РЕЗОНАТОР ФАБРИ–ПЕРО, ОБРАЗОВАННЫЙ ДВУМЯ ЭКРАНАМИ С ПРЯМОУГОЛЬНЫМИ ОТВЕРСТИЯМИ

The focus of this paper is to develop a low cost, light weight three dimensional (3D) frequency selective surface (FSS) with reduced fabrication complexity over 2D FSSs and can be used in the communication field. Nowadays, 3D FSS is taking too much attention because it provides high degree of freedom in controlling transmission/reflection response. Therefore, in this paper, a 3D FSS has been attempted by inserting three concentric conductive cylindrical rings in to a polyurethane foam. The proposed concentric triple cylindrical ring 3D FSS aims to work as a band stop in the GSM-900, UMTS-1800 and LTE-2300 frequencies. CST software is used to simulate and optimize the dimensions of FSS. After that, measurement of developed concentric triple cylindrical ring 3D FSS is carried out in free space. Measurement results are in good agreement with simulation results. To shield the communication band in the secure places, this type of low cost structure may be quite useful.

A three‐dimensional (3D) frequency selective surface (FSS) with a response that is independent of incident angle is presented in this study. The proposed FSS is a periodic array of 3D hollow‐tapered resonators. The proposed 3D FSS has reduced sensitivity to the angle of incidence of the electromagnetic wave compared with other 2D and 3D FSSs as a result of tapered structure. The transverse electric (TE) and transverse magnetic (TM) incident angle independences are obtained by tapering the width of a cylinder with a square cross‐section from the upper opening to the lower opening. Impressive frequency stability and transmission characteristics have been achieved up to 80° for both TE and TM incidence angles. The principles of operation along with guidelines for the design of the proposed FSS structures are presented in this study. A prototype of the proposed 3D‐tapered FSS is also fabricated and tested using a free‐space measurement system to verify performance.

PACS number: 07.57.-c Purpose: The conditions for formation of a wave with circular polarization and extremely achievable field density amplitude in the set directions of the main observation planes in the far zone, radiated by the oblique impedance wire dipole located over the rectangular perfectly conducting screen are determined. Design/methodology/approach: To solve the 3-D vector problem of diffraction of a field of arbitrarily oriented impedance thin wire dipole on the perfectly conducting rectangular screen the uniform geometric theory diffraction method is applied, and the asymptotic expressions for an electric current of the horizontal impedance wire dipole with electrical length 0.4 ≤ 2 l /λ ≤ 0.6 are used. Findings: The dipole’s slope angles at which the wave with equal amplitudes of orthogonal components of the electric field vector is radiated, and also the corresponding to them ellipticity coefficients and normalized squared absolute values of the electric field vector as functions of the observation angles and the distance between dipole and screen are calculated accounting for the diffraction effects on screen edges. Conclusions: The technique is developed for determination of an impedance wire dipole slope angle with account for the diffraction effects on screen edges at which the circularly polarized wave is radiated. It is shown that by the choice of an appropriate slope angle and distance of the resonant impedance wire dipole from the screen, the circularly polarized radiation with extremely achievable intensity in the given direction in one of the main observation planes can be realized. Key words: rectangular screen, surface impedance, resonant wire dipole, wave, circular polarization, ellipticity coefficient, field amplitude Manuscript submitted 31.03.2016 Radio phys. radio astron. 2016, 21(3): 216-230 REFERENCES 1. WOODWARD, O. W., 1957. A Circularly Polarized Corner Reflector Antenna. IRE Trans. Antennas Propag. vol. 5, is. 1, pp. 290–297. DOI: https://doi.org/10.1109/TAP.1957.1144512 2. NG, T. S. and LEE, K. F., 1982. Theory of Corner Reflector Antenna with Tilted Dipole. IEE Proc. vol. 129. is. 1, pp. 11–17. DOI: https://doi.org/10.1049/ip-h-1.1982.0003 3. Eliseeva, N. P., 2001. Optimizing the Directivity Factor of a Finite Corner Antenna with a Circularly PolarizedRadiation Field. J. Commun. Technol. Electron. vol. 46, no. 8, pp. 891–900. 4. GOROBETS, N. N. and YELISEYEVA, N. P., 2008. Synthesis of a Circular Polarized Field Radiated by an Electric Dipole Located over a Rectangular Screen. J. Commun.Technol. Electron. vol. 53, no. 1, pp. 26–33. DOI: https://doi.org/10.1134/S1064226908010038 5. PIMENOV, YU. V. and KHOD'KOV, D. A., 1990. Radiation of elementary electric vibrator placed above planescreen. Radiotekhnika. no. 11, pp. 60–63 (in Russian). 6. PIMENOV, YU. V. and KHOD'KOV, D. A., 1991. Radiation of elementary electrical vibrator placed parallel to plane rectangular screen. Radiotekhnika. no. 7, pp. 61–63 (in Russian). 7. TSAI, L. L., WILSON, O. R., HARRISON, M. G. and WRIGHT, E. H., 1972. A Comparison of Geometrical Theory of Diffraction and Integral Equation for Analysis of Reflector Antennas. IEEE Trans. Antennas Propag. vol. 20, no. 6, pp. 705–712. DOI: https://doi.org/10.1109/TAP.1972.1140326 8. IVANCHENKO, I. V., KOROLEV, A. M., PAZYNIN, V. L., POPENKO, N. A. and KHRUSLOV, M. M., 2006. The Features of Radiation Pattern Formation of the Monopole Antenna with Finite Screens. Telecommunications and Radio Engineering. vol. 65, is. 20, pp. 1859–1869. DOI: https://doi.org/10.1615/TelecomRadEng.v65.i20.30 9. GOROBETS, N. N., YELISEYEVA, N. P. and ANTONENKO, YE. A., 2012. Optimization of Radiation Characteristics of Wire-Screened Antennas. Telecommunications and Radio Engineering. vol. 71, is. 1, pp. 59–69. DOI: https://doi.org/10.1615/TelecomRadEng.v71.i1.60 10. Yeliseyeva, N. P. and Gorobets, N. N., 2009. Diffraction of radiation of the wire antenna on the rectangular and corner screen. Kharkiv: V. N. Karazin Kharkiv National University Publ. (in Russian). 11. Nesterenko, M. V., 2010. Analytical methods in the theory of thin impedance vibrators. Prog. Electromagn. Res. B. vol. 21, pp. 299–328. 12. NESTERENKO, M. V., KATRICH, V. A., PENKIN, Y. M., DAKHOV, V. M. and BERDNIK, S. L., 2011. Thin Impedance Vibrators. Theory and Applications. New York: Springer Science+Business Media Publ. DOI: https://doi.org/10.1007/978-1-4419-7850-9_1 13. YELISEYEVA, N. P., BERDNIK, S. L., KATRICH, V. A. and NESTERENKO, M. V., 2015. Electrodynamic characteristics of horizontal impedance vibrator located over a finite-dimensional perfectly conducting screen. Prog. Electromagn. Res. B. vol. 63. pp. 275–288. DOI: https://doi.org/10.2528/PIERB15043003 14. YELISEYEVA, N. P., BERDNIK, S. L., KATRICH, V. A. and NESTERENKO, M. V., 2016. Directional and polarization radiation characteristics of a horizontal impedance vibrator located above a rectangular screen. J. Commun. Technol. Electron. vol. 61, no. 2. pp. 99–111. DOI: https://doi.org/10.1134/S1064226908010038

A novel 3D Frequency Selective Surface (FSS) with horn shaped resonators is proposed which exhibits a very wide stop band. This new horn shaped resonator is a modification from a 3D FSS consisting of square cylinder unit elements. This feature introduces frequency-selective surfaces with the added advantage of lowering the sensitivity of the FSS frequency response with respect to the incidence angle. Simulation results prove that the FSS can realize broad selectivity of waves with the bandwidth more than 57%. The wideband transmission behavior is stable under oblique TM incidence angles from 0 to 80 degrees. The influence of various key parameters on 3D Horn Shape FSS characteristics has been investigated using the CST simulation software tool. By understanding the effect of each parameter, a comprehensive study for a better design of 3D Horn Shape FSS with wideband response is presented.

A novel 3D Frequency Selective Surface (FSS) architecture based on a circular ring unit element is presented. The circular ring was made 3D by creating a cylindrical element of a certain length, adding an extra degree of freedom into the structure. The length of the cylinder is shown through electromagnetic simulation to have a significant effect on the frequency characteristics of the FSS. Increasing the length of the cylinder can change the FSS from a band-stop to a band-pass filter response. The center frequency of both band pass and band stop responses can also be tuned with adjustment to the length. Dielectric materials are introduced in the center of the cylindrical unit cell elements to simultaneously obtain a stop and pass band with a sharp transition. For high dielectric filling materials, the 3D periodic structure exhibits negative refractive index metamaterial properties. A parametric analysis was conducted on these new cylindrical unit elements, and a prototype 3D FSS structure has been constructed and experimentally validated.

PACS numbers: 93.30.Ge, 94.20.Cf, 94.20.Dm, 94.20.Fg Purpose: to present temperature variations of electrons and ions obtained at the Institute of Ionosphere (Kharkiv) with an incoherent scatter radar during the 23rd solar cycle minimum, and compare the obtained results with the corresponding data of IRI-2012 model. Design/methodology/approach : Data are obtained by incoherent scattering. Method of solving the inverse radiophysics problem was used for analysis. Two-dimensional ambiguity function was used for specification. Findings: It has been found that in most cases the IRI-2012 model overestimates the values of electron and ion temperatures as against experimental data. The maximum differences are observed at night and can be about 500 K in summer, and 700 K in winter. Also, the effects of sunrise and sunset in magnetoconjugate area are considered. Conclusions: It is confirmed that to adequately describe processes in the ionosphere it is necessary to have a systematic approach which takes into account interaction in ionospheric regions located in magneto-conjugate area. Such regularities must be taken into account for correction of ionospheric model for the Central European region. Key words: method of incoherent scattering, electron temperature, ion temperature, magneto-conjugate area Manuscript submitted: 22.02.2016 Radio phys. radio astron. 2016, 21(2): 132-140 REFERENCES 1. CHERNOGOR, L. F., 2006. Earth–atmosphere–ionosphere–magnetosphere as an open dynamic nonlinear physical system (Part 1). Nelinejnyj mir. vol. 4, no. 12, pp. 655–697 (in Russian). 2. CHERNOGOR, L. F., 2007. Earth–atmosphere–ionosphere–magnetosphere as an open dynamic nonlinear physical system (Part 2). Nelinejnyj mir. vol. 5, no. 4, pp. 198–231 (in Russian). 3. EVANS, J. V., 1969. Theory and Practice of Ionospheric Study by Thomson Scatter Radar. Proc. IEEE. vol. 57, is. 4, pp. 496–530. https://doi.org/10.1109/PROC.1969.7005 4. BILITZA, D. and HOEGY, W. R., 1990. Solar activity variations of ionospheric plasma temperatures. Adv. Space Res. vol. 10, no. 8, pp. 81–90. DOI: https://doi.org/10.1016/0273-1177(90)90190-B 5. TRISKOVA, L., TRUHLIK, V. and SMILAUER, J., 2003. An empirical model of ion composition in the outer ionosphere. Adv. Space Res. vol. 31, no. 3, pp. 653–663. DOI: https://doi.org/10.1016/S0273-1177(03)00040-1 6. OYAMA, K., 1991. Electron temperature measurements carried out by Japanese scientific satellites. Adv. Space Res. vol. 11, no. 10, pp. 149–158. DOI: https://doi.org/10.1016/0273-1177(91)90337-J 7. ARAUJO-PRADERE, E. A., REDMON, R., FEDRIZZI, M., VIERECK, R. and FULLER-ROWELL, T. J., 2011. Some Characteristics of the Ionospheric Behavior During the Solar Cycle 23–24 Minimum. Sol. Phys. vol. 274, is. 1, pp. 439–456. DOI: https://doi.org/10.1007/s11207-011-9728-3 8. SOLOMON, S. C., WOODS, T. N., DIDKOVSKY, L. V., EMMERT, J. T. and QIAN, L., 2010. Anomalously low solar extreme ultraviolet irradiance and thermospheric density during solar minimum. Geophys. Res. Lett. vol. 37, id. L16103. DOI: https://doi.org/10.1029/2010GL044468 9. TARAN, V. I., 2001. Study of the ionosphere in the natural and artificially excited states dy method of incoherent scattering. Geomagnetizm i aeronomija. vol. 41, no. 5, pp. 659–666 (in Russian). 10. DOMNIN, I. F., KOTOV, D. V. and CHERNOGOR, L. F., 2012. Optimization of the ionospheric plasma parameters estimation using the incoherent scatter technique. Nelineinyi mir. vol. 10, no. 6, pp. 380–386 (in Russian). 11. SIUSIUK, M. N., KOTOV, D. V. and BOGOMAZ, A. V., 2011. Modeling two-dimensional uncertainty function in incoherent scatter radar. Vestnik Natsionalnogo tekhnicheskogo universiteta. no. 44, pp. 81–84 (in Russian). 12. TRUHLIK, V., BILITZA, D. and TRISKOVA, L, 2012. A new global empirical model of the electron temperature with the inclusion of the solar activity variations for IRI. Earth Planets Space. vol. 64, pp. 531–543. DOI: https://doi.org/10.5047/eps.2011.10.016 13. APONTE, N., BRUM, CH. G. M., SULZER, M. P. and GONZALEZ, S. A., 2013. Measurements of the O+ to H+ transition height and ion temperatures in the lower topside ionosphere over Arecibo for equinox conditions during the 2008–2009 extreme solar minimum. J. Geophys. Res. Space Phys. vol. 118, pp. 4465–4470. DOI: https://doi.org/10.1002/jgra.50416 14. PICONE, J. M., HEDIN, A. E. and DROB, D. P., 2002. NRLMSISE-00 empirical model of the atmosphere: Statistical comparisons and scientific issues. J. Geophys. Res. Space Phys. vol. 107, no. A12, id. 1468. DOI: 0.1029/2009JA009430 15. CARLSON, H. C., 1966. Ionospheric Heating by Magnetic Conjugate-Point Photoelectron. J. Geophys. Res. Space Phys. vol. 71, no. 1, pp. 195–199. DOI: 10.1029/JZ07li001p00195 16. KAKINAMI, Y., BALAN, N., LIU, J. Y. and OYAMA, K., 2010. Predawn ionospheric heating observed by Hinotori satellite. J. Geophys. Res. vol. 115, id. A01304. DOI: 10.1029/2009JA014334 17. Bryunelli, B. E. and Namgaladze, A. A., 1987. Physics of the ionosphere. Moscow: Nauka Publ. (in Russian).

Recently, 3D Frequency Selective Surface (FSS) designs have become popular due to their enhanced performance at oblique incidence angles as compared to planar designs. While planar FSS design has been successfully performed using discrete nature-inspired evolutionary optimization algorithms such as the Genetic Algorithm (GA) and Particle Swarm Optimization (PSO), these algorithms are not suited for the problem of 3D FSS design, due to the generation of non-contiguous structures, making manufacturing difficult. One alternative to these algorithms is the Ant Colony Optimization (ACO) technique, which guarantees contiguous segments are generated. However, traditional ACO methods require meanders to continue until they are trapped, potentially generating a PEC unit cell. In this paper, a Multi-Objective Lazy Ant Colony Optimization (MOLACO) algorithm will be applied to the problem of FSS design. The introduction of lazy ants allows exploration of solutions previously inaccessible by traditional implementations of ACO. Simulated results will show that it is well suited to the problem of 3D FSS design.

The problem on the diffraction of the electromagnetic plane wave on the impedance interface between two media is investigated. The impedance is assumed to be different from a constant on a segment of the interface, where the impedance is described by piecewise-linear, quadratic, or step functions. Bibliography: 4 titles.

It is shown that there exists a category of two-dimensional diffraction problems, which can be put into a ‘standard form‘ of dual integral equations. These diffraction problems include: diffraction of electromagnetic waves by a finite strip, a finite slit, the diffraction of scalar or vector elastic waves by a rigid strip or crack, etc. A general method for solving such dual integral equations is given by the artifice of constructing a set of functions of compact support biorthogonal to another given set of functions. The sufficient conditions for a given dual integral equations to be solvable in this manner are also determined. Hence, the method forms a complement to the Weiner-Hopf method. To illustrate the method solutions are obtained for a bench-mark problem : the diffraction of light by a finite perfectly conducting strip (or equivalently the diffraction of SH waves by a crack). Comparison with results obtained by others for low, intermediate and high frequencies show the utility and accuracy of the method for the entire range of frequencies. Both the near field and the far field are obtained, the latter is shown to correspond to the Fraunhoffer diffraction pattern for high frequency. It is also shown that for the equivalent crack problem the stress intensity factor (SIF) fluctuates rapidly with changes in the angle of incidence for high frequencies, thus making the SIF especially sensitive to angle of incidence at high frequencies.

A 2D theoretical model of the diffraction of a plane electromagnetic wave by a slot in a perfectly conducting screen is constructed based on the partial domain method. The Tikhonov regularization is used to solve a system of algebraic equations for the slot-mode amplitudes. This makes it possible to extend the domain of applicability of the theory to conducting screens of arbitrary thickness and to significantly increase the accuracy of solution in the cases when the slot width and the screen thickness are comparable to the wavelength of the diffracted radiation. The absence of a continuous passage to the limit of an infinitesimal screen thickness from the case of an arbitrarily small finite thickness is demonstrated. The boundary conditions for the energy-flux vector are considered. A concept of the energy potential that is convenient for the computer calculations of the energy-flux lines of 2D diffraction fields is introduced.

A theoretical study is made of the diffraction of surface electromagnetic waves by the open end of a strip optical microwaveguide. An approximation equivalent to the Kirchhoff approach is used to obtain analytic dependences for the angular distribution of diffracted waves in the far-field zone in the Fraunhofer diffraction case and a study is made of the distribution of electric fields of the diffracted waves in the near-field zone in the Fresnel diffraction case. It is shown that the angular distribution of the diffracted waves depends on the mode index of a strip microwaveguide and it differs considerably for thin-film and graded-index strip microwaveguides in a plane perpendicular to the waveguide. It is shown that in solving of the problem of the end contact between strip microwaveguides and fiber waveguides it is possible to ignore the distortion of the distribution of the electric field of the fundamental mode at the open end of a strip microwaveguide.

In order to create models of extended surfaces in the long and short wavelength parts of the wave spectrum, it is necessary to know the dispersion characteristics of tape-like obstacles perfectly located both in free space and on an extended surface. Methods of remote studying of extended surfaces, based on an analysis of signals that are generated by reflection or radiation of electromagnetic waves passing neoplasms allows us to view the topography, characteristics, and type of the different locations, sizes of various objects. One of the effective methods of study is to solve the problem of diffraction of electromagnetic waves on an infinitely extended object in free space. The purpose of this study is characteristics of electromagnetic waves during diffraction of electromagnetic waves at objects that can be used as radar systems. The method of statistical processing of experimental data from field tests and mathematical description of electromagnetic radar situation, as well as its computer simulation were used. The result of this study can be formulated as the development of analytical and software methods for analyzing diffraction pattern of electromagnetic waves in multi-wave mode of reception on infinitely extended object in free space, as well as a software method for calculating diffraction characteristics at frequencies exceeding the basic frequency, taking into account the inhomogeneity of electromagnetic fields in these conditions. The practical significance is the research results used in the development of a universal technique for design and development of radar systems capable of working adequately in conditions of electromagnetic environment in question. The results of this research will allow a complete description of the electrodynamic picture of wave propagation and its diffraction, namely, taking into account the diffraction properties of radar systems will allow us to develop a direction for their wider production and distribution.

The diffraction of electromagnetic waves by a conducting circular disc is investigated according to a method developed by Y. Nomura, et al. in the particular case where the incident wave is coming from an electric dipole which is placed at a finite distance from the disc and polarized parallel to the disc surface. The solution for the diffraction by an aperture with a magnetic dipole as a source is easily obtained by the application of Babinet's principle. Various physical quantities are evaluated for several distances between the disc and the dipole which is placed on the central axis of the disc. When the dipole is apart from the disc about five times of the radius, curves of the physical quantities resemble very much those for the normal incidence of plane waves.

A solution of the two-dimensional integro-differential equation describing diffraction of electromagnetic waves on metallic nanovibrators and on nanocrystals coated by a metallic film was obtained. Copper and gold nanoantenna characteristics were studied theoretically in the optical range. It was noted that the dependence of the scattered field on frequency is of a resonant character and the resonant wavelengths of nanovibrators are larger than those of an ideally conducting vibrator of the same size.

Formulation of the problem in general. During radio relay communication, electromagnetic waves propagate along the earth's surface, and due to refraction, the polarization of signals can change, which leads to loss of signal power. This problematic situation can be solved by polarization adaptation of antenna systems built on the basis of lattice structures that convert signals with any polarization into a circle. Such antenna arrays are polarization-holographic antennas.Analysis of recent researches and publications. In the theory of antenna synthesis, closed translucent surfaces, methods of synthesis of directional properties of reflective antenna arrays, which take into account the presence of mutual communication between irradiators of any type, as well as models of electrodynamic structures for arrays of different shapes are considered. This approach has a generalized nature and requires the adaptation of mathematical methods and models to antenna systems of a specific design. The polarization-holographic antenna can be considered as a non-homogeneous translucent structure, the problem of diffraction of electromagnetic waves in which it is expedient to solve the Fredholm integral equations of the first kind.Presenting the main material. The mathematical formalization of the electrodynamic model of a non-homogeneous translucent body, which in its properties corresponds to the polarization-adaptive antenna array, is considered as the formulation and solution of the inverse electrodynamic problem connecting the primary electromagnetic field, surface current, and surface impedance. This surface impedance is the holographic kernel of the integral equation, which makes it possible to synthesize the impedance surface for circularly polarized waves. Diffraction of electromagnetic waves on a multilayer impedance body is described by a system of Fredholm integral equations of the first kind for different resonant wavelengths.Conclusion. The method of Fredholm integral equations of the first kind makes it possible to determine the parameters of the antenna array through the transformation of the primary electromagnetic field into a secondary one based on the principles of holography. The result of solving the integral equation is its holographic core, which corresponds to the transparent (reflector) of the antenna. A system of integral equations was obtained, which mathematically formalizes the electrodynamic model of a planar antenna array with several layers, taking into account the mutual influence of these layers.The perspectives of future researches. Further studies should be considered the description of the propagation process of electromagnetic waves, taking into account their multiple reflections, in a planar impedance body and the improvement of the matrix method for determining the transmission and reflection coefficients in such bodies.