Showing papers in "Journal of Communications Technology and Electronics in 2007"
TL;DR: In this article, a classification scheme for placing electromagnetic materials with extreme values of parameters (very large or very small) can be placed and related to one another in order to classify them.
Abstract: Metamaterials are characterized by their nonconventional material parameters, examples being media that possess very large or very small, even negative, permittivities and permeabilities. This article discusses a classification scheme in which various electromagnetic materials with extreme values of parameters (very large or very small) can be placed and related to one another.
44 citations
TL;DR: In this article, the polarization of an electromagnetic wave by a 2D array of double-turn metal helices has been investigated both theoretically and experimentally, and the helix parameters that are optimal for radiation of a circularly polarized wave are calculated.
Abstract: Transformation of the polarization of an electromagnetic wave by a 2D array of double-turn metal helices is investigated both theoretically and experimentally. Electric and magnetic moments induced in an isolated helix by an incident linearly polarized wave are determined. A universal relationship between the projections of the induced moments onto the axis of a helix is derived. The helix parameters that are optimal for radiation of a circularly polarized wave are calculated. A 2D array composed of double-turn helical radiators with optimum parameters is manufactured. Experimental verification of the obtained theoretical results is performed.
28 citations
TL;DR: In this article, the authors investigated the possibility of obtaining wave beams of radiation with orthogonal polarizations of the electric field in high-power ultrawideband electromagnetic pulses.
Abstract: The results of investigation of the generation and radiation of high-power ultrawideband electromagnetic pulses are presented. The possibility of obtaining wave beams of radiation with orthogonal polarizations of the electric field is shown. The radiating system is a 16-element antenna array that can be separated into two subarrays operating in orthogonal polarizations and excited by pulses separated in time. Two design versions of orthogonal subarrays are studied.
26 citations
TL;DR: In this article, it was shown that the problem of excitation of a magnetodielectric layer with parameters ǫ and μ equal to minus unity by a point source is not always solvable.
Abstract: It is shown that the problem of excitation of a magnetodielectric layer with parameters ɛ and μ equal to minus unity by a point source is not always solvable. Conditions under which the problem has a solution are established. It is found that, in the vicinity of the singular point ɛ = μ = −1, determination of the field is an illposed problem: Small variations in these parameters result in large changes of the field.
22 citations
TL;DR: In this article, the results of calibration of the processing method with the use of speckle images of a single star are presented, and photographs of recorded and recovered images of the International Space Station and Saturn are presented.
Abstract: Experiments on the improvement of images of artificial Earth satellites are performed via the methods of digital postdetection filtering in the case when a telescope with an aperture diameter of approximately 1 m is employed to observe extended objects. The resolution obtained in white-light observations is three times higher than the atmosphere-limited resolution. The results of calibration of the processing method with the use of speckle images of a single star are presented. Photographs of recorded and recovered images of the International Space Station and Saturn are presented.
20 citations
TL;DR: In this article, a simple algorithm for calculating the magnetorefractive effect (MRE) in multilayers, granulated films, nanocomposites, and manganites is proposed.
Abstract: Studies of the magnetorefractive effect (MRE) in multilayers, granulated films, nanocomposites, and manganites are briefly reviewed. A simple algorithm for calculation of the MRE is proposed. The possibil- ity to enhance the MRE by means of multipath interference in 1D magnetophotonic crystals containing a nano- composite or manganite film as a defect is theoretically analyzed. It is shown that, in magnetophotonic crystals, the MRE may reach 50-60% in the presence of reflection. These values are three orders of magnitude larger than those observed for common magnetooptic phenomena, such as the equatorial Kerr effect, and two orders of magnitude larger than the MRE in one-layer structures.
17 citations
TL;DR: A critical look is taken at the promise of metamaterials for antenna performance enhancement and directions of possible future research on these materials are recommended.
Abstract: The main objective of this paper is to take a critical look at the promise of metamaterials for antenna performance enhancement and to recommend directions of possible future research on these materials.
16 citations
TL;DR: In this article, a new analytic method is developed and generalized for solving problems of radar imaging, which involves analytic determination of the functionals of stochastic backscattered fields and can be applied to solve a wide class of physical problems with allowance for the finite width of an antenna's pattern.
Abstract: The theory of wave scattering by anisotropic statistically rough surfaces, which is an important part of statistical radiophysics, is considered. A new analytic method is developed and generalized for solving problems of radar imaging. The method involves analytic determination of the functionals of stochastic backscattered fields and can be applied to solve a wide class of physical problems with allowance for the finite width of an antenna’s pattern. The unified approach based on this method is used to analyze the generalized frequency response of a scattering radio channel, a generalized correlator of scattered fields, spatial correlation functions of stochastic backscattered fields, frequency coherence functions of stochastic backscattered fields, the coherence band of a spatial-temporal scattering radar channel, the kernel of the generalized uncertainty function, and the measure of noise immunity characterizing radar probing of the Earth’s surface or extended targets. The introduced frequency coherence functions are applied for thorough and consistent study of techniques for measuring the characteristics of a rough surface, aircraft altitude, and distortions observed when radar signals are scattered by statistically rough, including fractal, surfaces. To exemplify urgent applications, radiophysical synthesis of detailed digital reference radar terrain maps and microwave radar images that was proposed earlier is considered and improved with the use of the theory of fractals.
16 citations
TL;DR: In this paper, the dispersion properties of magnetostatic waves in a metal/ferrite/magnetic-wall structure are investigated and a rule is formulated so that a dispersion relation for one of the structures can be used to derive the equation for any other structure.
Abstract: The dispersion relations for an in-plane-magnetized ferrite plate with an arbitrary combination of magnetic-wall or perfectly conducting plane boundary conditions imposed at a distance from the plate’s surfaces are compared. A rule is formulated so that a dispersion relation for one of the structures can be used to derive the equation for any other structure. The isofrequency and dispersion characteristics of magnetostatic waves in a metal/ferrite/magnetic-wall structure are investigated. It is found that, in this case, the waves are characterized not only by a unidirectional propagation over the entire range of their existence (∼5 GHz) but also by the presence of a nearly straight section of the dispersion curve (∼2 GHz). In this structure, volume waves, surface waves, and waves with an amplitude that is constant over the plate thickness are seen to exist within the same frequency interval.
15 citations
TL;DR: In this article, a method based on the solution of a nonlinear Fredholm integral equation of the second kind was developed for the detection of a plane electromagnetic wave by a dielectric layer in the resonance region.
Abstract: Diffraction of a plane electromagnetic wave by a dielectric layer is considered in the resonance region without allowance for multiple frequencies. The layer is assumed to be transversely inhomogeneous, isotropic, nonmagnetic, linearly polarized, and weakly Kerr nonlinear. A method based on solution of a nonlinear Fredholm integral equation of the second kind is developed. Sufficient conditions for the existence and uniqueness of a solution are obtained.
15 citations
TL;DR: In this paper, the behavior of the wave field is investigated in the case when the values of the constitutive parameters approach the singular point along the curve, where the transverse dimension of the field in the focal plane of the lens is smaller than the diffraction limit.
Abstract: Excitation of a magnetodielectric plate with the parameters ɛ → −1 and μ → −1 by an elementary electric dipole is considered. The behavior of the wave field is investigated in the case when the values of the constitutive parameters approach the singular point ɛ = μ = −1 along the curve ɛμ = 1. A condition is established under which the transverse dimension of the field in the focal plane of the lens is smaller than the diffraction limit. The dimension of the spot is expressed in an explicit form. It is shown, that, in the situation considered, the effect of longitudinal focusing is absent.
TL;DR: In this paper, the applicability of constitutive parameters for description of electromagnetic processes in heterogeneous media is studied at frequencies at which dimensions of the particles of the media are still substantially smaller than the wavelength in this medium but already are comparable with this parameter.
Abstract: The applicability of constitutive parameters for description of electromagnetic processes in heterogeneous media is studied at frequencies at which dimensions of the particles of the media are still substantially smaller than the wavelength in this medium but already are comparable with this parameter. It is proved that consideration for the retardation effects at distances comparable with the characteristic dimensions of inclusion not only changes formulas for constitutive parameters but also enhances the role played by the Drude transition layer in calculation of the reflection coefficient describing reflection of plane waves from a layer of a finite thickness. A modification of the Drude theory is developed that takes into account local anisotropy of the transition layer. It is shown that the developed theory almost eliminates discrepancies between the analytic theory and an exact numerical calculation in a certain frequency region that were observed in previous studies.
TL;DR: In this article, a new realization of AMCs based on two or more closely spaced capacitive gratings whose period is small relative to the wavelength is proposed. But it is shown that such structures behave as AMCs in a wide interval of the angles of incidence of TE and TM waves.
Abstract: New realizations of artificial magnetic conductors (AMCs) based on two or more closely spaced capacitive gratings whose period is small relative to the wavelength are proposed. Simple formulas are derived for estimation of the resonance frequencies and frequency bands in which the proposed structures behave as AMCs. Angular dependencies of the resonance frequencies are found for TE and TM waves. Propagation conditions for surface waves are considered. It is shown that, at resonance frequencies, such structures support only slow TM waves with small values of the slowing factor. It is confirmed experimentally that such structures behave as AMCs in a wide interval of the angles of incidence of TE and TM waves.
TL;DR: In this article, a method for the analysis of an array of parallel-plate waveguides with protruding longitudinally inhomogeneous dielectric elements is proposed, which consists in expansion of the transverse electric (for the case of E polarization) or magnetic field in the domain containing the dielectrics elements in terms of transverse functions of the Floquet channel.
Abstract: A method is proposed for the analysis of an array of parallel-plate waveguides with protruding longitudinally inhomogeneous dielectric elements. The method consists in expansion of the transverse electric (for the case of E polarization) or magnetic (for the case of H polarization) field in the domain containing the dielectric elements in terms of transverse functions of the Floquet channel. This expansion contains unknown variable coefficients. Projection of the Helmholtz equation for the aforementioned fields onto the transverse functions and application of a 1D finite-element method along the longitudinal coordinate in combination with projective matching of the fields in the waveguide apertures and at the boundary with free space reduces the problem to solution of a system of linear algebraic equations. The results of calculation of the reflection coefficient and the radiation pattern of an array element are presented. These results characterize both the efficiency of the proposed method and the possibility of formation of sector element patterns in the studied arrays.
TL;DR: In this paper, a nonrelativistic electron beam with a virtual cathode situated in the diode gap with a decelerating field is experimentally and theoretically studied.
Abstract: A nonrelativistic electron beam with a virtual cathode situated in the diode gap with a decelerating field is experimentally and theoretically studied. A 1D model of the electron beam in the presence of a decelerating field is constructed. Nonlinear nonstationary processes in this system are investigated by means of numerical analysis of the model. The processes are described and interpreted with regard to formation and interaction of structures in the electron flow. The theoretical results are qualitatively confirmed by the experimental data showing that the system under study can be considered as a promising controlled source of chaotic oscillations in the microwave range.
TL;DR: In this article, an image transmission principle related to the transformation of the spatial spectrum of a source into modes propagating in a metamaterial with a flat isof-frequency contour is proposed.
Abstract: An image transmission principle related to the transformation of the spatial spectrum of a source into modes propagating in a metamaterial with a flat isofrequency contour is proposed. This principle makes it possible to obtain a resolution much smaller than the wavelength. The proposed principle is implemented in the microwave, terahertz, and optical frequency bands with the use of a medium consisting of parallel metal wires. It is shown that the subwavelength transmission of images can be achieved in the visible optical band via the use of a periodic structure consisting of successive metal and dielectric layers. The resolution, operation bandwidth, and sensitivity to losses in component materials are estimated for all the proposed systems. The applicability of such structures in medicine, in near-field microscopy, and as components of optical data storages with increased capacity is considered.
TL;DR: In this article, the propagation of a short quasi-monochromatic electromagnetic (light or radio) signal (wave packet) is considered, and the carrier frequency is close to the frequency of the absorption spectral line of a medium.
Abstract: Propagation of a short quasi-monochromatic electromagnetic (light or radio) signal (wave packet) is considered. The carrier frequency of the signal is close to the frequency of the absorption spectral line (or group of lines) of a medium, and the spectrum width is large relative to the width of this spectral line (or group of lines). Analytic formulas for the temporal dependence of the signal are derived and numerically confirmed for paths of various lengths. It is shown that the signal is substantially distorted long before it noticeably decays owing to absorption. The signal’s temporal dependence turns out to be rather universal with respect to the form factor of the spectral line, the optical thickness of the substance layer, and the initial temporal dependence of the signal.
TL;DR: In this paper, a new method was developed for solving the problem of scattering by a thin metal screen placed in a planar waveguide, which can be applied for a screen of an arbitrary geometry and extended to problems of scatter by bodies and unclosed screens located in complex layered structures.
Abstract: A new method is developed for solving the problem of scattering by a thin metal screen placed in a planar waveguide. The method can be applied for a screen of an arbitrary geometry and extended to problems of scattering by bodies and unclosed screens located in complex layered structures.
TL;DR: In this article, the nonlinearity of signal transformation by an object is investigated via sensing of the object by two successive test signals and determining the non-linearity characteristic in terms of the difference between the convolutions of the test signal and the object responses.
Abstract: The nonlinearity of signal transformation by an object is investigated via sensing of the object by two successive test signals and determining the nonlinearity characteristic in terms of the difference between the convolutions of the test signals and the object responses. It is shown that, in such an approach, there is no need to prespecify the relationship between the test signals and predetermine the signal waveforms. An approach that takes into account the nonlinear signal distortions in a receiver is described. In an experimental investigation of the nonlinearity of the transformation of the test signal (magnetic field) by metal objects, it is shown that the considered nonlinearity characteristic is several times greater than the nonlinearity characteristic of signal transformation that can be obtained via determination of sideband spectral components.
TL;DR: In this article, a method to calculate the illumination of a 2D area via the 1D distribution of the illuminance along a line is proposed, and a comparative analysis of the uniformity of the illumination and energy consumption is performed in the case when LEDs with different concentrations of luminous fluxes are employed.
Abstract: Various variants of LED modules for local illumination are analyzed. The possibilities for approximation of LED luminous-intensity curves and for calculations of these curves in the TracePro system are considered. A method to calculate the illuminance of a 2D area via the 1D distribution of the illuminance along a line is proposed. A comparative analysis of the uniformity of the illumination and of the energy consumption is performed in the case when LEDs with different concentrations of luminous fluxes are employed. A possibility for rotation of LEDs via various optical systems for scattering and focusing of luminous fluxes is considered. In addition, the possibility of improving the uniformity of illumination through a decrease in the size of LED modules and a variation in the current of rotated LEDs is analyzed.
TL;DR: In this article, a compact X-ray tube with a field emitter based on carbon nanotubes is developed, which maintains an anode current of 300 μA and a voltage of 10 kV over a long time interval.
Abstract: A compact X-ray tube with a field emitter based on carbon nanotubes is developed. Over a long time interval, the X-ray tube maintains an anode current of 300 μA, an anode voltage of 10 kV, and the stable characteristics of the field emitter.
TL;DR: In this article, a model that describes the mechanism of radiation of electromagnetic waves by an arbitrary section of the right-handed double helix of DNA is proposed, based on the classical theory of dipole radiation.
Abstract: Interaction of the electromagnetic field with helical biological structures is studied theoretically by the example of deoxyribonucleic acid (DNA). A model that describes the mechanism of radiation of electromagnetic waves by an arbitrary section of the right-handed double helix of DNA is proposed. The model is based on the classical theory of dipole radiation. It is shown that the electromagnetic wave radiated by DNA under the conditions of the main resonance is circularly left-hand polarized. It is shown that this property of polarization selectivity of X-rays with the wavelength λ ∼ 7−8 nm that irradiate DNA holds true for any sequence of nitrogenous bases.
TL;DR: In this paper, the capacitance-voltage characteristics and capacitance spectra of 2a diamond photodetectors were examined and it was found that the ac conductivity of the photodets is purely capacitive and that the sample geometry is determined by their geometry.
Abstract: Ultraviolet photodetectors based on natural 2a diamond are fabricated and examined. From the capacitance-voltage characteristics and capacitance spectra, it is found that the ac conductivity of photodetectors is purely capacitive and that the capacitance of the samples is determined by their geometry. The dynamic range of the photodetectors is found to be no less than 104. The measured photosensitivity spectra and current-power characteristics bear evidence of the high sensitivity and selectivity of the photodetectors in the UV region, which favor their application for the detection of weak radiation signals, including detection during day-time.
TL;DR: In this paper, the authors proposed a discrete approximation based on decomposition of the electromagnetic field in normal or partial modes of electrodynamic structures (ESs) of microwave devices, which can be applied in first and second-level spectral models.
Abstract: Methods of calculation of nonstationary nonharmonic electromagnetic fields excited by electron streams in guiding electrodynamic structures (ESs) of microwave devices are considered. The methods can be applied in first- and second-level spectral models. The proposed discrete approximation is based on decompositions of the field in normal or partial modes of ESs. The continuous approximation proposed is based on decomposition of the field in regular modes of ESs.
TL;DR: In this paper, a microwave-band chaos generator based on a bipolar transistor is proposed and a mathematical model of this generator that comprises a self-oscillating system with 2.5 degrees of freedom is considered.
Abstract: A microwave-band chaos generator based on a bipolar transistor is proposed. A mathematical model of this generator that comprises a self-oscillating system with 2.5 degrees of freedom is considered. The dynamics of the generator is analyzed via the Advanced Design System (ADS) with the parameters of a real transistor, and the generator is simulated with allowance for the properties of the substrate. The results of the ADS-based simulation are compared with experimental data. It is demonstrated that application of the ADS simulation package for the analysis of the generator with regard to the effect of the board topology and the characteristics of the prototype materials makes it possible to reach a qualitative agreement between the numerical and experimental results.
TL;DR: It is shown that the developed procedures are based on an optimum symbol-by-symbol reception algorithm that uses the fast Walsh-Hadamard transform algorithm.
Abstract: Computational procedures for symbol-by-symbol reception of signal ensembles corresponding to binary high-rate convolutional codes and to turbo codes formed by these convolutional codes are described. It is shown that the developed procedures are based on an optimum symbol-by-symbol reception algorithm that uses the fast Walsh-Hadamard transform algorithm.
TL;DR: In this paper, a photoresistor-based system was proposed to generate amplitude and phase-modulated signals and operate as synchronous detectors and spectrum analyzers, and the factor of nonlinear distortions introduced by the photoresistors into a phase modulated signal was estimated.
Abstract: It is shown that the design of optoelectronic systems can be simplified considerably and their functionality can be extended through combined detection and processing of the information-carrying optical and electric signals by a photoresistor. Photoresistor-based devices that are used to generate amplitude-and phase-modulated signals and operate as synchronous detectors and spectrum analyzers are proposed. The factor of nonlinear distortions introduced by the photoresistor into a phase-modulated signal is estimated.
TL;DR: In this paper, the averaged electrodynamic boundary conditions are derived for an arbitrary conductivity of the plate, and the error of this method is several percent for planes with thicknesses up to 0.35 of the wavelength in the medium.
Abstract: The averaging method is used for calculation of the reflection and transmission coefficients of a 1D longitudinal electromagnetic wave and a 1D transverse electromagnetic wave that are incident along the normal onto a plane-parallel plate. The averaged electrodynamic boundary conditions are derived for an arbitrary conductivity of the plate. It is demonstrated that the averaging method enables one to simplify the calculations and resulting expressions owing to a decrease in the order of the system of equations and elimination of trigonometric functions. The error of this method is several percent for planes with thicknesses up to 0.35 of the wavelength in the medium.
TL;DR: In this paper, the transformation of the electromagnetic-wave polarization by a 2D grating of metal Ω elements was studied theoretically and experimentally, and the electric dipole moment and magnetic moment excited by a linearly polarized incident wave in a single Ω element were determined.
Abstract: Transformation of the electromagnetic-wave polarization by a 2D grating of metal Ω elements is studied theoretically and experimentally. The electric dipole moment and magnetic moment excited by a linearly polarized incident wave in a single Ω element are determined. The parameters of an Ω element that are optimal for radiation of a circularly polarized wave are calculated. A 2D grating consisting of Ω elements with optimal parameters is fabricated, and the obtained theoretical results are verified experimentally.
TL;DR: The switched nonuniform polar quantization is asymptotically analyzed for the case when the power of an input signal varies in a wide range and the suggested quantizer can be used for data compression where the saving can reach 1.5 bits/sample.
Abstract: In this paper, the switched nonuniform polar quantization is asymptotically analyzed for the case when the power of an input signal varies in a wide range. We observed two compression functions: logarithmic and optimum. For the suggested quantizer model we optimized the granular distortion in order to obtain the manner of the total distribution of points, i.e., we evaluated the expressions for the amplitude-level number and the phase-level number for on one amplitude level. In addition, we found the expression for granular distortion, which we used to estimate the suggested model. We compared the numerically obtained results with the G711 and G712 standards, and on these bases, we derived conclusions about the possibilities of this switched quantization application in speech processing. The suggested quantizer can be used for data compression where the saving can reach 1.5 bits/sample. This circumstance means that the technique that we presented in the paper can be applied for voice transmission over the Internet (VoIP) and in public switched telephone networks (PSTN).