally, the electromagnetic waves generated from the real small-scaled IPT system were measured and analyzed, and then the reliability check of predictions by FEM analysis were carried out.

Infrared limit in external field scattering

Scattering of electrons/positrons by external classical electromagnetic wave packet is considered in infrared limit. In this limit, the scattering operator exists and produces physical effects, although the scattering cross-section is trivial.

The Effect of Electromagnetic Waves on Multilayer Orthogonal Microstrip Lines With and Without Defected Microstrip Structure

A method for analysis of multilayer coupled transmission lines with and without defected microstrip structure (DMS) excited by an external electromagnetic wave is presented. The structure is first decomposed into coupled transmission-line sections and crosstalk regions, then a lumped circuit model for the crosstalk region and the DMS section is presented, and the forced terms associated with the incident wave are calculated. Finally, by using the modal decoupling method, the unknown modal coefficients and subsequently voltages and currents are obtained. The validity of the method is verified by comparison between the analytical and the simulated results of HFSS full-wave simulator.