In this work, the results of experimental study of eigen waves of periodical system that is formed of planar dielectric waveguide and grating are presented. Authors describe the features of system mode composition in frequency range of the second-order mode excitation. Also, the signs of inter-type mode transformation were detected.
The amplitudes and phases of the electric field in the near zone of the linear and planar equidistant antenna arrays of a large electrical length on the basis of a radiating coaxial-slit cable, that are designed to provide reliable radio communication in the underground tunnels and at the railway transport, are calculated. It is shown that such antenna arrays have shaped a searchlight beam in the near zone upon condition that three or four linear radiating cables have radiated.
The design of a cylindrical coaxial horn antenna with a generatrix bend and the central conductor mounted along its axis is proposed. Two constructions types (varieties) of such antenna are studied. In the first case, such conductor is a metal-dielectric rod, which does not reach the throat of the horn. In the second one it is a copper rod, reaching the throat of the horn. Experimentally confirmed that for certain sizes of the rod such antenna constructions provide reduced width of the antenna pattern by 120 and allow to receive electromagnetic wave with arbitrary polarization.
Using the vectorized Kirchhoff integral, the external problem of electrodynamics is solved for emission of continuous aperture antennas with a circular shape radiating opening. The mathematical support was developed and calculations of amplitude and phase characteristics of electric and magnetic fields in the direction of the normal to the radiating opening and on plane surfaces parallel to the opening were carried out, the amplitude and phase distribution of the field sources being constant, the change in the opening diameter from half to 100 wavelengths. It is shown that the searchlight beam in the near-zone of such antennas is formed, diameters of the radiating opening being larger than 1.5-2 wavelengths, the amplitude of electric and magnetic fields oscillate uniformly over a larger range of values compared with cases of square and rectangular opening.
Improved linear antenna array design capable of obtain the given side-lobe suppression with controlled value of antenna directivity is suggested. The antenna of supper selectivity properties is also suggested. A clear linear antenna design procedure has been presented that does not require the implementation of numerical optimization procedures. The efficiency of suggested design has been investigated.
The effect of low energy electromagnetic radiation with frequencies 1.8 GHz and 2.4 GHz on the heterochromatin granules quantity (HGQ) in the nuclei of human buccal epithelium cells was studied. Exfoliated cells were exposed to microwave radiation (frequency 1.8 GHz, surface power density 2.5 μW/cm2; and also frequency 2.4 GHZ, surface power density 2.3 μW/cm2). After exposure to microwaves during 1, 2, and 3 h, immediately or after delay of 1 or 2 h cells were stained with orcein (2% solution in 45% acetic acid). Cell exposure to microwaves induced condensation of chromatin. The biological and medical meanings of the data obtained are discussed.
Transformation of an electromagnetic pulse in a triply asymmetric electrodynamic problem is considered: transformation of an initial asymmetric Airy pulse on a boundary between two dielectric medium in one of which the refractive index changes in time by jump.
The cause-effect relations between the levels of pulsations of the antenna system, caused by main rotor rotating of the helicopter, and the probability of the bit error occurring in the digital data transmission channels were established. Graph-analytical method of error probability estimation was developed.
The autodyne characteristics are oifered to use for steady-state stability analysis of the UHF oscillators. Theoretical substantiation of the proposed method is performed on an example of the oscillating system's mathematical model presented in the form of two mutually-locked partial oscillators under a condition of strong coupling between them. Peculiarities of stable functioning zones for oscillating systems are described at different partial oscillator parameters and for various conditions of their mutual coupling. Experimental investigations are performed based on the 8mm-wavelength range double-diode oscillator.
The directivity diagrams of the Hertz dipole and a half-wave vibrator, which are situated parallel to the plane perfectly conducting infinite screen, are determined in the entire front half-space. It is shown that the width of the main lobe of the directivity pattern is increased when the radiator height above the screen is increased. After comparison with the known results it is proved that the calculation of the coefficient of directivity, which was obtained by integrating the directivity pattern over the entire space, made it possible to provide high accuracy of the calculation. It is also shown that the maximum of the coefficient of directivity of the Hertz dipole and the half-wave vibrator above the screen in the direction of the normal to the screen is equal to four times of the coefficient of directivity of these radiators in the free space.
The method of remote measurement of object surface deflections using an artificially created system of secondary radiators located on this surface is considered. The physical basis of the method is a change of the pattern of radiators system due to their displacement under the loads influence. Radiators displacements which are included in the expression for the distorted antenna radiation pattern are determined by minimizing of the functional using a genetic algorithm. Reconstruction errors of radiators displacements are identified for different situations taking into account the ambiguity of the problem. The best conditions for the functioning of the method are recommended for the practical use.
The necessary conditions which provide the circularly polarized radiation with maximum directive gain for the in-phase crossed impedance wire dipoles system located over a perfectly conducting square screen have been investigated in the normal direction to the screen. On the base of the uniform geometric diffraction theory method with using the asymptotical expression for a current of an impedance wire dipole located over an infinite perfectly conducting plane the fast active 3D algorithms have been developed. The appropriate distributed surface impedances of the in-phase crossed dipoles have been defined taking into account the diffraction effects on the screen edges. The detailed analysis of the surface impedance values, the radiation resistance and directive gain depending on the screen's sizes and the dipole removal from the screen is given.
Unconventional connection of ferroelectric capacitors to resonators of tunable filters is proposed. It has increased the required minimum of capacitance value and the frequency range from ku-band to K-band. The proposed method of connection is illustrated by an example of microstrip filter, which is tunable within the frequency range 18-20 GHz. The minimum capacitance of the ferroelectric capacitor, that was obtained, was C min = 0.22 pF, the maximum value - C max = 0.31 pF. In traditional connection scheme, capacitance value is C min = 0.11 pF, and it is not possible to implement ferroelectric capacitors in this case. Simulation results of the frequency responses of the filter are presented.
Examination of nonlinear periodic composite media based on opal matrices and metal-carbon nanostructures is conducted. This can constitute a new element base opening possibilities for the modern radioelectronics. The considered nanostructures have the substantial potential for their application in perspective nanotechnologies directed on creation of radioelectronic devices for SHF, EHF and HHF bands (microwave, sub-THz and THz ranges). They allow improving the functional characteristics of the arrangements made on their base. Nanostructures construction with preset properties is important for design of sub-THz and THz radioelectronics. Such properties can ensure an opportunity of nanostructures controlling, based on which it is possible to realize the nonlinear parametric zonal systems (NPS) resonance circuits functioning on current ultraharmonics in the highest zones of electromagnetic oscillations instability.
The antenna array of two arc monopoles which are located parallel to the surface of a perfectly conducting or impedance sphere is considered. The influences of the phase of excitation of a monopole, the distance to the sphere surface, and sphere radius and its surface impedance on the directivity of the radiator are considered. It is shown that the radiation pattern of the antenna for antiphase excitation is highly directional and has a single maximum in the plane of arrangement of the emitters.
Analysis results of coupling degree influence of the autodyne oscillator with an antenna are presented together with influence of the impedance characteristic type (soft or rigid) of the active element on the coefficients of autodyne amplification, autodyne frequency deviation and power transfer as well as on the noise parameters and characteristics. Analytical and numerical calculations of above-mentioned parameters and characteristics are performed, and results of experimental investigations of the 8mm-range Gunn diode autodyne are given.
The given work describes a new technique of image segmentation, in particular for building detection on radar or infrared Earth-observation images. The method is based on property of most man-made objects which consist in straight edges and mostly right angles. The developed 2D adaptive image filter assists to detect straight edges even if given image fragment has a low contrast and has been extremely noised, in addition, if an object edge has been distorted, for example, by interference in the SAR azimuth channel, the filter compensates for distortions which do not exceed the specified value. The next processing of line-segment list without image raster works faster and allows detecting a relatively small set of possible targets. This approach could be used as addition for neural networks as well as provide assistance in preparing of training data set.
The microwave irradiator in the form of a piece of a rectangular waveguide with a dielectric insert inside and a narrow slot in the end wall was experimentally investigated. The irradiated object is located near the slot in the outer region. It is shown that with the help of a dielectric insert it is possible to practically completely match this system, which ensures a high efficiency of irradiation of fragments of a material medium or dielectric samples of finite dimensions.
The problem of determining the electromagnetic fields, created by slotted coaxial line, is solved in the present work. To determine the coaxial-slot antenna near-fields the Kirchhoff's method has been applied. Electromagnetic field distributions in the near- zone of coaxial-slot radiator have been explored for different values of feeder parameters on a large range of wavelengths. Field diffraction patterns for the short distances from the slot radiators have been obtained.
