Limitations of the Thevenin and Norton equivalent circuits for a receiving antenna

The investigation carried out in this paper was stimulated by a recent paper published by Love (2002), in which the appropriateness of the use of the Thevenin and Norton equivalent circuits for a receiving antenna was questioned. A review of the available literature led to the conclusion that the limitations inherent in the Thevenin and Norton equivalent circuits had not been adequately examined, and this led to the investigation that is reported on in this paper. The Thevenin and Norton equivalent circuits are useful in the reduction of the equivalent circuit for a transmitting-receiving antenna system to simpler networks that facilitate the evaluation of the received power. One finds in the literature that the calculated power dissipation within these equivalent circuits is often equated to the reradiated and scattered power from the receiving antenna. Such calculations are not correct, because power dissipation in the network from which the Thevenin and Norton equivalent circuits were obtained cannot be made using the Thevenin and Norton equivalent circuits. However, as we will show, the Thevenin and Norton equivalent circuits can be used to find a reradiated electromagnetic field that is a part of the total field scattered by a receiving antenna. As part of the derivation of this new result, we develop a derivation of the Thevenin and Norton equivalent circuits from the basic principles of uniqueness and superposition applied to electromagnetic fields.     

Equivalent Transformations for Mixed-Lumped and Multiconductor Coupled Circuits

Distributed circuits consisting of a cascade connection of m -port stab circuits and multiconductor coupled transmission lines are equivalent to ones consisting of cascade connections of multiconductor coupled transmission lines whose characteristic impedances are different from original ones, m-port stub circuits, and an m-port ideal transformer bank. Because of the reciprocity of the circuit, values of transformer ratio must be identified. In the special case of a one conductor transmission line, these equivalent transformations are equivalent to Kuroda's identities. These extended equivalent transformations may be applied to mixed-lumped and multiconductor coupled circuits. By using these equivalent transformations, equivalent circuits and exact network functions of multiconductor nonuniform coupled transmission lines can be obtained.     

Two-Port Equivalent Circuits of Two-Wire Parabolic Tapered Coupled Transmission Lines

Two-port equivalent circuits of two-wire parabolic tapered coupled transmission lines (PTCTL) with open or short terminal conditions on the remaining two ports are presented. First, two-port equivalent circuits of PTCTL, whose characteristic admittances increase along the lines, are shown. Second, two-port equivalent circuits of PTCTL, whose characteristic impedances increase along the lines, the dual of the previous circuits, are shown. These two-port circuits of PTCTL are expressed in terms of two equivalent representations, one having mixed, lumped and uniform distributed circuits, and the other consisting of uncoupled nonuniform distributed circuits.     

Equivalent Representations of Lossy Nonuniform Transmission Lines

Equivalent transformations, which were recently derived for mixed lumped and distributed circuits, may be extended to circuits consisting of lumped reactance, resistors, and Iossy transmission lines. It is shown that circuits consisting of a cascade connection of lumped element sections and Iossy uniform transmission lines are equivalent to circuits consisting of a cascade connection of lossy nonuniform transmission lines, lumped elements, and ideal transformers. Furthermore, by considering the limiting case of these transformations, equivalent transformations for circuits consisting of a cascade connection of lumped reactance, resistors, and nonuniform transmission lines are obtained. Exact equivalent circuits of Iossy even-order binomial form transmission lines are derived from these equivalent transformations.     

含源T形电路和含源Ⅱ形电路的等效变换

本文讨论了含源T形电路和含源Ⅱ形电路的等效变换,扩展了T形电路和Ⅱ形电路等效变换的内容。根据含独立电源二端口网络的特性方程,推导了含源T形电路和含源Ⅱ形电路等效变换的条件。含源T形电路和含源Ⅱ形电路等效变换的结果不具有唯一性,但可通过附加一些条件使变换结果唯一,本文给出了这些附加条件。并通过实例说明了推导结果的正确性。本文的分析对电路教学具有一定的价值,可供教学参考。     

Representation of the SiGe HBT's thermal impedance by linear and recursive networks

In this paper, new methods for approximating the thermal spreading impedance of SiGe HBT devices with electrical equivalent circuits are presented. The electrical equivalent circuits permit an accurate representation of the fractional behavior of the thermal impedance. Using these equivalent circuits, the thermal model can be implemented in electrical SPICE type simulators.     

基于受控源转移和分裂节点的去耦等效法

目前,对互感电路进行去耦等效,一般只解决接在节点上不多于三条含互感支路的去耦等效问题。本文提出的受控源转移概念,利用受控源转移和分裂节点的方法,深入研究了接在节点上多于三条含互感支路的去耦等效问题。本文提出的方法通过对电路图等效变换,获得去耦等效电路。     

高压LDMOS I—V特性宏模型的建立

目前LDMOS已经广泛应用于功率集成电路和微波集成电路中,建立LDMOS的SPICE等效电路变得很重要。以往的模型都是将LDMOS分为线性区和饱和区两段来分析,公式复杂而且计算量大。因此在数值模拟的基础上提出了全导通区域的伏安特性方程,建立了LDMOSI-V特性的宏模型。该模型的特点是参数少,易于提取,得到的SPICE等效电路简单,仿真容易收敛。     

基于Pspice光发射机驱动电路的仿真分析

根据发光二极管（LED）和双异质结激光器（DH-LD）的Pspice等效子电路程序,将它们做成新的元件嵌入Pspice A/D 8.0电路仿真平台中。利用该平台对各种光发射机的光驱动回路进行模拟,证明用光电子器件的等效电路模型来模拟光电集成回路的可行性和便利性。     

晶体管混合π型参数与Y参数的关系

晶体管高频小信号等效电路模型可用两种方法得到:一是把晶体管视为一个二端口网络,列出电流、电压方程式,拟定满足方程的网络模型,常采用Y参数模型;二是根据晶体管内部发生的物理过程来拟定的模型,即π型参数模型;同一个晶体管应用在不同场合可用不同的等效电路表示,同一晶体管的各种等效电路之间又应该是互相等效的,各等效电路中的参数可互相转换。     

Tapped-Line Coupled Transmission Lines with Applications to Interdigital and Combline Filters

Exact, general, open-wire-line equivalent circuits for tapped-line combline and interdigital arrays are derived using a combination of graph transformations and induction. A significant feature of the equivalent circuits is that they do not require commensurate length sections. The equivalent circuit for tapped-line interdigital arrays is utilzed to develop design equations for tapped-line interdigital filters.     

Kuroda's Identity for Mixed Lumped and Distributed Circuits and Their Application to Nonuniform Transmission Lines

Kuroda's identities, which are used in analysis and synthesis of distributed transmision line circuits, may be applied to mixed lumped and distributed circuits. It is shown that circuits consisting of cascade connections of lumped reactances and uniform transmission lines are equivalent to circuits consisting of a cascade connection of nonuniform transmission lines, lumped reactances, and ideal transformers. Moreover, by using these equivalent transformations, network functions of some nonuniform transmisssion lines can be derived exactly.     

An improved GaAs MESFET equivalent circuit model for analog integrated circuit applications

An improved equivalent circuit model of a gallium-arsenide (GaAs) MESFET that is optimized for the design and analysis of precision analog integrated circuits is described. These circuits entail different modeling requirements from digital or microwave circuits, for which existing equivalent circuit models are optimized. Improved techniques are presented to model the drain-to-source conductance, device capacitance, and the functional dependence of drain-to-source current.     

压电微悬臂梁微弱压电信号检测

压电微悬臂梁是一种利用压电元件的逆压电效应驱动微悬臂梁使其振动，并利用压电元件的压电效应来检测梁的变形量的集成微驱动器和微传感器。文中讨论了压电微悬臂梁中的压电元件的两种等效电路模型，并且提出了检测微压电信号的检测系统以及两种前放电路。在检测微悬臂梁频率响应特性的实验中得到了较好的结果。     

Calculation of self-resonant frequencies of membrane structures with help of schematic design program package

It is proposed an application of finite-element mathematical model for obtaining of equivalent electrical circuit by mechanical components substitution. To reduce dimension of obtained circuits we propose to use RLC reduction. It is considered an example of equivalent electrical circuit of micro accelerometer obtain. Mentioned approach is spread to equivalent circuits of MEMS components obtaining.     

Thermal incremental equivalent circuits of integrated circuit devices

A procedure of thermal stability design of integrated-circuit devices, based on the use of thermal incremental equivalent circuits, is described. These circuits may be derived by inspection from the dc equivalent circuit. They offer insight into the interdependence of various components in determining temperature variations and simplify the conventional analysis.     

Equivalent Circuits and Characteristics of Inhomogeneous Nonsymmetrical Coupled-Iine Two-Port Circuits (Short Papers)

The equivalent circuits and the properties of nonsymmetrical coupled-line two-port prototype circuits in an inhomogeneous medium are presented. Potential applications include both symmetrical and non-symmetrical circuits for narrow- and wide-band applications as filters and impedance transformers.     

Modeling substrate effects in the design of high-speed Si-bipolarICs

In the design of high-speed IC's, the influence of the substrate on circuit performance must be considered carefully. Therefore, in this paper the contribution of the p^- substrate and channel stopper to the equivalent circuits of Si-bipolar transistors and bond pads are theoretically and experimentally investigated up to very high frequencies. Improved equivalent substrate circuits, well suited for standard circuit simulators (e,g., SPICE), are derived and checked by numerical simulation using a new simulator (called SUSI). The validity of both the numerical simulation results and the equivalent circuits are verified by on-wafer measurements up to 20 GHz. Finally, the simulator was successfully applied to investigate noise coupling via the substrate     

Transistor equivalent circuits

This paper surveys the history of the electric-circuit representation of the transistor over the past fifty years. During the first two decades after the transistor was announced in 1948, primary emphasis was on small-signal equivalent circuits, which could be used for linear-circuit analysis and design. In addition, parameters of many of these equivalent circuits for the bipolar junction transistor, which are described, were related to the physical construction of the device. Approximately two-thirds of the paper is devoted to this period, when the writer personally contributed to this effort. By the beginning of the third decade, transistor circuits had became more complex, and circuit analysis was carried out with the help of digital computers. Interest then shifted away from small-signal equivalent circuits to “models” for computer-aided circuit design (CACD). This transition, including the models used in the widely used CACD program SPICE, is described. MOS transistors are treated only briefly; by the time MOS transistors became commercially viable devices, emphasis then also had shifted to “models” for CACD. In conclusion, the writer notes that there is still hope for us aficionados of small-signal equivalent circuits; new types of transistors are still being characterized in this manner     

集成风速计片上系统的计算机模拟

将MEMS器件与CMOS电路集成在同一个芯片上具有体积小、噪声小、便于控制、易于大批量生产等优点 ,本文从风速计的工作场入手 ,运用了有限元、数据拟合、等效电路及SPICE宏单元的方法对片上系统进行模拟 ,从而直接模拟出信号状况 ,有利于片上处理电路和控制电路的匹配设计 ,提高了设计效率。文中给出了风速计流体场的有限元分析结果 ,并通过拟合的方法将输出的温度差输出到电路等效的热堆 ,信号和噪声经过片上集成的放大器输出到芯片外 ,有利于温度场、热敏感元件、放大电路的优化设计