TWO-DIMENSIONALLY PERIODIC GRATINGS. PART 3. ELEMENTS OF THE SPECTRAL THEORY
Velychko L.G., Kryvchikova A.A., Sirenko Yu.K.
The results required for constructing a spectral theory of three-dimensional periodic structures are presented in the paper. An analytical representation for the canonical Green function is derived, the natural domain for the spectral parameter (complex-valued frequency) is determined in the form of the infinite-sheeted Riemann surface. Some statements allowing one to estimate the location of the spectral set members are formulated.
GENERALIZED MODE-MATCHING TECHNIQUE IN THE THEORY OF MODE DIFFRACTION. PART I. FRESNEL FORMULAE FOR SCATTERING OPERATORS
Petrusenko I.V., Sirenko Yu.K.
A generalization of the classical mode-matching technique, which corresponds to a new formulation of the scalar problem of mode diffraction on the waveguide discontinuity, is proposed. The used matrix-operator formalism of the modal analysis is briefly presented. The Fresnel formulae for the sought-for operators of mode reflection and transmission are derived for the canonical problem of the step discontinuity in a rectangular waveguide. The correctness of the obtained matrix-operator model is proved analytically. It is shown that these results are valid for a class of the problems of wave diffraction on the abrupt discontinuity in a waveguide. This generalized mode-matching technique was developed for efficient and rigorous analysis of microwave devices.
NONTRIVIAL CROSS-POLARIZATION REGIMES IN THE CASCADES OF THE CROSSED STRIP GRATINGS
Shcherbak V.V.
We investigate in strict statement the cross-polarization effects in cascades of crossed gratings. Nonconventional resonant regimes of a polarization rotator of electromagnetic waves are found. It is proved, that these devices can be fulfilled on the basis of gratings with period, about a wavelength l . At the expense of flat-topped amplitude-frequency characteristic of polarizers and increase of period of gratings the working frequency band of devices is increased twofold. The constructions from two or three and more gratings with two directions of orientation and other non-standard variants of a polarization rotator are found. The nontrivial parasitic effect is revealed and the ways of its elimination are suggested.
TRANSIENT RESPONSE OF CIRCULAR WAVEGUIDE MODE TO THE CHANGE OF DIELECTRIC PERMITTIVITY IN THE CORE
Sakhnenko N.K.
This paper investigates transformation of the guided mode of the circular waveguide due to abrupt time change of the refractive index of the core on the basis of rigorous mathematical approach. Assumption of the sharp time change of the medium parameters allows obtaining the analytical solution in the Laplace transform domain. The inverse transform is derived by virtue of the residues estimation at singular points and evaluation of the integral along branch cut of the complex plane. Transient behavior of the processes, steady state regime, possibility of the frequency shift and chance to transform the guided mode into leaky modes have been studied in details.
ON RIGOROUS SIMULATION OF FREQUENCY-MODULATED PULSES COMPRESSION IN THE HOLLOW REGULAR WAVEGUIDES
Pazynin V.L.
The possibility of exact determination of the laws of the amplitude and frequency modulation of electromagnetic pulses for compression in segments of hollow regular waveguides are investigated with the rigorous transport operators in time domain. The compression of incoming pulse by more than 100 times at the length of plane-parallel waveguide segment equal to its 2 500 heights is demonstrated within performed numerical experiment.
Gorobets V.N.
RADIOMETRIC COHERENT IMAGING WITH KA-BAND NOISE WAVEFORM SYNTHETIC APERTURE RADAR EQUIPMENT
Kudriashov V.V., Lukin K.A., Palamarchuk V.P., Vyplavin P.L.
Radiometric monitoring allows obtaining unique information about emissivity of the objects. It doesn’t require generation and radiation of sounding signal. Known types of radiometers do not realize range and angle resolution when using small antennas. In the work, a principle for radiometric range – cross range imaging for short distances is considered. This principle comprises interferometric radiometer and antennas with synthesized patterns. The work describes the proposed imaging principle and obtained experimental results. Radiometric imaging was performed using the proposed algorithm implemented in ground based Ka-band noise waveform synthetic aperture radar. Radiometric images of the test object have been obtained. The possibility of detection of thermal radiation by the investigated equipment has been confirmed. The obtained results can be applied in security scanners which can detect concealed objects.
SURFACE ELECTROMAGNETIC STATES AT AN INTERFACE BETWEEN A PHOTONIC CRYSTAL AND A PLASMA-LIKE MEDIUM IN AN EXTERNAL CONSTANT MAGNETIC FIELD
Averkov Yu.O., Beletskii N.N., Tarapov S.I., Kharchenko A.A., Yakovenko V.M.
In this paper, we present the theoretical analysis of the influence of an external constant magnetic field on properties of the surface electromagnetic states (SEMS) at an interface between a plasma-like medium and a photonic crystal. Each of these media is supposed to be a semi-infinite one. We assume that the elementary cell of the photonic crystal is formed by two different non-magnetic dielectrics. It has been shown that SEMS can exist at frequencies exceeding the plasma frequency. The permanent magnetic field is found to cause the appearance of the SEMS energy flux that is parallel to the interface. In the case of the finite photonic crystal the reflection coefficient of the structure has been derived. As an example of the plasma-like medium we consider a wire medium with plasma frequency in microwave range. It has been found that the minimum of the reflection coefficient associated with the SEMS excitation shifts to low frequencies with increasing the magnetic field. It has been shown that this shift is caused by the magnetic field influence on the Voigt permittivity of the plasma-like medium. The SEMS excitation at the interface between the wire medium and the photonic crystal has been experimentally observed. The effective plasma frequency of the wire medium has been measured. We have demonstrated that the temperature affects on both the location and the amplitude of the transmission peak associated with the SEMS excitation.
Lutsenko V.I., Lutsenko I.V., Masalov S.A., Khomenko S.I.
A possibility of using embedded semi-Markov processes to create statistical models of the signals reflected from the interfaces (land and sea), as well as parts of «clear» sky was considered. Their constituent parameters were determined based on the experimental data. It is shown that nonstationary season changes in the refractive index of the troposphere can be accounted for describing its statistics by polygaussian models. Model parameters for each of the seasons were derived experimentally. The proposed approach can be used to create a simulation model of behavior of the refractive index using nested semi-Markov processes.
TRANSFORMATION OF FREQUENCY IN PN–I–PN STRUCTURES
Lukin K.A., Maksymov P.P., Shiyan Ju.A.
Within the framework of diffusive-drifting model of semiconductors, the process of transformation of frequency of signals is designed in Ge, Si and GaAs pn–i–pn-structures with abrupt avalanches p–n-junctions and the permanent reversed bias. Nonlinear, frequency and phase distortions of signal are explored. The new mechanism of transformation of frequency is considered. Factors influencing on transforming properties of pn–i–pn-structures are considered. It is shown that coefficient of transformation of frequencies is constant.
EFFICIENCY OF DIODES GENERATION WITH RESONANT-TUNNEL BOUNDARIES IN THE STRUCTURES OF THE «SANDWICH» TYPE
Prokhorov E.D., Botsyla O.V., Klimenko O.A., Storozhenko I.P.
We study the current-voltage characteristics and the efficiency of generation diodes with resonant-tunnel boundaries in the structures of the «sandwich» type based on GaAs. We consider single-level and two-level model of the resonant-tunnel border. Frequency limit of the diode with resonant-tunnel border was estimated. A possibility of harmonic generation and frequency multiplication of the diodes with resonant tunnel border in the range of tens to hundreds of GHz was shown.
Storozhenko I.P.
The drifting domain and current oscillations in devices based on graded-gap semiconductors are studied. It is shown that the use of graded-gap semiconductors can increase the width of the working frequency of Gunn diodes. The review of graded-gap semiconductors A3B5 having a similar effect is given.
Alexeev G.A.
A method of constructing approximate analytical solutions to a nonlinear problem in the theory of TWT-M, BWT-M using asymptotic estimates of integral members in equations for the HF-field amplitude and the method of counter-expansion is proposed. This method is developed as applicable to the TWT-M-type devices with regard for HF-energy ohmic losses and the variation in the election kinetic energy in the interaction process. An accuracy of the method is 5–10 % on different portions of the signal distribution distant curve. Of special interest is the analytical investigation into multiplicative properties of M-type beam devices. A possibility of creating a high performance single-section multiplier based upon the TWT-M is confirmed.
Bezborodov V.I., Kiseliov V.K., Kuleshov Ye.M., Nesterov P.K., Mizrakhi S.V., Yanovsky M.S.
Quasi-optical polarization-frequency reflectometry in subterahertz (sub-THz) frequency range has been considered as a nondestructive method for detecting of subsurface damage of composite materials. Such materials are used in modern aerospace industry to create a strong lightweight structures using adhesive technology. The present work is devoted to the investigation of the possibility of detecting volumetric moisture and thermal damage of the a carbon fibers reinforced plastic (CFRP) structures in order to evaluate a quality of surface preparation before CFRP samples bonding. For this purpose we have used a quasi-optical systems for beamguiding polarization measurements in the sub-THz frequency range (0.1...0.2 THz). The measurements of amplitude-frequency and polarization reflecting characteristics of the CFRP samples showed that the thermal effects and volumetric moisture lead to changes of reflecting characteristics of samples in this frequency range. The promising results are obtained to use this method when creating means for nondestructive testing and evaluation of the quality of the surface of the CFRP composites before bonding.
Gubin A.I., Lavrinovich A.A., Mironov I.I., Cherpak N.T.
The results of the analysis of non resonant techniques of conductors including high temperature superconductors (HTS) studies, at the grazing angels of incidence of electromagnetic wave on the sample under test are shown. On the basis of the data of simulation and experimental measurements the comparative analysis for different waveguide sections are presented, namely, for waveguide sections in the forms of corner bend and oblique short circuit termination. The study is carried out in Ka-band at different angles of wave incidence and different height of waveguide cross-sections.
Kokodii N.G., Lizogubenko S.V., Kaydash М.V.
The method to process the pattern of light scattering by micro-particles obtained by a digital camera is proposed. The object of the method is to measure size of small particles.