antenna array, horizontal polarization, double slots, slowing system.
Vestnik KhNU ¹927 Pages. 54-58
Energetic and directional characteristics of an antenna array (AA) with single transversal slots and double ones cut in a rectangular waveguide, partially filled with dielectric are investigated. In the case of single transversal slots and double transversal slots a dielectric layer is parallel to broad walls of the waveguide. It was shown the possibility to construct an AA with double transversal slots having the pattern without diffraction lobes and high level of radiation power in the wide frequency band.
slot, waveguide, dielectric, admittance, scattering parameters, slot-waveguide array.
Vestnik KhNU ¹927 Pages. 59-64
The scattering problem of a longitudinal slot system is cut in wide wall of rectangular waveguide with three-layer dielectric filling which parallel to wide wall of a waveguide was solved. The scattering parameters and gain of linear slotted-waveguide array are investigated in range of frequency. The gain optimization and synthesis of linear slotted-waveguide array were carried out using a genetic algorithm. The obtained gain weakly depends from frequency.
GaAs diodes, drift speed, lag, coefficient frequency conversion, maximum frequencies.
Vestnik KhNU ¹927 Pages. 11-14
Coefficient frequency conversion (KFC) diodes with intervalley transfer of electrons based on GaAs in a wide range of frequencies is investigated. It is shown that the threshold voltages of the KFC in mobility 8000 sm2/(V·s) (GaAs) more than the KFC in 1000 sm2/(V·s) mobility (without NDC) in 5 times. At the further increase voltages in the mobility ratio of KFC 8000 sm2/(V·s) to KFC for 1000 sm2/(V·s) mobility decreases (at 10 - 12 kV/cm is about 2, at 20 - 30 kV/cm ratio KFC close to unity). Take into account the inertia of the redistribution of electrons between the valleys of the conduction band of GaAs. It is shown that the transformation frequency conductivity GaAs diodes is possible at frequencies exceeding the maximum frequency of generation in the diode mode of a uniform field.
nitrides, intervalley electron transfer, Monte Carlo method, homogeneous field mode.
Vestnik KhNU ¹927 Pages. 7-10
À frequency properties of intervalley electrons transfer (IET) are considered in double nitride compound ALN. A frequency properties of AlN is determined by Monte Carlo method taking into account of all actual scattering mechanisms of electrons in the wide frequencies range to be corresponded to realization of limited space charge accumulation mode (LSA). The results of calculation of static characteristics and oscillation efficiency are presented. A frequency limits of oscillation efficiency of considered compound are defined. A region corresponding to neglecting of charge careers distribution inertia have been determined.
plane dielectric waveguide, inverted dielectric waveguide, Fourier transformation, Fredholm integral equation, dispersion equation.
Vestnik KhNU ¹927 Pages. 78-84
The eigenvawes problem of inverted dielectric waveguide is considered. The cross-section of waveguide is divided into partial domains in such way that the field in each domain is represented as a superposition of eigenwaves of a plane dielectric waveguide. Using the equality conditions of tangential components of electric and magnetic fields at the interface of domains two Fredholm integral equations of the second kind relatively waves amplitudes are obtained. The symmetric and asymmetric waves are considered. The dependencies of the propagation constant versus wave number and field distribution in the waveguide are presented.
thermophysical parameters, the coefficient of heat exchange, the efficiency factor of absorption, the heat constant time.
Vestnik KhNU ¹927 Pages. 36-42
The paper deals with thin wires that standing on the way of distribution of the laser beam. The measurements were performed for platinum bolometers with diameters 10 and 20 microns and for nickel bolometer with diameter 40 microns. The experimental research of heat properties of these bolometers (platinum and nickel) in the range of temperatures from room up to close to melting temperature is carried out. The dependence of the thermal parameters of bolometer temperature, as well as the error in determining these parameters is considered. The coefficient of heat exchange with external environment, the efficiency factor of radiation absorption in the visible range, the heat constant of bolometer cooling are measured. The polynomial approximation of the received data is made.
geomagnetic field variations, magnetoconjugate solar terminator
Vestnik KhNU ¹927 Pages. 85-89
This paper analyzes quasi-periodic geomagnetic field variations in 1 – 1000 s period range that connected with the magnetoconjugate solar terminator action in 2002 – 2008. The measurements have been made near Kharkiv city. The processing was made separately for two seasons: summer and winter solstices. Magnetoconjugate solar terminator causes the perturbations relatively the solar terminator moving at the height of 100 km with the lead time 80 – 100 min. Dominant periods were 10 – 12 min and the duration was 50 – 60 min. Their amplitudes attain a value of 1 – 2 nT. These variations are transferred from magnetospheric region by magnetoacoustic waves.
wavelet-analysis, continuous wavelet transform, dynamic energogram, space radio physics, powerful non-stationary disturbance sources.
Vestnik KhNU ¹927 Pages. 96-102
Development and improvement of methods of time-frequency analysis of signals with continuous wavelet transform usage were proposed. The new method consists in the simultaneous analysis of wavelet spectrum and dynamic energograms of the continuous wavelet transform. Using the example of analysis of real non-stationary, non-linear and ultra wideband signals and processes in space radio physics problems, in particular, using the analysis of effects, caused by the powerful, non-stationary action, the dynamic energogram method effectiveness was shown.
Wigner transform, Cohen’s transform class, space radio physics, signal processing, powerful non-stationary disturbance sources, volcano explosion, solar eruption.
Vestnik KhNU ¹927 Pages. 89-95
Being a member of Cohen’s class of integral transforms, non-linear integral Wigner transform for analysis of the real signals and processes in geospace radar methods is applied. At samples of the May 18, 1980, explosion of Mount St. Hellens and the December 5, 2006, very strong X-ray solar eruption, the effectiveness of Wigner transform application to the processing of non-stationary, non-linear, fractal and ultrawideband signals and processes in problems of space radio physics, in particular, to the investigations of processes, accompanying the effects of powerful non-stationary disturbance sources was shown.
microstrip resonant antenna, thermostabilization, temperature compensation, dielectric permeability, substrate, resonant frequency
Vestnik KhNU ¹927 Pages. 65-70
The results theoretical and experimental researches of opportunities thermostabilization of resonant frequency microstrip antennas are given by use two-layer dielectric of substrates with opposite on a symbol and temperature factors, close on size, dielectric of permeability. The optimum ratio between the thickness of layers in a composite two-layer substrate are given. It is shown that the experimental oscillator with temperature compensation for temperature changes from -50 to +80 ° C the deviation of resonance frequency in the optimal variant is less than 0,1%
polarization converter, Bragg reflector, anisotropy
Vestnik KhNU ¹927 Pages. 43-47
Today, there are two fundamental type polarization converters, passive and active, are widely used in optical circuits. In this paper, we present a passive polarization converter for near infrared range. The converter reported here is porous silicon-based structure consists of N distributed Bragg reflectors (DBR) separated by N-1 defects. The method of the electromagnetic field’s scalarization and finite difference technique were used for calculation of spectral characteristics. The transmittance spectra of the proposed polarization converters for the both polarization of the incident plane wave are presented
circular waveguide, coaxial waveguide, residues-calculus technique.
Vestnik KhNU ¹927 Pages. 71-77
Diffraction problem of H1m waves by the system of circular slots in a hollow inner conductor of a coaxial waveguide using the operator approach is considered. The space inside a slot and between the slots is filled by a dielectric material. The diffraction problem by the gap of a semiinfinite circular waveguide placed coaxially inside a circular waveguide of lager radius is solved as the key problem. Dependencies of the transmission and reflection coefficients of bounded and semiinfinite periodical structure versus wave number and period of slots displacement are analyzed.
radioholographic image, flat and unflat radiohologram, by volume image of object, effect of Dopler.
Vestnik KhNU ¹927 Pages. 48-53
The physical and structural features of construction of the radioholographic informative systems (RG IS) and their adaptive properties which show up at forming and treatment of the coherent wave field on a transmission and reception are examined. The method of registration of radiohologram is offered on the surfaces of arbitrary form and method of adaptation of frequency of supporting oscillation to different frequencies of signal at a cooperative reception and to frequency of Dopler.
laser, optical radiation, intensity, distribution, receiver, direct problem, inverse problem.
Vestnik KhNU ¹927 Pages. 31-35
In this paper has been considered the method of the measurement of the intensity distribution in the beam of optical radiation and the algorithm of processing of a signal from the receiver. The method is using the knife attenuator of the special shape. The power of the reflected radiation on knife was measured by using detector of photoelectric. The algorithm and program for handling of the signal from receiver are developed. The influence of errors in the measurement signal from the receiver on the results of calculations has been researched. The experiment has confirmed the serviceability of the method and the possible of their use in practice.
DKDP single crystals, dc electrical conductivity, concentration of L-defects, gamma -irradiation, first order kinetics.
Vestnik KhNU ¹927 Pages. 22-30
The dependence of electrical dc conductivity of KD2PO4 (DKDP) single crystals on the dose of ?-irradiation is investigated. The conductivity is found to decrease exponentially in a dosage range of 3.0 102÷2.8 104 Gy. The temperature dependences of the conductivity are described by the exponential law. The pre-exponential factor and activation energy values of conductivity are determined for the crystals irradiated with various doses. Analysis of the dose and temperature dependences shows that the radiation-induced decrease of the conductivity is associated with the decrease of L-defect concentration in the crystal. The concentration changes in accordance with the law of first order kinetics. Possible mechanisms of the L-defect concentration changes under gamma -irradiation of crystals are discussed.
stratified structure, chirality, Fibonacci sequence.
Vestnik KhNU ¹927 Pages. 15-21
Optical properties of both symmetrical and asymmetrical modified Fibonacci structures of chiral and achiral isotropic layers are studied. The localization and polarization transformation of linearly polarized waves are considered. The effect of the phase shift compensation in the reflected field is shown in the case of an asymmetrical modified Fibonacci multilayer and on the basis of the developed software the series of computing experiments testifying to perspective of use of such structures in optical systems.
Gunn diode, dipole domain, accumulation layers, transit frequency, efficiency generations
Vestnik KhNU ¹927 Pages. 3-6
Results of research of power and frequency characteristics of Gunn diodes on the basis of Al1-xInxN for various values of concentration of impurity in active area in biharmonic regime are present. It is shown, that using of voltage of the complex form leads to increase of efficiency generation at the basic harmonic in comparison with work in harmonic regime. The increase of impurity concentration in active area leads to increase of efficiency generation both on the first, and on the second harmonic. At the expense of effective work on the second harmonic there is a possibility of reception of generation to frequencies of a submillimetric range.
founded: 17 result (s)