Three-dimensional Electromagnetic Model Research Articles

Three‐dimensional electromagnetic parametric modelling and implementation of miniaturized lumped‐element power divider based on symmetrical configuration

Three-dimensional (3D) electromagnetic (EM) parametric modelling and implementation of miniaturized lumped-element power divider (PD) based on symmetrical configuration is investigated. The system design and schematic diagrams of PDs are first demonstrated; subsequently, the 3D EM field and field-circuit co-simulation models of PD utilizing computer simulation technology (CST) and advanced design system (ADS) tools are detailedly presented. Finally, one prototype is fabricated and measured. Simultaneously, the gain of the PD is −3.96 dB @ 100 MHz and the experimental curve is in excellent agreement with the simulation. As a conclusion, the novel design methodology applied in PD has important practical engineering value, which can be also applied in millimetre-wave (mmW) circuit

Erbium-ytterbium co-doped photonic crystal fiber amplifier supporting amplification for orbital angular momentum

In order to reduce the loss in orbital angular momentum (OAM) long-distance communication systems, an OAM erbium-ytterbium co-doped fiber amplifier (OAM-EYDFA) based on photonic crystal fiber (PCF) is proposed and investigated for the first time in this work. We set up a three-dimensional electromagnetic field model of the PCF in Comsol and solved it by the finite element method. Then, we designed a three-dimensional model of the OAM-EYDFA based on the proposed PCF using Comsol and MATLAB. The results reveal that the proposed OAM-EYDFA has a flat-high gain of about 47 dB, a differential mode gain of lower than 0.3 dB and a noise figure of lower than 3.4 dB. Compared with existing studies, its gain is increased by at least 25 dB, and other properties are also improved. The proposed OAM-EYDFA can provide a reference for OAM-based long-distance communication systems.

Design and test of an open portable MRI system

PurposeThe purpose of this paper is the design study and realisation of portable low-field open MRI system.Design/methodology/approachThe design of the magnetic resonance imaging (MRI) system is based on an optimization study using a genetic algorithm. Non-linear two-dimensional and three-dimensional numerical electromagnetic models are developed and inserted in the optimization environment.FindingsThe results are found to be consistent with those issued from fully experimental tests. The static field produced by the device is 0.295 T with a homogeneity of 2.8% (28,000 ppm) over 100 mm diameter sphere volume. The z-axis gradient coils are capable of generating switching gradients with an amplitude of 8 mT/m and a frequency of 1.2 kHz.Originality/valueOur system is an open portable MRI which can be used in an ambulance. The open topology permits an easy access into the lateral sides when a surgery using surgical instrument with video feedback is needed.

High torque density magnetorheological brake with multipole dual disc construction

This paper presents a magnetorheological (MR) brake with the intent of overcoming the problems of limited torque density and low manufacturability that conventional MR brakes come across. Firstly, the conceptual design of the proposed MR brake was finalized. High torque density was achieved by using the combined effect of the dual disc-type construction and multipole concept. High manufacturability was attained with a simple and lightweight mechanical construction. It was created with the major components, namely magnetically permeable stator cases, rotor discs, magnetic cores, winding coils, and MR fluid. The computer aided design (CAD) model and analytical models were also developed to study the performance of the proposed brake. Then, the dimensions of the brake were optimized through electromagnetic simulations. Further, the brake performance was simulated using a three-dimensional electromagnetic model. Finally, a prototype of the optimized MR brake was fabricated, and its performance was experimentally validated. It is clear from the computer simulations and experimental test results, that the proposed MR brake has achieved the objective. The maximum torque was 16.5 Nm, and the torque density of 79.3 Nm dm−3 was significantly higher than that of conventional MR brakes. This brake also exhibited a fairly rapid response with a response rate of 90 ms.

Notice of Retraction: Three-dimensional Electromagnetic Characteristics Analysis of Novel Linear Synchronous Motor under Lateral and Yaw Conditions of MAGLEV

Dynamic stability analysis of superconducting electro-dynamic maglev train under lateral and yawing motion condition is the key research content. The novel three-dimensional electromagnetic model of integrated linear synchronous motor in electro-dynamic maglev train with yawing operation condition is proposed, which can not only simultaneously achieve the propulsion, levitation and guidance performances of maglev vehicle, but also analyze the dynamic stability performance of train with yawing condition. The three-dimensional analytical method is introduced for analyzing the electromagnetic force characteristics of the linear synchronous motor with the yawing operation condition. Firstly, the topology structure and operation principle of the linear synchronous motor with yawing attitude are proposed. Secondly, the three-dimensional analytical model and expressions of electromagnetic characteristics are obtained by equivalent circuit method and Fourier decomposition method, such as levitation force, guidance force, propulsion force and yawing torque, etc. Finally, the three-dimensional electromagnetic characteristics of the linear synchronous motor are calculated under yawing operation conditions of maglev train, and the correctness of the analytical theory is verified by the finite element analysis and measured data on the test line.

A reconstructed three-dimensional HTS bulk electromagnetic model considering J c spatial inhomogeneity and its implementation in a bulks’ combination system

High-temperature superconducting (HTS) bulks in HTS Maglev systems are always arrayed in a combination to make full use of the applied magnetic field of the permanent magnet guideway (PMG). An excellent combination scheme improves the overall levitation and guidance performance significantly. In this paper, a three-dimensional (3D) electromagnetic model of the real HTS-PMG maglev system with an HTS bulk array was established. This model comprehensively expresses the influence of various factors on the E – J relationship and the 3D spatial distribution of J c, including internal factors such as the inhomogeneity and anisotropy of electromagnetic characteristics, as well as external factors such as applied magnetic field and working temperature. A ternary function was proposed to describe the uneven distribution of J c caused by the bulk’s growth process, which is an interesting phenomenological modeling attempt. In the simulations of the bulks’ combinations, perfect magnetic conductor boundary conditions were applied on the contact surface to simulate two bulks touching each other. Besides, the research target includes reproducing the shapes, the orientations, and the combination scheme of HTS bulks in the real PMG magnetic field. The calculation results of levitation force of the cylindrical bulk under different spatial orientations above the PMG were compared with the experimental results, through which the accuracy of the model was verified. On this basis, the influence of the magnetic field generated by the superconducting current on the nearby bulk was further explored. It was found that this magnetic field has a small contribution to the total levitation force and a relatively obvious influence on the guidance force. When the lateral displacement is large, such as 5 mm, the magnetic field generated by the superconducting current slightly increases the total guidance force stiffness. According to more simulated conditions, some optimization strategies on bulk combinations were proposed. This work provides not only a 3D descriptive model for fitting the real multi-bulk-combination maglev scenarios but also some optimization strategies for the HTS maglev transportation applications.

Three-dimensional controlled-source electromagnetic forward modeling by edge-based finite element with a divergence correction

We have developed an edge-based finite-element (FE) modeling algorithm with a divergence correction for calculating the controlled-source electromagnetic (CSEM) responses of a 3D conductivity earth model. We solve a curl-curl equation to directly calculate the secondary electric field to eliminate the source singularity. The choice of the edge-based FE method enables us to properly handle the discontinuity of the normal component of electric fields across conductivity boundaries. Although we can solve the resulting complex-symmetric linear system of equations efficiently by a quasiminimal residual (QMR) method preconditioned with an incomplete Cholesky decomposition for the high-frequency band, the iterative solution process encounters a common problem in the field formulation and does not converge within a practically feasible number of iterations for low frequencies. To overcome this difficulty and to accelerate the iterative solution process in general, we combine a divergence correction technique with the secondary field solution using the QMR solver. We have found that applying the divergence correction intermittently during the iterative solution process ensures the calculation of sufficiently accurate electric and magnetic fields and can significantly speed up the solution process by more than an order of magnitude. We have tested the efficiency and accuracy of our algorithm with 1D and 3D models, and we have found that the divergence correction technique is able to guide the electric field to satisfy the boundary conditions across conductivity interfaces. Although there is a computational overhead required for applying the divergence correction, that cost is significantly offset by the substantial gains in the solution accuracy and speed-up. The work makes the field-based curl-curl formulation using edge elements an efficient and practical method for CSEM simulations.

3-D electromagnetic-model-based absolute attitude estimation using a deep neural network

ABSTRACT With the improvement of range resolution, wideband radars can achieve not only the range and velocity but also signature information of the target, such as the target RCS and the distribution of the scattering centres. Since radar target signature is closely related to target’s geometric structure and attitude, it is possible to estimate attitude from wideband radar echoes. To this end, we propose a novel end-to-end Radar Target Attitude Estimation Network (RTAENet) to estimate the absolute attitude of the radar target. A difficulty for training the network is that a large dataset with ground truth is required. To solve this issue, we introduce the three-dimensional (3-D) electromagnetic model to generate training samples. Since the RTAENet requires very little feature engineering by hand and can take advantage of increases in the amount of available data, it achieves high accuracy for attitude estimation. Experiments using both data predicted by a high-frequency electromagnetic code and data measured in an anechoic chamber demonstrate the feasibility of the proposed method.

Research on Electromagnetic Field, Eddy Current Loss and Heat Transfer in the End Region of Synchronous Condenser with Different End Structures and Material Properties

Aiming at the problem of end structure heating caused by the excessive eddy current loss of large synchronous condensers used in ultra-high voltage (UHV) power transmission, combined with the actual operation characteristics of the synchronous condenser, a three-dimensional transient electromagnetic field physical model is established, and three schemes for adjusting the end structure of the condenser under rated condition are researched. The original structure has a copper shield and a steel clamping plate. Scheme 1 has no copper shield but has a steel clamping plate. Scheme 2 has no copper shield but has an aluminum clamping plate. By constructing a three-dimensional fluid–solid coupling heat transfer model in the end of the synchronous condenser, and giving the basic assumptions and boundary conditions, the eddy current loss of the structure calculated by the three schemes is applied to the end region of the synchronous condenser as the heat source, and the velocity distribution of the cooling medium and the temperature distribution of each structure under the three different schemes are obtained. In order to verify the rationality of the numerical analysis model and the effectiveness of the calculation method, the temperature of the inner edge of the copper shield in the end of the synchronous condenser is measured, and the temperature calculation results are consistent with the temperature measurement results, which provides a theoretical basis for the electromagnetic design, structural optimization, ventilation and cooling of the synchronous condenser.

TSPEM Parameter Extraction Method and Its Applications in the Modeling of Planar Schottky Diode in THz Band

In this paper, a new method for the parameter extraction of Schottky barrier diode (SBD) is presented to eliminate the influence of parasitic parameters on the intrinsic capacitance-voltage (C-V) characteristics of the Schottky diodes at high frequencies. The method is divided into the de-embedding and parameter extraction, including six auxiliary configurations and, is referred tos as Two-step Six-configuration Parameter Extraction Method (TSPEM). Compared to the traditional junction capacitance extraction method, this method can extract the value of junction capacitance at higher frequencies with higher accuracy. At the same time, compared to the other de-embedding methods, this method shows better performance in de-embedding the contributions of parasitic structures from the transmission line measurements. The intrinsic junction capacitances obtained by this method and the three-dimensional (3-D) electromagnetic model are combined to form a diode simulation model, which accurately characterizes the capacitance characteristics of the SBD. It was verified with a 200 GHz double frequency multiplier, and the simulation results and measurement results showed good consistency.

Fast 3D time-domain airborne EM forward modeling using random under-sampling

The high sampling rate of airborne electromagnetic (AEM) systems can create huge data volumes, causing major challenges for three-dimensional (3D) electromagnetic modeling and inversions and constraining the practical applicability of AEM. Rapid and accurate forward modeling is the key to efficient 3D inversion. Here a new strategy for improving the efficiency of 3D time-domain AEM forward modeling is presented, based on compressed-sensing theory combined with the finite-volume method. A Poisson disk random under-sampling method was used to obtain random survey stations and to calculate AEM responses via the finite-volume method at these sampling stations. Coefficients from the curvelet transform with anisotropic characteristics for sparse expression were used to analyze the sparsity of AEM data, with the AEM responses of all survey stations being obtained by reconstruction. Key factors influencing the accuracy of the reconstruction are also discussed, including the sampling method and rate, the sparse transformation, and the noise. To test the effectiveness of the method, reconstructed results were compared with those from traditional schemes for forward modeling using all stations. Results indicate that the new strategy requires only 20% ~ 50% of samples to achieve high-precision reconstruction of the AEM signal even for complex geoelectrical structures, and the efficiency of 3D forward modeling can be enhanced by a factor of two to five, laying a foundation for fast AEM inversions of large datasets and complex models.

Optimized design of silver nanoparticles for broadband and high efficiency light trapping in thin film solar cells

This paper reports a high-efficiency approach to improve the photoelectric-conversion efficiency of thin-film solar cells by plasmonic scattering and local near-field amplification of silver nanoparticles. We employ a three-dimensional (3D) electromagnetic model and use the finite-difference time-domain (FDTD) and rigorously coupled-wave analysis methods to investigate the interaction of light with such a metallic particle. The numerical results show that the absorption and scattering spectra depend upon the properties of the embedded particles and the refractive index of the surrounding material. Strong redshifts and high-order modes are observed in the response spectrum with the increase of the particle size and the refractive index of the surrounding material. With an optimized design having [Formula: see text], [Formula: see text], and [Formula: see text] nm, the performance of cell device is improved over a broad spectral range. Moreover, some of the absorption, in the resonance region, is beyond the Yablonovitch limit. The corresponding light-generated photocurrent is increased from 14.2 mA/cm2 to 18.3 mA/cm2, with a 28.9% enhancement compared with conventional cells with antireflective coatings (ARCs).

Advanced three-dimensional electromagnetic modelling using a nested integral equation approach

SUMMARY Most of the existing 3-D electromagnetic (EM) modelling solvers based on the integral equation (IE) method exploit fast Fourier transform (FFT) to accelerate the matrix–vector multiplications. This in turn requires a laterally uniform discretization of the modelling domain. However, there is often a need for multiscale modelling and inversion, for instance, to properly account for the effects of non-uniform distant structures and, at the same time, to accurately model the effects from local anomalies. In such scenarios, the usage of laterally uniform grids leads to excessive computational loads, in terms of both memory and time. To alleviate this problem, we developed an efficient 3-D EM modelling tool based on a multinested IE approach. Within this approach, the IE modelling is first performed at a large domain and on a (laterally uniform) coarse grid, and then the results are refined in the region of interest by performing modelling at a smaller domain and on a (laterally uniform) denser grid. At the latter stage, the modelling results obtained at the previous stage are exploited. The lateral uniformity of the grids at each stage allows us to keep using the FFT for the acceleration of matrix–vector multiplications. An important novelty of the paper is the development of a ‘rim domain’ concept that further improves the performance of the multinested IE approach. We verify the developed tool on both idealized and realistic 3-D conductivity models, and demonstrate its efficiency and accuracy.

Electromechanical Coupling Parameter Identification for Flexible Conductor Wire Interconnection Considering Interaction Effect in Microwave Circuits

With the huge requirement of high frequency, multi-function and high reliability, the quality of microwave circuit interconnection has become an important factor that significantly affects the improvement of microwave electronic system performance. This paper has presented an identification method for flexible conductor wire interconnection (FCWI) electromechanical coupling parameters in microwave circuits with the consideration of their interaction effect. First, a parametric characterization cascade function has been proposed to design the FCWI, and consequently, a three-dimensional electromagnetic structure model of FCWI has been developed and verified. In order to identify the electromechanical coupling parameters of the flexible interconnection considering the interaction effect effectively, this paper has used the range multi-objective function to select the optimal level of the configuration parameter of the flexible interconnection that affects the signal transmission loss. Based on the variance analysis and range analysis of the experimental results, the comprehensive judgment criterion of electromechanical coupling parameters of flexible interconnection can be defined, and therefore, the calculation of electromechanical coupling degree can be derived and the electromechanical coupling property identification of flexible interconnection has been obtained. An example has been used afterwards to verify the accuracy of the proposed method. The method proposed in this paper can be a promising tool for microwave circuit comprehensive design and the optimization of its interconnection, considering both mechanical reliability and electrical performance.

Three-Dimensional Analytical Modeling of an Eddy-Current-Based Non-Contact Speed Sensor

This paper presents a computationally efficient, three-dimensional electromagnetic model for eddy-current-based speed sensors featuring an injection coil, two or more pick-up coils and a magnetic yoke. The superposition of incident and reflected fields, which was adopted in previous works, is replaced by a direct formulation; and Maxwell's equations are solved for the magnetic flux density vector, rather than involving a higher-order vector potential. The injected current is accounted for in the boundary conditions, and special attention is given to the modeling of the in-plane spreading of the coils by deriving coil-linkage functions. The magnetic field and eddy current distributions in the whole problem space is obtained by algebraically solving a 12-by-12 linear equation system. Results of the model are compared to experimental results from earlier publications for verifying the validity of the models. Even though derived primarily with the eddy-current-based speed sensing application in mind, the analysis presented in this paper can potentially contribute to various other eddy-current-based applications such as non-destructive testing, where probes with a magnetic yoke are utilized.

Исследование параметров процесса электронно-волнового взаимодействия в двухзазорном фотонно-кристаллическом резонаторе низковольтного двуствольного многолучевого клистрона Х-диапазона.

This paper presents the results of comparing data from three-dimensional electromagnetic modeling of two designs of double-gap photonic crystal resonators of a two-barrel multi-beam klystron operating in the X-band at an accelerating voltage of 3.6 kV. These resonators are designed to operate on the main π-type oscillation with an output power level of about 2 kW. They are characterized by different profiles of the beam-let tubes. Each of the beam-let tubes in these structures contains 19 beam channels arranged in linear rows. The results of optimization of the complex of electronic and electro-dynamic parameters are presented. The optimal parameters and designs of resonant systems are found, which make it possible to significantly reduce the degree of inhomogeneity of the effective characteristic resistance in the interaction space.

Development of 340-GHz Transceiver Front End Based on GaAs Monolithic Integration Technology for THz Active Imaging Array

Frequency multipliers and mixers based on Schottky barrier diodes (SBDs) are widely used in terahertz (THz) imaging applications. However, they still face obstacles, such as poor performance consistency caused by discrete flip-chip diodes, as well as low efficiency and large receiving noise temperature. It is very hard to meet the requirement of multiple channels in THz imaging array. In order to solve this problem, 12-μm-thick gallium arsenide (GaAs) monolithic integrated technology was adopted. In the process, the diode chip shared the same GaAs substrate with the transmission line, and the diode’s pads were seamlessly connected to the transmission line without using silver glue. A three-dimensional (3D) electromagnetic (EM) model of the diode chip was established in Ansys High Frequency Structure Simulator (HFSS) to accurately characterize the parasitic parameters. Based on the model, by quantitatively analyzing the influence of the surface channel width and the diode anode junction area on the best efficiency, the final parameters and dimensions of the diode were further optimized and determined. Finally, three 0.34 THz triplers and subharmonic mixers (SHMs) were manufactured, assembled, and measured for demonstration, all of which comprised a waveguide housing, a GaAs circuit integrated with diodes, and other external connectors. Experimental results show that all the triplers and SHMs had great performance consistency. Typically, when the input power was 100 mW, the output power of the THz tripler was greater than 1 mW in the frequency range of 324 GHz to 352 GHz, and a peak efficiency of 6.8% was achieved at 338 GHz. The THz SHM exhibited quite a low double sideband (DSB) noise temperature of 900~1500 K and a DSB conversion loss of 6.9~9 dB over the frequency range of 325~352 GHz. It is indicated that the GaAs monolithic integrated process, diodes modeling, and circuits simulation method in this paper provide an effective way to design THz frequency multiplier and mixer circuits.

Modeling of electromagnetically excited noise and vibration of induction motor

For electric vehicles, acoustic noise of traction motor excited by electromagnetic force is one of the main sources of noise, especially when automobiles are driven at low speed where noise from other sources are comparatively low. To analyze the characteristics of the noise and propose noise reduction suggestions, an accurate noise prediction model is needed. In this paper, a multi-physics model to predict the electromagnetic force excited acoustic noise of induction motor is presented. First, a three-dimensional (3-D) transient electromagnetic model of the motor was established using finite-element method (FEM). The uneven distributed time-varying magnetic force was calculated, and the current harmonics due to pulse width modulation (PWM) supply were considered. Then, a structural model was built, in which the anisotropy characteristic of silicon sheets stacked stator core, as well as the influence of windings, were considered through the assignment of orthotropic parameters to the stator core. Through mesh mapping, the FEM calculated magnetic force was transferred onto the structural model and the forced vibration was calculated using mode superposition method. Base on that, the acoustic noise was further obtained using boundary-element method (BEM). Finally, the noise and vibration of the studied induction motor were tested in a semi-anechoic room. As the simulated results show a good accordance to the measured data, the accuracy of the model was verified.

Electromagnetic field simulation of large hollow reactor

The electromagnetic interference problems of large-scale hollow reactor equipment are special and increasingly widespread. In order to thoroughly understand the electromagnetic interference of large hollow reactors on various equipment in a substation, a field test was performed near a SVC in a substation, and the electromagnetic field was explained from three aspects: the main ground network induced circulation, the secondary cable shield current, and the DC system ripple interference. Interference issues. Furthermore, a three-dimensional electromagnetic field simulation model was established for SVC and nearby areas, and the equivalence of the model was verified by comparing it with the spatial magnetic field and induced current on the site. Based on this analysis, the electromagnetic interference improvement and the effect of inductance value changes at different reactor heights were analyzed. The results show that, during normal operation of large hollow reactors, the electromagnetic interference between the nearby grounding system and the DC system has approached or exceeded its rated operating conditions. In the design, attention should be paid to the spatial location of the reactor and the ground network, the control room and the secondary screen cabinet.

Interior Ballistic Characteristics of Electromagnetic Rail Launcher Considering the Dynamic Characteristics of Real Launcher

In this article, we have presented a three-dimensional transient electromagnetic (EM) force calculation model of the electromagnetic rail launcher (EMRL), which could quickly calculate the transient EM force of the armature and the rail through combining the finite-element method with experiment and proposed the model of structural stiffness nonlinearity of EMRL. To study the interior ballistic characteristics of the EMRL, through the self-programming and the development of commercial finite-element software for the second time, the article presents the first time that an interior ballistic simulation model (IBSM) of the EMRL with EM and structural coupling considering the structural stiffness nonlinearity of EMRL. The correction function is proposed to improve the prediction accuracy of armature dynamic parameters by IBSM and the calculation errors of displacement of IBSM can be guaranteed not to exceed 1% compared with the test results of magnetic probes array. A strain test platform with a demodulation frequency of 8000 Hz was established to verify the IBSM's ability to calculate dynamic characteristics of the armature and the rail. After considering the structural stiffness nonlinearity of EMRL, the simulation accuracy of IBSM has been greatly improved compared with that of linearity. The experimental test results show that the IBSM is ease of application and, meanwhile, performs satisfactorily in terms of high accuracy and low computation.