Kharkov National University of Radio Engineering and Electronics,
14, Lenin Ave, Kharkov, 61166, Ukraine
Non-Linear Effects in Wire Antennas with Non-Linear Surface Impedance
The results of computation of non-linear effects for the simplest radiators – symmetric and asymmetric dipoles with the inductive surface impedance are given. The input resistance of these radiators at different levels of their excitation are also analyzed. The difference in behavior of the current distribution along scatterers with the distributed and concentrated nonlinearities when exciting them with the plane wave field is noted.
Kharkov National University of Radio Engineering and Electronics,
14, Lenin Ave, Kharkiv, 61166, Ukraine
Fluctuations of Focal Spot within the Fresnel Zone of a Circular Focused Aperture with the Availability of Phase Errors
The focusing distance and the statistical parameters of the phase errors dependences on the maximum intensity coordinates of the field in the Fresnel zone of the focused circular aperture are investigated.
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura Str., Kharkiv 61085, Ukraine
On a Method for Determining Phase Distribution of MM-Wave Band Emitters
The problem the determining of phase distribution of mm-wave band emitters based on the holography concept (interference between volume signal and plane reference waves) is considered. Test measurements of phase characteristics of emitters and their comparison with popular physical notions and with the results of calculations are performed. Practical recommendations related to use of the described techniques in millimeter-wave band physics and equipment are provided.
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura St., Khirkov 61085, Ukraine
Origins of Giant Magnetic Impedance Effect in Magnetic Nanostructures in Millimeter Waveband
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura Str., Kharkiv 61085, Ukraine
Magnetoresistance of Magnetic Tunneling Junctions with Step-Like Potential Barriers
The influence of the bias voltage on the magnetoresistance of a magnetic tunneling junction with a step-like potential barrier has been studied theoretically in the frame of a two-band model of free electrons in ferromagnetic electrodes. It is shown that the dependence of the magnetoresistance of the magnetic tunneling junction on the bias voltage can be different according to the type and the thickness of the isolators forming a step-like tunneling potential barrier. It has been found that the magnetoresistance of the magnetic tunneling junction can change its sign and oscillate with increasing bias voltage. It has been shown that the sign reversal of the magnetoresistance is related to the increase in the transmission coefficient of majority electrons through the magnetic tunneling junction as the mutual orientation of magnetization of ferromagnetic electrodes switches from parallel to antiparallel.
1Dnipropetrovsk State University
13, Nauchnyy lane., Dnipropetrovsk, 49050, Ukraine
2A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura Str., Kharkiv 61085, Ukraine
Analytical Investigation Method for Electrodynamics Properties of Periodic Structures with Magnetic Layers
The paper deals with the periodic structure containing ferrite layers and isotropic stratified structures. The translation matrix for a period and the transformation matrix for M-periods have been obtained. It has been shown that the determinant of the transformation matrix is an important energy characteristic of a medium. The conditions of existence of periodic waves in the structure have been stipulated. The conditions of existence of periodic waves in the case of a two-layer period (ferrite layer – isotropic layer), at which the parameters of a gyrotropic layer do not have an influence on conditions of wave propagation, have been specified.
Communication System with Adaptive Antijamming Coding
An Identity-Based Signature Scheme Using Bilinear Mappings on Elliptic Curves
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura Str., Kharkiv 61085, Ukraine
HCN-Laser with a Hybrid Output Mirror
A waveguide HCN-laser with the lasant 1 m in length has been studied. An output mirror of the laser contains one-dimensional wire grating and an apertured flat mirror which are coupled. Dependence of laser output power on an aperture diameter, a grating period and a distance between the flat mirror and the grating has been studied experimentally.
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura Str., Kharkiv 61085, Ukraine
Study of Spatial Frequency Spectra for Solution of Focusing Problems
Method for focusing the objective lens based on analysis of a spatial spectrum of images, is described and its theoretical justification is presented. It is shown that there are one or several resonant spatial frequencies on a surface of any one object. For every resonance frequency a focal point has maximum intensity. It is associated with features of roughness formation. Processes of grinding and polishing result in that the rough surfaces are not absolutely random ones in terms of the probability theory. Consequently, optical fields generated by these objects are not also random. The conducted researches have allowed the combining process of fine focusing of a material-working laser with acquisition of a clearly defined image of a working surface.