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Possible ways of decreasing the reflectance of inhomogeneities in the adjoining medium for highspeed stealth aircraft аre investigated.
Wednesday, February 29, 2012 at 10:02PM
The Green's function for an infinite wedge has been examined in order to use it to solve the practical technical problems of antenna arrays.
Saturday, January 15, 2011 at 11:01AM
Green's tensor function has been used as a basis to get the expression for the radiation pattern of a rectangular waveguide radiator array located on an infinite perfectly conducting wedge. The obtained expression has been analyze, which has made it possible to calculate the integral in a complex plane with the help of the saddlepoint method.
Saturday, January 15, 2011 at 09:01AM
The method and algorithm of calculating the input characteristics for the radiators of antenna arrays with a small number of radiators have been developed.
Friday, October 15, 2010 at 02:10PM
The article briefly describes and grounds the possibility to build radiating elements of ultrabroadband wideangle antenna arrays and beam formers.
Monday, October 04, 2010 at 08:10AM
The quantitative analysis of physical processes that occur during the excitation of planar and rectangular waveguides with an infinite flange, with a bending flange and an array of planar and rectangular waveguide radiators on an infinite plane and on an infinite wedge has been carried out.
Monday, October 04, 2010 at 08:10AM
Equations for the “irregular” and “regular” transfer admittance of the waveguide radiators of an antenna array located on a side of an infinite ideally conductive wedge is deduced.
Sunday, October 03, 2010 at 12:10PM
The electrodynamic problem of the excitation of arrays of waveguide radiators located on the sides of an infinite ideally conductive wedge taking into account the mutual coupling between the array radiators is solved.
Saturday, April 24, 2010 at 09:04PM
The method of the continued boundary conditions (MCBC) is generalized on three–dimensional vector problems of waves diffraction on bodies of revolution.
Saturday, April 24, 2010 at 08:04PM
The explicit (asymptotic) solution of a problem is obtained in a case, when the scattering bodies are far enough from each other. It's established, that the obtained approximate analytical solution of a problem is suitable for calculations with an acceptable exactitude at distances between bodies down to their touch, if the sizes of bodies do not exceed a wave length of a field, incident on a group.
Saturday, April 24, 2010 at 08:04PM
The problem of synthesis of anizotropic impedance plane reflecting a plane uniform wave in a given direction at the desired polarization is solved. The distribution of the impedance is expressed analytically and constitutes a periodic structure. The restrictions on the class of the allowable scattering patterns are formulated for the reactive values of impedance. The reflection coefficients of the nonuniform anisotropic impedance plane are obtained. Numerical results are demonstrated.
Saturday, April 24, 2010 at 07:04PM
The description of wideband radiators on the base of symmetrical slot line is presented. Different types of slot and different variants of excitement unit are considered. Methods of slot antennas analysis are shown. In conclusion antenna arrays on the base of slot radiators are presented.
Wednesday, January 06, 2010 at 12:01AM
There was a study of mathematical modeling of microstrip oscillators with a substrate in the form of plane layered media based on the use of integral and integro–differential equations of the first kind; there was provided substantiation and the basics of building the algorithms of a numerical solution to the equations; examples of the numerical study of the equations for oscillators and layered media with varied topology were given; the case of microstrip oscillators with finite conductivity was studied; the integral equation for the current of the oscillator was derived and examples of its numerical study for oscillators made of high–temperature superconductors were given.
Sunday, May 17, 2009 at 12:05AM
Simple correlations allowing the radiation pattern structure of a spherical antenna array with ring radiators to be analyzed have been obtained with the help of the Poisson summation formula and the stationary phase approximation. Dependencies allowing the distance between radiators to be determined by the necessary radiation pattern type of an antenna array have been obtained.
Saturday, May 16, 2009 at 12:05AM
The input impedance of an electrical vibration generator has been defined as a ratio of the voltage in the gap to the current in the feed point; complex current distributions along the half–wave and full–wave vibration generator for various vibration generator radiuses normalized to the wavelength have been estimated; dependency charts for the real and imaginary components of the input impedance of the electrical vibration generator from the branch length of the vibration generator normalized to the wavelength for various values of the vibration generator radius normalized to the wavelength.
Thursday, May 14, 2009 at 12:05AM
The results of the theoretical estimations and experimental research of characteristics of some finite waveguide phased antenna arrays (PAA) consisting of waveguide elements having a cross–section of a complex shape has been considered; the estimated and experimental radiation patterns have been given; the mutual coupling coefficients, return loss and the level of lateral radiation for the finite PAA consisting of waveguides with a random crosssection working on both linear and circular polarization of the radiated field have been assessed.
Sunday, April 06, 2008 at 12:04AM
We present a method for matching waveguide radiators used in wide bandwidth phased antenna arrays with widescanning angle. In order to achieve matching, the following parameters are used: the geometrical parameters of waveguides, the dielectric parameters of materials inside the waveguides, waveguide transformators and reactive waveguide at the aperture, and also a matching device in the form of inductive rods and capacitive diaphragm.
Saturday, April 05, 2008 at 12:04AM
It is presented the electrodynamics analysis of complex crosssection waveguide phasedarray antennas with dual polarization. Energetic, polarization and frequency characteristics of crossridged circular and square waveguides as elements in phasedarray antennas with dielectric covers and supports are studied. An analysis chart is introduced to aid the computation of their mode of operation with sector scanning and frequency band.
Friday, April 04, 2008 at 12:04AM
Phased antenna arrays (PAA) of waveguides with complex cross sections are analyzed in this work. Particularly, the analysis focuses on linearly polarized waveguides with dielectric matching units (inserts, covers and waveguide transformers). The study of power and frequency characteristics of these PAA in scanning sectors is included. An optimization method for the design of this kind of arrays in order to achieve broad frequency band and scanning sectors is also presented.
Monday, March 31, 2008 at 12:03AM
A mathematical model of a printed radiator pattern on a screen with finite dimensions is developed. Results of numerical experiments are presented.
Sunday, March 30, 2008 at 12:03AM
Approach for the analysis and Q–factor estimates of patch antennas with artificial dielectrics substrates for decimeter and larger wavelengths have been considered. Parameters range not leading to significant normal dispersion have been estimated and treated. Also shown that a frame of periodic system of capacitive elements aligned along the patch wedges provides smaller Q compared to the homogeneous dielectric substrate with the same equivalent permittivity. Implementation samples for the high accurate positioning with the help of the Global Navigation Satellite Systems are shown.
Saturday, March 29, 2008 at 12:03AM
The method for estimating the characteristics of longitudinal printedcircuit oscillators in phased arrays with the help of a model in the form of an infinite flatplate array antenna.
Friday, March 28, 2008 at 12:03AM
The numerical research results of scattering characteristics of a microstrip–stubs reflectarrays, which have obtained due to a mathematical model, developed by the authors, are represented. The mathematical model of a reflectarray allows introducing into a construction of each microstrip element some shunts with controllable loads. It is shown, that due to shunts it is possible to control amplitude and phase of a scattering fields.
Thursday, March 27, 2008 at 12:03AM
The mathematical model of longitudinal printed radiators phased antenna array is developed based on integral equations method of electrodynamics. Numerical results and measurements of broadband microstrip radiators of the phased antenna arrays characteristics are presented. The obtained results can be used at designing the flat phased antenna arrays containing longitudinal printed radiators.
Wednesday, March 26, 2008 at 12:03AM
The algorithm of estimating the density of surface magnetic current induced on the array aperture has been obtained as a result of the rigorous solution of the problem of plane wave diffraction on a double periodic array of stripline elements of any shape with passive loads.
Sunday, March 23, 2008 at 12:03AM
A short digest of the methods that are applied for antennae decoupling decreasing in the presence of an underlying surface is given. The computation results of weakly directional antennae decoupling with the help of periodic ribbed and strip structures located on an underlying surface along a coupling line for antennae are prezented; recommendations for the optimal (in a frequency range) construction of a deconpling structure are formulated. In this case some experimental data that confirm the possibility of the guarantee of a sufficiently high deconpling level by means of periodical structures are presented.
Saturday, November 24, 2007 at 12:11AM
Asymptotic solution for the diffraction problem on a periodic array of microstrip radiators located above the surface of an infinite generalized cylinder, the curvature radius of which satisfies the condition of slow change along the guide, is considered. By using the matrix reflectivity coefficients, the problem is solved assuming the multilayer isotropic dielectric coating is present. For partial excitation the electric Green tensor function of Maxwell equations is written in closed form, which includes the Airy functions in the Fok definition and their first derivatives.
Friday, November 23, 2007 at 12:11AM
This work considers results of research of characteristics of rectangular printedcircuit radiators in plane phased antenna arrays. The research is conducted by using computer modeling and the mathematical model described in [1].
Thursday, November 22, 2007 at 12:11AM
Based on the asymptotic theory, characteristics of convex cylindrical antenna array consisting of director radiators are studied. To determine the distribution of currents of the radiator vibrators, the numeric projective method is used. Results of numeric computations are presented.
Wednesday, November 21, 2007 at 12:11AM
Based on the asymptotic diffraction theory methods, the problem of determining the near field of the convex cylindrical antenna array composed of aperture radiators is reduced to the boundary value problem in the single cell of the array, which is solved using the Galerkin method. The asymptotic theory is further developed, which provides representation of the radiator diagram in the convex cylindrical array as a sum of the direct wave from the excited radiator, the fast creeping waves and slow creeping waves. Results of numeric computations of the slot elliptical, particularly circular antenna arrays are presented.
Tuesday, November 20, 2007 at 12:11AM
Results of numeric modeling of impedance and polarizational characteristics of singlechannel printedcircuit radiator having circular polarization in the base of the antenna array are presented. Possibilities for optimizing the characteristics in the frequency band and scanning angle sector.
Monday, November 19, 2007 at 12:11AM
In this work, a space Hilbert problem is solved, with the boundary condition set on the boundary of the unlimited full bicircular region of class (T^{∞}) or on the boundary of the region D_{pq}={z∈C^{2}: z_{1}^{p}z_{2}^{q}<1; p,q∈N}. The main devices used for solving the space Hilbert problem are Temlyakov integrals of second kind.
Friday, November 16, 2007 at 12:11AM
The article presents a critical analysis of possible uses of metamaterials to improve operation of antenna devices and points out directions of necessary studies in the field of metamaterials.
Thursday, November 15, 2007 at 12:11AM
In this work, the theory of boundary value problems is applied to the problem of decomposition of integral functions of two complex variables of the class [n, σ_{D}] into quasiexponential basises (the received result generalizes the result received by G. D. Derevyanchenko and V. A. Kakichev) as well as to the problem of decomposition of functions, holomorphic in logarithmically convex limited full bicircular regions, into quasiexponential basises.
Monday, November 05, 2007 at 12:11AM
The results of research of characteristics of printedcircuit radiators in a plane phased antenna array is presented, based on the infinite plane antenna array model.
Friday, May 11, 2007 at 12:05AM
Solutions for boundary problems of electrodynamics in tensor form are examined. Equations and boundary conditions for Green tensor functions of general kind are formulated.
Monday, April 23, 2007 at 12:04AM
The optical properties of materials, such as magnetic metals or magnetic semiconductors, having simultaneously negative electrical and magnetic permeabilities are considered. One finds that the refractive index with respect to vacuum is negative; that the Poynting vector and the wave vector of propagating EM waves have opposite signs; that the sign of the Doppler effect is opposite that, for ordinary materials and that the Cherenkov radiation cone is directed backwards rather than forwards. Finally, the question of the mechanical forces arising from EM propagation in materials having a negative refractive index is discussed.
Thursday, April 19, 2007 at 12:04AM
Equations for waveguide, impedance and lens antenna arrays are formulated taking into account excitation conditions and interconnection between radiators. The arrays can be located on flat or curved surfaces.
Wednesday, April 18, 2007 at 12:04AM
General method for determining tensor Green functions corresponding to various classes of solutions for boundary problems is examined.
Thursday, April 05, 2007 at 12:04AM
Analytics inversion of hypersingular operator is derived and based on this, an efficient numerical–analytical method for solving hypersingular integral equations is constructed. Applications of analytical inversion of hypersingular operator in antenna theory are examined.
Monday, March 26, 2007 at 12:03AM
In the paper, the solution method for the problem of electromagnetic waves scattering by cylinder bodies is given. The method is based on 2*piperiodicity property of functions describing the parameters and distributions of fields and currents on cylinder bodies. The method advantage is the possibility of physical interpretation of results. The example of the proposed method application is given.
Thursday, December 07, 2006 at 12:12AM
The principal directions of radio absorbing materials and coatings used to solve the problems of scattered fields management are considered in the paper. The review of the basic methods of the task solution for the bodies of arbitrary geometry with radio absorbing materials and coating is given. The review is based on the use of impedance boundary conditions of different order.
Wednesday, December 06, 2006 at 12:12AM
An analysis of illposed electrodynamic problems formulated in the form of the 1st kind Fredholm integral equations (IE) is carried out. It is shown that the Tykhonoff regularization of illposed problems ensures stable solutions for electromagnetic field only on the surface, where the 1st kind Fredholm IE is posed. A wellposed method of physical regularization for electrodynamics boundaryvalue problems is proposed and justified.
Thursday, November 30, 2006 at 12:11AM
Partly systematizes the process of constructing of reactive chains of matching of broadband phased array radiators in the sector of angles and frequency band using FanoUla limitations. The given formulae can also be used when designing matching and correcting devices for wide application antennas.
Monday, January 23, 2006 at 12:01AM
A method and efficient numerical algorithms of solving the problem of diffraction of electromagnetic waves on a multilayer spherically symmetric structure, excited by a generalized Huygens, are considered. It is shown that the method is based on reducting the source vector problem to two scalar problems for Debye potentials. The amplifying ration and directional diagrams of antennas based on spherical dielectric lenses are researched and experimental estimation of numerical results is given.
Friday, January 20, 2006 at 12:01AM
A numerical algorithm for solving the problem of diffraction of electromagnetic waves on a multilayer dielectric lossy sphere when amplitudephase distribution of the exciting field is arbitrary is developed. The algorithm is based on representing the field on the source surface as an aggregate of the electrical and magnetic dipoles and reducting the vector problem to two scalar ones for the case of a point source. The results of calculating the directional diagrams and amplifying ratio are compared with the experimental ones.
Tuesday, January 17, 2006 at 12:01AM
The numerical research and optimizing the characteristics of antennas based of doublelayer spherical dielectric lenses, taking into account aberration effects, lens refelections, dielectric losses, radiator directivity diagrams and transition layers are carried out. As an optimization criterion, the maximum value of amplifying ratio of the antenna is used. The maximum possible antenna characteristics are determined. The antenna characteristics based on double–layer homogenous sphere and Luneberg lens are compared.
Saturday, December 31, 2005 at 12:12AM
Various schemes of projective methods: the incomplete Galerkin method scheme, used when researching the electromagnetic waves in waveguides, filled with anisotropic medium; incomplete Galerkin methods with impedance boundary conditions, modified projective linking method are considered.
Friday, December 30, 2005 at 12:12AM
The infinite array of stepped planeparallel waveguides with dielectric inserts and projected dielectric elements, excited by TEMwaves is analyzed in this article using the integral equation for electric field (polarization current) in the projected element and field linking method in the horn; the differential equation is solved using the Galerkin method using vector waves of the corresponding resonator as basis and weight functions; numerical results characterizing the suggested algorithm and array properties are supplied.
Thursday, December 29, 2005 at 12:12AM
The equation for the maximum working bank and coordination level, dependent on the electrical size of some ideal according to the Chu and Harrington criteria antenna is reduced. The characteristics of coordination is assumed to be rectangular and the contact ration can be arbitrary. The received equation expresses the limit of the Chu–Harrington limit for the relative line, coordination level and electrical size of the radiator. The results of computing dependent on the contact ration and electrical size are given as charts and tables.
Wednesday, December 28, 2005 at 12:12AM
The measurement inaccuracies of dispersion diagrams of an arbitrary body in Fresnel zone that arise because of the finite distance between the body and the radiating antenna, and the body and the receiving antenna, as well as the directivity of the antennas are considered. The measurement inaccuracies of dispersion diagrams in the near zone of collimator in case when the boundary wave effect can be ignored are studied.
Tuesday, December 27, 2005 at 12:12AM
The first three terms of the asymptotic decomposition of the transfer ration between two antennas with arbitrary directional diagrams and polarization types are obtained. The formulas for the distance that can be used to measure primary and lateral radiation with the given inaccuracy are derived.
Monday, December 26, 2005 at 12:12AM
Using the mathematical model of dispersion of electromagnetic waves on complexform objects, the article presents the method of estimating radiophysical parameters of local parts of the surface with claddings, based on the results of measuring angular dependence of effective dispersion surface.
Sunday, December 25, 2005 at 12:12AM
Using the generalized variational principle, the article derives the stationary formulas for metallic body dispersion diagram, with variation going to zero for exact values of surface currents, generated on the body by the primary incident wave.
Saturday, December 24, 2005 at 12:12AM
The calculating the characteristics of radiation of sharp pyramidal horns using aperture integrating when determining the field in a plane discontinuity point using approximating functions will be carried out. The calculation results are compared to the previous ones.
Friday, December 23, 2005 at 12:12AM
The solution to the inner problem of electrodynamics for horn radiators with perfectly conducting plane flange, powered by cylindrical waveguides, is considered. The results of numerical calculations for the pyramidal and sectorial horns powered by the rectangular waveguide are provided.
Thursday, December 22, 2005 at 12:12AM
Scattering of a plane wave by mirror antennas with vibrating radiators is considered. The Fourier coefficients of the vector function equal to the current density on the mirror metal and the tangent component of the electrical vector on the geometric surface, complementing the surface of the mirror to close in some complete function system. Using these coefficients, the series for the given vectorfunction, converging to the L_{2}(S_{0}) surface norm, with each of the terms satisfying to the corresponding Meissner conditions on the boundary of the mirror is built. Using the found current on the mirror and wellknown formulas, the dispersed field and differential diameter of dispersion of the mirror antenna are determined.
Wednesday, December 21, 2005 at 12:12AM
It is shown that the directivity factor of the antenna located in a lossy medium is limited and its maximum value is finite.
Tuesday, December 20, 2005 at 12:12AM
The formula that relates the integral diameter of the distance to the effective absorbing surface of the aperture receiving antenna is derived and using this formula, the conditions of minimizing the diameter and its value are found.
Monday, December 19, 2005 at 12:12AM
The method of solving problems of diffraction on nonRayleight bodies, composed of several Rayleigh bodies is explained. The scattered field is constructed as a sum of fields, created by the assemblage of multifields, each of them is located in the corresponding point of one of the composite bodies. The samples involving two tangent to the generatrix of the cylinder and two touching in the single point spheres are considered. For the former of these samples, the curves of distribution current density and scatterogram are given. The curves are compared with the corresponding curves, derived using the Kirhgoff approximation.
Sunday, December 18, 2005 at 12:12AM
The problem of diffraction of electromagnetic waves on a curvilinear surfaces with piecewise continuous admittance (impedance) boundary conditions, particularly on openended metallic surfaces is considered. It is shown that the coefficients of Fourier kind for some complete function system and the corresponding series for the function equal to the tangent component of the electric vector on the part of the surface where the admittance is finite and the surface electric current on the part where it is infinite, can be found by solving the inner and exterior boundary value problem. Each of the terms of the series satisfies the Meixner condition and the determined values of the tangent field on the given surface allow determining of the scattered field in the whole space. The method is illustrated with a sample of diffraction of a plane wave on a circular cylinder with the admittance periodically alternating in steps along the axis.
Saturday, December 17, 2005 at 12:12AM
The article expresses the conditions that must be met when measuring the radiolocating crosssection of a target in terms of amplitude and incident field phase variation. A number of minimal distance criteria are examined. The analysis of minimal distance for the cases when the antenna has a uniformly lighted square aperture is given, and the relation that binds the minimal distance to the sensitivity of measurements. The measurements of the reflection properties of small targets in near zones of focused and unfocused apertures are described. It is shown that the “minimal distance” can be substantially lowered using the suitable microwave lens when measuring the reflection properties of medium and largesized targets.
Friday, December 16, 2005 at 12:12AM
Researche and optimization of characteristics of lens antennas based on a homogenous dielectric sphere, taking into account the aberration effects, reflections, dielectric losses, radiator directional diagrams, matching layers and technological tolerance are carried out; the relation of antenna characteristics to its geometrical dimensions and dielectric parameters is derived; the maximum possible antenna characteristics are determined; the characteristics of antennas based on a homogenous sphere and Luneberg lens are compared; the estimation of hydrometeor (water, ice) effect on antenna characteristics is given.
Thursday, December 15, 2005 at 12:12AM
The method for calculating the electromagnetic field of a radiating object in its near zone, the derived singular integral representations for the components of the electromagnetic field allow for computing the field in any point of space by integrating the directaxis current is offered; the standard method uses the thin vibration generator method that leads to the Poklington or Hallen integral equations (Fredholm equation of 1^{st} kind)
Wednesday, December 14, 2005 at 12:12AM
The method of determining the antenna directional diagram using the amplitude and phase measurements in the Fresnel zone is considered; the mathematical rationale of the method is given along with the results of computer and experimental modeling and the samples of using when measuring the high aperture antennas in an anechoic room with a 80 m route on a measurement stand in a far zone.
Tuesday, December 13, 2005 at 12:12AM
It is obtained a new way to solve the problem of calculating radiation of horn antenna arrays, which is based on using the immersion method; the system of horns is considered a transition layer, coordinating the waveguides with the empty space and characterized by the matrix transparency coefficient. When deriving the immersion equation for transparency coefficient, both the interleaving method and integral equation method are used.
Monday, December 12, 2005 at 12:12AM
The problem of finding: distribution of current density on an open surface, satisfying the Meixner condition in its contour, using the given directional diagram is solved. The current is found as a series that converges to L2(s) surface norm. The conditions of realizability of the diagram are examined, and methods of determining current using the given unrealizable diagram are specified.
Sunday, December 11, 2005 at 12:12AM
This is given the overview of the known approximate methods of calculating the scattering of electromagnetic waves by antennas, including calculating the integral and differential surfaces of dispersion; simple formulas for estimating these values are given. In addition, some results that belong to the authors of the work are stated.
Saturday, December 10, 2005 at 12:12AM
It is offered the method that can be used to compute the scattering of the wave on one or several perfect conductors, as well as on bodies with impedance, heterogeneous and anisotropic boundary conditions. The auxiliary sources on some surfaces, situated inside these bodies are introduced; in particular, the surfaces can be spanned into points. Using the Lorenz lemma, the Fourier coefficients for the density of real or equivalent current on the surface of the bodies are determined and then the currents themselves and the dispersed fields generated by them are found.
The example of calculations is given. Friday, December 09, 2005 at 12:12AM
It is proved that when the primary incident field in a lossy medium is fixed, the power drawn by the antenna is finite. It is not necessary to limit the direction of the receiving antenna, unlike the case of a lossless medium when this is required to get a finite maximum.
The formulas for deriving the maximum received power and the optimal distribution the field on a specific surrounding area, which should be created by the antenna in the transmission mode for it to receive maximum power in the receiving mode, are given. The obtained results are illustrated using a linear wire antenna. Thursday, December 08, 2005 at 12:12AM
Are received various variants of formulas for computing the power, received by the receiver, which take into account the discrepancy between the ends of the feeder path, when the form of the incident wave is arbitrary. In the special case where the receiver is completely concordant with the path, one of them grades into the BursteinKinber formula.
For different additional conditions, the high bound of the received power is determined and the optimal distributions of the field that make this power maximum are found. Wednesday, December 07, 2005 at 12:12AM
An equation for the onaxis gain of a uniformly illuminated rectangular aperture is derived which is valid in the Optical Fresnel Zone. This equation is formulated in terms of the ordinary radiation field gain multiplied by a correction factor which depends upon the aperture dimensions and the distance, R, from the aperture at which the gain is measured.
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