Electromagnetic modeling of microstrip reflectarrays using scale changing technique

An efficient numerical technique called scale changing technique is applied here for the electromagnetic modeling of microstrip reflectarrays. Based on the partition of the array surface into further planar sub‐domains at various scale levels, this technique allows the computation of the equivalent multiport from the simple cascade of scale changing networks. Each network models accurately the electromagnetic coupling between the various sub‐domains, including the coupling between non‐identical cells in arrays. The high flexibility of the approach associated with advantages of the integral equation formulation renders this original technique powerful and rapid for designing antenna arrays. Because the computation of scale changing networks is mutually independent, processing and memory requirements can be reduced enormously by using multiple processing units. Copyright © 2012 John Wiley & Sons, Ltd.     

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     

Hybrid spatial‐spectral MoM analysis of microstrip structures

In this paper, a new hybrid method formulation to resolve the mixed potential integral equation in an efficient and a fast approach, which is based on a simultaneous formulation in both spatial and spectral domains, is proposed. The entries of the method of moments matrix are then given by the sum of two integrals. The first one is expressed in the spatial domain. This part is analytically evaluated after a development in Taylor series of the exponential terms in the function to integrate. The integrals expressed in the spectral domain have a finite range, and they are calculated using numerical integration. Then the convergence problem is avoided in this approach. A good agreement between the simulated and measured results has been achieved. Copyright © 2015 John Wiley & Sons, Ltd.     

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     

S波段宽频带微带正交模变换器

正交模变换器作为主要的馈电器件在天线的双极化馈电系统中起着重要的作用。本文结合天线的工作频带及馈电系统的尺寸限制,设计了微带结构S波段宽频带正交模变换器,采用宽带Marchand巴伦和功分器结构,在1.5:1的频带范围内实现了输入信号的功分和180°移相,测试结果表明,在2.6～3.95GHz频带范围内各端口的驻波比小于2.0,输出端口间的幅度不平度小于0.1dB,相位不平度为180±2°,插入损耗在0.5～0.6dB。此器件应用于双极化天线平衡馈电系统,对天线实现等幅反相馈电,取得了良好的效果。     

The method of lines for the analysis of composite‐metal lossy microstrip lines

A full‐wave analysis of the composite‐metal microstrip lines is presented. The effects of the composite metal to the loss of the microstrip lines are accurately investigated, which are often avoided by other methods. The metal layers of the microstrip lines are considered as lossy inhomogeneous layers. The effects of the thickness of the Au layer and Ti layer are given, respectively. And the reasons that lead to the differences between them are discussed for the first time by analyzing the longitudinal electric field on the strip. The results are compared with other published data. Copyright © 2010 John Wiley & Sons, Ltd.     

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     

一种宽频带微带线垂直过渡结构设计

针对微波多层电路的微带线垂直过渡问题,提出了一种新型的、适用于毫米波频段的微带线垂直过渡结构,通过微带线上的补偿结构实现了匹配设计,使得微波信号在微波多层结构中跨层传输.该过渡电路结构具有信号传输损耗小、频带宽,易于加工的特性,在微波电路设计方面具有较高的实用价值.将该微带线垂直过渡结构在三维电磁场仿真软件中进行了建模,并进行了实物加工和测试.实物测试结果表明,在0.5～38 GHz的频带范围内插入损耗小于2.7 dB(含两个K-2.92 mm接头及微带传输线损耗),回波损耗大于9 dB.     

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。     

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.     

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 analysis of abrupt heterojunction bipolar transistors

This paper presents a physical–mathematical model for abrupt heterojunction transistors and its solution using numerical methods with application to InP/InGaAs HBTs. The physical model is based on the combination of the drift–diffusion transport model in the bulk with thermionic emission and tunnelling transmission through the emitter–base interface. Fermi–Dirac statistics and bandgap narrowing distribution between the valence and conduction bands are considered in the model. A compact formulation is used that makes it easy to take into account other effects such as the non-parabolic nature of the bands or the presence of various subbands in the conduction process. The simulator has been implemented for distributed memory multicomputers, making use of the MPI message-passing standard library. In order to accelerate the solution process of the linear system, iterative methods with parallel incomplete factorization-based preconditioners have been used. © 1998 John Wiley & Sons, Ltd.     

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.     

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     

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。     

宽频带的微带等角螺旋天线设计

为了实现宽频带天线指定方向的高性能辐射,设计了一种宽频带的微带等角螺旋天线。为实现阻抗匹配,天线馈电部分设计了一种指数渐变式微带巴伦结构。经过实物测试参数,结果表明加入了指数渐变巴伦结构后天线实现了良好的阻抗匹配并具有良好的宽频带特性,其工作带宽为1.74～4.82 GHz,回波损耗最低达- 30 dB。同时设计了一个平底型金属反射腔用于反射背向电磁波,在保持宽频带工作特性的同时,使天线具有了良好的单向辐射特性,天线在整个工作频段内的增益均大于6 dB,与传统的螺旋天线相比,具有宽频、定向、高增益的特点,具有一定应用前景。