I. V. Ivanchenko

Effect of finite screen and monopole's height on radiation characteristics of monopole antenna

This paper presents the investigation results on the effect of separate element dimensions on the radiation characteristics of coaxial X-band monopole antenna. In particular, the variations of monopole height, ground-plane dimensions, and monopole location relative to the ground plane are analyzed in details. Based on FDTD simulations a contribution of EM fields scattered by these elements in the radiation pattern formation has been shown. As a result, the regularities in the elevation angle of peak directivity changing have been determined.

Waveguide antenna with a hybrid dielectric insertion

In this paper, the aperture X-band antenna with a hybrid dielectric insertion has been proposed. It is shown that the use of cylinders with different permittivities inside the dielectric matrix and a specific topology in their location gives rise to the significant extension of the operational frequency band up to 2.3GHz and varying the elevation angle of peak directivity in the H-plane.

Features of spin dynamics in HgCrCdSe and HgCrSe crystals in the vicinity of phase transitions

The inhomogeneously broadened EPR lines of the solid solutions Hg1–x–yCrxCdySe and Hg1–xCrxSe are represented in the form of spin packets and their temperature evolution is analyzed upon the transition of the crystals to ferromagnetic ordering. In this case, the spin packets being introduced into the consideration are identified with allowed transitions of the localized electrons and with the delocalized electrons. It is established that a characteristic feature of the subsystem of delocalized electrons is the anomalous behavior of the g-factor in the vicinity of the transition to the ferromagnetic state. The introduced spin subsystems, which characterize the localized and delocalized electronic states, allow for explaining the differences in scenarios of the transition to magnetic ordering of crystals with different cluster structures. Just significantly lower concentration of clusters in the HgCrSe crystal leads to a slowing down of flip-flop processes that explains the longer relaxation times of spin p...

X-band resonator for studying the various axially symmetric inhomogeneities in the frequency band

The problem related to the choice of an adequate microwave resonator for measuring the dielectric constant of substances with the high permittivity and losses is considered. Numerical modeling and experimental investigations of a rectangular X-band resonator with the axially symmetric inhomogeneities, such as a dielectric cylinder and the dielectric capillary filled with the solutions, which have the different dielectric permittivity, are carried out. Both optimal sample sizes depending on their dielectric permittivity and the geometric parameters of dielectric capillaries for studying the various liquids are determined.

Definition permittivity of weakly concentrated solutions in the microwave range

In this paper a modification of the well-known method of resonance dielectrometry is proposed with the aim to define a real part of the permittivity of weakly concentrated solutions in the microwave frequency band. By using the results of numerical simulations, the optimized electrodynamical module has been fabricated and tested. The experimental verification of the proposed method points out the high sensitivity and accuracy of measurements.

Original Ka-band fractional spiral antennas

The original fractional

Numerical modeling the resonance X-band structures with local inhomogeneities inside

-shape spiral antenna being fed from the Ka-band metal waveguide is proposed. The impedance bandwidth of such an antenna is 6.7GHz. Herewith, the axial ration does not exceed 3dB level within the limits of 34.2 - 37 GHz. The radiation pattern of such an antenna is similar to the monopole antenna with zero-radiation intensity in the antenna axis and with an elevation angle of peak directivity equal to about θ=20°. It is important, that the radiation pattern shape does not undergo any visible deformations through the operational frequency band. The use of near-field technology allows for explaining the basic reasons of the axial ratio changing through the antenna bandwidth. The proposed antenna seems to be very attractive for various practical applications in the millimeter range.

Benefits of near-field technology in the small-size antenna designing

The electrodynamic characteristics of two types of resonators with the local cylindrical inhomogeneities inside are analyzed with the aim to find the conditions of the most effective employment of such resonators as the resonance cells of X-band radio spectrometers. As the results of simulations the optimal geometrical dimensions of the conductive and low loss samples as well as their location in the resonance volume are determined.

X-Band Aperture Antenna with Hybrid Dielectric Inserts

In this paper three different types of small-size antennas are presented with the aim to illustrate the benefits of near-field technology for explaining the features of the antenna performance as well as for designing the antenna with characteristics given in advance. In particular, the axially-symmetrical mono-beam radiation pattern with the radiation maximum in the antenna axis can be realized in the DDA by introducing the additional passive dipoles. At the same time, the use of additional passive phase correctors in the rectangular patch antenna configuration one may change the radiation pattern shape, the elevation angle of peak directivity and antenna bandwidth.

X-band aperture radiator with artificial low losses dielectric

An X-band radiator as an open-ended waveguide with a hybrid dielectric insert is proposed. The insert is in the form of a parallelepiped, which fills the entire cross section of the waveguide and constitutes a Teflon matrix with local inhomogeneities in the form of dielectric cylinders with a different permittivity. The design allows for forming various near-field distributions and, hence, the radiator performance by means of definite combinations of the local inhomogeneities can be modified. A number of configurations in the location of air and quartz cylinders are investigated. The calculated and experimental results are in good agreement. The proposed approach to the near-field formation of the aperture antenna is promising, because the variety of possible configurations in the location of local inhomogeneities with different permittivity provides new opportunities in terms of designing both single radiators and antenna arrays.