Search

Purpose: Nowadays, in the millimeter frequency range, the dielectric waveguides of various modifications have certain advantages over the standard metal waveguides, primarily due to the possibility of creating functional units based on them. This is due to the relative simplicity and low cost of manufacturing the dielectric waveguides and functional units using them, the high degree of their integration with active elements, the use in their manufacture of different dielectrics and polymers with a wide range of material constants and a variety of mechanical properties (in particular, some materials have a significant flexibility). After making a series of physical experiments we have found the possibility of implementing the frequency selection and radiation into free space of electromagnetic waves by a hybrid metal-dielectric structure. Design/methodology/approach: The studied electrodynamic structure belongs to the class of hybrid metal-dielectric structures. It includes a modified inverted dielectric waveguide with a periodic sequence on the dielectric plate of fifteen dielectric rods with metallized coating on one of the faces placed outwards. The structure efficiency was estimated by the voltage standing-wave ratio (VSWR) values and power attenuation in the duct. The measurements were made with the reflectometer method. To estimate the degree of electromagnetic field concentration near the rod inhomogeneities in the near zone, the mobile probe method was used. The field structures were visualized with the method of isolines. Findings: The results of a series of experimental investigations showed the possibility of matching the structure with the external waveguides in the frequency range of 26.5-32.5 GHz with the voltage standing-wave ratio (VSWR) less than 1.8. The frequency dependence of attenuation is oscillatory with clearly expressed frequency ranges with small and large attenuation values. Moreover, the dependence is almost periodic, which is typical of periodic structures. The frequency response slope in the transition zones can be quite high and reach values of 41.26 dB/GHz. The degree of concentration of the electric field near the waveguide dielectric rod and the degree of excitation of the dielectric inhomogeneities was found by directly measured electric field strength in the near zone. Measurements of energy characteristics made under the short-circuit conditions for the main guide and in the mode of matched load of the main guide showed both the ability to control the polarization characteristics and the ability to change the appearance of the pattern and its orientation in space. Conclusions: It has been experimentally proven that a hybrid metal-dielectric structure, being a modified inverted dielectric waveguide with a periodic sequence on the dielectric plate of fifteen dielectric rods with metalized coating on one of the faces placed outwards, can be effectively integrated into a standard transmission line. It is found that this structure can be matched with the external circuits in a fairly wide frequency range. It is also found that in different frequency ranges this hybrid metal-dielectric structure shows the possibility of both efficient frequency selection and radiation in free space. Antenna measurements have shown the beam pattern shape controllability. Key words: inverted dielectric waveguide, periodic sequence, voltage standing-wave ratio (VSWR), attenuation, reflectometer method, mobile probe method, directivity pattern

Backlobe radiations are the key stumbling block to using microstrip patch antennas in wireless communication, but they can be minimised by using a slot-coupled feeding technique. This paper proposes a microstrip patch antenna with a multilayer structure. The Ansoft High Frequency Structure Simulation is used to describe and model this slot-fed antenna, which has an improved gain of 5.6dB and directivity of 5.9dB and resonates at a frequency of 2.25GHz.

Optical properties of a resonant trilayer metal-dielectric-metal (MDM) structure that consists of an upper metal layer, a dielectric layer, and a metal substrate are investigated. Using a multiple wave interference model, we prove that the reflection coefficient of the MDM structure may strictly vanish. The existence of a reflectance zero makes it possible to use the MDM structure as an optical differentiator. The numerical simulation results presented demonstrate the possibility of optical computation of the first derivative with respect to either time or spatial variable. The obtained results may find application in novel analog optical computing and optical information processing systems.

This paper addresses the determination of the dielectric constant of multilayer dielectric structures. One of the most-used methods for determining the dielectric constant of multilayer structures is reflection coefficient measurement by interferometry. In the general case, in interferometry measurements to one measured value of the reflection coefficient there may correspond an infinity of dielectric constants. This ambiguity may be resolved by first determining the effect of different parameters of the probing electromagnetic wave on the reflection coefficient. In particular, it is important to have a preliminary estimate of the effect of the incidence angle and the polarization on the range of variation of the reflection coefficient with the variation of one of the structure parameters. This allows one to estimate the boundaries of the range of variation of the reflection coefficient with the variation of the parameter under study. This paper considers the case where a plane H-polarized electromagnetic wave, i.e. a wave whose magnetic field is perpendicular to the incidence plane, is incident on a multilayer dielectric structure. The aim of this work is to develop a model of the propagation of an H-polarized electromagnetic wave through a multilayer dielectric structure at an arbitrary incidence angle and to determine the range of variation of the reflection coefficient with the variation of the dielectric constants of the layers. The paper presents a model of the propagation of an H-polarized electromagnetic wave in a two-layer dielectric structure. A metal base, which is an ideal conductor, underlies the structure. The electromagnetic wave is incident from the air at an arbitrary incidence angle. The model allows one to estimate the reflection coefficient of the structure as a function of its parameters and the incidence angle. The model also makes it possible to analytically estimate the range of variation of the reflection coefficient with the variation of the dielectric constant and the thickness of each layer of the structure. Using the model, the magnitude of the reflection coefficient was determined as a function of the incidence angle and the dielectric constant of the second layer.

Both static and dynamic characteristics of light reflected from a specially designed multilayer metal-dielectric structure with Kerr nonlinearity have been studied in this work. Various regimes of nonlinear reflection from the structure have been demonstrated, including bistable switching between low and high reflection states, which occurs at low intensity of the incident light due to a significant enhancement in the optical field in the nonlinear layer under conditions of total internal reflection. This nonlinear structure has been proposed to use as an optically controlled intracavity laser modulator.

Тема выпускной квалификационной работы: «Моделирование Ð¸Ð½Ñ‚ÐµÐ³Ñ€Ð°Ð»ÑŒÐ½Ñ‹Ñ Ñ„Ð°Ð·Ð¸Ñ€Ð¾Ð²Ð°Ð½Ð½Ñ‹Ñ Ð°Ð½Ñ‚ÐµÐ½Ð½Ñ‹Ñ Ñ€ÐµÑˆÐµÑ‚Ð¾ÐºÂ». Данная работа посвящена моделированию фазированной антенной решетки. Тема данной работы относится к области радиофизики. Для решения данной темы уделяется внимание согласованию волновода Ñ‚Ñ€ÐµÑ ÑÐ»Ð¾Ð¹Ð½Ð¾Ð¹ феррит-диэлектрик-феррит структуры со стандартным питающим волноводом посредством одноступенчатого и Ð´Ð²ÑƒÑ ÑÑ‚ÑƒÐ¿ÐµÐ½Ñ‡Ð°Ñ‚Ð¾Ð³Ð¾ согласователей. А также моделирование антенны на основе результатов согласователей. В работе исследуются две структуры: одноступенчатый согласователь для волновода феррит-диэлектрик-феррит (ФДФ) структуры и Ð´Ð²ÑƒÑ ÑÑ‚ÑƒÐ¿ÐµÐ½Ñ‡Ð°Ñ‚Ñ‹Ð¹ согласователь для ФДФ волновода. Цель работы: моделирование в программном пакете HFSS согласователя для структуры феррит-диэлектрик-феррит (ФДФ). Исследование проводится путем моделирования Ð´Ð°Ð½Ð½Ñ‹Ñ ÑÑ‚Ñ€ÑƒÐºÑ‚ÑƒÑ€ в программном пакете HFSS, методом ÐºÐ¾Ð½ÐµÑ‡Ð½Ñ‹Ñ ÑÐ»ÐµÐ¼ÐµÐ½Ñ‚Ð¾Ð².  Работа состоит из 3 Ð¾ÑÐ½Ð¾Ð²Ð½Ñ‹Ñ Ñ‡Ð°ÑÑ‚ÐµÐ¹. Первая часть посвящена фазированным антенным решеткам (ФАР), в особенности интегральным ФАРс Ñ‚Ñ€ÐµÑ ÑÐ»Ð¾Ð¹Ð½Ð¾Ð¹ волноведущей ФДФ-структурой. Вторая часть работы включает в себя модели Ð¸ÑÑÐ»ÐµÐ´ÑƒÐµÐ¼Ñ‹Ñ ÑÑ‚Ñ€ÑƒÐºÑ‚ÑƒÑ€ и результаты Ð¸Ñ Ð¼Ð¾Ð´ÐµÐ»Ð¸Ñ€Ð¾Ð²Ð°Ð½Ð¸Ñ, а именно: графики Ñ‡Ð°ÑÑ‚Ð¾Ñ‚Ð½Ñ‹Ñ Ð·Ð°Ð²Ð¸ÑÐ¸Ð¼Ð¾ÑÑ‚ÐµÐ¹ КСВ, S-параметров и распределения полей. Третья части включает в себя результаты моделирования линейной фазированной решетки., The subject of the graduate qualification work is “Modeling of integrated phased antenna arrays”.The given work is devoted to modeling a phased antenna array. The subject of this work relates to the field of radiophysics. To solve this problem, special attention is paid to matching the waveguide of a three-layer ferrite-dielectric-ferrite structure, which contributes to the power supply of the waveguide using one-stage and two-stage matching. As well as modeling antennas based on the results of approvals. Two structures are investigated in the work: a one-stage coordinator for a ferrite-dielectric-ferrite (FDF) waveguide and a two-stage coordinator for a FDF waveguide. Purpose of work: modeling in the HFSS software package a coordinator for a ferrite-dielectric-ferrite (FDF) structure. The study is carried out by modeling these structures in the HFSS software package using the finite element method.The work consists of 3 main parts. The first part is devoted to phased array antennas (PAR), in particular integrated phased array with a three-layer waveguide FDF structure. The second part of the work includes models of the structures under study and the results of their modeling, namely: graphs of the frequency dependences of the SWR, S-parameters, and field distribution. The third part includes the results of a linear phased array simulation.

Most dielectric materials and heterogeneous dielectric structures are operated under mechanical loads. Therefore, the usage of acoustic monitoring of the presence of defects and the destruction of such materials is difficult because of the high ultrasound damping decrement in these materials. This article presents assess the influence of the location of steel inclusions relative to the loading axis.

Interference thin film based on metamerism is the latest means in the field of optical anti-counterfeiting. In this paper, we propose a pair of metal-dielectric metameric interference thin films that could create a hidden image for optical security devices. To improve color match tolerance of the metameric pair, the angle insensitive metal-dielectric Fabry-Perot structure was designed as the metameric pair background film B; The logo film A adopts the five-layer angle sensitive structure to enhance the contrast. The film B is designed to have a weak color-shift effect as the observation angle is increased. When the observation angle increases from 0° to 15°, the reflectance spectrum of film B changes smoothly, and the color difference indexes between film A (0°) and film B (0°, 5°, 10°, 15°) are 0.968, 0.988, 1.798 and 3.778, respectively. This design is less sensitive to manufacturing errors and has a good color match effect. Color target optimization optimac method is utilized in the design process and remote plasma sputtering is used in the deposition process. The color difference index of the experiment is 2.753, which shows good hidden image effect for the optical security devices.

The daily Sun supplies the continents of the Earth with four times more energy than humanity consumes in a year. This enormous potential of solar energy to generate clean energy is therefore driving great efforts to replace conventional and unsustainable fossil fuel consumption that damages our climate and our environment. Solar photovoltaic (PV) is emerging as the fastest growing renewable energy technology in the world, yet its share to the electricity production currently is less than 3%. While coal and gas remain key to electricity production, the climate crisis demands a fast transition to a carbon-neutral energy system. In the year 2019, the PV industry produced solar panels with a capacity of about 115 GW. To reach multi-TW levels by 2030, PV production capacity needs to scale at high rates, and continued innovation is necessary. One way to increase production is to reduce silicon wafer thickness, making more cells from the amount of silicon produced. Thinning the cell will not only allow making more of them in less time but will also reduce the cost for a module, and for the electricity it generates. A thinner absorber reduces the absorption of sunlight. To counter this loss, optical concepts are needed. In this chapter, we review the most promising approaches in photonics that have made physically thinner but optically thicker solar cells possible. By enabling thinner solar cells, photonic solutions offer the possibility of efficiency enhancements at lower costs. We will explain their applications, discuss their challenges and estimate their impact on energy yield. Finally, we outline how non-silicon thin-film PV is opening up a plethora of consumer-oriented applications. Since the higher flexibility/bendability of thinner cells broadens their applicability range, thin-film PV will empower our transition to a 100% green society in many aspects of our lives.

The surface integral equation-based theory of characteristic modes (TCM) is presented for structures including perfect electric conductors (PECs) and lossy dielectric bodies. The formulation is a combination of the classical TCM formulation for PEC structures and a recently developed one for penetrable bodies. The potential of the methodology for practical antenna design problems is demonstrated by studying the coupling of the modes on a PEC plate (antenna ground plane) and an adjacent highly lossy dielectric block (user’s hand). This analysis reveals the existence of different types of modes having weak or strong interactions between PEC and dielectric parts.

Purpose: Determining the amplitude and phase characteristics of the surface wave in a planar dielectric structure excited by a two-layer microstrip array of rectangular radiators and ascertaining the possibilities of using it to excite the phased antenna arrays from segments of rectangular waveguides. Design/methodology/approach: The research method is based on application of the spectral method in approximation of a given distribution of surface current density on the array radiators, which is given by a function which describes the true current distribution fairly well and is convenient for further analysis. The essence of the spectral method is in representation of the Green’s function, the radiation field, and the current density as expansions in the Fourier integral. The investigations were carried out with taking into account the presence of surface waves in the dielectric layers and the mutual influence of the radiators. Findings: Using the developed technique, an algorithm for calculating the characteristics of a surface wave excited by a twolayer microstrip array of rectangular radiators is constructed. Analysis of the amplitude-phase distribution of electromagnetic field showed that at distance of ≥1.5λ of the grating edge the magnitude of the amplitude of the field of surface wave becomes practically constant, and its value in the case of a twolayer grating is approximately twice as large as in the case of a single-layer grating. It is established that in this structure it is possible to obtain an almost linear phase distribution of the electromagnetic field in the surface wave, and by shifting the phases of the current on the microstrip radiators to change its slope. Conclusions: The amplitude-phase characteristics of a surface wave in a planar dielectric structure excited by a two-layer microstrip array of rectangular radiators are investigated and the perspective of its application as a source of excitation of a phased antenna array from segments of rectangular waveguides are shown.

This paper describes a novel approach to understanding partial discharge (PD) dynamics and mapping of the discharge channels in a void. During long term PD exposure, discharges develop inside channels within a void, leading to a variation in the discharge area on the void wall as well as a clustering effect. In this paper, the development of a method for identifying localized changes in the dielectric structure, through the detection of dispersed channels with reduced resistivity which occur due to multichannel discharges, is described. Discharge spots in selected ranges of surface resistivity, occurring due to the energetic impact of PD, are mapped. This mapping shows both the distribution of local centers on the surface of the specimen, characterized by a reduced value of surface resistivity. Furthermore, during aging tests this surface resistivity exhibited a progressive reduction by four orders of magnitude, justifying the occurrence of an effective discharge area in the void source. This additionally impacts PD pattern modulation and can be a possible initiation of the formation of cross channels in the bulk isolation which, in the long term, can lead to complete discharge.

The modified driving waveform is proposed to improve the characteristic of the write discharge in the open dielectric structure of the AC type plasma display panel. An open dielectric is a ...

In this paper, a novel layer shaping method to reduce far-end crosstalk (FEXT) noise in multiple microstrip lines was proposed. To reduce FEXT noise induced in adjacent microstrip lines, mushroom-shaped dielectric structure (MSDS) was created between the microstrip lines. The prototypes were fabricated using 3D printer to avoid increased complexity, and the effect of the proposed MSDS was verifiedfrom simulated and measured results.

In this letter, an algorithm for synthetic aperture radar (SAR) imaging of electrically small targets embedded in multilayered cylindrical geometries (e.g., pipes) using non-uniform measurement points is presented. In contrast to previous approaches, this algorithm is able to efficiently handle non-uniform points without exhibiting relevant side lobes in the image. For these purposes, the approach exploits a flexible time-reversal (TR) algorithm enhanced by compressed sensing (CS). The theoretical performance of the algorithm is studied in terms of the point spread function (PSF) and several images are presented using synthetic full-wave data from CST Microwave Studio. In addition, the approach is empirically validated by performing microwave imaging of a PVC pipe. The results demonstrated that the TR-CS algorithm provides an effective focusing technique for dense non-uniform measurement points, as well as for sparse non-uniform measurement points., This work was supported in part by the Ministerio de Ciencia, Innovacinó y Universidades of Spain/FEDER under Project RTI2018-095825-B-I00, in part by the Gobierno del Principado de Asturias under Project GRUPINIDI-2018-000191, and in part by FPU under Grant FPU15/06431

Данная работа посвящена согласованию волновода трехслойной феррит-диэлектрик-феррит структуры со стандартным питающим волноводом посредством одноступенчатого и двухступенчатого согласователей. Тема данной работы относится к области радиофизики. В работе исследуются две структуры: одноступенчатый согласователь для волновода феррит-диэлектрик-феррит (ФДФ) структуры и двухступенчатый согласователь для ФДФ волновода. Цель работы: моделирование в программном пакете HFSS согласователя для структуры феррит-диэлектрик-феррит (ФДФ). Исследование проводится путем моделирования данных структур в программном пакете HFSS, методом конечных элементов. Работа состоит из двух основных частей. Первая часть посвящена фазированным антенным решеткам (ФАР), в особенности интегральным ФАР с трехслойной волноведущей ФДФ-структурой. Вторая часть работы включает в себя модели исследуемых структур и результаты их моделирования, а именно: графики частотных зависимостей КСВ, S-параметров и распределения полей. В результате получили полосы пропускания частот (по уровню КСВ 1.25): для одноступенчатого трансформатора порядка 1.7 ГГц; для двухступенчатого трансформатора около 2 ГГц., The given work is devoted to matching the waveguide of a three-layer ferrite-dielectric-ferrite structure with a standard supply waveguide by means of one-stage and two-stage coordinators. The subject of this work relates to the field of radiophysics. Two structures are investigated in the work: a one-stage coordinator for a ferrite-dielectric-ferrite (FDF) waveguide and a two-stage coordinator for a FDF waveguide. Purpose of work: modeling in the HFSS software package a coordinator for a ferrite-dielectric-ferrite (FDF) structure. The study is carried out by modeling these structures in the HFSS software package using the finite element method. The work consists of two main parts. The first part is devoted to phased array antennas (PAR), in particular integrated phased array with a three-layer waveguide FDF structure. The second part of the work includes models of the structures under study and the results of their modeling, namely: graphs of the frequency dependences of the SWR, S-parameters, and field distribution. As a result, we obtained the frequency bandwidths (at the SWR level of 1.25): for a single-stage transformer of the order of 1.7 GHz; for a two-stage transformer of about 2 GHz.

It is known that due to several current injection mechanisms, tunnel FETs can attain a subthreshold swing less than 60 mV/dec at normal temperature, which makes it alternative for MOSFETs, particularly in low power applications. This work investigates the electrical and analog performance of dual metal double gate hetero dielectric source pocket TFETs in contrast to dual metal double gate high-k dielectric source pocket TFETs. Numerical calculations were carried out to find the characteristics of both the devices. It is observed that for hetero-dielectric structure, the OFF current decreases significantly while having the marginal effect on the ON state current in contrast to double gate high-k dielectric structure.