M.S. Antyufeeva and O.A. Tretyakov
V. Karazin National University of Kharkov, 4, Svoboda Sq., Kharkov, 61077, Ukraine
Electromagnetic Fields in a Resonant Cavity Filled with a Non-Stationary Dielectric Material

The paper presents results of studying theoretically electromagnetic field variations with time in a cavity of arbitrary geometry filled with a homogeneous, non-stationary dispersion-free dielectric material. The 'modal basis' technique is applies. Analytic solutions are derived for the case where the cavity is excited by unit impulses, periodic or harmonic signals.

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À.A. Kirilenko, D.Yu. Kulik, L.A. Rud, and V.I. Tkachenko
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
An E-Plane Tee Diplexer Based on Channel Filters with Inductive Irises

The problems of analysis, synthesis and optimization of waveguide diplexers employing E-plane tees with a capacitive adjustment iris in the side arm and channel filters with asymmetric inductive irises in the direct arms are considered. Rigorous numerical models of the diplexer and its units are constructed with the use of the decomposition technique and several versions of the partial domain method. The synthesis of the filters is based on the Levy-Rhodes theory scheme. The design of diplexer as a whole is performed within the so-called Y-scheme, which leans upon the search of a united three-port junction with equal reflection factors in all ports. The special attention is given to constructing numerical algorithms for PCs to provide optimum characteristics.

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A.Yu. Panchenko
Kharkov National University of Radio Engineering and Electronics,
14, Lenin Ave, Kharkov, 61166, Ukraine
Determining the Frequency Shifts of Resonance Cavities that Result from Acoustic Disturbance of the Filling Medium

The frequency shifts of filled cavity resonators are analyzed for the case of simultaneously disturbed acoustic and electromagnetic waves. Power series expansions are used. The main factors determining the resonance frequency shift are analyzed.

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E.Yu. Kramarenko and N.A. Khizhnyak
V. Karazin National University of Kharkov, 4, Svoboda Sq., Kharkov, 61077, Ukraine
Effect of Periodic Faults in the Layer Thickness of a Dielectric Grating
upon its Dispersion Properties

The effect of periodic faults appearing in the structure of a dielectric grating upon its dispersion properties is analyzed. A dispersion relation is derived and analyzed numerically. The faults may result in splitting of the transmission zone pertinent to the periodic structure without errors of the kind. Stop bands where electromagnetic waves cannot propagate arise within the former transmission zone. The number of the stop band to appear depends on the repetition period of the fault.

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V.V. Dolzhikov
Kharkov National University of Radio Engineering and Electronics,
14, Lenin Ave, Kharkov, 61166, Ukraine
 A Technique for Synthesizing Circular Apertures with a Prescribed Radial Distribution of the Field in the Fresnel Zone

A technique is presented for synthesizing circular focused apertures to provide a given radial field distribution in the Fresnel zone, along an arbitrary direction. The synthesis is effectuated through minimizing a quadratic functional equal to the sum of squared errors in the function describing the given radial field distribution along a selected direction and in the given angular pattern. The potential of the suggested technique is illustrated by an example synthesis. A comparison is made with the result for the case of limitations on the amplitude and phase distribution norm.

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P.L. Tokarsky
Kharkov National University of Radio Engineering and Electronics,
14, Lenin Ave, Kharkov, 61166, Ukraine
 Coupling Impedances and Radiation Efficiencies of Horizontal Electric Dipoles Placed Above the Earth Surface

The radiation from coupled horizontal Hertz electrical dipoles placed near a plane interface of two media is analyzed. Expressions have been derived for the coupling impedance, coupling radiation resistance and loss resistance of the dipoles above the real earth. Relations are also given for estimating the radiation efficiency of an antenna array composed of such dipoles with arbitrary current distributions in the array. The coupling resistances of horizontal dipoles are analyzed as functions of the dipole separation, and the radiation efficiency of the array discussed in dependence on the phasing angle. Numerical results are discussed.

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A.P. Nickolaenko, A.V. Shvets, and E.I. Yatsevich
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
 Estimates of Level of the Global Lightning Activity Obtained from Schumann Resonance Monitoring

Schumann resonance measurements have been performed at Lekhta observatory during one year (from August 1999 to July 2000).The median dynamic spectra were constructed for the field components accumulated during the intervals one month long. Analysis of the spectra was performed from the point of view of global thunderstorm activity. The integrated estimates were obtained for the diurnal variations of the global thunderstorm activity and for seasonal changes in the thunderstorm centers.

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A.V. Shvets
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
 Spatial Distribution of the Thunderstorm Activity Recovered from the Direction Finding of VLF Atmospherics Made on Board of Moving Research Vessel

We propose a technique of tomographic reconstruction of the spatial distribution of lightning strokes based on the atmospherics multi-site direction finding. An effective algorithm was developed, which reduces the requirements on the computer resources. The estimates are presented of the spatial distribution of thunderstorm activity in Africa found from tomographic reconstruction based on the measurements of the azimuthal distributions of VLF atmospherics. The measurements were performed on board of the research vessel whose route encompassed the African continent The structure of the lightning activity recovered for the March-April, 1991 period demonstrates that zones of stable intense lightning activity occupy the basins of Niger and Congo rivers, the Madagascar, and the coastal part of the Guinea bay.

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Yu.L. Meister and D.M. Pisa
Zaporozhye National Technical University,
64, Zhukovskogo St., Zaporozhye, 69063, Ukraine
 Weight Functions for Short Discrete Fourier Transforms in Radar Systems of Signal Acquisition and Processing

Performance characteristics of radar signal filters based on short discrete Fourier transforms are analyzed for the case where time samples are weighted by some known "classical": window functions. It has been found that application of these functions is inefficient for discrete Fourier transforms of small number of points. It is shown that window functions specially constructed for short discrete Fourier transformations have considerably better characteristics.

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O.V. Gunko
Kharkov State Technical University of Radio Engineering and Electronics,
14, Lenin Ave, Kharkov, 61166, Ukraine
Integral Representation of Solutions to the Non-Linear Singular Integral Equation Governing Amplitude-Phase Relations in the Communication Theory

In the space U of all signals u=u(t) with compact-carrier spectra, an integral representation has been obtained for minimum-phase solutions of the non-linear singular integral equation u2+(Hu)2=A2, where H is the Hilbert transformation operator. The equation describes all signals of the form u(t)=A(t)cos(w0t +Ô(t))<U that correspond to the given Hilbertian amplitude A=A(t). The representation is derived, based on Privalov's fundamental lemma for the circle and proof of weighted integrability for the function lnA2(t).

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G.S. Vorobyov
Sumy State University, 2, Rymsky-Korsakov St., Sumy, 244007, Ukraine
Wave Simulation of Cerenkov-Diffracted Radiation in Space-Limited Metal-Dielectric Structures

A wave model of Cerenkov-diffracted radiation based on the analogy of the wave generation in the system under study and the planar dielectric waveguide for space-limited metal-dielectric structures has been developed. The physical processes that have been described in terms of the above model are experimentally borne out by wave simulation of radiation on rectangular prisms of different thickness. Practical recommendations for constructing Cerenkov and Cerencov-diffracted oscillators are provided.

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L.I. Sviderskaya
Kharkov National University of Radio Engineering and Electronics,
14, Lenin Ave, Kharkov, 61166, Ukraine
 A Method of Testing the Surface Resistance of Diffusion Conductor Structures

A possibility to determine the surface diffusion structure resistance using a MW-resonator technique has been analyzed. The theoretically derived relations indicate that for the particular value of the degree of coupling at which the Q-factor of the resonator filled up with two specimens-one with a diffusion layer and the other-of homogeneous nature are equal.

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Yu.Ye. Gordienko and A.I. Kocherzhin
Kharkov National University of Radio Engineering and Electronics,
14, Lenin Ave, Kharkov, 61166, Ukraine
 Upgrading of Metrological Characteristics of MW-Resonator Moisture Meter for Free-Flowing Bulk Materials

A procedure for density-independent moisture-content bulk-material measurement is suggested and the use of a resonator measuring transducer (RMT) is considered. It is recommended that the bulk-material moisture content be evaluated in terms of the ratio between the Q-factor variation and the resonance frequency within the range of transducer's small perturbations. The transducer in question comprises the aperture-coupled resonator and a measurement section in the form of a cut-off waveguide. The findings of experimental studies are presented.

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