APPLICATION OF PLASMA ANTENNA TECHNOLOGY TO IMPROVE RADIO COMMUNICATION STEALTH IN VHF BAND

Рассматривается плазменная вибраторная антенна, которая предназначена для работы в VHF диапазоне на частоте 140 МГц. Вибраторные плазменные антенны отличаются от обычных вибраторных антенн тем, что металлический проводник заменяется плазмой в газоразрядной трубке. Плазменный вибратор, создаваемый разрядом в трубке, способен включаться и выключаться за время порядка микросекунд. Применение плазменной антенны позволяет обеспечить два режима работы: активный, когда плазма индуцирует проводящую поверхность, и скрытый, когда антенна становится практически невидимой для электромагнитных волн, а плазменное облако отсутствует. Для определения характеристик антенны использовалось электродинамическое моделирование. Полученные результаты показывают, что характеристики плазменной вибраторной антенны близки к характеристикам эквивалентного ей металлического диполя, при этом длина плазменной антенны меньше. Для определения эффективности скрытного режима антенны производилось сравнение характеристик эффективной площади рассеяния плазменной антенны с выключенным плазменным облаком и эквивалентного металлического диполя. Полученные результаты показывают, что плазменная антенна обладает высокой эффективностью излучения, диаграммами направленности, схожими с эквивалентной дипольной антенной, и значительно меньшими значениями эффективной площади рассеяния (ЭПР) в выключенном режиме The article discusses a plasma dipole antenna, which is designed to operate in the VHF band at a frequency of 140 MHz. Plasma dipole antennas differ from conventional dipole antennas in that the metal conductor is replaced by plasma in the discharge tube. The plasma dipole created by the discharge in the tube is capable of turning on and off in times of the order of microseconds. The use of a plasma antenna makes it possible to provide two modes of operation: active, when the plasma induces a conductive surface, and hidden, when the antenna becomes practically invisible to electromagnetic waves, and the plasma cloud is absent. We used electrodynamic modeling to determine the characteristics of the antenna. The results show that the characteristics of the plasma dipole antenna are close to those of the equivalent metal dipole, while the length of the plasma antenna is shorter. To determine the efficiency of the hidden mode of the antenna, we compared the characteristics of radar cross-section of the plasma antenna with the plasma cloud turned off and the equivalent metal dipole. The results obtained show that the plasma antenna has a high radiation efficiency, directional patterns similar to an equivalent dipole antenna, and significantly lower RCS values in the off mode

SOME ASPECTS OF IMPORT SUBSTITUTION IN THE DOMESTIC SOFTWARE DEVELOPMENT FOR THE DESIGN OF ANTENNA-FEEDER DEVICES

Рассматриваются вопросы импортозамещения при создании отечественного программного обеспечения для проектирования антенно-фидерных устройств. Обозначены основные аспекты проблемы: импортозамещение при создании вычислительных ядер (решение электродинамических задач,задач анализа цепей СВЧ,расчет антенных характеристик и т.д.)и импортозамещение при создании пользовательских интерфейсов и средств электродинамического моделирования. Дается оценка состояния вопроса в отечественной теории и практике в указанных областях. С общих позиций анализируется круг задач, требующих решения для обеспечения процессов импортозамещения. Оцениваются возможности и перспективы реализации данных процессов на практике. The problems of import substitution in the domestic software development for the design of antenna-feeder devices are considered. The main aspects of the import substitution problem are outlined: calculation kernel design (electrodynamic simulation problem, RF-circuit analysis problem, antenna performance definition problem, etc.), user interface design, and electrodynamic modeling tools. The assessment of the state in the domestic theory and practice in these areas is given. From a general point of view, the authors analyze the range of tasks that need to be solved to ensure import substitution processes. The possibilities and prospects for the implementation of these processes in practice are evaluated.

Simulation of acousto-optical deflectors for scanning receiving tracks of radar systems.

A technique is proposed for electrodynamic modeling of electrode systems of deflectors of optoelectronic spectrum analyzers of receiving paths of radar systems, which makes it possible to analyze the matching characteristics and adjust at the level of the electrode structure model, which helps to reduce the labor intensity of their manufacture and adjustment.

Design Features of Antenna Arrays of Automotive Radars Based on Transmitting and Receiving Multi-Element Modules

Introduction. Modern vehicles are equipped with radars, which serve as the main sensors of driver assistance systems detecting objects in all weather conditions. Antenna arrays (AA) are the most common type of radar antennas. The coefficient of mutual coupling between adjacent antenna channels has a significant effect on the formed radiation pattern (RP) of an AA. This aspect is important for achieving the required values of gain and side-lobe level (SLL). This article analyses the effect of the proposed design solutions on the main parameters of an automotive radar AA, in particular, on the mutual coupling coefficient between the channels and the SLL of the DP.Aim. To develop an optimal approach to constructing an AA topology in terms of reducing the level of mutual influence of adjacent array channels and obtaining a DP with specified characteristics.Materials and methods. To achieve the required parameters of the designed AA topology, the coplanar and microstrip lines were calculated using the finite element method and shield models.Results. An electrodynamic modeling of a millimetre-wave AA was carried out. The effect of coplanar transmission lines on the RP was shown. The features of applying shielding elements in the AA structure were investigated. Antenna patterns were obtained for both an AA designed based on coplanar transmission lines and that based on the use of shields. The conducted comparative analysis determined the parameters of the substrate optimal for achieving a better level of decoupling between adjacent antenna channels. The values of AA RP obtained during modeling were presented.Conclusion. The use of coplanar transmission lines can significantly reduce the SLL of the DP in the elevation plane. When implementing the module structure of an array (using of sub-arrays), the power dividers are realized. In this case, instead of coplanar lines, it is advisable to use specific microstrip constructions covered with shielding surfaces. In this case, the formation of a given amplitude-phase distribution over aperture is possible. A comparative analysis of the AA topologies with different substrates was carried out with the purpose of achieving improved decoupling. The obtained values of the coefficient of mutual influence of adjacent array channels correspond to those of modern AA of automotive radars. The methods of reducing the parasitic radiation of transmission lines were considered. The AA RP obtained via electrodynamic modeling were presented. The use of a thin substrate with a higher dielectric constant makes it possible to improve the AA characteristics.

Mathematical model of a measuring complex for determining the external parameters of active phased antenna arrays in the near zone.

When measuring characteristics of the modern multi-element active phased antenna arrays amplifications method may have problems processing the results of measurements, due to the complexity of the exact adjustment of the overall active phased array, the fluctuations of the parameters of microwave amplifiers, the failure of individual elements, the inadmissibility of the full radiation of aperture antennas in an anechoic chamber. Electrodynamic modeling of active phased array antennas in specialized programs usually requires very large computational costs and it is very difficult to take into account fluctuations in parameters and failures of active phased array elements. In this regard, a mathematical model of the measuring complex is proposed for estimating the field distribution in the near zone of vibratory antenna arrays and generating radiation patterns. The estimation methodology is based on direct measurements of the amplitude-phase distribution of the field of the antenna system on the selected surface in the immediate vicinity of its aperture using a sounding antenna. The main relations for the model are the well-known expressions for calculating the field distribution in the near zone of a vertical symmetrical vibrator, the method of induced electromotive force, and matrix relations for converting the field into various coordinate systems. The model of the measuring complex is used to evaluate the characteristics of the active phased array in the near and far zones. However, it can be used to check real experimental data, taking into account fluctuations in the parameters of the amplitude-phase distribution in the aperture, and failures of antenna elements. The conducted research has shown a good agreement between the calculated characteristics of the active phased array using the proposed model and the aperture method. The time for calculating the antenna directivity characteristics in the proposed model is 30 minutes. The main time is associated with the addition of resistance matrices with elements related to each new position of the probe antenna. However, this time is not comparable to the time required to implement the measurement model in specialized electrodynamic modeling packages.

Use of Active Metamaterial as a Phase Shifter Integrated into the Waveguide

Active metamaterials usage is one of the most promising ways to control the characteristics of antennas, waveguides, and other microwave devices. This article proposes the controlled metamaterial design in the form of an electromagnetic crystal with switches located at the nodes of the crystal lattice. This metamaterial application for changing the fundamental mode phase of the WR-137 waveguide is investigated. Controlling the characteristics of the metamaterial is performed by switching pin diodes at the nodes of the lattice, so this control method allows you to achieve a high speed system, as well as to switch only certain pin diodes. Electrodynamic modeling was carried out, on the basis of which the characteristics of the waveguide were obtained for different metamaterial closed nodes combination, which changes the the electromagnetic wave phase.

Research of antenna complexes using chiral metamaterials and fractal geometry of radiators for MIMO systems

This article is devoted to the study of the possibilities of increasing spectral efficiency in MIMO systems by using antennas with substrates of biisotropic and bianisotropic chiral metamaterials and various types of fractal emitters, in particular, fractal structures in the form of a Sierpinski triangle, Koch and Gilbert curves, as well as a dipole triangular antenna of complex configuration FRM. The spectral efficiency was calculated by using one of the variations of the Shannon formula, which includes a complete matrix of Z-parameters. In turn, this matrix was determined using the software package of electrodynamic modeling. It is shown that the use of such antennas with the fractal geometry of the emitters located on chiral substrates reduces the mutual influence between the emitters, and, in turn, increases the spectral efficiency in several frequency ranges compared to traditional solutions.

STUDY OF THE INFLUENCE OF RFID TAG BENDING ON BASIC CHARACTERISTICS

Рассматривается пассивная радиочастотная метка, которая находится на гибкой подложке, что приводит к появлению проблемы с изменением характеристик при изгибе метки. В процессе исследования производилось моделирование для трех ситуаций: плоской метки, изогнутой внутрь и наружу. Благодаря современным методам электродинамического моделирования возможно определить все основные характеристики RFID метки - в активном режиме: обратные потери, диаграмму направленности; в пассивном режиме: диаграмму обратного рассеяния, токи и напряжения в нагрузке. При моделировании были построены графики зависимости амплитуд токов и напряжений в нагрузке от частоты, пиковые значения эффективной площади рассеяния. Благодаря полученным данным можно определить наиболее оптимальные частоты для облучения RFID метки, чтобы обеспечить ее работу в активном режиме (высокие токи и напряжения в нагрузке), а также в режиме обнаружения - большие значения ЭПР. Приводятся графики и таблицы для сравнения исследуемых случаев, по которым видны изменения характеристик при изгибе метки, что делает невозможным применение системы в широких диапазонах частот, так как стоит учитывать ее возможные изгибы The article discusses a passive RFID tag that sits on a flexible substrate, which leads to a problem with changing characteristics when the tag is bent. In the course of the study, we carried out modeling for three situations: a flat tag, curved inward and outward. Thanks to modern methods of electrodynamic modeling, it is possible to determine all the main characteristics of an RFID tag - in the active mode: return loss, radiation pattern; in passive mode: diagram of backscatter, currents and voltages in the load. During the simulation, we plotted graphs of the dependence of the amplitudes of currents and voltages in the load on frequency, peak values of the effective scattering area. Thanks to the data obtained, it is possible to determine the most optimal frequencies for irradiation of an RFID tag in order to ensure its operation in an active mode (high currents and voltages in the load), as well as in the detection mode - large ESR values. The article provides graphs and tables for comparing the cases under study, which show changes in characteristics when the tag is bent, which makes it impossible to use the system in wide frequency ranges, since its possible bends should be taken into account

DEPENDENCE OF VIVALDI ANTENNA CHARACTERISTICS ON THE SUBSTRATE METALLIZATION

Рассматривается антенна Вивальди, рабочий диапазон которой соответствует частотам, выделенным Государственной комиссией по радиочастотам для сетей пятого поколения. Применение различных проводниковых материалов при изготовлении излучателя позволяет достичь как экономических преимуществ, так и требуемых характеристик диаграмм направленности. В процессе моделирования были определены обратные потери антенны, а также влияние на них материала изготовления проводящей части антенны, диаграммы направленности, коэффициента полезного действия. Все характеристики определялись путем электродинамического моделирования. Исследование производилось для таких проводящих материалов, как медь, алюминий, золото, серебро, железо, платина, тантал, молибден. По полученным результатам было определено, что наилучшим проводником является серебро, при этом медь и алюминий не сильно уступают ему по характеристикам излучения и эффективности. Наихудшими материалами изготовления проводниковой части антенны являются тантал, железо и платина, так при их применении происходит снижение коэффициента полезного действия антенны, реального коэффициента усиления антенны. В статье представлены графики S-параметров для исследуемых случаев, произведено их сравнение, а также приведены основные характеристики диаграмм направленности и определено влияние на них проводниковых материалов The article considers a Vivaldi antenna, the operating range of which corresponds to the frequencies allocated by the State Commission on Radio Frequencies for fifth generation networks. The use of various conductive materials in the manufacture of the emitter allows one to achieve both economic advantages and the required characteristics of radiation patterns. In the process of modeling, we determined the return losses of the antenna, as well as the influence on them of the material of the conductive part of the antenna, the radiation pattern, and the efficiency. We determined all characteristics by electrodynamic modeling. The study was carried out for conductive materials such as copper, aluminum, gold, silver, iron, platinum, tantalum, molybdenum. Based on the results obtained, we determined that the best conductor is silver, while copper and aluminum are not much inferior to it in terms of radiation and efficiency. The worst materials for the manufacture of the conductive part of the antenna are tantalum, iron and platinum, so when they are used, the efficiency of the antenna, the real gain of the antenna, decreases. The article presents graphs of S-parameters for the cases under study, compares them, and also presents the main characteristics of the directional patterns and determines the effect of conductive material on them

Calculation of the impedance characteristics of a microstrip loop antenna with a metallized dielectric substrate

In connection with the intensive development of electronic technology, an urgent task is the development of antennas in a microstrip way, the advantages of which are small dimensions, a relatively simple manufacturing technology, and the ability to control their characteristics by using various materials and forms of radiators in their design. Currently, there are many mathematical models of microstrip antennas with vibrator radiators located on dielectric substrates, while models of microstrip antennas with other radiator shapes are presented much less often. As a rule, the calculation of the characteristics of such antennas is performed in electrodynamic modeling systems based on the use of «closed» algorithms. In this regard, there is a need to develop rigorous mathematical models of microstrip antennas with radiators of various shapes. This work is dedicated to the development of a rigorous model of a microstrip antenna with a frame radiator located on a dielectric substrate, based on the use of the method of integral equations. An integral equation is obtained for the unknown distribution function of the radial component of the current density over a frame radiator, the numerical solution of which is a correct mathematical problem. In addition, the numerical results of calculating the current density distribution, as well as the input impedance of such an antenna for various parameters of the radiator and substrate, are presented.