Crosstalk analysis between finite-length microstrip lines in neighborhood

If two transmission lines such as microstrip lines are set in the neighborhood, a coupling or crosstalk phenomenon may be generated between them. When the coupling level is low, the phenomenon can be considered as a coupling of external fields by one transmission line to the other transmission line; a set of nonhomogeneous differential equations with regard to a line voltage and current holds approximately. The fields can be obtained by estimating vector potentials of currents on the line section and the terminals in terms of a terminal voltage and current of the line concerned. Thus, a solution to the equations can be obtained in expression of a four-port network. Estimation of the coupling between microstrip lines is made by applying the terminal conditions to the expression. To confirm the theory, an experiment has been conducted; the experimental results are in good agreement with the theory. © 1998 Scripta Technica, Electr Eng Jpn, 123(2): 8–15, 1998     

FDTD analysis of finite-sized linear phased arrays of stacked microstrip antennas

Contents  The three-dimensional finite difference time domain (FDTD) algorithm is used to analyze finite-sized phased array antennas. Coaxially-fed, capacitively coupled stacked microstrip antennas are analyzed. A phase shift in the time domain is implemented to model the effects of scanning angle. A rigorous feed model, suitable for FDTD analysis with the perfectly matched layer (PML) is used. The S-parameters, from which input impedance and mutual coupling are evaluated, as well as other important indices are calculated and compared with measured results. Received: 7 September 2000     

基于有限元法的背腔微带贴片天线的散射研究

雷达散射截面(RCS)是目标天线的一个重要指标参数,雷达截面缩减就是控制和降低军用目标的雷达特征,迫使敌方电子探测系统和武器平台降低战斗效力,从而提高军用目标的突防能力和生存能力.因此,减小RCS一直是天线发展的重要方向.文中根据变分公式,计算新型背腔微带贴片天线的散射场.使用混合有限元边界积分法,将问题转化为一个矩阵方程的求解.通过分析不同的天线结构和不同的填充介质对天线RCS的影响,给出数值结果,从而看出这种方法的精确性和有效性.     

质子交换膜燃料电池三维性能数值仿真

采用CFDResearchCorporation(CFDRC)Ver .2 0 0 3软件进行模型的建立及数值求解。比较了不同流道设计对电池性能的影响。结果发现 :在低操作电压下 ,气体补充速度比反应速度慢 ,容易产生浓度极化 ;栅状流道的气体分布非常不均匀 ,也会有传质极限的现象发生。蛇行流道的气体分布较均匀 ,传质也较好 ,性能比栅状流道好     

An investigation of microstrip conductor loss

Microstrip conductor loss exhibits complicated behavior that is not generally recognized. Specifically, there are three frequency ranges of interest. At low frequency, current is uniform through the entire cross-section of the line, and the line behaves like a resistor. At medium frequency, the edge singularity forms. In this case, current concentrates on the edge of the line, increasing the resistance. At high frequency, the current splits into two sheets of current, one on top of the line, the other on the bottom of the line. Since microstrip dispersion causes the edge singularity to become larger and current to concentrate on the bottom side as frequency increases, the total resistance increases faster than the normally expected square root of frequency     

直流电机换向火花的数值分析

本文根据直流电机换向理论,给出了一种分析电机换向火花的方法。这种方法的基础是电机换向过程暂态电磁场的时步有限元法计算,其重点是采用磁场迭代法计算出实际的附加换向电流,通过直流电机火花因数的计算,可以把火花等级与换向性能分析直接联系起来。     

Numerical electromagnetic analysis of impulse voltage measuringsystems

The unit step response (USR) of lightning impulse voltage measuring systems is numerically calculated with the help of the Numerical Electromagnetic Code (NEC-2), which calculates the three-dimensional electromagnetic field around conducting wires. The accuracy of this analysis is proved satisfactory through comparison of the results of measurement with calculation. The advantage of this method is that the influence of the geometry of the circuit can automatically be calculated without evaluating stray capacitance in the system. Therefore, this method of analysis can be applied to the development of an impulse voltage divider, or in analyzing the influence of elements of a USR measuring circuit. The influence of the shield ring attached to a resistance divider, and of the vertical metal sheet in the IEC-recommended USR measuring circuit on the USR waveform is analyzed as an example     

Numerical analysis of a DAR IMPATT diode

The analysis and optimization of the n ⁺ pvnp ⁺ avalanche diode structure that includes two avalanche regions have been realized on basis of the nonlinear model and special optimization procedure. The admittance and energy characteristics of the DAR diode were analyzed in very wide frequency band from 30 up to 360 GHz. Output power level was optimized for the second frequency band near the 220 GHz.     

光伏窗太阳能发电量的数值分析

利用实验数据验证了内嵌于建筑能量与环境综合模拟软件ESP-r的光伏窗太阳能发电的数学模型,利用验证过的数学模型,以办公建筑为研究对象,将中国几个不同纬度、不同太阳辐射强度的城市气候数据作为气候文件,对不同朝向光伏外窗的太阳能发电进行了数值模拟,得到了太阳能发电量与光伏窗朝向、季节、建筑所处纬度之间的关系.     

微带线不连续性辐射研究

分析了微带不连续性辐射的基本原理,采用FDTD方法和坡印廷矢量法相结合,研究了拐角、短截线等微带不连续性的辐射特性,对微带不连续性和微带贴片天线的辐射机理进行了比较。仿真结果显示,不连续性表面波和空间波辐射损耗随着频率的增加而显著增大,低频时辐射损耗以空间波辐射为主,高频时表面波辐射有超过空间波的趋势。微带短截线的谐振辐射特性与矩形微带贴片天线类似,只是在辐射强度上有较大的差别。     

宽频带任意比功分器的微带线实现

本文给出了一种用多枝节匹配来设计宽频带上不等比功分器的方法。在此基础上讨论了用微带线来实现这种形式功分器的方法和计算机仿真验证步骤。最后给出了以微带线形式在0.6GHz-1.4GHz频带上实现这一类3dB宽频带功分器的设计和计算机仿真验证步骤,仿真结果证明了这种设计方法的有效性和可行性。     

Genetic algorithm optimization of broadband microstrip antenna

Genetic algorithm (GA) is utilized to design microstrip patch antenna shapes for broad bandwidth. A new project based on GA and high frequency simulation software (HFSS) is proposed to perform optimization. Reasonable agreement between simulated results and measured results of the GA-optimized design is obtained. The optimized patch design exhibits a three-fold enhancement in bandwidth when contrasted with a standard square microstrip antenna, showing the validity of this project.     

S型缝隙毫米波微带天线

提出了一种加载S型缝隙的方形切角毫米波微带天线。该天线的辐射贴片采用方形切角,在贴片中央进行非对称S型缝隙开槽,实现了双频点圆极化。在接地板上进行阶跃型缝隙开槽,改变了微带天线的辐射特性及阻抗特性。同时采用加载调谐支节的耦合馈电方式,实现了微带贴片天线频带的展宽。     

Numerical analysis of electrohydrodynamics in a round pipe

A numerical analysis on electrohydrodynamics (EHD) in a round pipe is presented based on the PISO (pressure-implicit with splitting of operators) scheme under a periodic boundary condition. The numerical results show that a vortex ring is generated between the electrodes due to the nonuniform distribution of velocity and charge density during the starting process. The increase of value of T (the ratio of electric stress to viscous stress) affects the developing process because of the unsteadiness repulsion among the charges will increase with T during this period. When the flow field finally reaches steady state, it becomes a fully developed pipe flow. The steady outlet velocity is in direct proportion to the square of the voltage imposed between electrodes. The spatial distribution of the pressure is similar to that of the electric potential between the electrodes because of the direct analogy between potential and pressure.     

Numerical performance analysis of semiconductor coatings for coronasuppression

Corona is initiated in high field regions. To suppress corona or to increase the corona inception voltage in HV insulators or bushings, suitable semiconductor coatings, able to relieve high electric fields, are commonly used. The choice of appropriate materials to be used for the most effective corona suppression is typically made on the basis of expensive and time consuming trial and error tests or on the basis of approximate theoretical analysis. In this paper a guideline, based on the adoption of a suitable numerical method, is provided in order to lead to the optimal choice of the electrical characteristics of semiconductor materials for the most effective corona suppression     

甲醇重整制氢系统的数值模拟与分析

利用化工流程模拟软件AspenPlus[1]建立了甲醇重整制氢系统模型,并通过自行设计的实验系统进行了验证。结果表明,该模型能够较准确地预测重整系统出口状态下的氢气体积含量,并且可用于分析操作参数对重整制氢系统性能的影响。另外,基于能量守恒原理,对系统的经济性进行了分析。研究结论可用于指导甲醇重整制氢系统重整方式的选择,工作参数选择及优化设计。     

Numerical thermal analysis of fuses for power semiconductors

This paper describes a simplified thermal model of fast fuse suitable for power electronic circuits, especially for power rectifiers. This model has been validated with a single-phase rectifier and can be used to analyse the thermal behaviour of fast fuses during transient conditions. The procedure for achieving the simplified model is also presented. The parameters’ model include all the necessary information about the fast fuse geometry, its components’ materials and heat dissipation to the surrounding area. On the basis of this simplified model, the transient thermal behaviour of fast fuse can be estimated for complex power electronic circuit with accuracy and speed.