Electromagnetic Field Distribution Research Articles

Wideband High-Gain Circularly Polarized Substrate Integrated Cavity Antenna Array for Millimeter-Wave Applications

A wideband high-gain circularly polarized (CP) substrate integrated cavity (SIC) antenna array is presented for millimeter-wave applications. The proposed antenna element is simply composed of a slot-coupled high-order-mode resonant square SIC and a pair of obliquely placed strip-shaped parasitic patches on the top surface of the SIC. The parasitic patches are used to adjust the aperture electromagnetic field distribution and phase of the two orthogonal resonant modes of TM211 and TM121 in the SIC to achieve a high-gain CP radiation and meanwhile introduce an additional cavity-backed slot-dipole CP radiation to extend axial ratio (AR) bandwidth of the proposed antenna element. By combining the above two high-gain CP radiation mechanisms, a wideband high-gain CP SIC antenna element is achieved. The simulated results of the proposed antenna element show an overlaid bandwidth of 20.36% from 26.20 to 32.14 GHz, while considering the −10 dB reflection coefficient, 3 dB AR, 3 dB gain bandwidths properties, and a maximum right-hand CP gain of 10.53 dBi at 29.40 GHz. On this basis, a wideband high-gain 8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 8 CP array fed by a full-corporate substrate integrated waveguide (SIW) network is designed and fabricated. The measured results show that the proposed array has an overlaid bandwidth of 21.72% from 25.85 to 32.15 GHz and a measured gain of up to 26.10 dBic at 29.00 GHz.

Rhodium-embedded UV photodetectors based on localized surface plasmon resonance on AlN/GaN.

We report a remarkably enhanced responsivity of metal-semiconductor-metal photodetectors embedded with a large-scale periodicity and highly uniform rhodium nanoparticle array based on localized surface plasmon resonance. In this study, we used theoretical simulations of the absorption, scattering, and extinction behaviors, as well as the near electromagnetic field distributions to predict the plasmon resonance wavelength of quasi-triangular-shaped rhodium nanoparticles. More specifically, we successfully implemented a hexagonal close-packed structure with the individual quasi-triangular-shaped rhodium nanoparticle on the AlN/GaN structure by self-assembly nanosphere technology. The characterization results showed that the device embedded with rhodium nanoparticles had a reduced dark current of 7 × 10-14 A, and the maximum responsivity was shifted to a longer wavelength of approximately 310 nm compared to the device without rhodium nanoparticles. Moreover, at a wavelength of 324 nm, the enhancement ratio of the responsivity was as high as 56. Our study makes a significant contribution to the literature with a highly uniform, large-scale distributed rhodium nanoparticle array for enhancing the performance of AlGaN-based photodetectors in the UV region.

Ternary Nickel/Molybdenum Dioxide/Carbon composited nanofibers for broadband and strong electromagnetic wave absorption

One-dimensional carbon-based nanofibers are considered as a group of the most promising candidates applied in electromagnetic wave absorption owing to their shape anisotropy, tractability, and stability. To further meet the requirements of lightweight, broadband and effective features, in this work, nickel/carbon nanofibers modified with molybdenum dioxide were resoundingly fabricated through electrospinning and subsequent carbonization. According to textural characteristic analyses, nickel nanoparticles with a diameter of approximately 30 nm were supported on the surface of the carbon nanofibers, while the smaller MoO2 grains were embedded inside. Under the premise of realizing an outstanding electromagnetic wave absorption intensity (−64.0 dB at 8.0 GHz), the ternary composites achieved a wide effective absorption bandwidth up to 6.9 GHz (9.5 GHz–16.4 GHz). Based on the investigations of electromagnetic parameters and field distribution simulation results, the interwoven network structure and the synergistic effect between each component not only endowed the materials with perfect impedance matching, but introduced manifold loss mechanisms including magnetic loss, conductivity loss and multiple polarization relaxation. Thus, this work provided theoretical guidance and enlightenment for the design of new generation fibrous electromagnetic wave absorbers.

Application of specialized software for calculation of magnetic field in the turns of switched reluctance motors stator windings

Background: The article describes the process of occurrence of additional losses in the extreme turns of the copper stator windings, based on physical laws. The causes of the skin effect in the stator windings of a switched reluctance motor (SRM) are presented, an assessment of the skin effect influence degree on additional losses in the SRM of medium and high power. 2D-model of the SRM sector in COMSOL Multiphysics software package is created to specify distribution of magnetic field in the SRM stator windings and to quantify the amount of additional losses. А comparison of the magnetic field distribution of the SRM configuration 12/8 obtained in the FEMM program and the SRM magnetic field distribution built in COMSOL Multiphysics software package is presented to assess the reliability of the results.&#x0D; Aim: Calculation of the magnetic field distribution in the turns of the stator winding by building a phased 2D-model of the SRM sector (pole division) in COMSOL Multiphysics software package to quantify the amount of additional losses caused by eddy currents in the windings.&#x0D; Methods: COMSOL Multiphysics software package is used to build 2D-sector of the SRM. To obtain results on the distribution of electromagnetic fields within the simulated area, finite element methods (FEM) are used to estimate income adjustments, the results are compared with calculations in the FEMM program.&#x0D; Results: The patterns of the magnetic field distribution of the SRM obtained in COMSOL Multiphysics software package and in FEMM program confirm the presence of a skin-effect in the extreme turns of the stator winding. It can reduce the energy efficiency of the SRM and cause local overheating of the winding turns. As a result of the simulation, the picture of the magnetic field distribution of the SRM obtained in the FEMM program is similar to the picture of the magnetic field distribution of the SRM obtained in COMSOL Multiphysics software package. Ratio error of the values of the magnetic induction of different parts of the SRM is 37 %. It is acceptable and it indicates the correctness of computer modeling in COMSOL Multiphysics software package.&#x0D; Conclusion: The patterns of the magnetic field distribution SRM in COMSOL Multiphysics software package and in the FEMM program confirm the presence of the skin-effect in the extreme turns of the stator winding, which will allow further research in the field of determining the numerical values of additional losses using 2D-model, and proceed from 2D-model to 3D-model of the SRM.

CONCEPTUAL MODELING OF THE DATABASE OF GIS MONITORING OF ELECTROMAGNETIC POLLUTION OF SETTLEMENTS

The article presents the results of conceptual modeling of the geospatial database for monitoring electromagnetic pollution of settlements. Recently, the world has seen a rapid increase in the number of sources and the level of electromagnetic radiation. This can negatively affect people's health and their environment. The analysis of the publications showed that today researchers have formed a theoretical base for assessing the impact of electromagnetic radiation on people and the environment, developed models of the propagation of electromagnetic waves, ways and methods of protection against their harmful effects. However, not enough attention has been paid to monitoring the electromagnetic pollution of settlements. Systematic measurements of electromagnetic field levels are carried out only by individual EU countries Systematic control of this type of pollution is not carried out in Ukraine, there are no regulatory documents regarding the procedure for its monitoring, but the maximum permissible levels of electromagnetic fields for the population are established. Data on the distribution of electromagnetic fields are interdisciplinary in nature and necessarily contain an indication of the location of objects. For their effective processing, it is advisable to use geo-information technologies. Based on the results of the analysis of the subject area of electromagnetic pollution monitoring, a conceptual data model was developed. It is described using UML tools. The model contains two sets of data. The basic set of geospatial data includes information about buildings of various purposes, land plots, streets, highways, railways, engineering communications, relief, soils, hydrography, territory zoning, facility addresses. The profile set includes data on electromagnetic radiation sources and their sanitary protection zones, control points, the results of calculations and measurements of radiation parameters, the relative level of electromagnetic fields and the building restriction zones. The proposed model can be the basis of the physical modeling of the settlement's electromagnetic pollution monitoring system. &#x0D;

Controlled Transport of Individual Microparticles Using Dielectrophoresis.

A dielectrophoretic device employing a planar array of microelectrodes is designed for controlled transport of individual microparticles. By exciting the electrodes in sequence, a moving dielectrophoretic force is created that can drag a particle across the electrodes in a straight line. The electrode shapes are designed to counter any lateral drift of the trapped particle during transport. This facilitates single particle transport by creating a narrow two-dimensional corridor for the moving dielectrophoretic force to operate on. The design and analysis processes are discussed in detail. Numerical simulations are performed to calculate the electromagnetic field distribution and the generated dielectrophoretic force near the electrodes. The Langevin equation is used for analyzing the trajectory of a microparticle under the influence of the external forces. The simulations show how the designed electrode geometry produces the necessary lateral confinement required for successful particle transport. Finally, experimental results are presented showing controlled bidirectional linear transport of single polystyrene beads of radius 10 and 5 μm for a distances 840 and 1100 μm, respectively. The capabilities of the proposed platform make it suitable for micro total analysis systems (μTAS) and lab-on-a-chip (LOC) applications.

Calculation and Analysis of Characteristic Parameters for Lossy Resonator

Resonator is widely employed in microwave and millimeter-wave fields. However, it is challenging and crucial to calculate the electromagnetic field distribution in the resonant cavity with various loss dielectrics. In this paper, according to the axisymmetric distribution characteristics of the lossy resonator, the electromagnetic function of each part in the cavity is established with the Borgnis function, the characteristic equation is obtained based on the mode-matching method, and the resonance frequency and Q factor of the eigenmode TM010 are numerically calculated. With the proposed method, the impact of various dielectric structures and characteristics parameters on the resonant properties of the TM010 mode may be thoroughly examined by taking into account the influence of the thickness as well as the materials of the lossy layer in the z direction. The relative error between the theoretical and the simulated results is below 0.7% at different structures and lossy dielectrics, which indicates that the general calculation approach, as well as crucial data and structure references, is suitable for a related device design in TM010 mode.

Polarization-sensitive broadband bidirectional absorber in the optical communication band

Here, we propose a polarization-sensitive broadband bidirectional plasmonic absorber in the optical communication band. The proposed structure can achieve an excellent absorption performance (>90%) under the TE wave illumination at the wavelength range from 1370 nm to 1630 nm within an incident angle up to 45°. The analysis of the electromagnetic field distribution reveals that the coupling of propagating surface plasmons resonance and local surface plasmon resonance dominates the perfect absorption performance. The symmetry of the structure determines that the device has the characteristics of bidirectional absorption. In addition, the effect of interlayer alignment accuracy on absorption performance is discussed, and the result indicates that low alignment accuracy is allowed. The bidirectional broadband plasmonic absorber shows a promising prospect in electromagnetic wave shielding, optical sensors, photodetectors, and communication.

Numerical Investigation on ELF Electromagnetic Field Distribution of Pipeline Robot Tracking and Positioning System Using UAV

Pipeline robot, as a new type of equipment for pipeline operations such as pigging and detection, will play an increasingly important role in the operation and maintenance of oil and gas pipeline networks. The tracking and positioning technology during its operation process is one of the essential topics to improve the operating performance of pipeline robots and eliminate potential pipeline accidents. This paper presents the overall design of the wireless tracking and positioning system for pipeline robots based on extremely low frequency (ELF) electromagnetic method using the unmanned aerial vehicle (UAV). Starting from the classical electromagnetic theory, a mathematical model for the distribution of ELF electromagnetic field in buried metal pipeline environment is established. According to the characteristics of ELF electromagnetic wave transceiver and the model based on classical theory, the equivalent magnetic dipole transmission model is deduced. Based on the equivalent model, the attenuation characteristics of the ELF electromagnetic wave in the external space of the pipeline are analyzed by numerical simulation. The influence of the geometrical dimensions, environmental and working parameters, and other factors on the electromagnetic field intensity outside the pipeline is given at the same time. Finally, the distribution of ELF electromagnetic field in pipeline environment is discussed for horizontal-laying pipeline and inclined-laying pipeline, and the tracking method of pipeline robot is proposed on this basis. The proposed scheme is practical and effective, and it is suitable for real-time tracking and positioning of robot working in the pipelines whose slope is no more than 60 degrees with known or unknown distribution.

Simplified modeling of implanted medical devices with metallic filamentary closed loops exposed to low or medium frequency magnetic fields

Background and objectivesElectric currents are induced in implanted medical devices with metallic filamentary closed loops (e.g., fixation grids, stents) when exposed to time varying magnetic fields, as those generated during certain diagnostic and therapeutic biomedical treatments. A simplified methodology to efficiently compute these currents, to estimate the altered electromagnetic field distribution in the biological tissues and to assess the consequent biological effects is proposed for low or medium frequency fields. MethodsThe proposed methodology is based on decoupling the handling of the filamentary wire and the anatomical body. To do this, a circuital solution is adopted to study the metallic filamentary implant and this solution is inserted in the electromagnetic field solution involving the biological tissues. The Joule losses computed in the implant are then used as a forcing term for the thermal problem defined by the bioheat Pennes’ equation. The methodology is validated against a model problem, where a reference solution is available. ResultsThe proposed simplified methodology is proved to be in good agreement with solutions provided by alternative approaches. In particular, errors in the amplitude of the currents induced in the wires result to be always lower than 3%. After the validation, the methodology is applied to check the interactions between the magnetic field generated by different biomedical devices and a skull grid, which represents a complex filamentary wire implant. ConclusionsThe proposed simplified methodology, suitable to be applied to closed loop wires in the low to intermediate frequency range, is found to be sufficiently accurate and easy to apply in realistic exposure scenarios. This modeling tool allows analyzing different types of small implants, from coronary and biliary duct stents to orthopedic grids, under a variety of exposure scenarios.

Computational dosimetry in MRI in presence of hip, knee or shoulder implants: do we need accurate surgery models?

Objective. To quantify the effects of different levels of realism in the description of the anatomy around hip, knee or shoulder implants when simulating, numerically, radiofrequency and gradient-induced heating in magnetic resonance imaging. This quantification is needed to define how precise the digital human model modified with the implant should be to get realistic dosimetric assessments. Approach. The analysis is based on a large number of numerical simulations where four ‘levels of realism’ have been adopted in modelling human bodies carrying orthopaedic implants. Main results. Results show that the quantification of the heating due to switched gradient fields does not strictly require a detailed local anatomical description when preparing the digital human model carrying an implant. In this case, a simple overlapping of the implant CAD with the body anatomy is sufficient to provide a quite good and conservative estimation of the heating. On the contrary, the evaluation of the electromagnetic field distribution and heating caused by the radiofrequency field requires an accurate description of the tissues around the prosthesis. Significance. The results of this paper provide hints for selecting the ‘level of realism’ in the definition of the anatomical models with embedded passive implants when performing simulations that should reproduce, as closely as possible, the in vivo scenarios of patients carrying orthopaedic implants.

Microwave pretreatment of biomass for conversion of lignocellulosic materials into renewable biofuels

For the conversion of lignocellulosic material into renewable biofuels the microwave pretreatment of raw material is a new and promising technology. This work presents a numerical simulation of microwave heating of materials derived from sugar cane, african palm and green algae in microwave domestic oven. The power absorption of biomasses is studied in cylindrical and spherical shapes, with volumes varying from 10−5 m3 to 100 × 10−5 m3, as function of humidity (from 20% to 80%). Maxwell equations were employed to calculate the microwave electromagnetic field distribution in the microwave cavity and in the samples, coupled to heat equation when the humidity is varied. Penetration depth varied from 2 × 10−2 to 10 m and tanδ from 2 × 10−3 to 7 × 10−1 as function of humidity. Plots of electric field and temperature distribution inside the oven were done for sugar cane, palm oil and green algae for cylindrical and spherical samples for 30% and 65% of humidity in the samples. The coefficient of variation (COV) varied between 0.05 and 0.18. The rate of heating efficiency was evaluated using the degree of thermal runaway ΔT (5K<ΔT<75K) and evolution of average temperature T‾ (300K<T‾<370K) and their relationship with the energy absorbed by the samples and COV, respectively. The comprehensive evaluation coefficient, that describes the usability of a specific lignocellulosic material in industry, varied between 0.3 and 10.0, was calculated for the biomasses shapes and sizes as function of power and humidity.

강 파이프의 고주파 전기저항 용접공정에 대한 수치 해석

The high-frequency electric resistance welding (HF-ERW) process is widely used in the steel pipes production because it can weld at a high speed, has excellent weldability, and attains clean and precise shapes. However, for process improvement, analytic studies on electromagnetic field and temperature distributions, and selection of appropriate process variables are required. In this study, finite element analysis models that can analyze the electromagnetic field distribution and temperature distribution in the HF-ERW of a steel pipe were proposed, in consideration of the characteristics of the process, including electromagnetic phenomena localized to the workpiece surface and fast welding speed. By applying the proposed analysis models, changes in current density, magnetic flux density, generated heat density, and fused width in the pipe could be predicted according to changes in process variables such as the V angle of the strip, the electrode position, and the source voltage. Through comparison with the analysis and the limited-case experiment, the analysis result predicted the actual fused width fairly well, and the validity of the proposed model could be verified.

Effect of Permanent Magnet Structure on The Performance of LSPMSM with a Power of 22 kW and 3000 rpm

Energy efficiency and sustainability are important goals for countries all over the world. With the advancement of material technology, many new generations of high-efficiency motors are being researched and developed to replace induction motors (IM) to save energy. Line-start permanent-magnet synchronous motors (LSPMSM) are high-performance and ultra-high-performance motors that are emerging as an alternative to squirrel-rotor induction motors. Constructing the permanent magnets in the rotor is critically important in ensuring LSPMSM performance. The study uses the finite element method to analyze the characteristics of the motor. The study presented the influence of the permanent magnet structure in the rotor of the LSPMSM with a power of 22 kW and a speed of 3000 rpm on the electromagnetic field distribution in the motor, as well as the motor’s working characteristics to optimize the permanent magnet structure to optimize the performance of the LSPMSM. The analysis results show that the proposed LSPMSM has a 92.6% higher efficiency than the same-type induction motor. This is a suitable replacement for high-power and high-speed IM, which contributes to energy efficiency, so using fewer fossil fuels to reduce environmental impact is a sustainable development solution.

Dual-Port Compact MIMO-DRAs: Exploiting Metallic Sheets to Increase Inter-Port Isolation at 28-GHz 5G-Band

This brief proposes a novel decoupling method based on metallic sheets to improve inter-port isolation in dual-port single-element multiple-input-multiple-output (MIMO) dielectric resonator antenna (DRA) systems. Two different structures, including an H-plane and an E-plane decoupled MIMO arrangement, have been investigated. The exploitation of metallic sheets can significantly impact the electromagnetic (EM) field distribution inside the dielectric resonator (DR) and restrict the strongest portion of the EM energy couple to the nearby slot. As a result, inter-port isolation can be improved significantly. As the single DR element is used and metallic sheets are embedded within the element, no additional footprint is required, making the MIMO antenna arrangements compact and simple. The outcomes convey a maximum enhancement in the inter-port isolation of the H-plane decoupled MIMO arrangement is about 23.45 dB, while that of the E-plane decoupled MIMO arrangement is about 17.08 dB across the operating frequency band.

Peculiarities of the Electromagnetic Field Distribution Inside a 1D Photonic Crystal with a Defect Layer

Peculiarities of the Electromagnetic Field Distribution Inside a 1D Photonic Crystal with a Defect Layer

Multifunctional Plasmon-Tunable Au Nanostars and Their Applications in Highly Efficient Photothermal Inactivation and Ultra-Sensitive SERS Detection

The development and application in different fields of multifunctional plasmonic nanoparticles (NPs) have always been research hotspots. Herein, multi-tip Au nanostars (NSs) with an anisotropic structure were fabricated for the photothermal therapy (PTT) of bacteria and surface-enhanced Raman scattering (SERS) detection of pollutants. The size and localized surface plasmon resonance (LSPR) characteristics of Au NSs were adjusted by varying Au seed additions. In addition, photothermal conversion performance of Au NSs with various Au seed additions was evaluated. Photothermal conversion efficiency of Au NSs with optimal Au seed additions (50 μL) was as high as 28.75% under 808 nm laser irradiation, and the heat generated was sufficient to kill Staphylococcus aureus (S. aureus). Importantly, Au NSs also exhibited excellent SERS activity for the 4-mercaptobenzoic acid (4-MBA) probe molecule, and the local electromagnetic field distribution of Au NSs was explored through finite-difference time-domain (FDTD) simulation. As verified by experiments, Au NSs' SERS substrate could achieve a highly sensitive detection of a low concentration of potentially toxic pollutants such as methylene blue (MB) and bilirubin (BR). This work demonstrates a promising multifunctional nanoplatform with great potential for efficient photothermal inactivation and ultra-sensitive SERS detection.

Theory and measurement of the single and hybrid-mode excitation and evolution in a lossy-dielectric-loaded waveguide

ABSTRACT This paper investigates the mode excited, evolved, and propagating properties of the lossy dielectric-loaded waveguide (DLW) used in a Ku-band TE11-mode gyrotron traveling wave tube (gyro-TWT). Theoretical calculation and numerical simulation show that different DLW eigenmodes can be excited by the hollow circular waveguide as a single or hybrid-mode. This study clearly reveals the transformation conditions of the single and hybrid-mode, and the mechanism of the resulting specific dispersion, loss, and electromagnetic field distribution. According to the mode excitation principle and its evolution laws, the propagating properties can be accurately controlled by adjusting the dielectric thickness, which can effectively suppress the potential oscillations and improve the electron bunching phase in the gyro-TWT. As a result, the dielectric loading scheme can be optimized by properly arranging the DLWs, thus enhancing the stability and gain of the gyro-TWT. The theory and simulation are verified by the vector network analyzer measurement at Ku-band, and the results show a good agreement.

Extremely wide-angle nonreciprocal thermal emitters based on Weyl semimetals with dielectric grating structure

Although various nonreciprocal thermal emitters have been suggested to break the balance between absorption and emission, the majority can only achieve nonreciprocal effect at one certain angle, and the angular range in which these structures exhibit nonreciprocal effect is heavily restricted. In this work, the scheme to realize extremely wide-angle nonreciprocal thermal radiation effect is proposed and investigated. It is achieved by placing a dielectric grating atop a Weyl semimetal film backed with a metal mirror. The results show that the emitter exhibits strong nonreciprocal radiation at the wavelength of 15.98 μm when the incident angle is 30°. What's more, the strong nonreciprocal radiation can be achieved in a wide angular range. Such behavior results from the guided mode resonance, which is revealed by investigating the distribution of electromagnetic field at the resonant wavelength and is also confirmed by the dispersion relation of guided mode. This work provides a new approach to the design of novel nonreciprocal thermal emitters.

A Simple Metamaterial for High-Performance Spectrum-Selective Absorption in the Visible Region

In this paper, we numerically demonstrated a simple metamaterial for wide-angle and polarization-insensitive absorption in the visible region, which simultaneously showed a strongly suppressed absorption in the near-infrared region. Numerical simulations demonstrated that under normal incidence the proposed absorber had a high absorptivity almost over 90% in the wavelength range from 340 nm to 770 nm, while a low absorptivity less than 10% from 1 μm to 2 μm. Because a small unit cell with four-fold symmetry was utilized, the selective absorption of this nanostructure was almost independent of the incident angle and polarization of the incident light. To understand the underlying physical mechanisms, the impedance and the electromagnetic field distributions in a unit cell were analyzed. Moreover, the influence of the structural geometry parameters on the absorption spectrum was systematically studied. Our results may provide a method for using a simple nanostructure to reduce the radiative heat loss for the visible light thermal conversion, or to depress the temperature rise induced by the absorption of below-bandgap photons for photovoltaic solar cells working in the visible region.