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Antenna array Complex directional antenna consists of separate near-omnidirectional antennas (radiating elements) positioned in the space and driven by high-frequency … (from 'Glossary' of our web–site)  |
Archives for 2005Paged 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 plane-parallel waveguides with dielectric inserts and projected dielectric elements, excited by TEM-waves 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 complex-form 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 vector-function, converging to the L2(S0) 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 well-known 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 non-Rayleight 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 open-ended 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 radio-locating cross-section 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 large-sized 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 direct-axis current is offered; the standard method uses the thin vibration generator method that leads to the Poklington or Hallen integral equations (Fredholm equation of 1st 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 Burstein-Kinber 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 on-axis 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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