Radio physics and electronics

15-36

Authors: A. А. Barannik, A.І. Gubin, A. А. Lavrinovich, N. T. Cherpak

The subject and purpose of the work. A review of the main results obtained by the authors in the process of microwave (MW) research of unconventional superconductors and the development of MW devices based on cuprate high-temperature superconductors (HTS) over the past 10–15 years is presented. Methods and methodology of work. Experimental studies were carried out by the methods of impedance measurements of superconducting samples. To this end, the authors developed two measurement techniques in the mm wavelength range: based on quasi-optical sapphire resonators and using the feature of reflection of a p-polarized wave from the surface of a superconductor at grazing angles of incidence. The results of the work.. The epitaxial films of the cuprate YBa2Cu3O7–d superconductor and Fe-containing superconductors in the form of single crystals of pnictide Ba (Fe0.926Co0.074)2As2 and epitaxial films of chalcogenide FeSexTe1–x (x = 0.5 and 0.7) are investigated. The results of the MW response of the electrodynamic structures with the samples under study served as the basis for finding the complex conductivity, including fluctuation one, and physical quantities related to it. In general, the results obtained confirm the scenario of d-wave symmetry of the gap function for cuprate superconductors and s±-wave symmetry for Fe superconductors. However, a number of detected features and effects, namely, an unusual frequency dependence of the residual surface resistance in YBa2Cu3O7–d in the form of w3./2, the growth of quasiparticle conductivity with decreasing temperature, starting from the critical one, as well as the avalanche-like transition from the superconducting to the strongly dissipative state in the nonlinear coplanar transmission line, require further study. New MW devices based on cuprate HTS films in the mm wavelength range have been developed and created: 1) a quasi-optical sapphire resonator with a radial gap and HTS end walls for studying Fe – superconductors in the form of small (1–2 mm in the plane a–b) samples; 2) planar quasi-optical resonator; 3) a band-pass filter with an E-plane insert in a cross-shaped waveguide. The possibility of contactless testing at room temperature of the homogeneity of the properties of massive superconductors is also shown. Conclusion. The temperature dependence of the complex conductivity of YBa2Cu3O7–d, Ba (Fe0.926Co0.074)2As2 and FeSexTe1–x (x = 0.5 and 0.7) superconductors and physical quantities related with it was obtained, which allows us to judge the confirmation of the corresponding wave symmetry scenarios of gap function function in the investigated superconductors. However, a number of detected features and effects require further study. The previously expressed assessment of the possibility of creating passive HTS-based MW devices with operating frequencies up to 40 GHz has been experimentally confirmed.

55-66

Authors: S. S. Apostolov, D. V. Kadygrob, Z. A.Маizelis, T. N. Rokhmanova, A. A. Shmat’ko, V. A. Yampol’skii

Subject and purpose. In this review the propagation of electromagnetic waves localized near the boundary of a sample of a layered superconductor with layers either parallel or perpendicular to its surface is discussed. The results obtained in a number of papers studying the dispersion law for such waves are generalized, classified and supplemented. Due to the strong anisotropy and nonlinearity of the Josephson plasma in layered superconductors, localized waves can have unusual dispersion properties, and their excitation can be accompanied by unusual resonance phenomena. Methods and methodology. The electromagnetic field in a layered superconductor is determined by the distribution of the gauge-invariant phase difference of the order parameter, which satisfies the system of coupled sin-Gordon equations. Based on the solution of these equations, as well as the Maxwell equations in the dielectric environment, dispersion relations can be obtained for localized electromagnetic modes. Results. In samples of a layered superconductor, whose layers are parallel to its boundary, both surface waves and waveguide modes with normal dispersion can propagate. For samples, the layers in which are perpendicular to the boundary, the dispersion law depends on the angle of propagation of the waves relative to the superconducting layers. In this paper it is shown for the first time that waves localized in a layered superconductor plate have an anomalous dispersion for all directions of propagation, except propagation strictly along the layers. Dispersion curves for such waves can have points of maximum and/or minimum, which can lead to nontrivial effects (e.g., stopping of light or internal reflection). Also, the excitation of localized waves and the unusual resonant phenomena are discussed in the work. Conclusions. Due to the strong anisotropy and nonlinearity of the layered superconductor, the dispersion laws for waves, localized both in semi-infinite samples and in plates have a number of interesting features that lead to new phenomena important for using in the physics of the terahertz range.

95-107

Authors: S.V.Nikolaev, V.V.Pozhar, M.I.Dzyubenko, K.S. Nikolayev

Subject and purpose. This article is devoted to a brief review of the main results of the research cycle aimed at developing solid active media based on dye-activated polyurethane compounds. The ultimate goal of these studies was the creation of solid-state active elements that make it possible to realize a wide-band solid-state dye laser (SSDL), which emits frequency-tunable radiation with a microsecond pulse duration. Methods and methodology. The problem was solved mainly by experimental methods. At the same time, the studies carried out included a full range of works, starting with the production of samples of solid-state active media to study the generation characteristics of the active elements created. Results. In the course of the work, laser-active media based on industrial polyurethanes of various grades activated with Rhodamin 6G, Sulforhodamine 101, Oxazin 17, and Oxazin 1 dyes have been created and their spectral-luminescent characteristics have been studied. Experimental samples of laser matrices are made. The optical properties of the media created are studied and the influence of the technique of making samples on the nature of possible distortions of their optical homogeneity is determined. The emission ability of polyurethane matrices was studied. With transverse monochromatic excitation laser emission was obtained on polyurethane matrices with an efficiency of 12 to 26% and energies from 23 to 127 mJ. Radiation resistance and possible service life of polyurethane media have been investigated The thermo-optical properties of polyurethane active media and their effect on the directivity of SSDL radiation are studied. The effect of induced birefringence, which occurs under conditions of asymmetric pumping of microsecond duration, is observed. It was found that under such conditions, polyurethane active elements emits polarized radiation even when excited by depolarized light. A possibilities of narrowing and tuning the emission spectrum of polyurethane matrices in dispersion resonators with angular and amplitude type of selection are investigated. The laboratory model of a tunable SSDL with replaceable polyurethane laser elements, generating a pulsed radiation of a microsecond duration in the spectral range of 565...700 nm is created and tested. Conclusions. The results of the performed studies allow to conclude that industrial polyurethane compounds can be successfully used as solid media for active elements of SSDL.

9-39

Authors: V. D. Yeryomka, O. F. Pishko

Subject and purpose. In the vacuum microwave electronics, with increasing the operating frequency of the source electromagnetic oscillations, most attention is paid to increasing the efficiency of electron-wave interaction on the Vavilov-Cherenkov effect of rectilinear electronic flows with a slow spatial harmonic of electromagnetic waves in metallic periodic slowing structures (PSS). At the same time, isufficient attention was paid to the study of the effect of the coefficient of the use of rectilinear electronic flows on the frequency energy Cherenkov oscillators and amplifiers of electromagnetic oscillations. Clinotron effect, reveated in 1956 in the process of development and research of O-type backward wave tubs (O-type BWT) of short-wave ranges Institute for Radiophysics and Electronics of Academy of Sciences of the Ukrainian SSR, demonstrated a significant influence of the utilization factor of a spatially developed rectilinear electronic flows on the frequency-energy characteristics of the O-type BWT. Methods and methodology. There is no publication in the scientific literature that summarizes the results of research into the frequency-energy characteristics of vacuum sources of terahertz (THz) electromagnetic oscillations with spatially developed electron currents, created during the last 50 years and differing in the principle of action, by theoretical and experimental methods of influence of the clinotronic effect on the frequency-energy characteristics. Results. The analysis of the frequency-energy characteristics of THz BWT-clinotrons, THz-clinoorotrons, THz-gyroclinotrons, THz-clinoorbictrons was carriedout. Based on the analysis of the results of the research, there is a conclusion about the existence of a close relationship between the value of the coefficient of the use of spatially-developed electron flows and frequency-energy and also the mass-size characteristics of vacuum sources of THz electromagnetic oscillations. Сonclusions. The use of the clinotronic effect in vacuum sources of electromagnetic oscillations with spatially developed electron currents contributes to the creation of compact generators and signal amplifiers in the "THz slit" of the spectrum of electromagnetic oscillations.

65-76

Authors: O. I. Kovalenko

Subject and purpose. Particularities of the targeted modification of functionals of the wheat seeds state by irradiation with a low-intensity electromagnetic field (EF) were investigated. The aim of the work was to investigate the effectiveness of low-intensity electromagnetic field mediated by water on wheat seeds depending on their initial state, evaluated statistically as “norm” and “pathology”, and to study the possibility of functional reconstruction of the wheat seeds with the “pathology” state. Methods and methodology. The work is experimental. Approved radio-physical, radio-technical, biological methods and techniques were used in this work. Generators Г4-141 (37.5…53.57 GHz) and Г4-142 (53.57…78.33 GHz) were used for electromagnetic field irradiation. Efficiency of the electromagnetic field influence was evaluated using functionals of the seed state: energy of growing, average length of roots and seedlings in each portion. Statistical methods were used in the processing and the analysis of the obtained results. Results of work. The possibility of a targeted modification of the functional parameters of wheat seeds upon their interaction with water, previously irradiated with EF, was established. Differences in the effectiveness of the water-mediated influence of EF depending on the frequency and exposure of the signal were shown. We found the dependence of biological reaction of the wheat seeds on the electromagnetic field irradiation mediated by water. The reaction depends on the initial state of the seeds: those in the “norm” state get oppressed, while those in the “pathology” state are stimulated. The application of water-mediated electromagnetic field influence on wheat seeds in the “pathology” state was shown to be promising for restoring of the lost functional properties. Efficient regimes of electromagnetic field influence mediated by water were established. Conclusion. Water-dissipative model of the electromagnetic field interaction with substance was confirmed. Method of the electromagnetic field influence mediated by water on wheat seeds was proposed. It allows stimulating their lost properties, which is promising for development of agricultural technologies.

9-21

Authors: V. V. Ovsyanikov, E. R. Beznosova

Subject and Purpose. The results of studies of actual methods for expanding the frequency range of vibrational curved whip and loop antennas, and antenna arrays based on them are presented. Optimal designs of broadband antennas with the concentrated reactive loads included in the shoulders are considered. Methods and methodology. Calculations of the electrical parameters of the antennas were performed by the integral equation method, which allowed us to investigate new variants of broadband pin and loop antennas and antenna arrays more deeply. Two types of antennas are investigated, which are promising for the use in the microstrip implementation in the form of single antennas and as part of antenna arrays. The first variant is a Z-shaped antenna of orthogonal linear polarization, supplemented by concentrated capacitive loads; the second one is a loop in the form of a frame also with capacitive loads. To approximate the actual application conditions, the antenna parameters were determined when they were placed at a small height above the conductive screen (plane). Results. As a result of calculations of the electrical parameters of Z-shaped antennas with capacitive loads and antenna arrays based on them in the wide frequency range of 0.9...1.2...2.7 GHz, we obtained a significant improvement (decrease) in the standing wave voltage coefficient up to values not exceeding five in comparison with similar antennas without loads, for which the values of this parameter reach thirty or more. Compared with conventional rectilinear antennas of the same length and thickness of the rod, the antenna gain factor with loads increased from 7.8 to 9.8 dB at a decrease in the standing wave voltage coefficient from 3.5 to 3.1 at the middle frequency of the investigated range. For loop antennas with capacitive loads, the values of the standing wave voltage coefficient were not more than five in the same range, and at the middle frequency of the range these values did not exceed 1.9, while in antennas without loads this parameter is much higher (up to thirty) and at the middle frequency of the band has a relatively high value up to 15. Coplanar linear in-phase antenna arrays of three Z-shaped and three loop antennas with capacitive loads have been investigated. It is shown that due to the difference in the conditions for the mutual arrangement of the antennas in the gratings, the standing wave voltage coefficient of the terminal array antennas differs from this parameter of the average antenna. Conclusions. To obtain the operating mode of a current close to the traveling wave mode in Z-shaped and loop antennas and antenna arrays based on them, and, as a consequence, to reduce the frequency dependence of the input parameters and radiation patterns of these antennas, it is sufficient to include no more than four capacitive loads in the symmetric antenna arm. This makes it possible to simplify broadband antennas and save the expenses of time and resources for their development and fabrication in comparison with the known works, where it was proposed to include several tens of capacitive loads in the antenna arm.

39-47

Authors: O. V. Sytnik, G. P. Pochanin, S. A. Masalov, V. P. Ruban, P. V. Kholod

Subject and Purpose. The subject of the study is a measuring system consisting of several spatially separated receiving points and a transmitter emitting video pulse signals. The aim of the work is to create an effective algorithm for processing signals from a multi-position observation system under conditions of correlated jamming to solve the problem of the operational detection of mobile objects hidden behind optically opaque obstacles. Methods and methodology of work are based on the difference-distance-measuring principle of calculation of the target coordinates. The informative signal from the target is not identified by direct methods because of the multiple reflections of the sounding signal from the walls of the room and objects located inside it. The procedure for suppressing the interference reflections of the probing signal is developed. The accumulation of a signal and the removal of interference is carried out in real time by subtracting the alternating samples of the observed process from the signals of each receiving point assuming that the object is slow moving or practically unmoving during the time of sounding signal propagation from transmitter to target and back. The delay of the probing signal during its propagation from the transmitter to the target and from the target to each of the receivers has been estimated using the proposed peak factor criterion. The same criterion is used to reject the struck lines on the radar image of the target's trajectory. Results. A high-speed algorithm is developed which, at the condition of a relatively high signal-to-noise ratio, makes it possible to use the signal peak factor as a criterion for jammers suppression at the radar's image. The simplicity of signal processing allowed to continuously display the data in a user-friendly form. The continuity of measurements of the delays of the reflected signals from the target to the receiving points is ensured by polynomial approximation of the object trajectories relative to each of the receivers. Conclusions. The high energy characteristics of the observation system, the stability of the parameters during the measurements, and the high accuracy of the reflected waveform reproduction allowed us to use digital signal processing methods in real time. The simulation results are confirmed by data that were accumulated and averaged over a series of similar experiments.

54-60

Authors: N. N. Beletskii, S. A. Borysenko

Subject and purpose. The effect of reflectionless transmission (tunneling) of electromagnetic waves through the three-layer structure containing a negative-permittivity layer is of great importance both for studying the fundamental properties of solids and for developing new types of unique technical devices. There is a need for investigation of the effect of reflectionless transmission of electromagnetic waves through the three-layer structure containing a negative-permittivity layer in a wide range of the three-layer structure parameters. Methods and methodology. A new approach based on the use of dimensionless thicknesses of a three-layer structure is presented. This approach makes it possible to study the effect of reflectionless transmission of electromagnetic waves for different wavelengths and different values of parameters of the three-layer structure with asymmetric dielectric surroundings. Results. It is shown that the presence of a negative-permittivity layer in the three-layer structure leads to a significant softening of limitations on the parameters of the positive-permittivity layers. Thus, the effect of reflectionless transmission of electromagnetic waves takes place at any preassigned positive value of the permittivity of the layers surrounding symmetrically the negative-permittivity layer. In this case, the parameters of the negative-permittivity layer should be chosen as required. Conclusions. The results of the research extend knowledge on the mechanisms of electromagnetic waves tunneling through the three-layer structures containing negative-permittivity layers. This effect can be used for development of new types of high-frequency solid-state devices operating in different wavelength ranges

69-75

Authors: M. I. Dzyubenko, Y. E. Kamenev, V. P. Radionov, Z. Y. Litvina

Subject and purpose. The terahertz frequency range currently attracts much attention due to the wide possibilities of its application for solving a number of problems in science, technology, and medicine. In this range, metal gratings with the period shorter than the wavelength are widely used as partially transparent mirrors of lasers and in various quasi-optical devices. The determination of the parameters of such gratings is an actual problem. Methods and methodology. The method of experimental comparison of the parameters (losses and transmittance) of metal gratings consisting of parallel conductors is presented in the paper. A THz laser with a smooth adjustment of the output of laser radiation from the resonator was used as a measuring device. The investigated metal grating serves as the exit mirror of this laser. The dihedral 90° mirror is the second mirror of the laser resonator. The adjustment of feedback is performed by rotation of the dihedral mirror around the resonator axis. The angle of rotation of the dihedral mirror, which provides the maximum power of laser radiation, characterizes the transmittance coefficient of the investigated grating. The value of the maximum power of laser radiation characterizes the magnitude of the losses in the investigated grating. This allows one to compare the grating parameters experimentally without the use of metrological instruments. Results. An experimental comparison of the parameters of metal gratings with different structures was carried out as an approbation of the method. Recommendations for the increase of the measurement reliability and further advancement of this method were developed. Conclusions. The proposed method is an effective tool for comparing the transmittance and loss factors in one-dimensional metal gratings for their control and culling. In addition, this method can serve as a measuring device, when reference gratings with known parameters are used for comparison.

10-18

Authors: Yu. A. Pedenko

The paper focuses on the problem of increasing the accuracy of radar measurements of the elevation angle of the low-altitude targets over the sea. The Matrix Pencil method, as one of the means to resolve this problem, is studied in the paper. This method refers to the methods of high spectral resolution, but in a number of publications, the possibility of its use for measuring the angles of arrival of radio waves is also considered. However, the extent of its suitability for solving the problem needs to be studied taking into account the specific conditions under which the measurement of the elevation angles of low-altitude targets is performed. The research was carried out by computer simulation. It covered the sea states with the conditions of both specular and strong diffuse reflection satisfied. One of the main goals of this work was to determine ultimate measurement accuracy achieved by the method when only the diffuse reflection from the sea is considered as a disturbance (a specular signal along with a direct signal from the target are considered as a measured signal). It was established that by this indicator the Matrix Pencil method does not concede to the well-known MUSIC method, but even exceeds it, especially for strong diffuse reflection (improvement reaches 20%). Another impor-tant task was to investigate the influence of the a priori parameters of the method on the measurement errors: the number of measured signals, the values of the so-called pencil-parameter and the number of spatial samples of the signal at the given antenna aperture. As a result, recommen-dations on the selection of these parameters have been developed, which make it possible to minimize the errors in the measurement of the elevation angles. This research expands the understanding of ways to increase the accuracy of mea-suring the angles of low-altitude targets over an agitated sea.

34-41

Authors: V. D. Karlov, Yu. V. Kirichenko

In the present paper, the plasma antenna with azimuthally asymmetrical traveling waves operating at a harmonic with an azimuth number m = 1 is investigated theoretically and numerically. In addition, the collisions of electrons with atoms are taken into account. Plasma is assumed to be cold and isotropic. The method of the dispersion equation is used. The propagation constant and the attenuation coefficient of the traveling wave can be obtained from the real and imaginary parts of the solution of this equation, respectively. In order to find the radiation patterns (RP), the delayed potentials in the far zone are calculated. The RP strongly depends on the slowing of waves in the antenna. The dependences of the slowing of the wave on the plasma density are obtained, and the dependence of RP on the plasma density, geometrical parameters of plasma cylinder and frequency of electron-atom collisions is investigated. The minimum values of plasma density, at which the normalized radiation patterns are highly directional and have a main lobe located at a zero angle to the antenna axis, are obtained. Advantages of antenna operating at harmonic with m = 1, as compared to the antenna working on an azimuthally-symmetrical wave, are shown: the working plasma density of such antenna is much lower; the radiation is in a strictly axial direction; a small level of the side lobes of the RP; the RP is less dependent on the electron-atom collisions. It is also shown that, by dispersion properties, a plasma antenna with m = 1 is closer to a metallic antenna than an antenna with m = 0.

53-60

Authors: V. А. Markov, V. D. Naumenko

One of the main problems faced by developers of modulators for spatial-harmonic magnetrons with cold secondary emission cathode is the selection of the correct shape of an anode voltage pulse that will ensure the stable operation of the magnetron. In this paper, the effect of the shape of the anode voltage pulse on the operation of transmitters based on magnetrons with cold secondary emission cathodes is investigated. The influence of different parts of the pulse on such parameters of the magnetron as the required current of the starting cathode necessary for stable excitation of secondary emission from the cold cathode, the stability of operation on the selected mode of oscillation, and the generation of the maximum power is experimentally studied. It is shown that the magnitude of the starting cathode current is determined, first of all, by the steepness of the pulse front. Its optimum value is usually about 150 kV/ms. In this case, starting cathode should provide a current of only a few tens of milliamperes, which can significantly increase the lifetime of the device. The article also shows that the presence of a pulse spike at the beginning of a voltage pulse facilitates a premature transition to a non-working mode of oscillation. As a result, this leads to a decrease in the output power of the magnetron. The duration of the decay determines the ability of the magnetron to operate at small pulse duration. For very short pulses, the energy expended on the microwave generation can be equal to the energy expended on the formation of the pulse decay. As a result, it was concluded that the usage of spatial-harmonic magnetrons with cold cathode requires a careful refinement of the characteristics of a pulse modulator. The steepness of the front of its output pulse should be about 150 kV/ms, and the pulse spike at the beginning of the voltage pulse should be as small as possible. When working on very short pulses it is necessary to provide a longer rate of pulse decay.

71-81

Authors: А. О. Puzanov

The torch discharge (TD) is applied in a number of areas of science and technology. However, the lag in theoretical research from ever-growing urgent needs makes the solution of many practical-oriented problems related to the TD relevant. In the present paper, the study of the proposed by the author original method for measuring the resistance of the TD (Rd) taking into account the TD inductance L is continued. The presented numerical calculations are supplemented by the previously performed estimations of the theory application area. The sought resistance Rd is considered as frequency independent within the theory. Performed estimations and calculations confirm the applicability of the approach presented both with and without taking into account the TD inductance in the frequency range from 1·10 ‑3 to 3.0 GHz. It is shown that a necessity to account the inductance of the torch discharge of the power below 1 kW and the choice of appropriate frequency pairs f0,1 have to be studied in each case separately. A possibility to excite the torch discharge at two sufficiently different frequencies is mandatory. Numerical calculations of Rd without taking the inductance into account show that calculations accuracy depend weakly on the height of the torch discharge location relative to the ground. The accuracy increases if the discharge diameter decreases; the discharge length increases; the value of Rd is small and less than 1 kОhm; f0,1 frequencies converge. It results in a necessity to add an equivalent inductance into the Neiman’s scheme making appropriate modifications of the calculation formulae. It is shown that the resonant frequency fr is approximately proportional to fmax, which is the upper limit of the frequency range where the circuit theory remains applicable for the discharge modeling. Thus, the knowledge of fr and fmax allows one to refine the values of the function a, which is the ratio of voltages at which the electrical and geometrical characteristics of the torch discharge remain unchanged. The approach proposed results in more effective using of industrial resources.