WAVE PROPAGATION THROUGH A WAVEGUIDE SEGMENT WITH RANDOMLY CORRUGATED WALLS: DUAL NATURE OF THE LOCALIZATION
Yu. V. Tarasov, L. D. Shostenko
A theory of wave propagation in waveguides incorporating a finite-length segment with randomly corrugated side boundaries is developed. We have shown that the dominant role in the waveguide state formation is played by the so-called gradient scattering mechanism, which is associated with surface asperity sharpness but not with their amplitude. The corrugated portion of the waveguide may be regarded as the modulated potential barrier, whose width is coincident with the length of the corrugated region whereas the height is determined by the corrugation sharpness. There are two possible types of wave localization in such a system. The first one manifests itself through the sharpness-induced mode cut-off which leads to rarefication of the entire (combined) waveguide spectrum, so that at some critical level of the asperity sharpness the waveguide becomes the evanescent-mode one. The other type of localization is a localization of Anderson nature. It is associated with multiple scattering of waves by random fluctuations of the effective potential. We have predicted a jump of the full transmittance of the waveguide at its transition to single-mode regime due to the mode cut-off. This phenomenon is associated with the absence of the inter-mode scattering in the single-mode regime.
A NUMERICAL ANALYTICAL METHOD FOR SOLVING REVERSE PROBLEMS OF WAVE DIFFRACTION BY LAYERED INHOMOGENEOUS MEDIA
A. V. Brovenko, A. A. Vertiy, N. P. Melezhik, P. N. Melezhik, A. Ye. Poyedinchuk
A numerical analytical method of the reverse problem solution is suggested for the relative permittivity profile of layered inhomogeneous media to be obtained from the frequency dependence of the reflection coefficient of a monochromatic plane electromagnetic wave. The idea of the method is to reduce the initial reverse problem to the optimal control problem of the Riccati equation. The solution scheme employs a numerical analytical method for the direct problem solution of monochromatic plane wave diffraction by layered inhomogeneous media and takes advantage of some algorithm developed for smoothing the gradient of the residual functional. With the algorithms elaborated for solving the direct and reverse problems of wave diffraction by layered structures, a series of numerical experiments has been performed, the efficiency of the suggested approach in not a direct determination of layered structure parameters is demonstrated.
MILLIMETER AND TERAHERTZ WAVE SCATTERING DIAGRAMS IN RAINS
V. L. Kostina, Yu. I. Malyshenko, A. N. Roenko
Detailed information about millimeter and terahertz wave scattering diagrams in rains is needed to develop millimeter and terahertz range radio engineering systems. It is rather difficult to measure scattering diagrams, the easier way is to calculate them. The prepared tables of scattering diagrams can be used for microwave range, but there are no such data for the terahertz one. This paper presents the results of scattering diagram calculation of millimeter and terahertz waves by raindrops. The calculations were using the exact formulas for all interval of raindrop sizes appeared in precipitation. Data base of scattering diagrams was developed on the basis of obtained results. It gives a wide opportunity for calculation scattering diagrams at various combination of initial data, i.e. radiation wave length, raindrop size distribution function and rain intensity value. The obtained results may be used for estimation of radiation power spatial distribution in millimeter and terahertz ranges.
DISTURBANCES OF LOWER IONOSPHERE ABOVE CENTER OF EARTHQUAKE AND ANOMALY IN THE GLOBAL ELECTROMAGNETIC RESONANCE SIGNAL
PART 1. MODELS OF IONOSPHERE
A. P. Nickolaenko, M. Hayakawa
We model an effect on the Schumann resonance signal recorded in Japan of the ionosphere non-uniformity centered above the earthquake at Taiwan. Changes in the resonance spectrum occur due to interference of the direct radio wave with one reflected from the ionosphere modification above the earthquake. The first part addresses typical models of ELF radio propagation constant and connects it with the vertical profile of atmospheric conductivity. The profile with a knee is analyzed, which is widely used for modeling the Schumann resonance. The four models are included suggested in literature for obtaining the frequency dependence of complex propagation constant of ELF radio waves. It is assumed that the pre-seismic and seismic activity locally reduces the height of the lower-boundary of the ionosphere above the earthquake. The maximum reduction reaches 20 km, and the horizontally symmetric perturbation is described by Gaussian curve having the scale of 1 000 km.
EVALUATING PARAMETERS OF CONDUCTIVITY PROFILE OF THE LOWER IONOSPHERE BY TWEEK-ATMOSPHERICS
A. V. Shvets, T. N. Serdiuk, A. P. Krivonos, Yu. V. Goryshnya
A method of determining the effective heights of the Earth-ionosphere waveguide for basic and higher types of normal waves (modes) and the distance to the radiation source – lightning is investigated by analyzing pulse signals in the range of extremely-low (ELF) and very low frequency (VLF) – tweek-atmospherics (tweeks). The resulted from analysis of multimode tweeks dependence of the effective height of the waveguide on the frequency is used for determining the parameters of the lower ionosphere conductivity profile. In computer simulations, waveforms of tweeks were synthesized in the frame of the Earth-ionosphere waveguide model with an exponential conductivity profile of the lower ionosphere. For the separation and analysis of individual waveguide modes in the signal the dynamic spectra of tweeks are used. The error in determining the effective height of the waveguide for different waveguide modes was 0.2…0.4 km, allowing estimating the parameters of the exponential conductivity profile of the lower ionosphere in the range of values typical for night conditions. Systematic and random error in determining the distance to the lightning were 10…40 km and 20…80 km, respectively, in the range of distances of 500…3000 km.
V. K. Ivanov, A. Ya. Matveev, V. N. Tsymbal, S. Ye. Yatsevich
Aeolian processes transporting sand and dust is a powerful erosive force that shapes the structure of the surface of the vast territories and loads the atmosphere with aerosols suspended dust spread by wind over long distances. The presence of atmospheric dust in the environment of the planet is one of the factors significantly affecting the temperature and climatic conditions of vast regions. There are no published data on the characteristics of the radio waves scattering features manifested in radar studies of aeolian sand and dust transport processes in desert regions, which can be used for determining the parameters of a remote transport. The article presents the results of the analysis of multiyear surveys of desert areas by side-looking radars (SLR) of “Cosmos-1500” and “Sich-1” satellites, synthetic aperture radars (SAR) of ERS-1, ERS-2 and Envisat-1, aimed at identifying the radio waves scattering features manifested in radar studies of aeolian sand and dust transportation processes in desert regions, which can be used for remote determining the parameters of transportation. It was proposed to explain the mechanism of the effect of a highly directional intense radio waves backscatter, which manifests itself in areas covered with deep sand at the direction of irradiating the surface towards the general direction of the surface wind in the range of local irradiation angle surface Q » 31¸34°, due to their interaction with consistently oriented ionized air layers bordering on sand ripples structures in the process of forming it with aeolian transportation of sand-dust mixture. Ionization is caused by strong inhomogeneous electric field arising in the aeolian transport process. Results of the study allow to create new remote monitoring methods of processes in desert areas that affect the climate of vast regions of the Earth.
I. M. Mytsenko, D. D. Khalameyda
Energy of solar eclipses significantly influences the variation of geophysical fields and leads to a change of processes in the subsystems of the Earth and to disturbance of the existing interactions between them. Observations of each solar eclipse allow to specify related physical processes and their impact on the radio waves propagation in the troposphere. The effects of the solar eclipse are widely discussed in the scientific world, but the studies of radio wave propagation in the troposphere during a solar eclipse are absent. The results of observations of the interaction between solar eclipses and levels of microwave radio signals in a variety of conditions, including land and sea transhorizon radio communication, as well as a geostationary satellite – Earth radio path and others are presented. In order to analyze conditions that accompany these phenomena, the method of superposed epochs comprising correlation, spectral and dispersion analysis of measured values is used. It is shown that the signal level change occur in the direction of increasing in most cases. The study extends the knowledge about the influence of the Sun on the propagation of radio waves in the atmosphere.
N. N. Beletskii, S. A. Borysenko, N. I. Gvozdev
The defect photonic crystals bordering on the solid-state plasma-like media are worthy of special attention. These structures are of interest due to the occurrence of the plasma and defective waves which can interact resonantly with each other. The effect of resonance interaction of different types of electromagnetic waves in defective photonic crystals is not adequately investigated. In this paper, the resonance interaction of plasma and defective TM-electromagnetic waves in a one-dimensional defect dielectric photonic crystal, bordering on the solid-state plasma-like medium, is studied on the basis of the numerical solution of the dispersion equation. The dispersive and energy properties of plasma and defective waves are investigated in accordance with the dielectric constant of the crystal lattice of the solid-state plasma-like medium. It is found that the resonance interaction of plasma and defective waves depends strongly on the type of solid-state plasma-like media. It is established that the effect of resonance interaction between the plasma and the defective waves takes place when the defective photonic crystal borders on the semiconductor plasma. It is shown that the resonance interaction of plasma and defective waves disappears in the case when the defective photonic crystal borders on metal. The results of the study extend significantly our knowledge about the nature of the resonance interaction of plasma and defective waves in defect photonic crystals. The obtained results can be used in developing new devices of microelectronics and photonics.
Y. P. Galyuk
Application of digital devices removes many experimental obstacles, as the physical elements are replaced by their virtual computer analogs. A receiver is realized in an ordinary computer supplied by the ADC (analog-digital converter) board and by the appropriate soft. Such a device appears to be much cheaper than an analog one, since the computers and ADC boards are universal pieces of equipment manufactured in great series, and there is a substantial competition in the market. Tuning and adjustments of a digital receiver is simpler than those of an ordinary one and is made much faster: it is reduced to simple editing of the program listing and its re-compilation. However, one must be able to write the programs in the languages of high level and to know the update techniques of signal processing. In the present study, we provide optimal solutions for digital receivers. As an example, we present the organization of a real VLF/LF receiver. Appendix contains the listings of typical program blocks in the C/C++ and Assembler languages.
R. I. Bilous, S. P. Martynyuk, A. P. Motornenko, I. G. Skuratovskiy
The resonance structures serve as the basis for many electronic devices. Therefore the creation of the effective tunable resonator is the actual and important problem. Using of the waveguide-dielectric resonator insures opportunity for the mechanical frequency tuning over a wide range but at the same time the Q-factor is changed. The last investigations suggested that the decrease of the eigen Q-factor of the tuning waveguide-dielectric resonator in the section of the circular cut-off waveguide can be decreased by using the resonance short-circuit plunger calculated on the given frequency. The investigations have been conducted for the 3-cm waveband. This paper is devoted to investigation of the possibility to increase Q-factor of the resonator of the waveguide-dielectric type in the millimeter band where influence of the contact imperfection between the plunger and waveguide walls is essential. As a result of the conducted investigations the Q-factor more than 2 000 in over the band of the tuning frequency was obtained for the resonator made of the section of the circuit cut-off waveguide with the Teflon dielectric in the 8-mm waveband.
S. L. Berdnik, V. A. Katrich, M. V. Nesterenko, Yu. M. Penkin
Rectangular waveguide junctions are widely used in antennas and waveguide devices, therefore studying of their electrodynamic characteristics is important for practical application. Mathematical model of diffraction fields for E-plane T-junction of rectangular waveguides with a vibrator-slot coupling structure was built using the approximate analytical solution of the equations system for the currents by the generalized method of induced electro-magneto-motive forces. The model is characterized by the variable surface impedance on the monopole and constant surface impedance, distributed over the end wall of the semi-infinite waveguide. Multi-parameter studies of energy characteristics for the T-junction in the wavelength range of single-mode waveguides were carried out. The possibility of effective use of the impedance monopole as a control element for power dividing between the output shoulders of the junction in predetermined proportions has been shown.
Yu. A. Nestryzhenko
The laser emission polarization and control of its spectrum by means of low-loss prisms is a problem of considerable importance which has been addressed in a great number of research papers. The known polarizers, especially straight view prisms, are characterized by certain disadvantages arising from losses of light energy and/or a need for additional reflecting coatings. These are not always acceptable for laser application, and the problem of spectral control may require the use of additional elements in the laser cavity. In this paper a four-facet, straight view spectral polarizing prism is described involving no cemented components for controlling the laser polarization and spectrum. The effect is due to additional total internal reflection surfaces inside the prism. Theoretical calculations have confirmed feasibility of such a prism for relatively simple, e. g. rhomboid configuration, and the possibility of manufacturing the device in a simple way. The prototype embodied has been tested and showed an effective laser polarization and possibility of its spectral control. This prism can greatly simplify the procedures for laser tuning, providing new possibilities for polarizational and spectral control of the laser emission and generation of two orthogonal polarized rays which may be useful for effective frequency conversation in nonlinear crystals.