Benchmarking of GFET devices for amplifier application using multiscale simulation approach

Starting from advanced NEGF physical simulation of a 100 nm gate length Graphene FET, we attempt to use these results as a starting point to evaluate this technology for microwave circuit benchmarking. Using an improved compact model carefully adjusted on NEGF simulation data, in both DC and AC regime, we use this model to design a mmW amplifier at 140 GHz. In the first part of the design procedure, we use the ADS compact model for coplanar waveguide of passive elements. The complete design is then verified using electromagnetic FEM simulation which gives more reliable results at very high frequencies for passive elements and interconnections. This analysis has shown that unlike first GFET generations, impedance matching problems may be naturally solved with transistor performance improvements. Finally, the GFET device and circuit is compared to HEMT technologies and shows promising performances.     

A novel course on microwave monolithic integrated circuit design, theory, and characterization

A novel course conducted for the past three years at the National University of Singapore is described. The course design projects introduce students to microwave monolithic integrated circuit (MMIC) component and subsystem design and expose them to modern computer-aided design (CAD) tools, industry standard test equipment, and procedures. In addition, since the proposed topics are industry-collaborated research projects, students gain new enthusiasm for the circuit design and directly see the importance and relevance in the engineering field. In contrast to the available MMIC courses conducted in the other universities or organizations, these students are given the complete freedom to implement the hardware within a fixed time frame. Implementation of these MMIC circuitries using external foundries, such as United Monolithic Semi-conductor (UMS), Philips Microwave Limeil (PML), and Triquint, has proven to be highly motivational and educational and, eventually, has led to increased enrollments in other higher level electromagnetic and microwave circuit modules.     

Mass minimization and sensitivity analysis of high power modular multilevel converter

Optimal design and selection of passive components has been known as a challenging issue in the field of MMC converter especially in high power applications. Global optimization is an integrated optimization loop consisted of several sub-models such as circuit model, electromagnetic and thermal model, constraints, goal function and nonlinear solver. Global optimization algorithm is utilized to minimize the total converter volume regarding to the technical and manufacturing constraints. The most important factor to achieve the reliable optimization results is to employ the precise models. In this paper, several optimization algorithm with different level of complexity are proposed and developed to minimize the total MMC volume. The first model is consisted of a time-domain steady-state circuit model that determines the circuit value of passive components. Unlike the conventional model, the proposed circuit model does not neglect the switching frequency and saturation effect of arm inductance. The second model employs the circuit model in combination with the dimension and thermal model of arm inductance. Finally, a hybrid optimization algorithm is proposed which is consisted of an internal correction loop using finite element method to enhance the model accuracy. Also, a comprehensive sensitivity analysis has done to evaluate the total converter mass sensitivity against the different converter parameters and constraints.     

基于非均匀FDTD混合算法的微带电路电磁耦合分析

微带电路包含微带线以及电路元件等局部精细结构,采用传统的FDTD方法进行电磁波照射PCB板电磁耦合的全波模拟,因网格剖分得很细,导致网格量大,计算效率低下.将非均匀FDTD方法与多网格集总元件FDTD方法结合起来,形成一种新的FDTD混合算法,模拟了电磁脉冲对带有集总元件微带电路的电磁耦合,能够快速计算得到集总元件上耦合产生的瞬态电压和电流响应.通过与有限积分法软件的仿真结果进行对比,验证了该时域混合算法的正确性,并分析了不同电磁脉冲类型以及微带线线间距对微带电路电磁耦合的影响.     

Reduced‐cost microwave component modeling using space mapping‐enhanced electromagnetic‐based kriging surrogates

We present a versatile technique for constructing fast microwave component models at a low computational cost. Our modeling procedure consists of two stages: (i) kriging interpolation of coarsely discretized electromagnetic simulation data of the device under consideration and (ii) enhancing the kriging model by using space mapping and a limited amount of high‐fidelity electromagnetic simulation data. The use of coarse discretization data allows for low‐cost model generation, whereas space mapping is a convenient way of ensuring its accuracy. Our approach can be applied to almost any type of microwave device; it can also work with other types of nonsmooth or costly low‐fidelity models. The operation and performance of our methodology is demonstrated using a variety of microwave components, including a microstrip filter, a planar ultrawideband antenna, and a microstrip‐to‐coplanar waveguide transition. Copyright © 2012 John Wiley & Sons, Ltd.     

Electromagnetic simulation of some common balun structures

Baluns serve many applications in RF and microwave communications, radar, and instrumentation equipment. The word balun is an acronym for balanced-to-unbalanced converter, and the function is employed to change a single-ended signal, i.e., a signal that is referenced to ground, to a balanced signal with equal potentials with respect to ground but opposite polarity. These balun structures are employed in such common RF and. microwave components as mixers' antenna-feed networks, and frequency multipliers. In this paper some common balun structures are investigated using the electromagnetic simulation software package Microwave Office, available from Applied Wave Research. The Microwave Office design suite is an integrated software package that includes an object-oriented linear and nonlinear circuit simulator as well as a full-wave, electromagnetic analysis of planar, physical structures that may be imported within the circuit simulator.     

超高压发电机运行特性的分析与计算

本文运用电机和电磁场理论建立了发电机运行特性的数学模型,给出了有限元求解二维电磁场的方法。为满足运行特性的计算要求,将电机内电磁场的有限元计算与外部电路相结合,计算出了不同工况下超高压发电机的特性曲线,包括短路特性、空载特性、调整特性和外特性。通过和实验结果的对比,证明了数值仿真的正确性,从而为超高压发电机的实际应用提供了参考依据。     

基于FPGA微波炉控制器设计

该设计用VHDL语言在MAX4-PLUSⅡ软件平台上通过编译、模拟仿真,完成了微波炉控制功能,实现了微波炉的测试、时间设置、烹调计时、完成提示等设计,并对时钟分频作了一定的探讨。此设计采用了现场可编程逻辑器件FPGA的ASIC设计,由控制模块、装载模块、计时模块和显示模块四大模块组成,而且它可以将所有器件集成在一块芯片上,体积大大减小,且外围电路很简单,易于实现。     

Multi-port equivalencing of external systems for simulation ofswitching transients

A multi-port external system equivalent model to simulate switching transients is developed based on direct time domain techniques, as opposed to the currently available models based on frequency domain methods. The model comprises discrete-time filters, which are built using the external system's response at each of the M ports to a multisine excitation signal and solving a system identification problem. At each port, the filters obtained are converted into an equivalent Norton circuit consisting of M current sources (in parallel). A unique feature of the model is that it explicitly incorporates the travel time delay between the ports. The complete M-port model, having M decoupled equivalent Norton circuits, is easily integrated into the discrete-time representation of the study subsystem. The proposed model is validated by simulating the line energization and post-fault transients in a study subsystem connected at two ports to an external system     

Application of the short‐open calibration technique to vector finite element method for analysis of microwave circuits

A novel numerical de‐embedding scheme called the short‐open calibration (SOC) technique, in conjunction with the vector finite element method (FEM), has been developed to characterize two‐port network of arbitrarily shaped, three‐dimensional discontinuities in microwave circuits. This SOC technique is effectively implemented into the FEM for boundary truncation of the unbounded circuit structures. In such a manner, fast convergence of iterative solver for large‐sparse linear matrix equations from FEM is achieved. The SOC technique is used to remove parasitic effects brought by the approximation of the impressed voltage source and also the problem of resulting consistency between the two‐ and three‐dimensional simulations. Scattering parameters of discontinuous sections are constructed from the definition of port voltages and currents. Numerical solutions are well compared with those published in the available literatures. It is demonstrated that the features of the SOC technique are advantageous when combined with FEM for electromagnetic problems. Copyright © 2002 John Wiley & Sons, Ltd.     

Advanced microwave effective medium theory for two-component nonmagnetic metamaterials: fundamentals and antenna substrate application

A modification of effective medium theory for two-component nonmagnetic metal–dielectric metamaterials is developed for use in the microwave frequency range. The metamaterial is represented as an unbounded isotropic dielectric host material with periodically embedded nonmagnetic metallic inclusions of cylindrical or spherical shape. The effective electromagnetic response of the metamaterial is represented by the tensor of the effective relative permittivity and tensor of the effective relative permeability. The losses of the metamaterial are also evaluated in this study. A physical interpretation for the nature of the effective properties of such metamaterials is given. Analytical models of the proposed effective medium theory are benchmarked against numerical simulations using commercial electromagnetic software. Two compact microwave rectangular dual-band patch antennas on such metamaterial substrates are designed in this study.     

电磁阀电磁场有限元计算软件

针对电磁阀计算的手工演算程序和基于磁路方法的不足,根据工程需求情况,选择了简单、成熟的二维有限元法,提出了电磁阀的二维电磁场有限元计算模型,为利用已有的计算程序,对外施电压约束采取了迭代计算的处理方法。软件界面采用易于掌握的VB编程,计算结果的后处理则利用了Manab的强大功能。该方法有效地解决了常用的基于磁路方法无法处理涡流场问题,并减少了设计、开发的工作量。     

A symmetric lattice-based wideband wide phase range digital phase shifter topology

In this paper, a novel digital phase shifter topology that achieves wideband and wide phase range is proposed. Wide frequency band operation is accomplished employing symmetrical all-pass lattice structures. Compact phase shifter size is obtained utilizing the miniaturized microwave monolithic integrated circuit (MMIC) design implementation technology. Therefore, resulting phase shifter units are suitable for various communication systems such as radar and cellular communication smart antenna arrays. This paper provides complete design equations together with design algorithm for the selected phase shift and the center frequency. Design algorithm is developed on MatLab environment. The proposed phase shifting circuit is implemented employing the commercially available 0.18-μm silicon CMOS technology. The new phase shifter topology provides 0⁰ to 360⁰ phase shift range over X-band, even beyond.     

Research on an integrated electromagnetic auxiliary disc brake device for motor vehicle

In view of low chassis and limited space of small vehicles, this paper presents an integrated electromagnetic auxiliary disc brake device. The device is formed by an excitation winding and the main magnetic circuit, both of which are located on the structure of the conventional brake caliper. The excitation winding is powered synergistically with the antilock braking system. Based on the presented main magnetic circuit, we construct the physical model of the proposed system, analyze the working principle, electromagnetic braking power, and torque, and calculate electromagnetic braking torque with conventional algorithms. To calculate the eddy current and magnetic field distribution on the disc, using three‐dimensional finite element simulation method taking full account of the penetration depth and the marginal effect, we compare the electromagnetic braking torques obtained using the conventional algorithm and finite element simulation. Results show that the braking effect is effective and obvious, especially at medium and high speeds. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Complementary split rings resonators (CSRRs): Towards the miniaturization of microwave device design

In this paper, it is demonstrated that complementary split rings resonators (CSRRs), a new type of planar resonators recently introduced by some of the authors, are key elements for the miniaturization of microwave devices implemented in planar technology, such as filters and diplexers. These devices essentially consist on a host transmission medium (microstrip line) to which the CSRRs are electrically coupled, and additional microstructure in order to achieve the required device performance. From the analysis and numerical simulations of the equivalent circuit model of the basic device cell, as well as electromagnetic simulations of actual structures, it is confirmed that CSRRs are useful resonators for the synthesis of planar microwave filters where dimensions, out-of-band performance and bandwidth can be simultaneously optimized. The simultaneous fulfillment of these aspects is a relevant advantage of the proposed structures. The possibility to implement band pass filters with wide bandwidth and high performance, the small electrical size of CSRRs, as well as their potential applications in other microwave devices, make these particles of actual interest in microwave engineering.     

An integrated microelectromechanical microwave switch based on piezoelectric actuation

In the field of microwave applications, microelectromechanical systems (MEMS) are attractive devices in order to force miniaturization by on chip integration. Here, we describe the design, fabrication and testing of a silicon based micromachined switch using piezo-electrically actuated elements. The microwave circuit consists of a coplanar waveguide (CPW) design with two piezoelectric activated beams integrated between the middle line and the ground planes. During operation the beams short the CPW by two overhanging bridge contacts and therefore the transmission characteristics of the microwave circuit change. The CPW is realized by 3 µm thick electroplated copper to yield good transmission characteristics, whereas the clamped—clamped beams benefit from a 250 nm thin PZT film between 100 nm thin Pt electrodes on top of a SiO₂ layer. By the use of double side clamped beams awkward stress compensation of the piezoelectric stack is omitted. Instead the system relies on some initial mechanical stress. Measurements prove deflections of more than 13 µm for a 1400 µm long beam with operation voltages below 10 V. This is in good agreement with finite element simulations. The novel RF-MEMS is predicted to reach an isolation (in “on” state) of more than 20 dB up to 15 GHz.     

电网换相换流器整体化电磁暂态仿真模型及算法

现有的电磁暂态仿真算法能够准确刻画基于电网换相换流器的高压直流(LCC-HVDC)输电系统的运行特性,但计算量较大。为了提高LCC-HVDC输电系统的仿真效率,对现有常用的电网换相换流器电磁暂态仿真模型进行了简化,提出电网换相换流器整体化电磁暂态仿真模型与求解算法。整体化模型包含换流变压器与换流阀,换流变压器采用简化模型,换流阀采用理想开关模型,能够对换流器的电气网络结构进行简化。该算法将换流器电气网络拓扑结构分割为主网络与副网络,首先对主网络求解,然后根据得到的结果对副网络求解,最后更新当前仿真步长各换流阀的电流和电压。在PSModel仿真软件中对整体化电磁暂态仿真模型及算法进行了编程实现,并与PSCAD/EMTDC仿真结果进行对比,验证了其高效性与准确性。     

多绕组电力变压器内部短路稳态分析:（一）建模与仿真

电力变压器线圈之间的耦合特性使其内部短路故障的外部特性具有复杂性.为了正确设计和整定变压器内部故障的继电保护方案,必须逐个地针对每种变压器内部短路故障分布情况找到外部故障特征.文中提出了一种分析电力变压器内部短路故障的电路模型和分析方法,并以一台双绕组变压器为例,对线圈内部对地短路、匝间短路、相间短路分别进行了仿真计算,给出了外特性随故障类型和故障位置变化的规律.     

Noise performance of a preamplifier for high-speed optical receiver front-ends

This paper reports on an optical receiver employing a p-i-n diode and a GaAs HBT monolithic microwave integrated circuit (MMIC) distributed preamplifier combination. The design is the first to have a photodiode mounted directly on the MMIC chip. The p-i-n preamplifier displays a measured average equivalent input noise current density of 24 pA/Hz. Good agreement is obtained between the predicted and measured noise performance. The monolithic eight-stage distributed amplifier is implemented using Nortels GaAs HBT (fT = 70 GHz) process, and makes use of a coplanar waveguide regime having a large input impedance optimized for noise performance and bandwidth. The p-i-n photodiode employed is an InGaAs vertically illuminated structure, also from Nortel. While the voltage gain of the amplifier displays a 3 dB bandwidth extending to nearly 40 GHz, the bandwidth of the complete optical receiver is found to be only 22 GHz. Packaging effects are believed to be responsible for this shrinkage.