Electromagnetic Field Simulation Research Articles

Development of an open-ended microstrip stub apparatus and technique for the dielectric characterization of powders

A new apparatus and method to characterize the complex dielectric permittivity of powders is described. The apparatus and technique are used to determine the dielectric properties of detergent powder agglomerates at different conditions. The technique is based on the measurement of scattering-parameters of an open circuit microstrip stub partly loaded with the test powder material. The scattering parameters relate the voltage waves incident on the ports of a microwave network to those reflected from the ports and can easily be measured with a vector network analyzer. A 3D finite element electromagnetic field simulation tool HFSS (High frequency structural simulator) is used to replicate the measured S-parameters and then extract the complex permittivity data from it. The method has been verified by measuring the dielectric properties of disks of known dielectric materials – specifically Duriod 5880 and Teflon. Results are in good agreement with manufacturer data sheets.The complex permittivity of a range of detergent powder agglomerates with different moisture levels, at ambient and elevated temperatures, has been determined using this technique. Results are consistent with predictions of how the water interacts with the different components of the detergent particles at these different conditions.

Research on the Correlation of Control Malfunction with Induced Voltage of Control Signal Line According to Voltage Change of a Power Line

This induced voltage measurement test and electromagnetic field simulation are related to the possibility of control signal malfunction by power line. Through an experiment, this research analyzed whether the voltage causing control malfunction according to the on/off status of power permitted to power line was induced to control signal line. Also, the research calculated the voltage induced to control signal line and examined the phenomenon by conducting an electro-magnetic field-specific simulation through the finite element method for the cable model used in the experiment.

Power Performance Profiling of 3-D Stencil Computation on an FPGA Accelerator for Efficient Pipeline Optimization

This paper discusses power-performance optimization for 3-D stencil computing on a stream-oriented FPGA accelerator with highlevel synthesis. Taking a heat conduction simulation and an FDTD electromagnetic field simulation as benchmark applications, powerperformance profiling results are presented focusing on the effect of high-level pipeline parameters. As a result, it is shown that the optimal power efficiency can be achieved basically by optimizing the execution performance. The relationship between power efficiency and the clock frequency is also discussed.

Electrodynamics and radiofrequency antenna concepts for human magnetic resonance at 23.5T (1GHz) and beyond.

This work investigates electrodynamic constraints, explores RF antenna concepts and examines the transmission fields (B 1 (+) ) and RF power deposition of dipole antenna arrays for (1)H magnetic resonance of the human brain at 1GHz (23.5T). Electromagnetic field (EMF) simulations are performed in phantoms with average tissue simulants for dipole antennae using discrete frequencies [300MHz (7.0T) to 3GHz (70.0T)]. To advance to a human setup EMF simulations are conducted in anatomical human voxel models of the human head using a 20-element dipole array operating at 1GHz. Our results demonstrate that transmission fields suitable for (1)H MR of the human brain can be achieved at 1GHz. An increase in transmit channel density around the human head helps to enhance B 1 (+) in the center of the brain. The calculated relative increase in specific absorption rate at 23.5 versus 7.0T was below 1.4 (in-phase phase setting) and 2.7 (circular polarized phase setting) for the dipole antennae array. The benefits of multi-channel dipole antennae at higher frequencies render MR at 23.5T feasible from an electrodynamic standpoint. This very preliminary finding opens the door on further explorations that might be catalyzed into a 20-T class human MR system.

Comparison between single- and multiple-zone induction heating of largely curved mold surfaces

This study applied three-dimensional steady-state finite-element numerical simulations of electromagnetic fields and temperature distributions to evaluate the effects of various coil geometries, regional depositions, and magnetic shielding materials on the induction heating of a curved mold plate surface used for fabricating automotive spoilers. Conventionally, the induction heating of large mold surfaces by using a set of long inductive coils entails employing a costly, high-power induction heating device. This study proposes a multizone induction heating approach that entails dividing a target surface into several zones and then applying numerous sets of short inductive coils that require only low-power induction heating devices to the individual regional zones for heating. In this approach, the coil design is relatively simple for efficiently heating these small-area zones. The simulation results are described as follows: (1) the geometry of the inductive coils with respect to the processed workpiece demonstrated a considerable effect on the electromagnetic field distribution and the heating efficiency of the system. (2) Magnetic shielding materials facilitated eliminating the proximity effect, which produces a nonuniform heating pattern along the workpiece wall. (3) Compared with single-zone induction heating, the multiple-zone induction heating of a largely curved mold surface enhanced the heating rate and uniformity performance.

Development of HTS Pickup Coils for 700-MHz NMR: Resonance Frequency Tuning Using a Sapphire Plate

In this study, we developed a new frequency-tuning method for 700-MHz nuclear magnetic resonance (NMR) pickup coils. We determined an optimal Helmholtz-type one-turn coil, by using an electromagnetic simulator, and fabricated a pickup coil using YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-δ</sub> (YBCO) thin films. We examined the resonance frequency shift of the pickup coils obtained with a sapphire plate by using a 3-D electromagnetic-field simulator and obtained a 31.5-MHz shift. We also examined the frequency shift obtained using a quasi-NMR pickup coil system and found that it was 29.3 MHz. This value is sufficient for the frequency tuning in an actual NMR system. It became clear that resonance frequency tuning using a sapphire plate was possible.

Numerical simulation and prediction of radio frequency inductively coupled plasma spheroidization

An inductively coupled radio frequency (RF) plasma system was employed to produce spherical TiAl based alloy powders, and the spheroidization process was investigated by means of numerical simulation. Based on the coupled simulation of electromagnetic and thermal fluid fields, the plasma system model was developed and applied to calculate the motion trajectories and the temperature variation of injected particles, which provides the evidence for judging the physical state of individual particle after passing through plasma system. For the fed TiAl alloy powders with different granulometric characteristics, the collection rate, the spheroidization rate and the size distribution curves of the spheroidized powders can be predicted by statistical analysis. The results show that the predictions are close to the experimental data, indicating the numerical simulations of both plasma system and particle behaviors during the spheroidization process are reliable.

Backward spoof surface wave in plasmonic metamaterial of ultrathin metallic structure.

Backward wave with anti-parallel phase and group velocities is one of the basic properties associated with negative refraction and sub-diffraction image that have attracted considerable interest in the context of photonic metamaterials. It has been predicted theoretically that some plasmonic structures can also support backward wave propagation of surface plasmon polaritons (SPPs), however direct experimental demonstration has not been reported, to the best of our knowledge. In this paper, a specially designed plasmonic metamaterial of corrugated metallic strip has been proposed that can support backward spoof SPP wave propagation. The dispersion analysis, the full electromagnetic field simulation and the transmission measurement of the plasmonic metamaterial waveguide have clearly validated the backward wave propagation with dispersion relation possessing negative slope and opposite directions of group and phase velocities. As a further verification and application, a contra-directional coupler is designed and tested that can route the microwave signal to opposite terminals at different operating frequencies, indicating new application opportunities of plasmonic metamaterial in integrated functional devices and circuits for microwave and terahertz radiation.

High‐efficiency CMOS push‐pull power amplifier with multilayer center‐tapped transformer

This paper describes the design of a push‐pull power amplifier (PA) with a center‐tapped transformer for transmitter applications on the 5.2‐GHz band using 0.18μm CMOS technology. The type of the proposed PA is based on a double‐ended push–pull (DEPP) configuration. DEPP has a simple construction with only transistors and transformers. The PA has reverse‐phased cascode‐connected transistors. The proposed transformer has a multilayer structure and was designed using electromagnetic field simulation. To achieve high power added efficiency (PAE), we assumed the optimized output impedance technique with a tunable impedance antenna. The PA has 13.2 dB linearity gain, 14.9 dBm 1‐dB compression point (P1dB), and 27.4% maximum PAE. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

31P CSI of the human brain in healthy subjects and tumor patients at 9.4 T with a three-layered multi-nuclear coil: initial results

Investigation of the feasibility and performance of phosphorus ((31)P) magnetic resonance spectroscopic imaging (MRSI) at 9.4 T with a three-layered phosphorus/proton coil in human normal brain tissue and tumor. A multi-channel (31)P coil was designed to enable MRSI of the entire human brain. The performance of the coil was evaluated by means of electromagnetic field simulations and actual measurements. A 3D chemical shift imaging approach with a variable repetition time and flip angle was used to increase the achievable signal-to-noise ratio of the acquired (31)P spectra. The impact of the resulting k-space modulation was investigated by simulations. Three tumor patients and three healthy volunteers were scanned and differences between spectra from healthy and cancerous tissue were evaluated qualitatively. The high sensitivity provided by the 27-channel (31)P coil allowed acquiring CSI data in 22min with a nominal voxel size of 15×15×15mm(3). Shimming and anatomical localization could be performed with the integrated four-channel proton dipole array. The amplitudes of the phosphodiesters and phosphoethanolamine appeared reduced in tumorous tissue for all three patients. A neutral or slightly alkaline pH was measured within the brain lesions. These initial results demonstrate that (31)P 3D CSI is feasible at 9.4T and could be performed successfully in healthy subjects and tumor patients in under 30min.

SAR of a birdcage coil with variable number of rungs at 300 MHz

The specific absorption rate produced in a rat’s brain phantom inside of quadrature birdcage coil as a function of the rung number was studied at 300MHz. Electromagnetic field simulations and specific absorption rate and loss return responses were performed using a rat’s brain phantom weighing 100mg. To assure optimal simulations and to evaluate coil performance, S-parameters were simulated and compared with experimentally data. Simulations showed that magnetic field uniformity improves and that electric field is increased with the number of rungs. Specific absorption rate and temperature values obtained from axial bi-dimensional maps increase as the number of rungs grows. These results corroborated very well with published data. A quadrature 16-rung birdcage coil was developed for comparison and phantom images were acquired to show its feasibility. The presented approach yields information on specific absorption rate allowing to previously develop RF coils and their possible effects on the biological sample.

Modeling and Simulation of Terahertz Resonant Tunneling Diode-Based Circuits

Circuit models of transmission line elements and of a terahertz resonant tunneling diode (RTD) have been developed. The models allow for a reliable design of RTD-based oscillator and detector circuits. The transmission line elements have been modeled based on electromagnetic field simulations and dc measurements. Their accuracy has been verified through S-parameter measurements. The RTD has been modeled on the basis of dc and S-parameter measurements. The models have been used for the circuit design. A new circuit has been developed that can provide a load impedance that allows for high-output-power oscillators and high-sensitivity detectors. The circuit has been manufactured and measured as an oscillator and as a detector at frequencies around 300 GHz. An excellent agreement between measurement and simulation has been obtained, proving the accuracy of the developed models.

Extended P21-Based Benchmarking

This paper highlights two important aspects of the electromagnetic field modeling and simulation when used for industrial applications, namely the application based benchmarking activities and the magnetic material modeling. It emphasizes the relationship between the two, and briefly reviews the recent progress in extending the TEAM (Testing Electromagnetic Analysis Methods) Problem 21 Family (P21) and the related modeling results, and proposes a new benchmarking project which includes the upgraded benchmark models that can handle extreme excitations, i.e. current sources with a DC bias, as well as multiple harmonics.

Center-Constricted Magnetic Core-Coil Structures for Resonant Wireless Power Transfer

Magnetic core-coil structures for resonant wireless power transfer are proposed to enhance power transfer efficiency between opposed flat coils. A central region in the direction perpendicular to the plane of a magnetic core plate is constricted with a coil wound closely around the region to increase the figure of merit kQ, the product of the coupling coefficient k and the quality factor Q. The proposed effect is analyzed in terms of a magnetic circuit model. Electromagnetic field simulation of the systems determines the equivalent circuit parameters and confirms quantitatively the increase in kQ by the center-constricted structures.

Modelling, Simulation and Experimental Analysis of a Metal-Polymer Hybrid Fibre Based Microstrip Resonator for High Frequency Characterisation

Conductive multifilament fibres are the fundamental core for wearable technology in the biomedical engineering fields, as conductors in sensors or in bio-sensing textiles for healthcare. This contribution presents a model, simulation and the experimental analysis of a metal-polymer hybrid fibre based microstrip resonator for high frequency characterisation. The high frequency electromagnetic field simulation (HFSS) by ANSYS® is used for the modelling and finite element based simulation. It follows the design and manufacturing of the metal-polymer hybrid fibre based microstrip resonator for analysis of the scattering parameter measurements and the quality factors to 10GHz with a vector network analyser (VNA) by Rohde & Schwarz®. Simulations and analysis also compare solid matter wire with the metal-polymer hybrid fibre.

CIP法による雷電磁界・サージ解析

The constrained interpolation profile (CIP) method, which is one sort of the finite-difference methods, has been recently applied to transient electromagnetic field simulations. Differently from the finite-difference time-domain (FDTD) method, the CIP method considers not only electric- and magnetic-field values at grid points but also their spatial derivative values there. In principle, therefore, it could suppress numerical dispersion and instability even when a relatively coarse grid is used. In this technical note, fundamentals of the CIP method and its formulations for computing electromagnetic fields in the 3D Cartesian coordinate system and in the 2D cylindrical coordinate system are briefly explained. Representative applications are also shown.

Complex interaction of passive multiport structures and their description by separate discrete models

It is demonstrated, using the example of a T-junction, that not every multiport structure can be accurately described by a discrete and separated modelling approach at millimetre and sub-millimetre wavelengths. It is shown that especially stub-networks, which are typically used in RF-matching networks, are affected. In this case, the discrete modelling approach predicts a different resonance frequency than the S-parameter measurement as well as the 3D electromagnetic field simulation (3D-EMFS) of the whole structure. However, these resonances are of particular importance for the design of a RF matching network and should be predicted by the model as precisely as possible. Therefore, the reason for the mismatch by accurate 3D-EMFS is investigated and a possible solution on how to model the so-called complex interactions in passive multiport structures at millimetre and sub-millimetre wavelengths is provided.

Development of computational small animal models and their applications in preclinical imaging and therapy research.

The development of multimodality preclinical imaging techniques and the rapid growth of realistic computer simulation tools have promoted the construction and application of computational laboratory animal models in preclinical research. Since the early 1990s, over 120 realistic computational animal models have been reported in the literature and used as surrogates to characterize the anatomy of actual animals for the simulation of preclinical studies involving the use of bioluminescence tomography, fluorescence molecular tomography, positron emission tomography, single-photon emission computed tomography, microcomputed tomography, magnetic resonance imaging, and optical imaging. Other applications include electromagnetic field simulation, ionizing and nonionizing radiation dosimetry, and the development and evaluation of new methodologies for multimodality image coregistration, segmentation, and reconstruction of small animal images. This paper provides a comprehensive review of the history and fundamental technologies used for the development of computational small animal models with a particular focus on their application in preclinical imaging as well as nonionizing and ionizing radiation dosimetry calculations. An overview of the overall process involved in the design of these models, including the fundamental elements used for the construction of different types of computational models, the identification of original anatomical data, the simulation tools used for solving various computational problems, and the applications of computational animal models in preclinical research. The authors also analyze the characteristics of categories of computational models (stylized, voxel-based, and boundary representation) and discuss the technical challenges faced at the present time as well as research needs in the future.

Effects of Anatomical Differences on Electromagnetic Fields, SAR, and Temperature Change.

Electromagnetic field simulations are increasingly used to assure RF safety of patients during MRI exams. In practice, however, tissue property distribution of the patient being imaged is not known, but may be represented with a pre-existing model. Repeatedly, agreement in transmit magnetic (B1+) field distributions between two geometries has been used to suggest agreement in heating distributions. Here we examine relative effects of anatomical differences on B1+ distribution, Specific Absorption Rate (SAR) and temperature change (ΔT). Numerical simulations were performed for a single surface coil positioned adjacent a homogeneous phantom and bovine phantom, each with slight geometric variations, and adjacent two different human body models. Experimental demonstration was performed on a bovine phantom using MR thermometry and B1+ mapping. Simulations and experiments demonstrate that B1+ distributions in different samples can be well correlated, while notable difference in maximum SAR and ΔT occur. This work illustrates challenges associated with utilizing simulations or experiments for RF safety assurance purposes. Reliance on B1+ distributions alone for validation of simulations and/or experiments with a sample or subject for assurance of safety in another should be performed with caution.

Hybrid equivalent source – 3D ray-launching simulation technique for deterministic estimation of radiated emissions of electrical appliances

In this work, a method for modeling the leaked radiofrequency radiation from electrical appliances is presented, with the aim of obtaining a model for a 3D ray-launching algorithm. The domestic microwave oven is the appliance under analysis, as it radiates a substantial amount of power and it is spread worldwide. The method uses numerical electromagnetic field simulations to obtain the exterior oven radiation. Due to the complexity of the metallic mesh of the oven door, a retrieval process has been implemented in order to accelerate the electromagnetic field simulation. This result is incorporated to a proprietary 3D ray-launching algorithm by obtaining equivalent radiation sources. Finally, the microwave oven leakage is obtained for the complete volume of an indoor scenario. The numerical results are then compared with experimental measurements, with good agreement. The proposed model is useful to predict accurately the leakage of the domestic microwave oven within a complete complex indoor scenario, aiding in further radioplanning considerations.