Electromagnetic Wave Radiation Research Articles

Resistive Grounding Technique of Heat Sink for Reducing Radiation Noise

Heat sink has been used to help an electrical device operate in normal temperature condition. But heat sink radiates unwanted electromagnetic wave, which may cause electromagnetic interference problem. A resistance loaded grounding technique is proposed to reduce electromagnetic wave radiation by a heat sink. Numerical simulations are accomplished to find optimal loading resistance. Also electromagnetic fields radiated by from a heat sink are measured and compared with the simulation results. The test results verify the usefulness of the proposed technique.

Propagation of electromagnetic waves generated by modulated moving source in dispersive lossy media

AbstractWe apply the complex two‐dimensional stationary‐phase method for problems of electromagnetic waves radiation from the moving modulated sources in dispersive and lossy medium. The explicit formulas for fields generated by a moving source, the Doppler effect, and the retarded time are obtained. We apply the developed approach to numerical study of the Cherenkov radiation in a dispersive medium (Drude model). Our simulations have shown that in double negative dispersive metamaterials, the Cherenkov cone splits in two branches. Copyright © 2014 John Wiley & Sons, Ltd.

The dynamic Casimir effect within a vibrating metal photonic crystal

The lattice-vibrating metal photonic crystal is exactly a system of dynamical Casimir effect connected in series, and so we can expect that a dynamical Casimir effect is enhanced by the photonic band effect. In the present study, when an electromagnetic field between metal plates is in the ground state in a one-dimensional metal photonic crystal, the radiation of electromagnetic wave in excited states has been investigated by artificially introducing lattice vibration to the photonic crystal. In this case as well as a dynamical Casimir effect, it has been shown that the harmonics of a ground state are generated just by vibrating a photonic crystal even without an incident wave. The dependencies of the radiating power on the number of layers and on the wavenumber of the lattice vibration are remarkable. It has been found that the radiation amplitude on lower excited states is not necessarily large and radiation on specific excited levels is large.

Does the Helmholtz theorem of vector decomposition apply to the wave fields of electromagnetic radiation?

The derivation of the Helmholtz theorem of vector decomposition of a three-vector field requires that the field satisfy certain convergence properties at spatial infinity. This paper investigates if time-dependent electromagnetic radiation wave fields of point sources, which are of long range, satisfy these requirements. It is found that the requirements are satisfied because the fields give rise to integrals over the radial distance r of integrands of the form sin(kr)/r and cos(kr)/r. These Dirichlet integrals converge at infinity as required.

Terahertz transition radiation of bulk and surface electromagnetic waves by an electron entering a layered superconductor

We theoretically study the transition radiation of bulk and surface electromagnetic waves by an electron crossing an interface between a layered superconductor and an isotropic dielectric. We assume that the direction of the electron motion and the orientation of the superconducting layers are perpendicular to the interface. We derive the analytical expressions for the strongly anisotropic radiation fields and for the time-integrated energy fluxes of bulk and oblique surface electromagnetic waves (OSWs). We show that the OSWs with frequencies close to the Josephson plasma frequency $\omega_J$ provide the main contribution to the OSWs energy flux. Moreover, for frequencies close to the Josephson plasma frequency, the spectral density of the OSWs radiation diverges at some critical value of the azimuth angle $\varphi$. At the angles $\varphi=0$ and $\varphi=90^o$, the radiation field has a transverse magnetic polarization. We have also studied the Cherenkov radiation by the electron escaping from the layered superconductor and show that this radiation is almost monochromatic. A remarkable feature of the Cherenkov radiation in a layered superconductor is that, contrary to the isotropic case, the Cherenkov radiation distinctly manifests itself in the angular dependence of the radiation energy flux.

The Gyrotron at 50: Historical Overview

Gyrotrons form a specific group of devices in the class of fast-wave vacuum electronic sources of coherent electromagnetic wave radiation known as electron cyclotron masers (ECMs) or cyclotron resonance masers (CRMs). The operation of CRMs is based on the cyclotron maser instability which originates from the relativistic dependence of the electron cyclotron frequency on the electron energy. This relativistic effect can be pronounced even at low voltages when the electron kinetic energy is small in comparison with the rest energy. The free energy for generation of electromagnetic (EM) waves is the energy of electron gyration in an external magnetic field. As in any fast-wave device, the EM field in a gyrotron interaction space is not localized near a circuit wall (like in slow-wave devices), but can occupy large volumes. Due to possibilities of using various methods of mode selection (electrodynamical and electronic ones), gyrotrons can operate in very high order modes. Since the use of large, oversized cavities and waveguides reduces the role of ohmic wall losses and breakdown limitations, gyrotrons are capable of producing very high power radiation at millimeter and submillimeter wavelengths. The present review is restricted primarily by the description of the development and the present state-of-the-art of gyrotrons for controlled thermonuclear fusion plasma applications. The first gyrotron was invented, designed and tested in Gorky, USSR (now Nizhny Novgorod, Russia), in 1964.

Modern methods for optimal spatio-temporal signal processing in active, passive, and combined active-passive radio-engineering systems

Using the concept of the search for the optimal signal parameter estimates and related to them parameters of electromagnetic and regression models of scattering and radio-thermal radiation of electromagnetic waves by various objects and natural medias on the basis of modern theory of statistical decisions and estimates of probability distribution parameters, a number of fundamental results developing the theory and methods of optimal spatio-temporal signal processing are obtained for the first time. Corresponding directions of their practical application in active, passive, and combined (complex) active-passive radar and remote-sensing radio systems are considered. Special attention is given to application of Kravchenko weight functions (windows) in problems of radio engineering systems synthesis.

The Necessity of Interdisciplinary Collaboration for the Improvement of the Electromagnetic Environment in Medical Settings

Modern clinical medicine uses a wide variety of highly technical medical devices on which advanced medicine increasingly relies. These devices often use internet and communication technology. Some medical devices pick up weak biomedical signals and others function by generating a powerful magnetic field. Wireless LAN and wireless voice communication are useful in clinical settings. Because of the recent availability of technical reports and our educational efforts to show that medical devices and wireless communication apparatus are safe and compatible, there is reduced anxiety among medical professionals and thus demand is increasing for technically advanced systems. For safety and security reasons, it is necessary to prevent both the radiation of strong electromagnetic waves from apparatus inside the hospital and to block the invasion of electromagnetic waves from outside. These problems can be solved by the use of electromagnetic shielding technology. The above are all related to the necessity of controlling electromagnetic fields. At present, adequate techniques for the control of the fields commonly found in medical settings have not been established. The best results will be attained if collaboration is done with people from the variety of fields working on or who will work on the project, such as those involved in material, architectural, and structural engineering, as well as the medical staff. In order to insure the safe use of wireless communications in medical settings it will be necessary to improve the EMC standards and to disseminate information about electromagnetic field control to the medical staff. To insure safety and meet the needs of this rapidly changing environment, electromagnetic field control techniques must be established and constantly improved to meet the requirements of the environment in which medical devices are used. To achieve this, interdisciplinary collaboration is indispensable.

Current progress on the modification of carbon nanotubes and their application in electromagnetic wave absorption

In modern times, with the rapid development of technology, science and economy, applications of electromagnetic (EM) wave absorption in both commercial and military fields have increased. Meanwhile, the problems brought by EM wave absorption have gradually become obvious, such as signal interference, back-radiation of microstrip radiators and so on. Furthermore, the impact of EM wave radiation on human health has also attracted much public attention. In this regard, the application of EM wave absorbing materials has become a focus of current research. Due to their unique chemical, physical, and mechanical properties, carbon nanotubes (CNTs), through certain modifications for light mass, wide range and strong absorption, have great potential to be used as excellent EM wave absorbents. This review highlights recent research into the modification of CNTs, with special emphasis on their EM wave absorbing ability.

Polarization radiation of vortex electrons with large orbital angular momentum

Vortex electrons, - freely propagating electrons whose wavefunction has helical wavefronts, - could become a novel tool in the physics of electromagnetic radiation. They carry a non-zero intrinsic orbital angular momentum (OAM) $\ell$ with respect to the propagation axis and, for \ell \gg 1, a large OAM-induced magnetic moment, \mu ~ \ell \mu_B (\mu_B is the Bohr magneton), which influences the radiation of electromagnetic waves. Here, we consider in detail the OAM-induced effects by such electrons in two forms of polarization radiation, namely in Cherenkov radiation and transition radiation. Thanks to the large \ell, we can neglect quantum or spin-induced effects, which are of the order of \hbar \omega/E_e \ll 1, but retain the magnetic moment contribution \ell \hbar \omega/E_e \lesssim 1, which makes the quasiclassical approach to polarization radiation applicable. We discuss the magnetic moment contribution to polarization radiation, which has never been experimentally observed, and study how its visibility depends on the kinematical parameters and the medium permittivity. In particular, it is shown that this contribution can, in principle, be detected in azimuthally non-symmetrical problems, for example when vortex electrons obliquely cross a metallic screen (transition radiation) or move nearby it (diffraction radiation). We predict a left-right angular asymmetry of the transition radiation (in the plane where the charge radiation distributions would stay symmetric), which appears due to an effective interference between the charge radiation field and the magnetic moment one. Numerical values of this asymmetry for vortex electrons with E_e = 300keV and \ell = O(100-1000) are O(0.1-1%), and we argue that this effect could be detected with existing technology. The finite conductivity of the target and frequency dispersion play the crucial roles in these predictions.

Young Scientists Summer School and the International Conference on Radiation and Scattering of Electromagnetic Waves (RSEMW 2013)

The traditional 8th International Scientific Conference on Radiation and Scattering of Electromagnetic Waves, RSEMW 2013, was held in Russia this past summer (Figure 1). RSEMW 2013 was organized by the Russian Ministry of Education and Science, the Moscow IEEE AP-S Chapter, the Russian Foundation for Basic Research, and Southern Federal University (Russia). The conference was supported by Rohde & Schwarz Russia and the Russian branch of Agilent Technologies Company.

Antiepileptic effects of short-wave radiation in hypogeomagnetic conditions

Abstract The work was dedicated to investigation of dynamics of epileptic activity in conditions of extremely high frequency electromagnetic waves (EHF) radiation (7,1 mm, 0,1 mW/cm2) upon focal epileptic activity. Epileptic activity was penicillin-induced (10,000 IU/ml) in the frontal region of the brain cortex in myorelaxed and artificially ventilated rats under acute experimental condition. Thermal effects were absent as far as absorbed dosage of energy did not exceed 0,1 J/ animal. It was established that preliminarily performed hypogeomagnetic period (3,0 h) with the inductivity of geomagnetic field at 5×10−8 Tesla caused the intensification of antiepileptic effects of EHF (15,0 min of exposure). It was pronounced in the form of decrease of foci intensity and significant reduction of lifespan of foci — up to 115,3±13,4 minutes, which was both significant when compared with separate effects of hypogeomagnetic influence (187,3±12,5 min) and EHF (15,0 minutes of exposure) effect (164,2±12,5 minutes) (P<0,05). Besides, EHF (15,0 min) which was made after 3,0 h exposure to hypogeomagnetic influence suppressed generalized seizures in amygdalarly kindled rats.

Assessment of nuclear abnormalities in exfoliated cells from the oral epithelium of mobile phone users

Transmission and reception of mobile telephony signals take place through electromagnetic wave radiation, or electromagnetic radiofrequency fields, between the mobile terminal and the radio base station. Based on reports in the literature on adverse effects from exposure to this type of radiation, the objective of this study was to evaluate the genotoxic and cytotoxic potential of such exposure, by means of the micronucleus test on exfoliated cells from the oral epithelium. The sample included 45 individuals distributed in 3 groups according to the amount of time in hours per week (t) spent using mobile phones: group I, t > 5 h; group II, t > 1 h and ≤ 5 h; and group III, t ≤ 1 h. Cells from the oral mucosa were analyzed to assess the numbers of micronuclei, broken egg structures and degenerative nuclear abnormalities indicative of apoptosis (condensed chromatin, karyorrhexis and pyknosis) or necrosis (karyolysis in addition to these changes). The occurrences of micronuclei and degenerative nuclear abnormalities did not differ between the groups, but the number of broken egg (structures that may be associated with gene amplification) was significantly greater in the individuals in group I (p < 0.05).

Smartphones jetzt noch smarter? - Möglichkeit des Einsatzes als „Dosiswarner“

Smartphone apps for measuring ionizing radiation use the capability of (CMOS) camera chips to detect not only perceivable light but also electromagnetic wave radiation. The present study evaluates the accuracy of hardware and software and defines possible applications for the detection of X-ray radiation fields. 2 apps and 2 different devices were tested in comparison with a calibrated ionization chamber and a personal electronic dosimeter. A calibration curve was determined for dose rates between 12 700 µSv/h and 5.7 µSv/h generated by a C-arm system. The measured scattered radiation produced by an Alderson-Rando phantom ranged from 117 µSv/h (at a distance of 2 m) to 5910 µSv/h (at a distance of 0.3 m) and was 1.4 times less than the values of the ionization chamber. The exposure rate for the operator's thyroid was within 4200 - 4400 µSv/h. We found a strong dependence of the measurements on the angulation of the Smartphone, especially for short distances from the phantom (at a distance of 0.3 m, a 45° rotation downwards in a vertical direction caused a decrease from 3000 µSv/h to 972 µSv/h, while an upwards rotation resulted in an increase to 5000 µSv/h). For a distance of 1 m, this effect was remarkably smaller. Smartphones can be used to detect ionizing radiation but showed limited accuracy and are heavily dependent on the angulation of the device. Qualitative measurements and utilization for dose alerts are possible.

무배전기식 불꽃 점화 시스템의 점화 플러그 케이블에서 발생되는 전자파의 분석

It is an analysis about electromagnetic wave which is generated from a Spark plug cable of Distributorless spark ignition system. In case of Distributorless spark ignition system, high frequency generation is an ignition coil and Spark plug cable and Spark plug could be activated with electromagnetic wave radiation antenna. I calculated a resonant frequency with HFSS by measuring length of Spark plug cable and Spark plug. The antenna was considered as monopole antenna in this calculation. According to power spectrum measurement analysis of engine room radiated electromagnetic wave and calculated Resonant frequency, it is possible to find out that the Distributorless spark ignition system radiates high frequency energy in certain frequency band.

Radiation of electromagnetic waves in uniaxial media

A rigorous solution for a system of Maxwell equations for monochromatic fields radiated into homogeneous nonabsorbing uniaxial media is presented. Two conditions to be satisfied are determined for the field source distribution functions ensuring the appearance of either only ordinary or only extraordinary waves in the medium. If none of these conditions is satisfied, the distribution function of the field sources can be uniquely represented as a sum of two summands each of which satisfies one of the aforesaid conditions. Thus, one of the summands is responsible for the radiation of the ordinary wave; the second one, for the radiation of the extraordinary wave.

Monitoring the Radiation Injury of Red Blood Cells to Micowave Radiation with Different Power Density

Multiple state-of-the-art techniques, such as multi-dimensional micro-imaging, fast multi-channel micro-spetrophoto-metry, and dynamic micro-imaging analysis, were used to dynamically investigate various effects of cell under the 900MHzelectromagnetic radiation. Cell changes in shape, size under different power density electromagnetic waves radiation were presented in this paper. Experimental results indicated that the isolated human red blood cells (RBCs) do not have obviously real-time responses to the ultra-low density (15 μW/cm2, 31 μW/cm2) electromagnetic wave radiation when the radiation time is not more than 30 minutes; however, the cells do have significant reactions in shape, size to the electromagnetic waves radiation with power densities of 1 mW/cm2and 5 mW/cm2. The data reveals the possible influences and statistical relationships among living human cell functions, radiation amount and exposure time with high-frequency electromagnetic waves. The results of this study may be significant on protection of human being and other living organisms against possible radiation affections of the high-frequency electromagnetic waves.

On The Origin of Electromagnetic Waves from Lightning Discharges

Interaction of up going ion beam forming current flow in the pre-ionized stepped leader plasma and the way, how the kinetic energy of the beam particles is converted into electromagnetic energy have been discussed. The ion beam interaction with the plasma wave modes in the stepped leader channel produces perturbations in the return stroke current flow and changes its uniformity and becomes non-uniform. In the present study, the return current is taken to be deeply modulated at a given modulation frequency, and considered that it behaves like an antenna for electromagnetic radiation. In this paper the total amount of energy associated with return stroke is given to electromagnetic waves is estimated. I. Introduction Lightning return stroke is an up going ion beam within a pre-ionized channel called stepped leader in which the excessive electrons deposited during the leader process are drained to the earth. The partially ionized stepped leader channel is supposed to bring the negative charge from the cloud base and distributes it homogeneously along the channel. The front of the return stroke moves upward with the velocity near to the velocity of light in the partially ionized channel (1 - 6). The electromagnetic energy radiated by lightning return stroke covers a wide frequency range, extending from a few hertz in the ELF band to the visible light (7 - 11). The exact physical processes, due to which radiation of electromagnetic waves from the ionized channel, taking place is not known clearly. The current in the channel is the main cause of electromagnetic radiation. The approximate assumption of the simple harmonic form of return current flow in the pre-ionized channel of stepped leader largely governs the radiated electromagnetic power and its spectral characteristics (12 - 13). The double exponential form of return current flow does explain certain features of atmospherics but it is not based on the plasma processes taking place in the return stroke current flow in the lightning channel. Singh and Singh (13) have reported in their presentation that the upwelling ion beam interacts with the pre-ionized channel and gives rise to resulting return current. The resulting current in the lightning channel may become an oscillatory as a result of plasma wave interaction. The energy extraction from upwelling ion beam requires, for emission of the electromagnetic waves, that the phase matching between waves and particles should be maintained for as long as possible. This desirable property is maintained by Cernkov and Cyclotron resonances. In this presentation, the idea of modulated current which flows into the pre-ionized plasma channel is taken (14 - 16) and is applied to the electromagnetic emission from the ion beam forming the return stroke. For this study it is considered that the modulated beam behaves like an antenna for the electromagnetic radiation. The value of modulation frequency, Ω is chosen such that force resonance condition (i.e. ω = ± Ω) may be sustained (ω = + ω for Cernkov resonance, and ω = - Ω for cyclotron resonance). In this presentation it has been reported that the electromagnetic power as a form of ion whistler Anomalous Doppler Shifted (ADS) mode is radiated from lightning return stroke channel. The energy in an ion whistler ADS mode is mainly due to the oscillatory damping of lower and upper wave modes in the stepped leader channel (10). The electromagnetic radiation from an oscillatory current source becomes variable. Such variations in recorded whistler are often observed in whistler sonograms. This paper is organized as follows: In sec. (II) return stroke ion beam interaction with pre-ionized stepped leader is discussed. Sec. (III) is devoted to describe the beam model on the basis of subsequent considerations. In sec. (IV) expression of electromagnetic power for ion whistler ADS mode is carried out. In sec. (V) applications of our proposal and its validity are argued. Results are presented and discussed in this section of the study. Finally, sec. (VI) states the conclusions.

ELECTROMAGNETIC WAVES RADIATION INTO THE SPACE OVER A SPHERE BY A SLOT IN THE END-WALL OF A SEMI-INFINITE RECTANGULAR WAVEGUIDE

The problem of electromagnetic waves radiation into a space outside a perfectly conducting sphere through a narrow slot, cut in an end-wall of a semi-inflnite rectangular waveguide, excited by a fundamental wave of H10 type is solved using a rigorous self-consistent formulation. The starting point for the analysis is the one-dimensional integral equation for the equivalent magnetic current in the slot, obtained by using the efiective thickness of the slot. The asymptotic solution of the equation was found by the generalized method of induced magnetomotive forces (MMF). The physical adequacy of the constructed mathematical model to the real physical process is conflrmed by experimental data. In∞uence of the sphere radius upon energy characteristics of the slot radiator was investigated numerically. It was shown that at any frequency of waveguide single-mode range, the radiation coe-cient of a spherical antenna can be made close to one by choosing the slot length, the sphere radius and the waveguide height. Conditions for correct application of inflnite screen approximation for spherical scatterers with su-ciently large radii are formulated.

An optical nano-antenna system design for radio therapeutic use

This paper proposes a nano-antenna system using the optical spins generated by a PANDA ring resonator for radio therapeutic applications. Initially, the magnetic field is induced by the coupling effects between aluminium plate (Al) and TE and TM light modes. The generated electromagnetic wave radiation is controlled by a soliton power, coupling coefficients, and ring radii within the system, where finally the near field radio wave is transmitted to the required therapeutic target (neural cells). Simulation results have shown that the temperature within the range from 40°C to about 46°C can be controlled and achieved.