Two-dimensional simulation of conducted currents characteristics inelectrical discharges

In this paper, a simple general electrical discharges circuit model for electrical discharge current waveform simulation in overvoltaged air gaps is presented. A macroscopic circuital method of simulation utilizing the standard SPICE network simulator, based on a two-dimensional (2-D) nonlinear impedances network has been proposed. The structure of the simulation framework is designed to take into account the electrode geometries in a straightforward way. A study of conducted current waveform for different electrode geometries has been done. Experimental data have been used to validate the simulation results     

一种特殊结构高频高速材料PCB加工问题探讨

随着电子、通讯产业的飞速发展,高频、RF设计越来越广泛,PCB上越来越多的运用到高频材料来满足信号传输的要求。为了满足客户对信号完整性以及信号接收与屏蔽匹配性等的要求,在PCB设计上经常采用混压及设计盲槽等方式,来满足其信号传输速度和灵敏度,但给PCB制造带来了一些其它工艺问题。通过对PTFE材料+热塑性PP金属盲槽流胶、成型板边毛边等关键工艺问题进行探讨,提供一种简单可行的解决方案与同行共勉。     

Finite element modeling of electrode-skin contact impedance inelectrical impedance tomography

In electrical impedance tomography (EIT), the measured voltages are sensitive to electrode-skin contact impedance because the contact impedance and the current density through it are both high. Large electrodes were used to provide a more uniform current distribution and reduce the contact impedance. A large electrode differs from a point electrode in that it has shunting and edge effects that cannot be modeled by a single resistor. The finite-element method (FEM) was used to study the electric field distributions underneath an electrode, and three models were developed: a FEM model, a simplified FEM model, and a weighted load model. The FEM models considered both shunting and edge effects and closely matched the experimental measurements. It is concluded that FEM models of electrodes can be used to improve the performance of an electrical impedance tomography reconstruction algorithm     

Transient simulation of silicon devices and circuits

In this paper, we present an overview of the physical principles and numerical methods used to solve the coupled system of non-linear partial differential equations that model the transient behavior of silicon VLSI device structures. We also describe how the same techniques are applicable to circuit simulation. A composite linear multistep formula is introduced as the time-integration scheme. Newton-iterative methods are exploited to solve the nonlinear equations that arise at each time step. We also present a simple data structure for nonsymmetric matrices with symmetric nonzero structures that facilitates iterative or direct methods with substantial efficiency gains over other storage schemes. Several computational examples, including a CMOS latchup problem, are presented and discussed.     

Transient simulation of resonant cavity enhanced heterojunctionphotodiodes

The transient response of heterojunction photodiodes under pulse illumination has been simulated. By solving discretized time dependent drift-diffusion and Poisson equations, the local potential and carrier concentrations are computed at each time step. The device-level simulation is carried out by a circuit simulator in which localized carrier transport is modeled by circuit elements such as voltage controlled current sources, capacitors, and resistors. Results on conventional AlGaAs/GaAs and resonant cavity enhanced (RCE) GaAs/InGaAs heterojunction p-i-n photodiodes are presented. For a 10-μm×10-μm area detector, more than 40% bandwidth improvement along with a two-fold increase in the efficiency is predicted for RCE devices over optimized conventional photodiodes     

Influence of lamination parameters on mechanical properties of low temperature co-fired ceramic tapes

For the development of force sensors, manufactured in LTCC (low temperature co-fired ceramics) technology for musical wind instruments, the mechanical properties of laminated LTCC tapes were characterized. Since one layer of LTCC tape is not always fulfilling the requirements of the force sensor’s loading capacity, the influence of lamination parameters for different number of layers were investigated. The measurements were carried out with miniaturized (2 × 1 mm²) beam samples of four different LTCC tape materials, namely Heraeus AHT01-005, AHT08-047, CT707; and CeramTec GC. The results of the measurements can be used to determine the proper LTCC tape material, the lamination pressure and the number of layers to allow the development of customized force sensors, not only for musical wind instruments.     

层压叠板平整性研究

随着电子元器件向着微型化的方向发展,线路板BGA（球栅阵列）区域间距大小也从0.80 mm发展到0.40 mm,这要求更高的层压对位精度,文章通过研究层压芯板叠层与其受力的规律,在现有设备工艺条件下,把层压对位精度大幅提升至0.038 mm。     

A comparison of dissipated power and signal-to-noise ratios inelectrical and optical interconnects

A comparison between dissipated power and signal-to-noise ratios (SNR's) in electrical and optical interconnects is performed. It is shown that in the absence of amplification to logic voltage levels the electrical interconnection requires much lower signal powers. However, if the amplification in the receiver is included, comparable total power dissipation and SNR's result under the constraint of equal output voltage     

Transient latch-up: experimental analysis and device simulation

A set-up consisting of at least one pulse generator with baseline functionality was used for transient latch-up (TLU) investigations. Dependencies of the TLU sensitivity of test structures on the pulse width and the rise time have been analyzed. Device simulation could reproduce the tendencies and reveals the root cause for the dependencies. In a bipolar product, which is immune against static latch-up, transient latch-up could be triggered, showing clearly the importance of a TLU characterization and the capability of the set-up.     

Transient simulation of heterojunction photodiodes-part I:computational methods

A novel approach is presented for incorporating the transient solution of one-dimensional semiconductor drift-diffusion equations within a general circuit simulation tool. This approach allows simple representation of localized carrier transport models of simulated devices through equivalent circuit elements such as voltage controlled current sources and capacitors. It also lends itself to mixed-mode transient simulation of devices and circuits. The utility of the new simulation approach in state-of-the-art device design is demonstrated by the transient response analysis of a GaAs heterojunction p-i-n photodiode, and by the time-domain analysis of an integrated photoreceiver circuit     

硬脆性材料在磨削过程中的热瞬态仿真分析

硬脆性材料在磨削过程中的加工质量和效率成为目前制约硬脆性材料应用的主要问题之一,如何在加工工艺环节提高生产效率和加工质量成为亟待解决的问题,制约问题解决的主要原因是加工效率在很大程度上会引起加工质量变差,在提高加工效率的同时保证良好的加工质量极其困难。主要从影响加工质量的因素之一磨削温度入手,以硬脆性材料中的碳化硅、氧化铝为例,利用有限元分析软件对硬脆性材料的磨削过程进行热瞬态分析,分析了在不同的磨削加工参数(砂轮转速、磨削深度和工件速度)即不同加工效率时大口径碳化硅工件和氧化铝工件的最高温度及其变化曲线,并横向对比了氧化铝材料和碳化硅材料在同等磨削加工参数时的磨削热状态。针对性地研究了硬脆性材料在磨削加工过程中的一些特性,为硬脆性材料的加工工艺提供参考。     

Current control of permanent magnet synchronous machines.Experimental and simulation study

The control structure of a PWM (pulsewidth modulation) inverter-fed sinusoidal synchronous motor commonly includes two or three current control loops. Previous simulation studies have shown that the three-loop structure should be preferred: hence the neutral-point voltage can move freely. To obtain the same results with the two-loop structure, a more complex control variable limitation strategy is compulsory. However, the three-loop structure is very sensitive to imperfections in the control system (gain errors and offsets). Simulation and experimental results for both structures are compared and the influence of a neutral-point voltage (NPV) feedback loop to cancel homopolar errors in the three-loop structure is discussed     

Amplifying properties of bulk negative-resistance material

It is shown that a thin block amplifies on transmission but a thick block attenuates. A thick block amplifies by reflection, but this is a surface effect only. Both thin and thick blocks can generate oscillations, but in the latter, the bulk of the material does not contribute.     

Fault simulation on massively parallel SIMD machines algorithms,implementations and results

Two algorithms for fault simulation of combinational networks on massively parallel SIMD machines are presented. One algorithm uses a variant of the PPSFP [1] approach, while the other uses a mixture of parallel fault simulation [2] and PPSFP [1]. The algorithms have been implemented on the [Thinking Machines Corporation's] Connection Machine [3]. The second algorithm compares very favorably with published results for well known serial algorithms on the ISCAS benchmark circuits [4]. The results indicate that parallel processing could be a valuable tool for accelerating VLSI CAD applications.     

Transient simulation and optimization of InP/InGaAs unitraveling carrier photodetector

The transient photoresponse of a backside-illuminated InP/InGaAs uni-traveling carrier photodetector(UTC-PD) is simulated by a 2D drift-diffusion approach utilizing a commercial numerical device simulator(ATLAS).The effects of the epitaxial layer structure and device biasing are taken into account.The simulation results indicate that the absorption region has a critical effect on the photoresponse pulse,and an optimized epitaxial layer structure is given to achieve a fast response while maintaining a reason...     

IMPATT device simulation and properties

The purpose of this paper is to shed further light on the operating characteristics and limitations of IMPATT diodes, particularly those with Read or modified Read structures. This has been achieved by developing efficient and economical computer Programs which incorporate all of the important material parameters and doping profiles in an exact manner. These computer programs are then employed to study the properties of high-efficiency Si and GaAs structures. Some very interesting properties of these devices and the effects of material parameters and doping profiles on their performance are presented and discussed. This leads to a better understanding of these devices and their limitations. Preliminary calculations have also been carried out on an InP IMPATT diode and the results are presented.     

Transient modeling and simulation of a SMES coil and the powerelectronics interface

This paper presents the modeling and simulation results of a superconducting magnetic energy storage (SMES) system for power transmission applications. This is the largest SMES coil ever built for power utility applications and has the following unique design characteristics: 50 MW (96 MW peak), 100 MJ, 24 kV dc interface. As a consequence of the high-power and high-voltage interface, special care needs to be taken with overvoltages that can stress the insulation of the SMES coil, especially in its cryogenic operating environment. The transient overvoltages impressed on the SMES coil are the focus of this investigation. Suppression methods were also studied to minimize transients. The simulation is based on detailed coil and multiphase gate turn-off (GTO)-based chopper models. The study was performed to assist in the design of the SMES coil insulation, transient protection, and the power electronics specification and interface requirements     

磁耦数字隔离器瞬态共模抑制性能的电路仿真方法

为解决磁耦数字隔离器的瞬态共模抑制(CMTI)不能准确测试的问题,研究了磁耦合数字隔离器瞬态共模抑制的测试及耦合机理。对耦合电阻、电容两个耦合参数进行了仿真验证,对仿真得到的器件输出波形进行抓取与分析,说明了电路中不同测试条件对仿真结果的影响。以ADI公司的典型磁耦数字隔离器ADUM1200型为例,采用小电容大电阻模型模拟实际耦合,分析并且明确了耦合电容大小状态,验证磁耦合数字隔离器瞬态共模抑制仿真方法是否具有一定的有效性。     

Thermal properties of diamond/copper composite material

Thermal considerations are becoming increasingly important for the reliabilities of the electronics parts as the electronics technologies make continuous progress such as the higher output power of laser diodes or the higher level of integration of ICs. For this reason the desire for improving thermal properties of materials for electronics component parts is getting stronger and the material performance has become a critical design consideration for packages. To meet the demands for a high performance material for heat spreader materials and packages, a new composite material composed of diamond and copper was successfully manufactured under high pressure and high temperature. The effects of diamond particle sizes and the volume fractions of diamond on both thermal conductivity and the coefficient of thermal expansion (CTE) were investigated. The thermal conductivity of the composite material was dependent on both the particle size and the volume fraction of diamond, while the CTE was dependent only on the volume fraction of diamond. At the higher diamond volume fraction, the experimentally obtained thermal conductivities of the composite materials were above the theoretically expected values and the experimentally obtained CTE were between the two theoretical Kerner lines. This may be due to the fact that at the higher diamond volume fraction the diamond particles are closely packed to form bondings between each particle. The composite of diamond and copper have a potential for a heat spreading substrate with high performance and high reliability because not only its thermal conductivity is high but its coefficient of thermal expansion can be tailored according to a semiconductor material of electronics devices.     

Transient changes in material conductivity due to impact ionisation in a Gunn-effect domain

An interesting phenomenon is reported which occurs when a long sample of GaAs containing a high-field domain is subjected to an increased level of drive during part of it first cycle. Under such conditions there is produced locally, at the position where the domain is situated when the overdrive is applied, an increase in the free-carrier concentration, which then decays relatively slowly (approximately 1 ?s). The effect is very similar to that first observed by Owens and Kino and ascribed by them to the generation of a second stable domain while the first is in transit through the device.