NUMERICAL-ANALYTICAL METHOD FOR SOLUTION TO THE PROBLEM OF ELECTROMAGNETIC WAVE RADIATION FROM FLAT WAVEGUIDE WITH FINITE NUMBER OF SLOTS
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.
SCATTERING INDICATRIX OF SNOW CRYSTALS
G. Veselovska, G. Khlopov
Radar methods of investigation of clouds and precipitation are the most effective methods of remote sensing of the atmosphere. The advantages of radar techniques are the abilities to measure quickly the characteristics of precipitation over large areas. In the context of the turbulent medium the particles may be at a different angle relatively to the incident field, so in the paper there was an attempt to study the scattering indicatrix of snow crystals (dependence of the radar cross-section (RCS) on the incidence angle of the electromagnetic wave), which allowed to evaluate the variability of the RCS of snow crystals at the variations of the elevation angle of the radar antenna. For the numerical simulation of the scattering properties of the snow crystals we used two types of particles at various angles of observation, at that in the paper we consider two azimuthal angles of incidence of electromagnetic field in a wide frequency range.
ON THE SPECTRUM OF ELECTROMAGNETIC WAVES IN ONE-DIMENSIONAL DEFECTIVE PHOTON CRYSTAL BORDERING ON CONDUCTING MEDIUM
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.
THE INSTABILITY OF HOLLOW ELECTRON BEAM INTERACTING WITH PLASMA-LIKE MEDIUM
Yu. O. Averkov, Yu. V. Prokopenko, V. M. Yakovenko
Nowadays a good deal of attention is focused on problems of generation of millimeter and submillimeter electromagnetic waves under the interaction of fluxes of charged particles with solids. However, today there is no consistent theoretical description of this type of effects. In this connection we present the detailed theoretical research on the instability effect of non-relativistic infinitely thin hollow electron beam which moves in vacuum above a dielectric (plasma) cylinder. The calculations have been performed in electrostatic approximation due to the non-relativistic velocity of the beam electrons. The cases where the dielectric permittivity is constant and depends on the frequency have been considered. The dispersion curves of exited modes have been constructed. The dependences of the increments (decrements) of the modes on the value of the bunch radius and on the azimuth mode index have been studied. It has been shown that for both the dielectric and plasma media the largest values of the increments (decrements) of the excited modes occur for zero value of the azimuth mode index. The maximum values of the increments (decrements) decrease with increasing the azimuth mode index. It has been established that the frequency dependence of the dielectric permittivity leads to the absolute instability. This instability exists in the corresponding finite interval of the longitudinal wave number.
THE FREQUENCY TUNNING RANGE OF DIFFRACTION RADIATION OSCILLATOR WITH PERIODICAL STRUCTURE IN A DOUBLE GRATING FORM
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.
SIMULATION AND EXPERIMENTAL RESEARCH ON CW CLINOTRON IN FRQUENCY RANGE 125…135 GHZ
Yu. S. Kovshov, S. A. Kishko , S. S. Ponomarenko, S. A. Vlasenko, Yu. S. Novikova-Korotun, V. V. Zavertanniy, A. N. Kuleshov
The development of compact oscillators of electromagnetic radiation capable of providing the output power higher than several Watt in millimeter and sub-millimeter ranges is an actual task for a large number of practical applications, in particular, to enhance the sensitivity of DNP NMR spectroscopy. The simulation of 130 GHz CW Clinotron was carried out on basis of experimental results of the earlier developed CW Clinotrons in 2mm wavelength range. Basing on the analysis of oscillator operation characteristics, the space charge dependence on frequency, Pierce parameter and the system electrical length were determined. The obtained results were used in the simulation of grating and in further simulation of operation parameters of clinotron tubes. Basing on simulation results, the clinotrons with homogeneous and four-stage grating were designed. The output power more than one Watt in CW clinotron with homogeneous grating in the frequency range 125…135 GHz was experimentally obtained. Start current and required focusing magnetic field were obtained in the experimental test in electromagnet. The experimental test also shows the close fit between simulation results and experimental data. The proposed methodic can be used in the simulation of CW clinotrons in both millimeter and sub-millimeter ranges.
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.
DOUBLE SPLITTING OF MULTIPLICATION LAYER IN AVALANCHE GENERATING DIODES AND GENERATION OF TWO-FREQUENCY SELF-OSCILLATIONS
K. A. Lukin, P. P. Maksymov
Design of sources of powerful electromagnetic oscillations in microwave and THz frequency bands is a challenge for radio-electronic engineers. Design of avalanche-generating diodes that generate two phase locked oscillations in microwave and THz ranges is considered in the paper. Summation of two generating oscillations with either close or different frequencies allows managing power and spectral characteristics of the output signal. The physical processes occurring in the avalanche-generating diodes on the basis of abrupt Si and GaAs p–n-junctions at the constant reverse biased voltage are investigated. The effect of the double splitting of the multiplication layer has been revealed. In the suggested avalanche-generating diodes, regular and chaotic self-oscillations of electrons and holes components of the output power are excited in p- and n-regions of the p–n-junction, respectively.
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.
THE MEASUREMENT CELL BASED ON THE QUARTZ QUAZIOPTICAL RESONATOR FOR RESEARCH ON DIELECTRIC LIQUIDS IN THE SUB-THZ RANGE
A. A. Barannik, S. A. Vitusevich, А. I. Gubin, I. A. Protsenko, N. T. Cherpak
Using WGM resonators allow achieving high accuracy in determining the substances permittivities due to the high Q-factor. The resonator with a microfluidic channel is promising for the study of small-volume liquids, which is especially important for bioliquids. In a Ka-band a sapphire resonator with microfluidic channel has been proposed as a measurement cell, but in the sub-THz range a quartz resonator has more suitable characteristics due to its high Q-factor. In the paper we propose a measurement cell for the determination of complex permittivity of liquids in sub-THz range on the basis of quasi-optical quartz resonator with a layer of plastic comprising a microfluidic channel. Experimental studies of the resonator structure are carried out and a model for numerical research in the software COMSOL Multiphysics is proposed. By means of c omparing the resonator frequencies and Q-factors values with the corresponding values obtained with the numerical model the correction of the model has been carried out for the water-filled microfluidic channel. It is shown that the model for numerical studies correctly describes the resonator structure. The values of the resonator frequency and Q-factor obtained experimentally and numerically, for the microfluidic channel filled with the substances with well-known complex permittivity (methanol, propanol, ethanol, acetone), are in good agreement, which indicates the possibility of using the resonator as a measurement cell allowing the research on small-liquid permittivity using the special calibration procedure.
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.
R. I. Bilous, M. V. Vovnyuk, I. G. Skuratovskiy, O. I. Khazov, A. S. Shakhova
The rapid development of electronic technology is characterized by continuous expanding the potentials of new types of created elements, devices and systems that use porous plastics. Therefore, it is necessary to study the main electrophysical characteristics of these materials. The effective solution to this problem is impossible without the accurate determination of the dielectric constant (e ). This paper presents two methods of measuring the relative low e (1.02...1.1) of foams using a cylindrical waveguide-dielectric resonator on the evanescent waveguide. The measurements of the e were carried out for four types of foams in the frequency range 10...12 GHz and the estimation errors are presented. In the “direct” method the test material is used as a dielectric element of the resonator. In the “indirect” method the dielectric element is made from ftoroplast, and the test material filled the evanescent sections of the waveguide. The investigations have shown that the “indirect” method gives a decrease of the measurement error in 2.5–5 times compared to the “direct” one. But the “direct” method is easier and allows to measure any permittivities.