INVESTIGATION OF THERMAL RADIATION ANGULAR AND POLARIZATION CHARACTERISTICS OF ONE-DIMENSIONAL PHOTONIC STRUCTURES ON A FINITE SUBSTRATE

One-dimensional photonic structures (PS) are the layered metamaterials, which optical properties are due to interference effects within the structure. Due to the interaction of electromagnetic waves with the periodic structure, the thermal radiation (TR) of such PS has the features of coherent: it has a selective spectrum and a petal pattern. The relevance of TR PS research is due to the search for new materials to create sources of infrared (IR) radiation in the middle and far IR range (with a wavelength > 5 μm). The second important area of application of the radiating properties of the PS is the creation of non-radiating coatings to remove unwanted TR from the heated surfaces of the IR devices. Despite the fact that the irradiative properties of PS have been studied quite well, in the literature insufficient attention is paid to the influence of the finite substrate on the parameters of TR structures. The influence of a finite incoherent substrate on the angular and polarization characteristics of the thermal radiation of the system (photonic structure)/substrate has been investigated. Systems consisting of plane-parallel Ge or Si plates as PS and incoherent BaF2, BaF2/Al and Al substrates were used in experimental studies. It has been established, the contrast and amplitude of the directional diagram petals of the TR system depend on the ratio of the optical characteristics of the photonic structure and the substrate. The presence of a strongly reflective substrate eliminates the difference between the angular dependences of the s- and p-polarized components of the TR. In the case when the PS is placed on a transparent incoherent substrate with a lower refractive index, there is an increase in the p-polarized component of the TR and the suppression of the s-polarized. The thermal imaging picture of the TR angular distribution of the Si/Al system has been recorded and it was experimentally proved that the TR of photonic systems exhibits circular patterns. The results of the work can be used in the development of narrowband emitters in the middle and far infrared range, coatings to increase radiation energy exchange and coatings with minimal emissivity that are invisible in the thermal range.

TRANSITION RADIATION OF A RELATIVISTIC ELECTRON BUNCH ON A SEMI-INFINITE METAL CYLINDER

Transition radiation of a relativistic electron bunch, which arises when it collides with the end face of a semi-infinite ideally conducting cylinder, is considered. An electron bunch moves along the axis of a semi-infinite cylin-der. Expressions for the field strength of electromagnetic radiation in the wave zone are obtained. The influence of the guiding properties of an ideally conducting cylinder on the directional diagram of the transition radiation is investigated.

Axial-Symmetric Diffraction Radiation Antenna with a Very Narrow Funnel-Shaped Directional Diagram

The paper is focused on reliable modeling and analysis of axially symmetric radiators with a very narrow (throat) funnel-shaped radiation pattern. When such a diagram is formed, a wave analogue of Smith–Purcell coherent radiation is realized—the surface wave of a radial dielectric waveguide ‘sweeps out’ with its exponentially decaying part a concentric periodic grating, the fundamental spatial harmonic of which, propagating without attenuation in a direction close to the symmetry axis of the structure, generates a radiation field with the required characteristics.

Information technologies for creating spatiotemporal modems multiposition active-passive radar systems

The methods of synthesis of the directional diagram of active transmitting antenna arrays when receiving signals reflected from radar targets are considered. It is shown that when using multifrequency orthogonal coherent signals in the elements and addressable access at their reception it is possible to provide a small level of the side lobes of the spatial uncertainty function in a given sector of observation by selecting the type of intrapulse modulation of partial signals. Orthogonalization of antenna basis of transmitting and receiving antennas allows digital spectral-correlation processing of samples of aggregate signal from each target to solve the technological problem of multidimensional observation space in multiposition systems of coherent radiolocation when detecting, resolving, estimating coordinates and motion parameters of targets. The results of simulation modeling of spatio-temporal radar modems implemented according to the stated principles are given.

ACCOUNTING THE DIRECTIONAL DIAGRAM OF THE ON-BOARD ANTENNA IN ANALYSIS OF THE COMMUNICATION CHANNEL WITH THE AIRCRAFT

Синтез оптимальной с точки зрения дальности диаграммы направленности является одной из основных задач построения канала связи. Для многих приложений, таких как 2D вторичный локатор, канал связи с БЛА, оптимальной является косекансная диаграмма направленности. В первом приближении антенна, установленная на борту, обладает практически постоянным коэффициентом усиления в направлении на стационарную антенну. Характеристики бортовой антенны получаются из решения задачи в свободном пространстве. Учёт рассеивающих свойств объектов сложной геометрической формы с размерами в десятки длин волн является актуальной, но сложной задачей. При перемещении по поверхности носителя диаграмма направленности бортовой антенны может меняться существенным образом. Современные системы автоматизированного проектирования на основе приближённых численных методов электродинамики позволяют получать характеристики антенн, размещённых на реальных объектах. Ввиду увеличения количества полезных нагрузок на борту не всегда удаётся разместить бортовую антенну в таком месте, которое позволяет пренебречь влиянием геометрии носителя. В результате в диаграмме направленности бортовой антенны появятся интерференционные провалы или минимумы. Дальность работы будет зависеть от перемещения носителя. Рассматривается метод учета характеристик ДН бортовой антенны, позволяющий минимизировать запас на замирания The synthesis of the optimal, in terms of range, directional pattern is one of the main tasks of building a communication channel. For many applications, such as a 2D secondary locator, a communication channel with a UAV, the cosecant radiation pattern is optimal. As a first approximation, the on-board antenna has an almost constant gain towards the stationary antenna. The characteristics of the onboard antenna are obtained by solving the problem in free space. Taking into account the scattering properties of objects of complex geometric shapes with dimensions of tens of wavelengths is an urgent but difficult task. When moving over the surface of the carrier, the radiation pattern of the onboard antenna can change significantly. Modern computer-aided design systems based on approximate numerical methods of electrodynamics make it possible to obtain the characteristics of antennas placed on real objects. Due to the increase in the number of payloads on board, it is not always possible to place the onboard antenna in such a place that makes it possible to neglect the influence of the carrier geometry. As a result, interference dips or minima will appear in the directional pattern of the onboard antenna. The operating range will depend on the movement of the media. We considered a method for taking into account the characteristics of the antenna pattern of an airborne antenna, which allows minimizing the margin for fading

Excitation of the Round Infinite Impedance Cylinder by Internal Extrinsic Current: Far-Field Radiation

The paper considers the method of solving the problem of excitation a circular infinite impedance cylinder by means of extrinsic current with an arbitrary spatial orientation. The formal solution of the problem is based on the method of expanding the fields in a complete system of eigenfunctions. Arbitrary distribution of extrinsic currents is taken into account factors excitation. An approximate solution of the problem in the far field is presented. The effect of a dielectric cylinder on the directional diagram of an axial electric dipole is studied.

FORMATION OF THE OPTOELECTRONIC SYSTEM DIRECTIONAL DIAGRAM USING FIBER-OPTIC CABLE

The method of forming directional diagrams (RD) with the possibility of controlling it in space is described. The method of forming of the object location detection zone of complex shape in the transmitter-receiver optical system with the help of fiber-optic cables (OIC) is substantiated and created. The problem of a circular field of view of a multi-channel optoelectronic system (ECO) creating, designed for advanced high-speed objects at short distance detection has been solved. According to the results of laboratory tests of the developed ECO model is established that in the working range of distances of a location of 0,5 ... 10,0 m reliable detection of the target high-speed and high-precision registration of object in all DS directions is reached.

Methods for determining focal mechanisms in laboratory experiments

<p>In laboratory experiments, acoustic emission (AE) caused by the deformation of geomaterial reflects changes in the strength and stress state of the sample. By analogy with the solution of focal mechanisms of earthquake sources, there are several methods for determining the mechanisms and types of AE sources using the amplitudes and signs of the first arrival of an elastic wave on sensors that register acoustic signals. With 16 receiving acoustic sensors, the number of polarity determinations of the incoming wave usually does not exceed 5-10, while the sign determination on some sensors is often incorrect due to the omission of the first half-period of the weak signal by the automatic registration algorithm. This reduces the reliability of determining the mechanism of the focus in laboratory tests of rocks by wellknown methods based on the distribution of signs of the first arrival of the AE wave. We propose a method for determining the directions of the axes and the values of compression and tension in the AE source. The algorithm uses information about the coordinates of events and receivers, values of amplitudes and signs of the first half-period of P-waves coming to the receivers. In this case, the model of the AE source is assumed as a quadrupole with compression and tension axes. The source-receiver distance, the directional diagram of the receiver, and the emission diagram of the source are taken into account for each of the receivers to calculate the value of displacements in the source. To test the proposed algorithm and compare it with the known methods, there was developed a program for generating an acoustic signal source of a given type with random coordinates and directions of the compression and tension axes. An array of signs and amplitudes of the first arrivals coming to the receivers was calculated from simulated data. The high efficiency of the proposed algorithm was shown. The usage of this method together with the determination of AE event types [Zang et.al., 1998] in real laboratory experiments allows us to characterize the prevailing processes of destruction during separate phases of the experiment on triaxial loading of rocks in more detail. The developed algorithm makes it possible to determine the directions of the axes and the values of compression-tension with a minimum number of signs of the arrivals of P- waves, to estimate the components of the seismic moment tensor and obtain more complete information about the mechanism of the AE source.</p><p>The work was supported partly by the mega-grant program of the Russian Federation Ministry of Science and Education under the project no. 14.W03.31.0033 and partly by the state assignment of the Ministry to IPE RAS.</p>

ABOUT THE PALEOCANAL OF THE RIVER ASHAMBA IN BLUE BAY ACCORDING TO THE DATA OF BROADBAND SEISMOACOUSTIC PROFILING

A paleochannel and paleotributary of the Ashamba River at the bottom of the Blue Bay in Black Sea near the city of Gelendzhik were discovered and studied using broadband seismoacoustic profiling. A basic description of the geomorphology of the Blue Bay bottom is presented. The technology for studying bottom paleostructures of the coastal sea zone by means of broadband seismoacoustic profiling with a different directional diagram and GPS navigation is presented. The composition and main characteristics of the equipment used are presented. The results of profiling and transverse profiles of the paleochannel and paleotributary of the Ashamba River are presented, as well as their geomorphological analysis. Gas flares accompanying the paleochannel of the Ashamba River were discovered. A detailed map of the river paleostructures of the Blue Bay bottom and the discovered gas flares has been compiled.