3D Electromagnetic Simulation Research Articles

Magnetic signals from oceanic tides: new satellite observations and applications.

The tidal flow of seawater across the Earth's magnetic field induces electric currents and magnetic fields within the ocean and solid Earth. The amplitude and phase of the induced fields depend on the electrical properties of both seawater and the solid Earth, and thus can be used as proxies to study the seabed properties or potentially for monitoring long-term trends in the global ocean climatology. This article presents new global oceanic tidal magnetic field models and their uncertainties for four tidal constituents, including [Formula: see text] and even [Formula: see text], which was not reliably retrieved previously. Models are obtained through a robust least-squares analysis of magnetic field observations from the Swarm and CHAMP satellites using a specially designed data selection scheme. We compare the retrieved magnetic signals with several alternative models reported in the literature. Additionally, we validate them using a series of high-resolution global three-dimensional (3D) electromagnetic simulations and place constraints on the conductivity of the sub-oceanic mantle for all tidal constituents, revealing an excellent agreement between all tidal constituents and the oceanic upper mantle structure.This article is part of the theme issue 'Magnetometric remote sensing of Earth and planetary oceans'.

3D electromagnetic simulation of the coupling characteristics and double-stub Ferrite tuners impedance matching for EAST ICRH four-strap antenna

A program developed with COMSOL software integrates EAST four-strap antenna coupling with the double-stub Ferrite tuners (FT) impedance matching, obtaining physical quantities crucial for predicting the overall performance of the ion cyclotron resonance heating (ICRH) antenna and matching system. These quantities encompass S-matrix, port complex impedance, reflection coefficients, electric field and voltage distribution, and optimal matching settings. In this study, we explore the relationship between S-matrix, reflection coefficients, port complex impedance, and frequency. Then, we analyze the impact of Faraday screens placement position and transparency, the distance from the Faraday screen (FS) to the current straps (CS), the relative distance between ports, and the characteristic impedance of the transmission line on the coupling characteristic impedance of the EAST ICRH system. Finally, we simulate the electric field distribution and voltage distribution of the EAST ICRH system for plasma heating with double-stub FT impedance matching. Using optimized parameters, the coupling power of the ICRH system can be approximately doubled. The results present herein may offer guidance for the design of high-power, long-pulse operation ICRH antenna systems.

Ultra-Wideband Common-Mode Rejection Structure with Autonomous Phase Balancing for Ultra-High-Speed Digital Transmission.

For ultra-high-speed digital transmission, required by 5G/6G communications, ultra-wideband common-mode rejection (CMR) structures with autonomous phase-balancing capability are proposed. Common-mode noise, caused by phase and amplitude unbalances, is one of the most undesired disturbances affecting modern digital circuits. According to the circuit design guides with a typically used differential line (DL) for high-speed digital transmission, common-mode rejection is achieved using CMR filters, and the unbalanced phase, caused by a length difference between the two signal lines of a DL, is compensated by inserting an additional delay line. However, due to nonlinear phase interactions between the two DLs and unbalanced electromagnetic (EM) interferences, the conventional compensation method is frequency-limited at around 10 GHz. To significantly enhance the common-mode rejection level and extend the phase recovery bandwidth, the proposed CMR structure utilizes a planar balanced line (BL), such as a coplanar stripline (CPS) or a parallel stripline (PSL), along with additional conductor strips arranged laterally near the BL. To demonstrate the performance of the proposed BL-based CMR structures, various types of CMR structures are fabricated, and the measurement results are compared with the 3D EM simulation results. As a result, it is proven that the proposed BL-based CMR structures have the capability to reject the common-mode noise with suppression levels of more than 10 dB and to simultaneously recover the phase balance from near DC to over 40 GHz.

A Novel 4-port MIMO Antenna with Chamfered Edge for 5G NR n77/n78/n79 Bands and WLAN Applications

Abstract A novel, compact and low-cost four-element multiple-input multiple-output (MIMO) antenna with a high gain is proposed in this work. The suggested antenna structure uses easily accessible substrate material and has been designed and simulated using Ansys HFSS 3D electromagnetic simulation software. The radiating elements are placed orthogonally, and each of them consists of two circular rings. To improve the impedance matching and reduce mutual coupling, the corners are chamfered and partial ground structure is applied. For further enhancement in isolation, Defected Ground Structure (DGS) method is applied which makes the isolation as high as -55 dB. The measured gain of the proposed antenna is more than 12 dB over the considered frequency range. The antenna covers a frequency range from 3.3-6 GHz. The value of diversity gain is found to be more than 9.99 dB and envelope correlation coefficient is less than 0.006 respectively. Also, the mean effective gain, channel capacity loss, and total active reflection coefficient results are within the optimal range. These make the designed antenna suitable for the sub-6 GHz, 5G new radio (NR) n77/n78/n79 where n77 (3.3-4.2 GHz), n78 (3.3-3.8 GHz), and n79 (4.4-5 GHz) bands along with WLAN (5.1-5.8 GHz) applications.

Mechanically Adjustable 4-Channel RF Transceiver Coil Array for Rat Brain Imaging in a Whole-Body 7 T MR Scanner.

Investigations of human brain disorders are frequently conducted in rodent models using magnetic resonance imaging. Due to the small specimen size and the increase in signal-to-noise ratio with the static magnetic field strength, dedicated small-bore animal scanners can be used to acquire high-resolution data. Ultra-high-field (≥7 T) whole-body human scanners are increasingly available, and they can also be used for animal investigations. Dedicated sensors, in this case, radiofrequency coils, are required to achieve sufficient sensitivity for the high spatial resolution needed for imaging small anatomical structures. In this work, a four-channel transceiver coil array for rat brain imaging at 7 T is presented, which can be adjusted for use on a wide range of differently sized rats, from infants to large adults. Three suitable array designs (with two to four elements covering the whole rat brain) were compared using full-wave 3D electromagnetic simulation. An optimized static B1+ shim was derived to maximize B1+ in the rat brain for both small and big rats. The design, together with a 3D-printed adjustable coil housing, was tested and validated in ex vivo rat bench and MRI measurements.

Design and optimization of THz coupling in zirconia MAS rotors for dynamic nuclear polarization NMR

We present 3D electromagnetic simulations of the coupling of a 250 GHz beam to the sample in a 380 MHz DNP NMR spectrometer. To obtain accurate results for magic angle spinning (MAS) geometries, we first measured the complex dielectric constants of zirconia, sapphire, and the sample matrix material (DNP juice) from room temperature down to cryogenic temperatures and from 220 to 325 GHz with a VNA and up to 1 THz with a THz TDS system. Simulations of the coupling to the sample were carried out with the ANSYS HFSS code as a function of the rotor wall material (zirconia or sapphire), the rotor wall thickness, and the THz beam focusing (lens or no lens). For a zirconia rotor, the B1 field in the sample was found to be strongly dependent on the rotor wall thickness, which is attributed to the high refractive index of zirconia. The optimum thickness of the wall is likely due to a transmission maximum but is offset from the thickness predicted by a simple calculation for a flat slab of the wall material. The B1 value was found to be larger for a sapphire rotor than for a zirconia rotor for all cases studied. The results found in this work provide new insights into the coupling of THz radiation to the sample and should lead to improved designs of future DNP NMR instrumentation.

Optimization design of TEM cell based on multi-stage curved edge transition structure and magnetic loss method

This article describes how to raise the TEM cells' operating bandwidth and lower their VSWR. A multi-stage curved-edge transition structure for minimizing VSWR and a magnetic loss mechanism for extending the operating bandwidth are proposed by evaluating the workings and constraints of TEM cells. A hybrid simulation strategy based on the particle swarm algorithm and 3D electromagnetic simulation (EM) software is suggested in order to identify the optimal quickly. In the 3D EM simulation software, the TEM cell's 3D model is created, the VSWR and return loss were solved for. It is possible to raise the operational bandwidth from 0–2 GHz to 0–5 GHz. At 0-3 GHz, measurement and simulation results are practically equal. At 3-4.5 GHz, measurement results differ somewhat from simulation results. At 4.5-5 GHz, measurement results greatly diverge from simulation results, and the parameters no longer fulfill standard criteria.

Research on Vibration Characteristic Analysis and Fault Diagnosis Method of Oil‐Immersed Transformer Based on Multi‐Physics Coupling

The oil‐immersed transformer is a crucial power equipment in power system, which is prone to abnormality or failure under long running. In order to improve the level of operation and maintenance and ensure the safe and reliable operation of the power grid, it is necessary to diagnose the fault of the oil‐immersed transformer in time. Most of the traditional fault vibration methods are off‐line detection, and are easily disturbed by mechanical deterioration. In order to solve the above problems, this paper established a 3D electromagnetic and stress coupling simulation model of oil‐immersed transformer by finite element simulation software. The vibration characteristics of oil‐immersed transformer core winding are obtained, and at the same time, this paper obtained the vibration signals at different positions on transformer core winding and oil tank. According to the vibration signal of the transformer, the best measuring point position of the tank wall is proposed to accurately reflect the vibration characteristics of the transformer. The signal data is preprocessed by CEEMDAN decomposition method, and the signal data is classified by GWO‐BP composite classification algorithm. This paper proposed an online transformer fault diagnosis method based on vibration signal, which achieves the purpose of accurately diagnosing oil‐immersed transformer faults. The test results show that in the case of oil‐immersed transformers the accuracy of the proposed transformer fault diagnosis method is more than 93%, which provides important guiding significance for the safe and stable operation of the transformer. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

A synthetic diagnostics platform for microwave imaging diagnostics in tokamaks

Interpreting experimental diagnostics data in tokamaks, while considering non-ideal effects, is challenging due to the complexity of plasmas. To address this challenge, a general synthetic diagnostics (GSD) platform has been established that facilitates microwave imaging reflectometry and electron cyclotron emission imaging. This platform utilizes plasma profiles as input and incorporates the finite-difference time domain, ray tracing and the radiative transfer equation to calculate the propagation of plasma spontaneous radiation and the external electromagnetic field in plasmas. Benchmark tests for classical cases have been conducted to verify the accuracy of every core module in the GSD platform. Finally, 2D imaging of a typical electron temperature distribution is reproduced by this platform and the results are consistent with the given real experimental data. This platform also has the potential to be extended to 3D electromagnetic field simulations and other microwave diagnostics such as cross-polarization scattering.

Electromagnetic Environment Assessment and Safety Research of Electrified High-Speed Railway Carriages

With the advent of modern, high-speed electrified rail systems, there has been increasing concern about electromagnetic safety in rail carriages. The aim of this study was to assess the electromagnetic safety of passengers on trains by utilizing advanced 3D electromagnetic simulation software. A comprehensive model of the electromagnetic environment experienced by passengers on a CR400AF train, specifically under the influence of catenary radiation, was constructed. We analyzed the magnetic field strength, electric field strength, and current density in the brains of 20 passengers in various positions in the train. The findings revealed that among the 20 passengers analyzed, the maximum and minimum magnetic induction intensity recorded in the brain were 8.41 and 0.01 μT, respectively. The maximum and minimum induced electric field intensities were 1110 and 10 μV/m, respectively. Lastly, the maximum and minimum induced current densities were 1200 and 10 μA/m2, respectively. The results show that when people ride on the CR400AF train, the magnetic induction intensity, induced electric field strength, and induced current density in the brain are below the recommended basic limits of exposure to power frequency electromagnetic fields in the guidelines of the International Committee on Non-Ionizing Radiation Protection. The power frequency magnetic field generated by the catenary can be effectively shielded by the aluminum alloy car body. The final result of this study indicates that the electromagnetic exposure from the contact wire at the level 25 kV does not pose a threat to the health of passengers on the CR400AF train.

Partitioning surface wave propagation on reconfigurable porous plane

This paper introduces a novel reconfigurable technique for partitioning the propagation of surface waves by utilizing a T-shaped structure and pathways established through the introduction of fluid metal or metal pins into evenly spaced cylindrical cavities within a porous surface wave platform. Notably, the co-printing of metal and dielectric materials via 3D printing is employed, resulting in an expedited fabrication process. Extensive 3D electromagnetic simulations and experimental investigations validate the proposed approach’s efficacy in achieving surface wave division while minimizing interference. The study encompasses an exploration of diverse power distribution ratios achievable within the distributed surface waves. Critical physical parameters of the T-junction are comprehensively examined, including partition depth, junction geometry, output port symmetry, and asymmetry. Additionally, the research delves into the frequency-dependent behaviours of asymmetric T-junctions and pathways. These findings establish the groundwork for adaptable architectures, facilitating concurrent communication among multiple devices within a unified surface wave communication network. This innovation holds potential to enhance various applications through improved communication capabilities.

The enhancing energy efficiency in hyperthermia treatment: a frequency-reconfigurable L-Shape antenna design and analysis

The object of research is a frequency-reconfigurable L-Shape antenna. This paper presents an innovative study focusing on the design and analysis of a frequency-reconfigurable L-Shape antenna with a specific application in Hyperthermia Treatment. The antenna, operating in the frequency range of 2.5 to 8 GHz, utilizes a varactor to achieve agility and simplify design, thereby reducing component count. Constructed with a Roggers RT5880 (lossy) substrate, the L-Shape configuration ensures optimal performance. The incorporation of a single varactor, acting as a junction capacitance, not only enables straightforward tuning but also contributes to enhanced energy efficiency by reducing overall power consumption in the reconfigurable antenna system. The study employed CST Microwave Studio's 3D Electromagnetic field simulation software for time domain solver-based simulations, with validation conducted using the frequency domain solver. Results from the simulations showcase the antenna's performance at different frequency states. At the tuning state frequency of 2.7 GHz, the antenna exhibits an impressive gain of 1.905 dB and a directivity of 7.530 dB. Similarly, at the tuning state frequency of 6.89 GHz, the gain is measured at 6.806 dB with a directivity of 7.490 dB. The proposed L-Shape antenna design not only demonstrates significant potential for Hyperthermia Treatment, allowing targeted heating within the 2.5 to 8 GHz frequency range but also aligns with the multidisciplinary focus of medical science. This contribution reflects the commitment to advancing medical science through original research, fostering innovation, and promoting energy-efficient solutions with practical applications in clinical settings.

An efficient and low-profile metasurface-based polarization converter with linear and circular polarization efficiencies for X- and Ku-Band applications

In this study, a metasurface-based linear and circular polarization converter operating on the reflection mode is proposed for X- and Ku-band microwave applications. The proposed converter offers an optimum performance with a polarization conversion ratio (PCR) and polarization matching ratio (PMR) greater than 93 in the bandwidth for a linearly polarized in the y-direction and right-handed circular polarized (RHCP) incident waves. Besides, the design performs over 80 PCR performance up to under oblique incidence. Moreover, the proposed converter is capable of left-handed circular polarization conversion between 7.42 and 7.68 GHz for a y-polarized incident wave. The design offers a relative bandwidth (RBW) of 71.36. The converter design is constructed with metal termination, an easily accessible FR-4 substrate and a simple design metasurface. Surface currents of the polarization converter at resonance frequencies of 8.77, 12.88 and were examined to understand its working mechanism. In addition, when the proposed design is rearranged with the appropriate geometry, the monostatic RCS reduction value in the 8.0–17.7 range is observed to be higher than 10 dB. CST program (a commercial 3D electromagnetic simulator) was used in simulations. The simulated device was fabricated with a traditional board fabrication technique. Simulation results were verified with free space measurements calibrated by the thru-reflect-line calibration procedure. The performance and efficiency of the proposed polarization converter were compared with other converters in the literature.

High-frequency signal transmission in a coplanar waveguide structure with different surface finishes

Continuous pursuits for higher data rate, larger network capacity, low-latency communication, and better energy efficiency have motivated the development of the fifth generation (5 G) mobile communication technologies in recent years. Under a high-frequency transmission, the alternating electric current (AC) tends to distribute to the outer of a conductor due to the so-called “skin effect”; therefore, the surface coatings of Cu interconnect becomes an indispensable factor of the signal transmission characteristics. The focus of this study is to deeply probe into the effect of surface coatings on the high-frequency signal transmission (1–100 GHz) of Cu interconnects. We investigated six different surface finishes over a coplanar waveguide (CPW) transmission line structure, including immersion tin (ImSn), immersion silver (ImAg), immersion gold (IG), electroless palladium/immersion gold (EPIG), immersion gold/electroless palladium/immersion gold (IGEPIG), and ultrathin-Ni(P)-type ENEPIG. The high-frequency signal performance of the CPW transmission line was analyzed through the finite element analysis (FEA) method by using a 3D electromagnetic simulation software. Furthermore, experimental measurements were conducted by using a vector network analyzer (VNA) to characterize the signal loss arising from different surface finishes, so as to validate the numerical simulation results. The FEA and VNA results showed that a noticeable current redistribution might be induced by a high conductivity/permeability of surface coating(s), i.e., ImSn and ultrathin-Ni(P)-type ENEPIG, which significantly increases the signal insertion loss at high frequencies. Thus, an appropriate surface coating over Cu interconnects was necessary for enhancing the high-frequency signal transmission performance.

Design of a silicon Mach–Zehnder modulator via deep learning and evolutionary algorithms

As an essential block in optical communication systems, silicon (Si) Mach–Zehnder modulators (MZMs) are approaching the limits of possible performance for high-speed applications. However, due to a large number of design parameters and the complex simulation of these devices, achieving high-performance configuration employing conventional optimization methods result in prohibitively long times and use of resources. Here, we propose a design methodology based on artificial neural networks and heuristic optimization that significantly reduces the complexity of the optimization process. First, we implemented a deep neural network model to substitute the 3D electromagnetic simulation of a Si-based MZM, whereas subsequently, this model is used to estimate the figure of merit within the heuristic optimizer, which, in our case, is the differential evolution algorithm. By applying this method to CMOS-compatible MZMs, we find new optimized configurations in terms of electro-optical bandwidth, insertion loss, and half-wave voltage. In particular, we achieve configurations of MZMs with a 40~text {GHz} bandwidth and a driving voltage of 6.25~text {V}, or, alternatively, 47.5~text {GHz} with a driving voltage of 8~text {V}. Furthermore, the faster simulation allowed optimizing MZM subject to different constraints, which permits us to explore the possible performance boundary of this type of MZMs.

Complementary analysis of specific absorption rate safety for an 8Tx/16Rx array with central symmetry of elements for magnetic resonance imaging of the human heart and abdominopelvic organs at 7 T.

A complementary safety assessment of the specific absorption rate (SAR) of the electromagnetic energy was performed in a prototype 8Tx/16Rx RF array for cardiac magnetic resonance imaging (MRI) at 7 T. The study aimed to address two critical aspects of 7-T SAR safety not always explicitly examined by coil vendors: (i) the influence of an RF-array position on a peak SAR value, and (ii) the risk of exceeding the permitted maximal SAR in the tissue surrounding conductive passive implants. The full-wave 3D electromagnetic simulations for the thorax with shifted array position and the whole-body volume in the presence of a dental retainer, an intrauterine contraceptive device (IUD), and a hip joint implant, were performed for two human voxel models. The effect of the array displacement on the SAR was simulated for seven array locations on the thorax shifted from the central position in different directions on 50 mm. The peak SAR values for both models were analyzed for the three phase-only transmit vectors optimized for B1 + homogeneity and transmit efficiency. Peak SAR values due to the shifts of the array position increase up to ≈50%. The worst-case peak SAR value for a dental retainer was found to be in the range of 10% of the maximal SAR in the tissue within the array's borders. For the IUD and artificial hip joint implants the effect was found to be negligible (peak SAR < 1% of the SAR within array borders). In addition to simulations for cardiac MRI, we performed a preliminary B1 + shimming and SAR-safety analysis for the same RF-array at various positions lower on the body trunk to assess a potential application in imaging abdominopelvic organs (prostate, kidney, and liver). The most promising target for an ad hoc alternative application of the array was found to be the prostate.

Methodology for Electromagnetic Optimization of a Partially Superconducting 1.4 MW Electric Machine for Electrified Aircraft Propulsion

Large transport aircraft with electrified propulsion systems require MW-class electric machines that have higher efficiency and power-to-weight ratio than existing machines. Superconducting machines are being evaluated as potential solutions. This paper presents a method to optimize the electromagnetic design of a partially superconducting machine in terms of these metrics and the approximate fuel burn of the aircraft. The optimization is based on 2D electromagnetic finite element simulations, a prediction of the superconducting coils' critical current, and geometry relations that design the superconducting coils based on dependent variables while constraining the total cost of superconductor and ensuring adequate space for structure. The design process is completed by (1) a 3D electromagnetic finite element simulation to improve the prediction of torque and assess magnetic flux leakage, (2) refinement of the superconductor width for each individual racetrack coil, and (3) evaluating inverter-produced stator current harmonics on eddy current losses in the rotor.

Improving the Performance of Patch Antenna by Applying Bandwidth Enhancement Techniques for 5G Applications

In this study, various Rectangular Microstrip Antenna (RMA) designs operating at 28 GHz frequency for 5G-communication system are performed. All designs are generated and analyzed using a 3D electromagnetic simulation program, ANSYS HFSS (High-Frequency Structure Simulator). Single and array type RMA designs are constructed by using non-contact inset-fed feeding technique. Subsequently, the bandwidth of RMAs is increased by slotting on the ground surface, and adding a parasitic element to the antenna structure. Because of these analyses, for single type RMA, the bandwidth increases from 2.09 GHz to 3.45 GHz. Moreover, for 1 × 2 and 1 × 4 array type RMAs, very wide bandwidths of 7.53 GHz and 4.53 GHz, respectively, are obtained by applying bandwidth enhancement techniques. The success of the study has been demonstrated by comparing outputs of the designs with the some similar, experimental or simulation studies published in the literature.

Electromagnetic and Chemical Analysis and Performance Comparison of Inset‐fed Rectangular Microstrip Antennas

AbstractA simple method for creating lightweight and inexpensive microstrip patch antennas using reduced graphene oxide or acetylene black added epoxy resin was developed. The biggest goal in the method is optimizing the appropriate chemicals and production processes for producing the materials with the designed properties. Five examples of an inset‐fed microstrip patch antenna operating at approximately 2.0–12.0 GHz were designed based on the antenna‘s basic analytical formula. Their models were created in a 3D electromagnetic simulation environment. After examining the performance results of the design, the appropriate design models were produced with both 3D printer technology and wet‐chemical methods, and the experimental results were compared with the simulation results. The produced reduced graphene oxide or acetylene black added samples′ structure was illuminated with scanning electron microscope images, FTIR and Raman spectroscopy analysis. The measured S11 characteristics of the antennas provide better performance as compared to the simulated results. The measured S11 parameters for the two and three frequency bands fell substantially below −10 dB. As a result of the dielectric constants of the materials and the fabrication of the radiation plane, horizontal shifts were detected in the measurement outcomes.

Study on Electromagnetic Radiation Characteristics Based on HTS Maglev Levitation Test Line

As a new type of magnetic levitation train with the characteristics of self-stabilization and self-suspension, high-temperature superconducting magnetic levitation has developed to the test line research stage. In order to promote the rapid development of high-temperature superconducting magnetic levitation train engineering, and the main electromagnetic radiation sources are clarified by analyzing their working principles and structures. Then Ansoft Maxwell EM was used to build a 3D magnetic levitation train electromagnetic environment simulation model to simulate and predict the electromagnetic radiation characteristics of the magnetic levitation train system. Finally, a field EMF test was carried out to verify and assess the impact on the EM environment in the system. The results show that the permanent magnet track on the ground and the synchronous linear motor are the primary electromagnetic radiation sources, and the generated fields are mainly low-frequency fields and static magnetic fields. The low-frequency magnetic field inside the train decreases with the increase of frequency and is partially shielded by the carriage; The static magnetic field cannot be weakened by the carriage, and the static magnetic field inside the car decreases with the increase of height. All types of electromagnetic fields are far below the requirements of the relevant electromagnetic environmental standard limits, and have no effect on the electromagnetic radiation safety of the personnel inside the train and the surrounding environment; In considering of the special people who have pacemakers, static magnetic field suppression measures are studied, and the results show that the trains with high magnetic permeability permalloy as the shielding layer at the bottom of the vehicle greatly lower the static magnetic field within the train.