Radio physics and electronics

3-10

Authors: E. A. Velichko, A. P. Nickolaenko

Development of new antennas for reception of radio signals was and remains an actual problem. We model and estimate the efficiency of unusual design of the vertical electric antenna detecting ELF (3…3 000 Hz) radio signals. The antenna must be sensitive to the vertical electric field of radio waves traveling in the spherical Earth–ionosphere cavity at frequencies of global electromagnetic (Schumann) resonance ranging from 4 to 40 Hz. It is formed by a couple of electrodes fixed at the tree trunk at different heights separated by several meters. Such a design is unusual, and its workability might seem dubious. We show with the help of model computations that the tree antenna is a rather effective ELF sensor, especially in fair weather condition. We also discuss the requirements for the tree antenna pre-amplifier.

20-29

Authors: A. V. Brovenko, P. N. Melezhik, S. B. Panin, A. Ye. Poyedinchuk

We suggest an analytical-numerical method for determining the diffraction characteristics of the plane linearly polarized electromagnetic wave scattered by a circular inhomogeneous isotropic magnetodielectric cylinder, which material parameters depend on the radial coordinate. The method is based on the construction of special solutions to Cauchy problem for Riccati equation and allows within a unified approach to investigate the processes of wave diffraction by both radially layered and continuous magnetodielectric cylindrical inhomogeneities. The efficiency of the proposed method was demonstrated by several examples of numerical solution of diffraction problems for circular non-uniform isotropic dielectric cylinders. We studied the total cross section of Luneberg lens for a number of focal parameters and the behavior of its field longitudinal component at resonant frequency when geometrical parameters vary.

40-48

Authors: O. M. Stadnyk, O. O. Silin

The flat lens conception was considered in the pioneering work of V. G. Veselago, who considered the possibility of electromagnetic waves propagation in media with simultaneously negative permittivity and permeability (according to modern terminology – in the left-handed metamaterials). Later, J. B. Pendry put forward the idea of so-called “superlens”, the resolution of which would exceed the diffraction limit. In view of the prospects for the practical applications it has caused a discussion on the possibility of antiparallelism of phase and group velocities and the actual superresolution implementation for the source in the form of a monopole. However, using the ray theory approximation reduced the generality of the results, neglecting losses radically distorted them, and errors in the theoretical analysis led to the wrong physical interpretation. In this paper, we obtained a rigorous solution to the problem of focusing radiation from elementary electric dipole located perpendicularly to the plane layer of finite thickness made of the left-handed metamaterial with absorption. Spatial distribution of the electromagnetic field in the layer, as well as the incident and reflected fields at various heights of the dipole, layer thickness and losses in each environment are numerically simulated.The analysis of the calculated spatial structure of the electromagnetic field confirmed the focusing ability of the interfaces between ordinary and left-handed media, as well as a flat lens.

56-59

Authors: Yu. V. Levadnyi , Yu. I. Malyshenko, T. E. Chistova

Heavy rains considerably attenuate radio signals transmitted by modern millimetre wave high-speed communication lines. Therefore, this interference in the form of fast and deep changes of rain rates demands further investigations. Industrially manufactured rain gauges are not suitable for these investigations because of their inertia and insufficient precision of measurements. In this connection in this work the tipping-bucket rain gauge, has been modified and made. As a result the precision has lightly improved but the rapidity – more than in ten times (up to a few seconds in heavy rains) owing to considerable diminishing the cuvette size and weight and also due to configuration which removed drop adhesivity on its surface. The inclusion of an inexpensive microcontroller into the gauge composition also increased its precision and provided a better display of rain rate values on a built-in monitor and interface to a computer for registration.

68-76

Authors: Yu. O. Averkov, Yu. V. Prokopenko, V. M. Yakovenko

Nowadays a good deal of attention is focused on problems of generating electromagnetic oscillations on the basis of the interaction of charged particles with the structures containing dielectric and plasma-like media. This is due to the sufficiently high efficiency of conversion of the electron beam kinetic energy into electromagnetic radiation. The currently available theoretical results give only qualitative descriptions of experiments. Therefore, it is important to give a detailed description of such effects maximally close to the real conditions of the experiment. In this connection the detailed theoretical study of the instability of the non-relativistic infinitely thin tubular beam of electrons moving in a vacuum above a dielectric cylinder has been performed. It has been shown that either Cherenkov effect or anomalous Doppler effect occurs in relation to the distance (the impact parameter) between the beam and the dielectric.

83-88

Authors: O. V. Botsula, К. H. Pryhodko, V. A. Zozulia

The development of millimeter and terahertz wave ranges is one of the main objectives of radiophysics. However, there are not many active elements that can operate in those ranges. Impact ionization in wide gap semiconductors is a fast process and can be used in active elements operating in these ranges. In this paper the charge transfer in short diodes (the length of the active area is less than 0.3 m) is considered. The purpose of the study is to determine the appearance conditions and peculiarities of impact ionization. The influence of impact ionization on devises characteristics is determined. The possibility of creating localized high electric field region is shown. The field magnitude is enough for obtaining impact ionization. It is a possibility to operate the impact ionization by changing the AlzGa1–zN composition distribution along the diode. The result of the study is the determination of properties of impact ionization in the proposed structures. They can be used for further detailed analysis of physical processes of the structures and their manufacturing.

5-10

Authors: A. A. Kurayev, V. V. Matveyenko, T. L. Popkova

This article describes the algorithms with correcting and stabilizing coefficients to provide sustainable solutions to systems of equations related to poorly determined tasks of electrodynamics and nonlinear dynamics. It demonstrates the use of the modified algorithms in the task of E0i-waves propagation in irregular waveguide and dynamic model of Rössler’s chaos. In the latter case the article demonstrates that “deterministic” (i. e. regenerating) chaos is impossible.

18-24

Authors: V. A. Kabanov

The most accurate information on the dielectric structure of the atmosphere can be obtained by radiorefractometers. These devices are essential when measuring a fine structure of the refractive index of the medium under investigation. The information obtained through them is particularly important in studies of tropospheric radio propagation conditions. Despite the advantages of refractometers compared with meteorological measurements, the task of calibration remains important. A brief description of a microwave refractometer developed by the author is presented. It shows the ability to set up and calibrate the instrument using standard meteorological measurements without a special reference chamber in a closed room.

33-39

Authors: A. Linkova, G. Khlopov

The study of integral and microstructure characteristics of liquid precipitation is of great practical interest for solution of many problems of national economy. Particularly, monitoring rain intensity is important for design of collecting systems and engineering structures, as well as it essentially influences productivity of agriculture. Radar methods for study of liquid precipitation permit to measure rain parameters over the large areas in real time. That is why they are more preferable in comparison with contact methods based on raingauges and disdrometers. A three-frequency method for radar remote sensing of liquid precipitation is proposed and studied in this paper, which allows restoring spatial profile of rain parameters. The results of numerical simulation of three-frequency radar remote sensing of liquid precipitation are presented; they were obtained for different sets of operating wavelengths of radar for the range of rain intensity 0…30 mm/h. It is shown that the usage of millimeter wavelengths is not reasonable due to strong attenuation of signal power at large distances and for large rain intensities. However, application of longer wavelengths permits to reduce influence of attenuation and to decrease measurement errors of rain parameters. The maximal measurement error of rain intensity is not more than 7 %.

48-51

Authors: V. I. Khizhnyi, A. P. Korolyuk, T. M. Khizhnaya

High temperature antiferromagnets such as iron borate, hematite etc., have high magnetoelastic coupling. As a result, in the conditions of birefringence effect, there is a possibility to control parameters of sound waves by a small external magnetic field. On the other hand, high magnetoelastic coupling raises the sensitivity of sample magnetic system to external mechanical influences, for example from the side of acoustic contacts with piezotransdusers. In this paper the effect of contactless (electromagnetic) sound generation in external magnetic field, while minimizing the impact of external mechanical stresses on the magnetic properties of the sample is experimentally studied. As a result, the birefringence effect at the electromagnetic excitation of high-frequency ultrasonic wave is detected, which is of interest from the viewpoint of its instrument application. Comparison of a theory of birefringence effect with experimental data is conducted. The magnitude of a magnetoelastic gap for iron borate is obtained.

58-73

Authors: V. V. Ovsyanikov

The present paper analyses the period of birth and development of science and technology of dipole antennas with reactive and complex loads, microwave dielectric and plasma antennas, as well as dipole and helical electrically small antennas, multi-frequency, broadband and pin antennas with improved radiation pattern, loop antennas and antenna arrays. We have considered the methods of evaluation and calculation of the basic parameters of antennas, such as the current distribution, input impedance, voltage standing-wave ratio, efficiency, radiation pattern and polarization characteristics. The results of calculations and the design features of these antennas were considered.

83-87

Authors: N. G. Kokodii, V. О. Timaniuk,E. Ya. Levitin, M. V. Kaydash

Nowadays, methods for determining the optical properties of nanoparticles are being actively developed and improved. The most popular are optical methods, in particular those that investigate the dependence of the spectral intensity of radiation passed through the medium with the particles, because they are less sensitive to a particle shape. In the scientific literature there are many works studying separately the scattering and absorption of light. There are few applied scientific works studying attenuation of light. In this paper the algorithm for processing the measurement data of the light attenuation by suspension of nanoparticles is proposed. The algorithm consists of three phases and provides information about the size and the complex refractive index of the particles. In this study, firstly, the average particle size was measured by method of power function, secondly, the optical properties of the particles were measured by method of spectral transparency and thirdly, the function of the particle size distribution was determined. The algorithm has been successfully tested during the measurement of the size and optical properties of Ag–Fe3O4 nanoparticles in water.

3-14

Authors: S. N. Vorobyov

Characteristics of radiation of electromagnetic waves from flat metallic waveguide filled with a dielectric and having the finite number of not equidistant parallel slots on one side of the waveguide excited by a fundamental waveguide wave are studied. This structure allows an accurate electrodynamical solution with minimum known radiophysical assumptions and as a model might correspond to real antennas fabricated of thin foiled dielectric having electrically long slots. The problem is solved by the method of analytical semi-inversion of original problem operator combined with the method of moments. The near and far radiation fields (Е and Н-field components), as well as power characteristics of reflected and propagated in the waveguide fields are analyzed.

22-27

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

Currently much attention is paid to investigation of electromagnetic properties of defective photon crystals. This is stipulated by both the occurrence of plasma and defective waves in such crystals and the zone nature of the waves spectrum. One of the most interesting of the electromagnetic properties of the photon crystals is the resonance interaction of plasma and defective waves. It is found that the resonant interaction is observed most distinctly in the second forbidden band of the photon crystal. In this regard, the relevant problem is the study of the properties of the electromagnetic waves in various types of defective photon crystals. This paper is devoted to the study of the effect of resonant interaction of plasma and defective electromagnetic waves in one-dimensional defective photon crystals bordering on a conducting medium subject to the condition that the defective layer is plasma like. It is shown that the best conditions for observing the effect of resonant interaction of plasma and defective electromagnetic waves take place in the case when the defective photon crystal borders on the semiconductor plasma and the magnitude of the dielectric permeability of the defective layer is positive and having an intermediate value between the values of the dielectric permeability of two layers of a unit cell of the photon crystal. The obtained results are of great practical importance for developing new devices of microelectronics and photonics.

36-44

Authors: I. O. Kovalov, V. S. Miroshnichenko

The diffraction radiation oscillator is one of the perspective sources for millimeter and T-wave, and it demands further improvement of its output characteristics. In the present work the influence of parameters of the periodic structure in a double grating form on the tuning range width of diffraction radiation oscillator is considered. It is shown that the tuning range width significantly depends on the H10-wave elongation in elementary waveguides, composed by the opposing slots of the double grating. The results of experimental measurements and 2D-modeling of the open resonant system properties are shown. The results allow choosing the double grating optimum parameters for diffraction radiation oscillator by the criterion of “extended tuning range plus high Q-factor of oscillations”. The experimental results of the DRO properties for 8-mm wavelength with several variants of the double grating parameters are presented.

53-58

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

Recently the trend connected with creation of new effective laser media representing the composites made of dye molecules and nanostructures of noble metals has been developing very rapidly. It is known that adding the nanoparticles of metals in the active media can be used for improving the media emission characteristics. Thus, for realization of this possibility it is necessary to research the nature of component interaction for each specific combination. In this work, the dependence of fluorescence intensity of Rhodamine 6G and Sulforhodamine 101 liquid solutions on concentration of silver nanoparticles with a radius ~ (32 ± 5) nm is investigated with a different frequency of exciting radiation. It was determined that the increase of the nanocomponent concentration increases fluorescence intensity of both dyes. It is shown that the fluorescence intensity increases when the wavelength of exciting radiation approaches the maximum of nanoparticles plasmon resonance range. Basing on the received dependences, the conclusion is drawn on existence of nanocomponent optimum concentration, the exceeding of which will lead to suppression of fluorescence due to the increase of probability of nonradiative deactivation of molecules excited states.

66-73

Authors: K. A. Lukin, P. P. Maksymov

Multifrequency avalanche-generator diodes (AGD) based on abrupt Si and GaAs p–n-junction from a high-alloy n-region were investigated. The time of realization of output power was calculated and a projection of the attractors in the 2D phase space of AGD was provided. The spectral analysis of output power was completed and electronic efficiency was defined. It is shown that the multi-frequency self-oscillations are excited synchronously in n- and p-regions of abrupt p–n-junction at higher harmonics of the external signal. The presented numerical results may be of interest to developers of powerful sources of electromagnetic waves of the microwave and terahertz range. The considered mode of synchronous generation of dual-frequency oscillations can be considered as the basis for the generation of so-called associated/confusing states of the electromagnetic field (Entangled Photons), i.e. the signals of different frequencies oscillating in time while phase ratios for different sensor and radar systems.

79-86

Authors: E. A. Velichko, A. P. Nickolaenko

Cylindrical sensors of noble metals exploiting the plasmon surface resonance are widely used in the bio-medical research and environmental studies and studying their characteristics in different wavelength bands is an actual task. We analyze scattering of a plane H-polarized electromagnetic wave in the visible range of wavelengths by a silver nanocylinder with a concentric dielectric coating. The arising plasmon resonances are treated using both the conventional classic presentation of the spatial distribution of the field amplitude nearby the object and by the spatial distribution of the Umov-Poynting vector. We demonstrate that plasmon description by the Umov-Poynting vector has obvious advantages, as the standing and traveling waves become clearly visible while the boundaries of the objects are evident in the spatial distribution. A paradox influence of the dielectric constant of the coating on the type of the plasmon resonance and spatial field distribution is illustrated.

4-14

Authors: S. L. Berdnik, V. A. Katrich, V. I. Kiyko, M. V. Nesterenko, Yu. M. Penkin

The study of peculiarity of influence of the impedance insertions on the electrodynamic characteristics of the rectangular waveguide junctions, which are widely used in the antenna-waveguide devices, is important for practical applications. A mathe-matical model for E-plane T-junction of rectangular waveguides with a three-element vibrator-slot coupling structure was built using approximate analytical solutions of equations for induced currents by a generalized method of electro-magneto-motive forces. The distinctive feature of the model is the usage of variable surface impedance along the monopole axes and constant impedance, distributed over the end wall of the lateral semi-infinite waveguide. Multiparameter energy characteristics of the junction in the single-mode waveguides are presented including the case of meta-material coating the end wall of the lateral waveguide. The possibility of efficient use of impedance coatings as control element for power division between the output waveguide junction arms is shown.

22-30

Authors: Yu. A. Pedenko

The work is devoted to improvement of the accuracy of radar measurements of elevation angles of low-altitude targets above sea level when using the root-MUSIC, which is considered by experts as one of the means to solve this problem. Unlike previous studies, which take into account the multipath only, in this study the clutter is complicated by thermal noise of radar. This allows to evaluate the capabilities of the method and provide guidance on its application in the conditions close to reality. The study was carried out by computer simulation. It covered various sea states at which the conditions from specula to strong diffuse reflection were complied. In the simulation a wide range of signal/noise ratio was used. The main focus was the study of effects on measurement errors of a priori parameters of the method: the signal subspace dimension and the order of autocorrelation matrix of signals received by a multi-element antenna array. The recommendations of their choice, allowing to minimize the errors of elevation measurement in different conditions, have been developed. The results of the study extend the knowledge of how to improve the methods for measuring the target elevation angle above the sea.

40-47

Authors: V. V. Ovsyanikov

The actual problem of studying the basic properties and searching for methods of improving the plasma radiator array, which is similar to the array of metal or dielectric antennas, has been considered. This problem is not sufficiently covered in the well-known publications, however, the great interest of professionals to emitters based on cold plasma is due to the prospect of creating effective multi-beam scanning selective plasma reconfigurable systems or the plasma array of radiators (PAR). The article studies the main electrodynamics parameters of PAR in the microwave range, characterizing it on the one hand, as the load for the generator (receiver) of electromagnetic (EM) signal. On the other hand, PAR is tested as transmitter of EM energy from the point of view of its direction pattern (DP) and the main parameters of radiation of PAR. When scanning DP beam, impedance distortion of PAR transmitters and DP deformation are investigated. For comparison, similar studies were carried out for the same design and configuration of the pattern antenna (PA) of metal antennas. The studies have been carried out by PAR modeling and their parameters calculations on computer in software environment FEKO by integral equation method and method of moments for linear PAR from 4 emitters in the form of loop dielectric tubes filled with cold plasma under reduced pressure. When studying the self and mutual impedances of the PAR and metal PA in common mode for the distance between the transmitters 0.5l0, where l0 is the central wavelength of the test range, it has been determined that electromagnetic interference between antennas in PAR is less than in the metal antenna array, and when reducing the distance between transmitters grating with 0.5l0 – 0.25l0 the relative change in value of units of the input impedance of each radiator of PAR is twice less than for a lattice of aluminum, which allows to bring together the radiator of PAR without a substantial increase in interference between them. From comparison of DP of radiant systems of PAR and aluminum arrays while scanning, it is obvious that DP of PAR are less distorted than aluminum array. The obtained results can be used for calculations and design of plasma array of radiators.

55-60

Authors: P. P. Maksymov

Construction of powerful sources of electromagnetic oscillations of microwave range is an actual task for creating modern semiconductor devices. In this paper the creation of powerful sources of electromagnetic oscillations based on reverse-biased abrupt p–n-junctions of avalanche-generator diodes (AGD) with external signal has been theoretically grounded. Classification of modes of avalanche-generator diodes has been carried out. The choice of oscillations generation mode is determined by the parameters of AGD and input signal. It is shown that coherent, multifrequency and broadband oscillations are generated in AGD. Power and spectral descriptions of oscillations of AGD are presented. The research results are of interest for the developers of powerful diode generators with the required range, power and spectral characteristics.

71-76

Authors: Z. А. Maizelis

For detecting and establishing the nature of frequency noises in the oscillating system, it is very important to separate different types of noises. For determination of characteristics of the frequency noise it is necessary to study statistical properties not of actual coordinate and its derivative, but of complex coordinate of oscillator. Its moments do not depend on the amplitude noises that often can prevail in the system. The growing interest in noises of frequency is related to the fact that they determine the loss of coherence of vibrations in many systems, from the devices based on Josephson contacts, to the nanomechanical resonators. The knowledge of statistical characteristics of frequency noises inevitably present in the devices of information read-out in quantum computers will allow correct processing of the information in them. Here the influence of the telegraph unbalanced noise of frequency on properties of electromechanical resonator is studied. It is shown that the dependencies of the higher cumulants contain features, which allow to separate the effects related to the presence of noise of frequency. The results may be useful in the theory of nanomechanical resonators, in processing the data, obtained in the radio-technical devices and devices, based on Josephson contacts, in quantum computers, in the estimation of precision of atomic clock.

85-91

Authors: V. P. Ruban

The estimation of synchronization instability becomes actual in GPR due to the fact that this phenomenon affects the accuracy of recording and reproducing the received signal forms and, accordingly, the efficiency of use of digital signal processing algorithms. The existing method for estimation of jitter of the GPR receiver using errors of the converted signal amplitude is not universal and should be corrected for the case of converter with incomplete charging of the storage capacitor. Simulation of the stroboscopic conversion with instability of sampling interval for cases of full charging (when the evaluation method gives correct results) and incomplete charging of the storage capacitor has been done in this paper. The relationship between the forms of probabilistic distribution of jitter and errors of amplitude after stroboscopic conversion has been analyzed. The jitter values originally specified in the simulation and the ones calculated (reconstructed) by a known method also have been analyzed. According to the simulation results, the limits of applicability of this method were determined. It is shown that the direct application of the jitter evaluation method which is right for the converter with a full charging gives incorrect estimates for the one with incomplete charging of storage capacitor. Due to this, the signal amplitude recovery procedure which allows obtaining a correct estimate of the jitter of synchronization of GPR receivers operating in the mode of incomplete charge storage capacitor has been suggested.

3-9

Authors: Y. P. Galyuk

The interest in the phenomenon of Schumann resonances arises from the fact that it is one of the few tools that can help you learn the properties of the lower ionosphere, the measurement of which by direct methods is extremely difficult (the satellites are flying above, and weather balloons – below). The phenomenon is caused by the presence of circumnavigation electromagnetic waves in the range of ultra-low frequencies, caused by the global thunderstorm activity. In solving inverse problems it is extremely important to have the most adequate mathematical model of the phenomenon, changing the parameters of which, one can achieve the perfect match between theory and experiment. The article sets out strict methods of calculation of ELF fields in the model of regular waveguide “Earth-isotropic ionosphere”, as well as the electric and magnetic components of the noise power.

18-23

Authors: U. Goncharenko, G. Farquharson, V. Gorobets

Nearshore zones have a significant impact on life and economics. Along with the weather and climate stabilizing factor, caused by the water proximity, on the border of land and sea occur specific gradients and flows of heat, moist, pressure, etc. They might cause dangerous nature phenomena such as hurricanes, floods, etc. which need to be predicted and monitored. The remote sensing of neashore zone might be a part of such monitoring. The results of microwave remote sensing of neashore zone of New River inlet obtained by frequency-modulated continuous wave along-track interferometric synthetic aperture radar are presented. The estimation of neashore waves parameters such as wave height, phase velocity, etc. using ATI SAR images are performed. The algorithm for the estimation of bandwidth and shape of the radial velocity spectrum of braking wave is proposed and the dependence of the bandwidth of radial velocity spectrum on significant wave height is obtained.

31-38

Authors: R. V. Golovashchenko, V. N. Derkach, S. I. Tarapov

The development and manufacture of new materials for micro- and nanoelectronics are inextricably linked with the problem of studying the electromagnetic energy loss mechanisms in these materials in the gigahertz band. The reasonable technique of search for these mechanisms is the analysis of the temperature dependence of the loss tangent of such materials at temperatures from cryogenic ones to room ones. In this paper, the phenomenological simulation of loss in low-absorbing materials having a diamond-like crystal lattice is performed on the basis of experimental data. The experiments were carried out in the frequency range 60…120 GHz and at temperatures 1…300 K. The technique of measuring energy characteristics of the whispering gallery mode disk dielectric resonator is applied. As a result, the roles of main loss mechanisms for the materials under research are clarified and the values of basic physical parameters of materials are determined.

45-53

Authors: K. A. Lukin, P. P. Maksymov

Creation of modern solid-state microwave power sources is based on the application of active elements with expanded functionality. The reverse-biased p–n-junctions with DC voltage are active elements of diodes generators. Avalanche-generator diodes (AGD) based on reverse-biased abrupt p–n-junctions with DC voltage are promising for creating diode generators. We investigated the static current-voltage characteristic of AGD by the methods of diffusion-drift theory. The induced current in the AGD external circuit was investigated. It was found that the spectrum of induced current is determined by the spectrum of auto oscillations of AGD. The results of the research are the theoretical basis for the creation of diode microwave generators with the requisite energy and spectral characteristics.

62-69

Authors: E. A. Velichko, A. P. Nickolaenko

Nanowires and nanotubes made of noble metals are widely used in today’s technologies as elements of lasers, biosensors and other devices. However, not all possible problems arising in study of such objects are presented in literature. In this paper, by means of numerical simulation, the cylindrical nanoobjects made of gold and silver are considered as a specific prism that is capable of selecting isolated wavelength bands and scattering them at different angles. For this purpose a plane H-polarized electromagnetic wave scattering by nanocylinders with or without concentric dielectric cover or nanotubes made out of silver and gold in the visible range of wavelengths are studied. The scattering problem is solved in the classical manner, by separation of variables in polar coordinates. The complex permittivity is used in computations of gold and silver based on published experimental data. The results suggest that the studied nanoobjects can serve as a frequency-selective receiver or an optical filter which selects and rejects at different angles some wavelengths, but there is a great influence of geometrical parameters of scatterers and the dielectric constant of the coating.

80-86

Authors: V. V. Glamazdin, M. P. Natarov,V. N. Skresanov, A. I. Shubnyj

The coupling radiation loss of the whispering gallery mode mirror dielectric disk resonator (MDDR) with mismatched waveguides was researched. The findings are of particular interest to the developers of MDDR solid-state oscillators where semi-conductor devices and impedance matching circuits are located in the waveguide, forming a complex load in the waveguide. The dependences of MDDR resonance frequency and Q-factor on the amplitude and phase of the wave reflected from inhomogeneities in the waveguide back to the resonator are measured. Two types of couplers (a hole in the diaphragm on the mirror and an open end of the narrower waveguide on the mirror) are studied. For the open end type coupler it has been shown that MDDR resonant frequency and Q-factor can be calculated using the proposed lumped elements scheme of MDDR coupler and measuring procedure described in the first part of this paper. Coupling radiation loss and Joule loss in the load which are brought in MDDR by the complex load in the waveguide are calculated.

92-97

Authors: A.V. Brovenko, A.A. Vertii, N. P. Melezhik, P. N. Melezhik, A. Ye. Poyedinchuk

The problem of permittivity profile reconstruction from reflection coefficient data for a stratified dielectric medium illuminated with a probing plane electromagnetic wave at a finite set of frequencies is considered to deal with a topical problem in the context of the development of state-of-the-art nondestructive methods of testing. The initial problem is reduced to the search of an optimal control (permittivity profile) of the Cauchy problem for the Riccati equation. The optimal control is treated in the class of polynomial functions and is based on the minimization of a relevant functional. A criterion is suggested for choosing polynomial approximations to the permittivity profile, which separates input data sets between training and test sequences of probing frequencies. Error analysis made for the reconstruction of the permittivity imaginary part in a stratified medium shows that the relative error of the reconstruction does not exceed 10 % when the permittivity imaginary part is small (Ime ~ 10–4) and it is under 1 % when the permittivity imaginary part is large (Ime ³ 0.1). The developed algorithms can reconstruct the complex permittivity in a stratified medium to accuracy appropriate for practical applications.