A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
Numerical Simulation of 2-D Elliptic Dielectric Lens Employed for Improvement of Directivity of an Aperture Source
Numerical analysis of the effect of a 2-D electric lens on the directivity of an aperture light or microwave sources was performed. The lens is simulated by an elliptic dielectric cylinder. An algorithm is based on the concept of analytical regularization: the problem is reduced to the set of the first-kind integral Fredholm equations by representation of fields in the form of surface potentials along the scatterer contour. Using the analytic transformation of a part of the integral operator kernel that corresponds to the circular cylinder, this equation was transformed into the second-kind infinite matrix Fredholm equations being solved numerically with a ensured accuracy. Basic properties of the algorithm are studied. The paper presents the numerical results for an elliptic lens and an incident field in the form of a wave beam simulated by the complex source point (ÑSP) localized inside the lens.
Kharkov State Economical University,
9A, Lenin Ave., Kharkov, 61059, Ukraine
Two-Dimensional Scattering of H-Wave by a Dielectric Cylinder Half-Embedded in a Ground Plane
Two-dimensional problem of H-polarized plane wave scattering from a right dielectric cylinder of arbitrary dimensions and properties half-embedded in a ground plane has been rigorously solved. The Rayleigh series expansion and partial orthogonality of trigonometric functions were utilized in the solution. The infinite system obtained for the Fourier coefficients has been shown to have a unique solution. The rate of its convergence is estimated. The obtained solution is compared with a known solution by another method. Close agreement of the solutions gives an evidence of adequacy of the proposed method. Wave scattering in the case of lossy dielectric is considered. Backscatter is found to decrease significantly when slight loss is present, especially for the oblique incidence.
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
Eigen Wavelength and Q-Factors of Circular Waveguide-Dielectric Resonator
Characteristics of the waveguide-dielectric resonator based on a circular evanescent waveguide have been investigated. A calculation method of this resonator with short-circuit plunger has been presented. Computer results of the parameters of the WDR for the basic H111 oscillation have been made. Experimental investigations of the eigen wavelengths and Q-factors of the resonator under study have been carried out over a microwave range. Good agreement between the calculation and experimental data have been obtained.
Zaporozhye National Technical University,
64, Zhukovskogo St., Zaporozhye, 69063, Ukraine
Calculation of the Magnetic Wave Attenuation in a Rectangular Waveguide with Fractal Walls
The results from the study into a rectangular metallic waveguide with fractal walls operating over the frequency range of 25 - 300 GHz are presented in this paper. A fractional integral differential calculus was applied to find the attenuation factor of magnetic waves propagating in this structure. The dependence of attenuation factor upon values of scaling index that characterizes the wall fractality degree in the waveguide has been found. The computational results are in agreement with the experimental values is shown.
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
Interaction of Electromagnetic Wave with an Anisotropic Dielectric Substrate in the Presence of Periodic Shields
Interaction of an electromagnetic wave with an anisotropic dielectric substrate in presence of periodic shields has been investigated. The fields reflected from the structure have been obtained in analytic form.
V. Karazin National University of Kharkov,
4, Svoboda Sq., Kharkov, 61077, Ukraine
* Institute of Radio Astronomy, National Academy of Sciences of Ukraine
4, Krasnoznamennaya St., Kharkov 61002, Ukraine
Experimental Investigation into the Frequency Dependence of the Transmission Factor Module of a Double-Periodic Array Consisting of C-shaped Stripline Elements
The results from the experimental investigation into the double-periodic array comprising the metallic C-shaped stripline elements are presented. A measuring technique is described. A comparison is made between the measurement results and theoretical calculations. The most sharply defined resonances of electromagnetic (e.m.) wave transmission through an array are physically explained.
Ukrainian State Academy of Railway Transport
A Technique for Estimating the Symbol-Error Probability in Walsh Function-Based Channels with Fast Fadings
A technique is suggested for estimating the error probability in channels with short-term fadings of signals formed on the basis of the Walsh functions. Formulas and computed curves of error probability in dependence on parameters of the communication channel are presented for the case where either one or two pulses of the group signal are damaged.
V. Karazin National University of Kharkov, 4, Svoboda Sq., Kharkov, 61077, Ukraine
A New Semianalytic Method for Analyzing the Wave Fields of Coaxial Gyrotrons
A new approach is suggested to solving the spectral problem for a gyrotron with parallel corrugations. The technique is based on reducing the rigorous boundary-value problem for Maxwell's equations to a singular integral equation for its subsequent numerical analysis with the use of quadrature interpolation formulas. The method that has been developed is applicable in any frequency range and for arbitrary sizes of the corrugations.
Radioastronomy Institute, National Academy of Sciences of Ukraine
4, Krasnoznamyonnaya St., 61002 Kharkov, Ukraine
Selecting the Starter Cathode for the Pulsed Magnetron with a Cold Secondary-Emission Cathode
The paper presents results of durability investigations made for a variety of dispenser cathodes with the aim of selecting the type of the starter cathode for the three millimeter band magnetron with a platinum secondary-emission main cathode. The disk starter cathode, placed instead of one of the end shields, is intended for triggering the secondary emission at the beginning of the anode voltage pulse. Along with standard impregnated cathodes, cathodes with silicon or scandium oxide additions to the standard impregnation and those with an osmium film applied over the emissive surface have been studied. The tests were done after an express method, using a specially designed test bed. The results have shown that all four types of cathodes were capable of providing the required durability of 5000 hours, given the available reserve of their active substance and an operating temperature ensuring a 1 A/cm2 density of the emission current. However, the best results with respect to durability and reproducibility of performance were shown by the cathodes with an osmium film. They have been chosen as starter cathodes to be used in durable magnetrons. The current tests of such magnetrons have proven the validity of this choice, as the operating time of all three devices has reached 5000 hours, which greatly exceeds the results previously-obtained for this waveband.
Sumy State University, Sumy, Ukraine
The Smith-Pursell Effect Amplification of the Electromagnetic Waves in an Open Waveguide with a Metal-Dielectric Layer
Linear self-consistent theory of the amplification using the Smith-Pursell effect under interaction between the electron flux and the fields of the periodic metal structure and the metal-dielectric layer has been developed. The influence of metal-dielectric layer of the electromagnetic wave excitation condition has been determined via the dispersion equation analysis. The experimental technique and results of the measurements of spatial and waveguide characteristics of the Smith-Pursell effect amplifier have been provided.
Kharkov National University of Radio Engineering and Electronics,
14, Lenin Ave, Kharkov, 61166, Ukraine
Testing of a Software of Poisson's Equation Solution for Mathematical Model of a Millimeter Wave Magnetron
An accuracy of Poisson's equation solution by numerical method for cross-field systems is considered in the paper. A comparison is made between the numerical and analytical results of Poisson's equation solution for some classes of the spatial charge distribution function. Comparative characteristics of Poisson's equation solution by the numerical and analytical methods are given.
Institute of Radio Astronomy, National Academy of Sciences of Ukraine
4, Krasnoznamennaya St., Kharkov 61002, Ukraine
Excitation of Oscillations in Magnetrons with Secondary-Emission Cathode by Means of an External Microwave Signal
The paper presents the results from the experiments on excitation of electromagnetic oscillations in magnetrons with a cold secondary-emission cathodes by injecting an external MW-signal. The conditions under which the oscillations are induced in Ka-band (8-mm wave) magnetrons has been explored in terms of the exciting-signal parameters. It is shown that excitation of oscillations can be made possible at the external power level of around 500 W.
State-owned Research and Industrial Association [SRIA] "Metrology",
42, Mironositskaya St., 61002, Kharkov, Ukraine
On the Development and Application of Extremely-High-Frequency Generators Operating in a Wide Frequency Range
Possible design schemes are considered for stabilized sources of extremely-high-frequency (EHF) oscillations, to be operate in a wide frequency range. A version of the source developed is described, and its metrological characteristics analyzed and possible applications considered.
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
Excitation of Surface Waves in Magnetoactive Plasma by a Moving Charged Particle
The Cherenkov radiation of surface waves by a particle moving along the spiral line relative to the constant magnetic field has been studied on a magnetoactive medium/dielectric (vacuum) interface. Low-frequency and high-frequency ranges where surface electrostatic and helicon waves are excited have been considered.
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
The Optimized Microwave Plasmatron with Nonequilibrium Plasma
The conditions of the maximal service power entrancein a microwave plasmatron with a flow of strongly nonequilibrium stationary plasma are investigated at atmospheric pressure of gas (argon). The waveguide-coaxial design of a microwave plasmatron with two movable plungers is used. The efficiency of absorption of microwave power (10 GHz) in a torch of plasmatron is higher than 99% at excitation power up to 12W.
V. Karazin National University of Kharkov,
4, Svoboda Sq., Kharkov, 61077, Ukraine
Dielectric Loss Measurement in Anisotropic Crystals
This work is the continuation of a series of works [1, 2, 5] devoted to the investigation of anisotropic materials electric properties. The electrodynamic and numerical calculation of Q-factor of high quality H- and E- type electromagnetic modes in waveguide junctions filled single-axial crystal with tetragonal and biaxial crystal with rhombic type of crystal symmetry is carried out in this work. The non-destructive methods of loss measurement in crystals along main directions of dielectric permeability tensor is developed.
Tavriya National University,
4, Yaltinskaya St., Simpheropol, 95022, Ukraine
An Influence of Heat Processes on the Drift Characteristics of Semiconductor Structures
The given work presents the calculated results of drift characteristics of GaAs and Si-based semiconductor structures. The results are obtained in the processes of heating a crystal by the current of free-charge carriers. It is shown that under the high current conditions the drifting velocity growth depends on heating of a semiconductor structure.
Chernivtsi National University,
2 Kotsiubynsky str., 58012 Chernivtsi, Ukraine
Photodetectors Based on the Gallium Phosphide-Arsenide Heterojunctions Produced by Isovalent Substitution Method
Institute of Radio Astronomy, National Academy of Sciences of Ukraine
4, Krasnoznamennaya St., Kharkov 61002, Ukraine
On an Increase in Stability of Low-Noise HEMT Amplifiers
Increasing the stability of HEMT amplifiers through the direct cascading and local feedback are presented in paper. A possibility to prevent the spurious oscillations outside of the operating frequency band is evident from theoretical and experimental results.
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
Electron Trajectories in Magnetic Field of MPFS with Varying Longitudinal Component
The theoretical and experimental researches of electron behavior in MPFS with varying longitudinal component are given in this paper. We obtain the analytical expressions for description of electron motion in such systems. It is shown that we can effectively influence on the beam focusing and beam passing to the collector by choosing the initial electron velocities.
National Scientific Center "Kharkov Physical and Technological Institute",
1, Academicheskaya St., Kharkov, 61108, Ukraine
Resonance Fine Structure of Electromagnetic Waves in a Dielectric Sphere
Recently a number of papers have appeared discussing model artificial dielectric materials which simultaneously possess negative values of permittivity and permeability within a certain frequency band [1, 2]. As was shown as long ago as in paper [3], the process of electromagnetic wave propagation through such media is characterized by effects that are important for out understanding of the interaction of electromagnetic radiation with living tissues. It has been shown in this paper that such tissues are encountered only too often in the organic world and the formation mechanism of simultaneously negative values of
and 
is intrinsically contained in their physical structure. Moreover, experimental facts are known that confirm the existence of positive and negative values of 
and 
in narrow frequency bands that unfortunately remained only poorly understood until recently.
A. Usikov Institute of Radio Physics and Electronics, National Academy of Sciences of Ukraine
12, Academician Proskura St., Kharkov 61085, Ukraine
Near Fields of a Three-Element Radiator in a Lossy Medium
A comparative analysis is given of near-zone electric fields from a three-element, axially symmetric radiator consisting of either insulated or noninsulated dipoles, in a lossy medium like adipose or muscular tissue, for such applications as HF or UHF hyperthermia. It is shown that with in-phase excitation of the HF dipoles the uniformly heated area between the dipoles space gets extended. It has been found that a promising design of the radiator, capable of forming a directional external irradiation of the lossy medium for microwave hyperthermia, is that where one of the dipole is used as an active reflector.