多导体传输线瞬态响应研究

针对多导体传输线瞬态响应的无源性问题,提出了基于集总等效源模型的多导体传输线瞬态响应模型. 从外场激励下的多导体传输线的频域电报方程解出发,将外场在传输线上激励的分布电压源和电流源与传输线指数矩阵解耦,建立了集总等效电压源和电流源模型. 为避免复杂的傅里叶反变换及卷积运算,推导了集总源模型的时域递推方程. 在此基础上,采用时域有限差分法建立了端接线性负载、非线性负载和外场激励下的不等长多导体传输线瞬态响应离散递推方程. 通过对无损传输线的仿真对比,验证了方法的有效性. 最后,对端接线性负载、非线性负载和外场激励下的不等长多导体传输线瞬态响应进行了试验和仿真分析.       

多导体传输线瞬态响应研究

针对多导体传输线瞬态响应的无源性问题,提出了基于集总等效源模型的多导体传输线瞬态响应模型.从外场激励下的多导体传输线的频域电报方程解出发,将外场在传输线上激励的分布电压源和电流源与传输线指数矩阵解耦,建立了集总等效电压源和电流源模型.为避免复杂的傅里叶反变换及卷积运算,推导了集总源模型的时域递推方程.在此基础上,采用时域有限差分法建立了端接线性负载、非线性负载和外场激励下的不等长多导体传输线瞬态响应离散递推方程.通过对无损传输线的仿真对比,验证了方法的有效性.最后,对端接线性负载、非线性负载和外场激励下的不等长多导体传输线瞬态响应进行了试验和仿真分析.     

传输线集总模型的严格理论推导

借助于负的集总电阻、电感、电导和电容的感念,本文建立了传输线系统的电路模型、双端口π型网络和T型网络模型。从传输线的N段梯形等效电路出发,应用连分数理论,获得了输入阻抗在输出端三种状态下(短路、断路和匹配)的表达式,进而得到了以集总参数RLGC给出的 表达式。再依据传输线的输入导纳公式、导纳矩阵和BACD矩阵,建立了传输线的集总电路模型、π型网络和T型网络模型,并分别在时域和频域进行了验证。     

电缆EMP耦合SPICE模型仿真分析方法

基于SPICE模型耦合问题分析的集总电路法和分布源等效法,对电磁脉冲(EMP)线缆耦合问题进行了仿真。阐述了两种方法的基本原理:集总电路法把电缆分段等效为集总电路,并分段加载激励源;而等效源法把分布源等效为集总源,在电缆两端加载激励源。仿真算例表明:SPICE模型方法分析线缆的EMP耦合问题方便快捷、效率高、精度可靠。     

基于路的方法导出耦合微带线的传输方程

在研究传输线时,当传输线的几何尺寸l与工作频率所对应的波长λ可相比拟时,传输线就要用分布参数电路来讨论,在研究分布参数电路时,可以应用电磁场理论,也可以采用电路理论,采用后者,用等效的方法将耦合微带传输线等效为分布参数电路模型,然后用基尔霍夫定律求出其传输线方程。     

基于高阶时域有限差分法与改进节点分析法混合求解复杂传输线网络瞬态响应

该文提出一种用于求解复杂传输线网络瞬态响应的新型混合算法.通过构建混合单端口网络模型将传输线分布参数系统与集总电路分开,分别采用高阶FDTD(2,4)与改进节点电压分析法(MNA)分析传输线与端口电路瞬态响应.与以往暂态分析方法相比,高阶FDTD(2,4)的低数值色散特性,使得求解传输线时可采用粗网格离散,能方便处理电长度较长的传输线.同时直接采用电路分析方法求解端口电路,能够获取电路中各节点的电压电流波过程.通过几组数值实例验证了该方法的有效性及准确性.     

一种用于毫米波的共面波导间的宽带互联结构

在多芯片组件中,微波传输线间一般使用金丝键合的方式进行连接。受金丝自身的等效电感和其与基板及壳体间存在的寄生电容的影响,键合金丝结构在毫米波频段下带来了较大的阻抗失配。为了解决该问题,文中从等效集总元件角度出发,对阻抗变换公式进行了推导,分析得出串联低阻抗传输线可以等效为并联集总电容的结论,可以与键合金丝的等效模型一起,构成等效低通滤波器,完成阻抗匹配。文中使用共面波导结构制作了键合金丝匹配结构测试件,测试结果显示,在30～40 GHz内S_(11)<-20 dB、S_(21)>-0.2 dB,具有优良的传输性能。该结构具有较强的实用性,可以用于毫米波频段下的微波组件设计。     

具有谐波抑制特性的小型化分支线耦合器

提出了一种具有谐波抑制特性的小型化分支线耦合器。通过分析枝节加载传输线的传输特性,发现可以采用小型化的枝节加载传输线去等效替换传统分支线耦合器中的四分之一波长传输线,此方法可以极大地减小分支线耦合器的电路尺寸。同时,由于枝节引入传输零点,耦合器的谐波响应也得到抑制。为了验证理论分析的有效性,建立了等效电路模型和传输线方程,对电路性能进行分析,最后进行了仿真以及实验验证。     

基于螺旋电感的Wilkinson功分器设计

Wilkinson功分器是一种常用的无源器件,随着通信设备小型化的要求越来越高,无源器件的体积成为其发展瓶颈。为解决这个问题,在分析螺旋电感主要参数及等效电路基础上,提出了一种基于π型等效1/4波长传输线原理,利用集总参数元件组成等效微带线电路的集总参数方法,设计出Si沉底上的螺旋电感和片上电容来实现微波单片集成(MMIC)电路的Wil-kinson功分器。实验表明,同等性能情况下,该方法设计的Wilkinson功分器可以有效减少Wil-kinson功分器的外形尺寸。     

端接任意负载传输线的分步CN-FDTD分析方法

为了高效精确地求解端接任意负载的传输线结构电磁瞬态响应,该文提出了一种基于分裂时间步技术的Crank-Nicolson(CN)-FDTD方法,通过理论分析证明了该方法具有无条件稳定特性。与混合单端口等效模型相结合,有效地将传输线系统分解为分布参数子系统与集总电路子系统,采用改进节点分析法(Modified Nodal Analysis,MNA)能够快速求解复杂终端电路网络。与以往瞬态分析方法相比,该方法时间步长的选取不受稳定条件的限制,且通过采用精细子时间步技术极大地削减了因大时间步长引入的色散误差。利用该方法计算双导体传输系统的电磁暂态响应,计算结果表明该算法具有很好的稳定性,在保证数值精度的基础上有效地提高了计算效率。     

Guaranteed passive direct lumped-element modeling of transmission lines

A novel approach to the reduced-order modeling of the frequency-dependent skin-effect (R-L) parameters of a transmission-line interconnect is proposed. A lumped-element circuit model for a short length of the lines is obtained directly from the finite-element method matrix equations. Only the most "important" eigenvalues and eigenvectors of the finite-element matrix are used, based on the contribution they make to the line parameters. The resulting reduced-order equivalent circuit is always passive and stable without the need for special modifications. The model can thus be immediately applied to problems where the transmission line is connected to nonlinear circuits. The model should find practical use in the design of flexible interconnect circuits as well as in other areas of high-speed digital electronics.     

Methods of theoretical analysis and computer modeling of theshaping of electrical pulses by nonlinear transmission lines andlumped-element delay lines

The mechanism by which high-power electrical pulses can be sharpened by propagation along nonlinear transmission lines and lumped-element delay lines is described with emphasis on the production of pulses with very fast leading or trailing edges. A survey of some of the mathematical techniques that have been applied to the propagation of electrical signals along nonlinear lines and ladder networks is presented, and the limitations of these techniques are discussed. The processes that both produce and limit pulse sharpening on nonlinear lumped-element delay lines are examined, and it is found that the wave equation, which describes the propagation of electrical signals along such networks, predicts that an electrical pulse will decompose into an array of solitons. An approximate formula for estimating the degree of pulse sharpening that can be produced on a delay line with a given number of sections is derived, and its accuracy is compared with experimental results. Numerical integration techniques for solving the nonlinear differential and difference equations that result from the mathematical analysis of nonlinear lines and networks are discussed, and the propagation of a voltage pulse along a lumped-element delay line containing nonlinear capacitors is simulated using a computer model based on an efficient algorithm     

Lumped-element analysis and design of CMOS distributed amplifiers with image impedance termination

This paper presents a systematic matrix-based lumped-element analysis of CMOS distributed amplifiers (DAs). Since transmission lines (TLs) of the DAs are artificially constructed from a ladder of a finite number of inductors and capacitors, the conventional TL-based analysis of microwave DAs can not be accurately applied to CMOS DAs. The proposed lumped-analysis method is also more intuitive for analog circuit designers than the TL analysis adapted from microwave amplifiers analysis because it provides the performance characteristics of the amplifiers as functions of circuit elements values, and not the TL characteristics. The image impedance technique is used for the design of input/output terminating networks. A new image impudence matrix is defined to accommodate the extension of the theory from two- to four-port networks, and a practical realization of the image impedance matrix is presented using the available circuit elements in CMOS technology. The simulation results clearly indicate an improved voltage gain and a better gain uniformity over the bandwidth of the proposed DA design terminated at its image impedance compared with the amplifier terminated at its nominal TL characteristics impedance.     

Compact Left-Handed Transmission Line as a Linear Phase–Voltage Modulator and Efficient Harmonic Generator

We construct a synthetic left-handed transmission line with cascaded varactors and shunt inductors. By modulating dc bias, the capacitance of the varactors can be changed and modulation of the output phase state is possible. For frequencies from 4.7 to 6.4 GHz, a very linear phase variation versus voltages of over 200deg phase variation with low insertion-loss variation (plusmn0.5dB) is demonstrated. This circuit can also act as an efficient harmonic generator when a large signal is applied. Since the left-handed transmission line shows high-pass filter response, harmonics generated are not seriously attenuated. However, because this synthetic transmission line is a very dispersive medium, strong dispersions and instabilities may arise. The circuit size is determined by the diode size and lumped-element inductor, allowing it to be compact     

Synthesis of Quarter-Wave Coupled Circulators with Chebyshev Characteristics (Short Papers)

The purpose of this short paper is to give an exact theory of quarter-wave coupled circulators with Chebyshev characteristics. The synthesis starts by replacing the lumped-element equivalent shunt resonator of the circulator by a distributed one that has the same susceptance slope parameter as the original circuit. In this way the overall network involves commensurate transmission lines only. The bandwidth over which the assumed form of the equivalent circuit applies is carefully discussed in terms of the two split frequencies of the magnetized junction. Tables for the required circulator parameters and transformer admittances for one and two transformer sections as a function of VSWR and bandwidth are included. The realizable solution for the latter arrangement is severely restricted by the equivalent circuit of the basic junction. Experimental results on an octave-band stripline circulator, with a two-section transformer, are also included.     

Accurate modeling and parameter extraction for meander-line N-well resistors

Accurate modeling and efficient parameter extraction of a scalable lumped-element model for n-well meander-line resistors that are suitable for radio frequency integrated circuit (RF IC) applications is presented. The equivalent circuit is similar to the spiral inductor model but with modifications to the element equations. Direct extraction of component values is performed by analysis of measured Y-parameters. The extracted results of the component values are physically meaningful and match those calculated using the scalable lumped-element model equations. The simulated S-parameter data from the equivalent lumped-element model shows very good agreement with the measured data up to 20 GHz.     

Variational solution of microwave circuits and structures

A unified variational formulation for microwave planar transmission lines and lumped-element impedances is developed and applied to an isolated stripline power splitter. Scattering parameters are calculated via the transfinite-element method and the numerical results are corroborated by three-port experimental measurements. The microwave impedance of a thin-film isolation resistor is separately measured and included in the model     

Systematic Lumped-Element Modeling of Differential IC Transmission Lines

In this paper, we report a systematic and efficient approach to obtain lumped-element models for differential integrated-circuit interconnect transmission lines covering both the low-frequency R/C as well as the high-frequency quasi-TEM behavior. To accurately model signal delay and loss, and to preserve causality, the frequency dependence of both line resistance as well as the line inductance is included in our model. The impact of ground inductance is also properly covered by the model. The validity of our approach is verified against experimental data collected up to 120 GHz for the even and odd modes on these differential transmission lines. We predict that these lines can transport data over 1-cm distance with rates up to 40 Gb/s, even with some imbalance in differential drive.      

Circuit-Based Analysis of Electromagnetic Field Coupling With Nonuniform Transmission Lines

This paper presents a new algorithm for simulating electromagnetic (EM) field coupling with nonuniform multiconductor transmission lines in a circuit simulation environment. The proposed algorithm is based on the concept of passive model-order reduction, whereby an algorithmically developed passive reduced-order model, coupled with a set of equivalent sources representing the incident filed, are shown to accurately capture the behavior of the transmission line under EM excitation. The reduced-order model is developed independently from the particular shape of the incident field pulse, in the sense that, in constructing the model, one does not need prior knowledge about the waveform of the incident pulse of the EM field. In addition, it is also shown that the model developed can be used to simulate the transmission line in the absence of the EM field. The derived equivalent sources, representing the field coupling, are given directly in the time domain, thereby making simulation under nonlinear circuit terminations an easy task. Although the proposed work is aimed mainly at simulating nonuniform transmission lines, it can be applied to uniform lines as a special case. The proposed algorithm has been validated numerically with several examples.     

A Compact Broad-Band Thin-Film Lumped-Element L-Band Circulator

Impedance matrices including magnetic losses are developed for a number of lumped-element ferrite-loaded symmetrical three-port junctions. The scattering matrix eigenvalues corresponding to these matrices are determined as functions of frequency and circuit parameters and are used to analyze these three-ports with emphasis on their properties as circulators. A very compact broad-band thin-film lumped-element circulator is derived from the idealized equivalent circuit. An experimental model approximately represented by this circuit is shown to have a 20-dB isolation bandwidth of greater than 30 percent with an insertion loss of less than 0.6 decibel. A switchable circulator which requires no magnetic-field switching is treated using this same analytical approach. It is suggested that this type of analysis together with additional experimental refinement of equivalent circuits will lead eventually to a computerized design of lumped-element circulators.