A comparison between the equivalent circuit model and moment method to analyze FSS

Shared‐aperture antenna arrays are attractive for 5G base stations, owing to their compact size and multi‐band frequency coverage. Decoupling surfaces are effective for suppressing crossband mutual coupling. However, their designs typically rely on full‐wave simulations of scattering parameters, which may not ensure a good radiation performance and is time‐consuming. A systematic methodology based on the hybrid equivalent circuit model and plane wave spectrum method is proposed for decoupling surface designs. The decoupling surface is represented by its equivalent circuit and the spectral expression converts the electromagnetic field into a circuit problem. Both the scattering parameter and radiation pattern can be solved with the circuit, offering an efficient design method that ensures consistent radiation patterns between the model and full‐wave simulations. A double‐layer decoupling surface with wide stopbands, high transmission property, and sharp roll‐off transition was realised. Furthermore, to reduce the overall profile height, the reflection phase of the decoupling surface was tuned. A triple‐band shared‐aperture base station antenna array was developed. Simulated and measured results demonstrate the array works properly in the 0.69–0.96 GHz, 1.7–2.7 GHz, and 3.3–3.8 GHz frequency bands with stable radiation patterns, and crossband mutual coupling is well suppressed, validating the effectiveness of the proposed methodology.

In design process of power transformer for the insulation of the vertical structure, the calculation of winding wave process is an important reference. This article describes the simplified equivalent circuit model and calculation method of wave process. Based on Matlab, the computer program of power transformer winding wave process is written, and both electric potential and gradient distribution of transformer winding is calculated, in order to find insulation weak point. Calculation result is validated by comparing with test value or by an example of the product.

This paper proposed a novel segmented equivalent circuit modeling method of TSV, which is the key technology of 3D-IC. The electrical parameters of TSV are extracted firstly and then used to finish the equivalent circuit of single TSV and double TSVs structure. The segmented modeling method is realized by segmenting the TSV structure into three parts, namely the top, middle and bottom of the TSV structure. The electrical parameters of the middle part are obtained by analytical formulas, while the parameters of the top and bottom parts are obtained by 3D field solver more accurately. The equivalent circuit of TSV got by this novel method is more accurate compared with the general method. The simulation results of S parameter of the equivalent circuit model are matched well with the simulation results of HFSS while the simulation time is much shorter, and the simulation results show that the equivalent model can reflect the transmission characteristics of TSV accurately.

An analytical model is presented in this paper for a coupled cavity slow-wave structure (CCSWS) with double in-line slots, also known as the “Chodorow” structure. Under matching boundary conditions in conjunction with Green’s function techniques and moment method (MOM), the formulae for discussing the high frequency characteristics of the SWS, including dispersion and interaction impedance, are given. The frequency characteristics for an X band Chodorow structure are calculated using these formulae, Ansoft HFSS code and equivalent circuit model. Results show that the dispersion and interaction impedance obtained with the formulae are in good agreement with those calculated by Ansoft HFSS code, while its calculation rate is more rapid than that with the code, and its calculation precision is higher than that with equivalent circuit method, which is helpful for the engineering design.

Line start permanent magnet synchronous motors (LS-PMSM) are energy-efficient synchronous motors that can start asynchronously due to a squirrel cage in the rotor. The drawback, however, with this motor type is the chance of failure to synchronize after start-up. To identify the problem, and the stable operation limits, the synchronization at various parameter combinations is investigated. For accurate knowledge of the operation limits to assure synchronization with the utility grid, an accurate classification of parameter combinations is needed. As for this, many simulations have to be executed, a rapid evaluation method is indispensable. To simulate the dynamic behavior in the time domain, several modeling methods exist. In this paper, a discussion is held with respect to different modeling methods. In order to include spatial factors and magnetic nonlinearities, on the one hand, and to restrict the computation time on the other hand, a magnetic equivalent circuit (MEC) modeling method is developed. In order to accelerate numerical convergence, a mesh-based analysis method is applied. The novelty in this paper is the implementation of support vector machine (SVM) to classify the results of simulations at various parameter combinations into successful or unsuccessful synchronization, in order to define the synchronization capability limits. It is explained how these techniques can benefit the simulation time and the evaluation process. The results of the MEC modeling correspond to those obtained with finite element analysis (FEA), despite the reduced computation time. In addition, simulation results obtained with MEC modeling are experimentally validated.

The coupled thermo-mechanical field analysis of TSV interposer is a typical multiscale simulation problem, it faces great difficulty of numerous TSVs and complex micro structures. To get balance between accuracy and efficiency, global/local finite element (GLFE) strategy often be used in the multiscale coupled field analysis. In steps of the GLFE strategy, global coarse mesh evaluation plays the key role and the mesh model of this step determines the calculation effect. Currently, finite element modeling for TSV interposer is mostly finished manually with the help of comprehensive finite element software. To improve the laboriously and time-consuming manual modeling procedures, a finite element modeling method specifically oriented for TSV interposer is proposed. The modeling method is an imitation of fabrication procedures, it consists of layer based geometry modeling, parametric meshing, automatic contact detection, automatic boundary condition building and automatic loading processes. TSV discretization methods affected the quality of the mesh model directly, 4 kinds of TSV discretization methods are proposed in this paper, namely: Fine Mesh Method, Single Point Method, Single Mesh Method and Equivalent Model Method, they reach different equilibrium points on model size and accuracy, feeding need of different simulation scenarios. As the implementation of the modeling method a SAAS cloud system is built, the system run in B/S mode and it can make the modeling procedures easier. Finally, with the help of the modeling method and the SAAS cloud system, a thermo-mechanical analysis of TSV interposer based 2.5D RF module is done. The comparison of the time consumption and results with comprehensive finite element software ANSYS Workbench indicates that the cloud system can get great efficiency with enough accuracy.

Mode matching method and equivalent circuit method are the two main waveguide filter design methods. The mode matching method have well calculation accuracy, especially when the waveguide size is relatively large compared with operating wavelength, but this method does not provide physical insights, therefore traditional filter design theories and methods cannot be applied. However, in most of the engineering applications, the size of the waveguide filter is not large to prevent higher-order modes from affecting the performance of the entire system. Under this condition, the equivalent circuit, providing physical insight, and efficient with acceptable accuracy, becomes the preferred method when designing waveguide filters. Unfortunately, the equivalent circuit of the waveguide filter that has been established so far is realized by connecting multiple Y-parameter elements with transmission lines. This method does not show the internal structure of the waveguide filter cavity, so in fact it cannot provide physical insight. Moreover, compared with the mode matching method, the reduction of the calculation amount is also very limited. This paper gives the complete equivalent circuit model of the waveguide filter with analytical expressions for the first time. The establishing process of equivalent circuit represents by capacitors and inductors are given in detail by taking circular waveguide filter excited by TM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</inf> mode as an example. The effectiveness of the proposed method is verified by finite element simulations and experiments.

Modeling of a millimeter wave planar Schottky diode using both improved equivalent circuit model and 3D-EM model

Bond behavior between multi-strand tendons and surrounding grout: Interface equivalent modeling method

A 2.4 GHz range surface acoustic wave (SAW)-based pressure sensor was fabricated on a 41/spl deg/ YX LiNbO/sub 3/ substrate for a mechanical compression force measurement. For the first time, fabricated sensors were characterised wirelessly using the network analyser. Electron beam lithography was used for fine line patterning. Metal ground shielding was covered all over the cavity to reduce a coupling loss of the propagating SAW to the surrounding atmosphere. Equivalent circuit model and finite element methods were used to determine optimal design parameters. The three sharp peaks were obtained from three reflectors. As a mechanical force was applied to the piezoelectric diaphragm, the diaphragm was bended, resulting in the phase shifts of the reflected peaks. Obtained sensitivity was 2.9/spl deg//kPa.

To effectively study the dynamics of power systems with large-scale wind farms (WFs), an equivalent model needs to be developed. It is well known that back-to-back converters and their controllers are important for the dynamic responses of the wind turbine (WT) under disturbances. However, the detailed structure and parameters of the back-to-back converters and their controllers are usually unknown to power grid operators. Hence, it is difficult to build an accurate equivalent model for the WF using the component model-based equivalent modeling method. In this paper, a transfer function based equivalent modeling method for the WF is proposed. During modeling, the detailed structure and parameters of the WF are not required. The objective of the method is reproducing the output dynamics of the WF under the variation of the wind speed and power grid faults. A decoupled parameter-estimation strategy is also developed to estimate the parameters of the equivalent model. A WF that consists of 16 WTs is used to test the proposed equivalent model. Additionally, the proposed equivalent modeling method is applied to build the equivalent model for a real WF in Northwest China. The effectiveness of the proposed method is validated by the real measurement data.

In this paper, a new equivalent circuit and modeling method for a uniform arrowhead-defected-ground-structure slot are proposed for the design of a DGS-cascade lowpass or bandstop filter. The effect of the geometry of a defected ground structure (DGS) on the performance of the cascaded-LPF or BSF and the effect of the cascaded-method is also examined. The proposed LPF or BSF based on pi-arrowhead DGS slot is 70% shorter than a conventional LPF. Only three cells of the proposed structure are necessary for a 15-dB stopband at 6 GHz. The validity of the proposed equivalent circuit model is established by comparing their response to the full-wave EM simulation of several structures. Measured results show that the new designs exhibit better performance by suppressing ripples and enlarging stopband bandwidth

Technology is advancing daily and it has impacted almost every aspect of our life today. We show that growth in the number of miniaturized communications systems that are covering different wireless services capable of achieving a wide frequency range. These systems require reconfigurable antenna systems to meet their performance needs. A single reconfigurable antenna makes it possible to reach all the desired frequencies so there is no need for complicated wideband and multiband antenna solutions. In this context, the present work aims to propose a detailed study of a reconfigurable antenna commanded by a PIN diode as a switching component. Our study is essentially composed of two parts; the first one is a study of gap discontinuity in the antenna aiming to propose a good approximation of PIN diodes dimensions ensuring the switch operation and the second part is the analysis of a frequency reconfigurable antenna controlled by the PIN diode of appropriate dimensions. The proposed structures are modeled by a new rigorous formulation combining the moment method and generalized equivalent circuit's methods (MoM-GEC). The input impedance, the reflection parameter ( S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ) and the current distribution density obtained with this method are presented and discussed.

Transformer is one of the most essential equipment in the electric systems, which plays the role of electromagnetic energy conversion and transmission. Statistically, winding deformation produced by huge and dynamical electromagnetic forces under short-circuit fault is one of the most serious problem which may make the transformer fault. In practice, the transformer is like to be a black-box. It is very hard to diagnose the winding deformation accurately by using the present approaches [1], such as the Correlation Coefficient Method (CCM). During the frequency response analysis (FRA) studies, the equivalent circuit model of transformer is usually used to solve the forward problem [2], as shown in Fig. 1, but how to determine the increments of equivalent electromagnetic parameters, such as the inductance, capacitance and resistance, is an important inverse problem. The diagnosis of winding deformation for transformer is a typical inverse problem. This paper proposes a novel method for diagnosing winding deformation in transformer more accurately and intuitively, based on Equivalent Circuit Model Updating (ECMU) at a high-frequency range (10Hz ~10MHz). In fact, the ECMUM is an inverse method to determine the electromagnetic parameters states under FRA excitation. It is a challenge to find a unique and accurate solution during inverse updating operation. In our study, thanks to the ECMU and frequency selection, the certainty and qualitative relationship between FRA error data and electromagnetic parameter increments of transformer equivalent circuit model can be determined easily. Also, the maximum approximate unique solution can be obtained exactly.

The rapid development of battery energy storage technology has provided a new solution for integrating large scale renewable power generation; however, the accurate model of battery energy storage system (BESS) in multi-time scales has not been developed yet. The BESS model consists of battery model, power electronics interface model and controller model. There are still no certain math expressions about the parameters of battery model, the model of power electronics and controller are also different in different applications. Considering different applications in power system, the multi-time scales model of BESS should be established to take account of the transient, steady and dynamic state. In this paper, an equivalent modeling method of BESS was developed. First, the different equivalent circuit models of battery were summarized, according to the comparison, the thevenin equivalent circuit model was supposed as the effective model for power system application. So, taking into account the relations between the parameters such as current, internal resistance, and state of charge (SOC), the battery parameters were fitted based on experimental date. Then, the power electronics interface model including DC/AC and DC/DC converter were introduced, and the control method with different operations were proposed. Finally, the BESS model were built and verified on the platform of BESS experiment. The results show that the model can represent the multi-state characteristics of battery and has quick response.