基于测量S参数的有源器件FDTD建模方法

该文提出了一种新的基于测量s参数的有源器件FDTD建模方法。该方法借助于矢量拟合技术(VF)和分段递推卷积技术(PLRC)完成建模,不必知道器件的等效电路,并保留了传统FDTD算法显式差分的特点,得到了一般性的FDTD迭代公式。另外,该方法的数据处理过程主要在所需频段内操作,避免了传统方法中由直接逆傅里叶变换所引起的非因果时域误差。对于全波分析包含实际有源器件的微波电路具有一定的实用价值。     

微波组件设计中的腔体效应

微波有源模块因为腔体的原因造成自激和传输参数的恶化一直是微波电路设计的难点之一.目前没有完整的理论来支持微波有源电路模块的腔体设计.本文从理论上分析了以微带线作为主要微波传输载体的微波组件的腔体效应,借助电磁场仿真工具HFSS对装有微带电路的微波组件进行了仿真.根据仿真结果设计X波段微波组件,并对S参数进行了测试,测试...     

网络展开图与符号网络分析

采用封闭网络模型,按照电路元件参数,采用开路、短路和着色运算,将电路图逐层分解,得到网络展开图.给出网络展开图的概念和运算规则,指出网络展开图中从根到末稍每个路径的值就是网络行列式展开式中的一个有效项,从而由网络展开图得到符号网络函数.该方法直接对电路图进行运算,不需要建立任何形式的电路方程和行列式,适用于一般的有源电路,而且能生成各种类型的网络函数.     

利用电流传送器设计微波有源电感

本文借鉴低频电路中用电流传送器综合低频有源电感的思路提出一种设计微波有源电感的新方法.根据这种方法.获得了八种微波有源电感的电路结构.并且实际设计制作了一个小型化低损耗的芯片有源电感.这种方法非常适合于设计MMIC微波有源电感或有源滤波器.     

对一道电路习题的思考

近几年来,在我校无线电系的电路课教学中,较早地引入了运算放大器理想电路模型,并在后面的有关章节中讲授了“含运算放大器的电阻电路的分析”,以及“含运算放大器的阻容电路及其网络函数”.对于一般的高阶有源电路,以二阶电路为例,采用了解电路的通用方法(节点法)进行分析.在课外训练环节上,考虑学生近期刚做完“交流电桥”的实验研究,我们布置了电路如图1所示的这样一道习题.     

用Cauer网络综合技术提取PBG等效电路模型

本文从全波场分析结果出发,提取了PBG单元结构的集总等效有耗电路模型。对每个PBG单元采用时域有限差分（FDTD）方法进行全波分析,然后用Cauer部分分式展开形式和网络综合技术,由全波分析结果提取等效有损电路模型参数,并将提取获得的PBG单元等儿电路模型嵌入HP－ADS软件对整个PBG结构进行SPICE分析,得到的散射参量和全波分析结果比较基本一致,证明了该模型的准确性。这种模型可以嵌入电路分析和设计软件中,用来对应用了PBG结构的无源和有源电路进行优化与设计。     

运用负反馈模型分析实际运算放大器电路

对工作在深度负反馈状态的运算放大器电路,常采用虚短虚断技术得出的理想参数代替实际参数。这种方法忽略了理想模型与实际电路之间的误差。为了知道这个误差给实际运算放大器电路带来的影响,通过将运算放大器电路等效成对应的负反馈系统模型,并计算反馈系数,运用该模型的等效参数来更加近似的分析实际运算放大器电路闭环参数及其稳定性。     

四端网络S、Y、Z、G、H参数换算的TI-59程序

四端网络的特性可用S、Y、Z、G、H(或A.T)等任一种参数描述,不同型式参数间具有一定的换算关系.对于微波四端网络,采用S参数表示是方便的,因为它较易于与具有指定输入和输出线特性阻抗的待测四端器件在微波频率下的入射波和反射波测量结果联系起来;另一方面,在微波频率,导纳和阻抗测量要求实现器件输入(或输出)端口的绝对短路和开路,直接精确测定Y、Z、G、H参数是困难的.尽管如此,工程师们仍常常要求知道网络的惯用参数,也就是需要对网络的各种参数表示进行换算,本文给出的TI-59程序将有助于他们作出S、Y、Z、G、H参数的相互转换.     

微带线匹配负载的FDTD建模

提出了一种有效的微带线端接匹配负载的FDTD模型.该模型将微带线的有效阻抗作为匹配负载电阻,然后按适当的比例分布到端接面的网格中.和传统的FDTD方法相比, 该模型可以有效地减少负载的反射,改善负载的匹配特性,并且通过一次FDTD计算就可以得到电路的S-参数.     

用线性变换运算电流放大器(TOCA)的电流处理电路

本文描述最近引入的新的多功能有源器件—线性变换运算电流放大器的基本性质以及它在电流处理电路中的应用.     

Time-domain fields exterior to a two-dimensional FDTD space

A transformation algorithm for the near-zone and far-zone fields exterior to a two-dimensional (2-D) finite-difference time-domain (FDTD) field lattice has been developed entirely in the time domain. The fields are found from a surface integration of the convolution of the time derivative of equivalent currents and charges along a contour that encloses the scatterer or radiator of interest. The kernel of the convolution integral has a square-root singularity for which an efficient numerical integration rule is presented. Using this technique, a very accurate solution is obtained; however, convolution integrals are computationally expensive with or without singularities. As an alternative, a rapidly convergent approximate series expansion for the convolution integral is presented, which can be used both in the near and far zone. Results using the new 2-D transform are compared with analytical expressions for the fields generated by a modulated Gaussian pulse for TE and TM line sources. In addition, the 2-D transform solution for the near-zone fields scattered from an open-ended cavity for a TE incident modulated Gaussian pulse plane wave is compared against a full-grid FDTD solution for accuracy and efficiency. The 2-D transform far-zone fields are compared against an alternative technique, which uses a double Fourier transform to perform the convolution in the frequency domain     

Incorporating two-port networks with S-parameters into FDTD

A modeling approach for incorporating a two-port network with S-parameters in the finite-difference time-domain (FDTD) method is reported. The proposed method utilizes the time-domain Y-parameters to describe the network characteristics, and incorporates the Y-parameters into the FDTD algorithm. The generalized pencil-of-function technique is applied to improve the memory efficiency of this algorithm by generating a complex exponential series for the Y-parameters and using recursive convolution in the FDTD updating equations. A modeling example is given, which shows that this approach is effective and accurate. This modeling technique can be extended for incorporating any number of N-port networks in the FDTD modeling     

Simple Trapezoidal Recursive Convolution Technique for the Frequency-Dependent FDTD Analysis of a Drude–Lorentz Model

A concise formulation of the frequency-dependent finite-difference time-domain (FDTD) method is presented using the trapezoidal recursive convolution (TRC) technique for the analysis of a Drude-Lorentz model. The TRC technique requires single convolution integral in the formulation as in the recursive convolution (RC) technique, while maintaining the accuracy comparable to the piecewise linear RC (PLRC) technique with two convolution integrals. The TRC technique is introduced not only to the traditional explicit FDTD, but also to the unconditionally stable implicit FDTD based on the locally one-dimensional (LOD) scheme. Through the analysis of a surface plasmon waveguide, the effectiveness of the TRC technique is investigated for both explicit FDTD and LOD-FDTD, along with the existing RC and PLRC techniques.     

区域分解时域有限差分方法(DD-FDTD)及其在散射问题中的应用

本文提出一种区域分解的时域有限差分算法(DD-FDTD).依据待解问题的特点,把待解问题分解为几个子区域,在各个子区域中,采用适合于该区域的共形网格进行划分计算,通过一种有效的信息传递方案,把各个子区域综合起来,获得原问题的解.通过采用这种方法,一个复杂的问题可以得到简化,从而变得适于求解,同时,共形网格和精确的信息传递方案的使用,大幅度提高了计算精度.文中,用该算法对二维电磁散射问题进行了分析计算,获得了精确的计算结果.     

FDTD-PLRC Technique for Modeling of Anisotropic-Dispersive Media and Metamaterial Devices

The goal of this paper is to develop a versatile computational engine based on the finite-difference time-domain (FDTD) technique to comprehensively demonstrate the broadband behaviors of devices designed utilizing anisotropic-dispersive metamaterials. In this regard, the frequency-dependent behavior of dispersive materials is incorporated into the FDTD equations with the use of a piecewise linear recursive convolution (PLRC) approach. The FDTD domain is effectively terminated utilizing convolutional perfectly matched layered (CPML) absorbing walls, which are derived from the complex frequency-shifted (CFS) formulation. The CPML has the advantage that it operates only on the filed intensities and has nothing to do with the and constitutive relationships. The CPML is also highly absorptive to both propagating and evanescent waves. Therefore, it would be of great interest for terminating metamaterials having complex constitutive parameters. The developed method is also capable of characterizing periodic configurations illuminated by normal incident plane waves. The FDTD engine is successfully validated through the analyses of several complex metamaterials. The design and characterization of novel devices such as a patch antenna printed on metasubstrate with anisotropic epsiv (omega) - mu (omega)parameters, an electrically small antenna embedded in negative permittivity resonator, and an anisotropic-dispersive self-biased hexagonal ferrite-coupled line (FCL) circulator are highlighted.     

Finite-difference Time-domain Algorithm for Plasma Based on Trapezoidal Recursive Convolution Technique

The electromagnetic wave propagation in plasma media is modeled using finite-difference time-domain (FDTD) method based on the trapezoidal recursive convolution (TRC) Technique. The TRC Technique requires single convolution integral in the formulation as in the recursive convolution (RC) method, while maintaining the accuracy comparable to the piecewise linear convolution integral (PLRC) method with two convolution integrals. The three dimensional (3-D) TRC-FDTD formulations for plasma are derived. The high accuracy and efficiency of the presented method is confirmed by computing the transmission and reflection coefficients for a unmagnetized collision plasma slab. The backward radar cross section (RCS) of perfectly conducting sphere covered by homogeneous and inhomogeneous plasma is calculated.     

时域散射问题中近场－远场转换的新途径

本文针对散射问题中时域近场一远场转换问题，探讨了两种新的算法．其一是采用Ｓｔｒａｔｔｏｎ－Ｃｈｕ散射场的积分表示式，由表面感应流直接求时域散射远场．其二是采用拉氏变换和卷积的方法，导出求解３－Ｄ和２－Ｄ时域散射远场形式上统一的公式．文中以规则形体为计算实例，验证了算法的可行性．     

基于时域体面积分方程的分块预条件方法

时域体电场积分方程性态较好,但时域面积分方程性态较差,这就造成体面耦合的时域电场积分方程在迭代求解时经常遇到收敛较慢的问题,无法满足工程需要,并且一般预条件技术获得的加速效果也不甚理想。因此,时域体面积分方程迭代求解时间过长已成为体面积分方程在实际工程应用中的核心问题。针对时域体面电场积分方程矩阵性态差的问题,提出一种引入分块预条件方法(BMP),可以加快矩阵迭代收敛的速度。将时域体面积分方程的矩阵分解成3块矩阵相乘的形式,而这3块矩阵都是稀疏的,并通过几个体面算例说明该预条件技术的效率。     

FDTD结合最小二乘拟合法分析PBG滤波结构

为了能应用FDTD方法快速有效地分析各种PBG滤波结构电磁特性,该文应用FDTD结合最小二乘拟合法对两类新型PBG滤波结构进行了具体分析,给出了FDTD结合最小二乘拟合法计算的最小迭代步数和如何选出谐振段去除振荡原则,最后通过数值仿真结果,表明该方法能有效减少FDTD的迭代步数,节省计算时间,特别适用于大周期和复杂的PBG滤波结构分析。     

各向异性等离子体衬底的二维光子晶体带隙特性分析

利用基于拉氏变换的电流密度卷积(LT-JEC)时域有限差分(FDTD)方法处理等离子体复杂介质;同时通过引入周期边界条件,将无限大周期结构转换为单个元胞的有限区域的计算,实现了抽象模型向实际计算模型的转变,计算了以等离子为背景的二维等离子光子晶体的功率反射和透射系数。研究了二维等离子体光子晶体带隙特性随等离子体各参数变化的变化规律,为实际制作等离子体光子晶体提供了理论基础。