RF MEMS for ubiquitous wireless connectivity. Part II. Application

This paper reports on RF-MEMS switchable capacitors, varactors, and ohmic switch technology attribute for both base stations and handsets in realizing frequency-agile RF/wireless systems capable of serving multiple frequency bands. For the handset, this leads to a smaller footprint combined with low power consumption of the RF radio. For the base station the benefit lies in ability for reconfiguration of the air interface, which leads to high logistical savings for infrastructure vendors through a reduction in the number of product variants. Reconfigurable frequency-agile radios are a perfect addition to reconfigurable baseband processing. Both together form the basis of a realistic and reasonable approach to realize software radios.     

Equivalent circuit for RF flexural free-free MEMS resonators

A method to extract a lumped-parameter equivalent circuit for a free-free flexural MEMS resonator, based on the Euler-Bernoulli beam equation and exploiting a modal analysis approach, is presented. The dynamic behaviour predicted by the equivalent circuit is compared with FEM simulations, and the effect of a geometrical mismatch is investigated as well. The resonance frequency and the quality factor are correctly predicted. The method could be used for more complex systems of interconnected beams. The circuit can be used as a quick and intuitive analysis tool for the system-level designer and to allow the simulation of the device in a system-level design environment.     

国外对宇航用射频MEMS开关的研究

本文介绍了国外对宇航用射频MEMS开关的研究,包括其性能、结构、技术成熟度、生产制造、可靠性及环境应力。     

Reliability of SiGe HBTs for Power Amplifiers—Part I: Large-Signal RF Performance and Operating Limits

This paper examines the performance and reliability implications associated with aggressively biased cascode SiGe HBT power-amplifier cores under large-signal RF operating conditions. The role of high-power RF stress on device degradation and failure is examined in detail. General expressions for a large-signal RF safe-operating area, which account for the effect of load impedance on the dynamic output current and voltage characteristics, are presented. These show excellent agreement with experimental results. Useful operating guidelines for reliable large-signal operation are provided.      

A QoS control scheme using dynamic window size control for wide area ubiquitous wireless network

This paper describes a quality‐of‐service (QoS) control scheme for a wide‐area ubiquitous wireless network which is designed to accommodate many wireless terminals (WTs), such as sensors and actuators, in a large cell area. The purpose of this paper is to establish a QoS control scheme in a medium access control (MAC) layer that can hold the transmission delay of high‐priority class traffic within a predefined value regardless of how much low‐priority class traffic there is. Several QoS control schemes for wireless communication use have been proposed. However, in the wide‐area ubiquitous wireless network, an access point (AP) accommodates many WTs and the AP traffic volume often drastically changes. Therefore, conventional schemes sometimes cannot control the QoS of high‐priority traffic. To solve this problem, we propose a QoS control scheme that calculates a suitable initial back‐off window size of random access for each QoS class by using equations derived from a Markov chain behavior model. The proposed scheme adjusts the window size so as to prevent increased transmission delay of high‐priority traffic. The scheme's performance is clarified by computer simulation. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

TD-SCDMA无线通信终端接收模块的设计

基于现在射频电路的设计水平,TD-SCDMA终端要求最大程度的保证信号的完整性。提出了一种用于TD-SCDMA终端综测仪的射频接收系统,基于TD-SCDMA标准,射频频率为1800~2400 MHz,在910 kHz的分辨率带宽下,系统要求接收最小-80 dBm的信号,动态范围为60 dBm,中频频率为91~101 MHz。具有结构简单、易于仿真、成本较低等优点。实际测试结果与利用ADS软件仿真结果基本一致,性能指标能够达到设计要求。     

RF MEMS器件时变结构电磁特性数值计算方法

准确掌握射频微机电(RF MEMS)器件的电磁特性是WSN节点射频收发前端设计可靠与否的关键,为解决RF MEMS器件时变结构的电磁特性数值计算问题,建立了RF MEMS器件垂直运动结构的机电耦合模型,实现了模型的时域离散,在时域有限差分的基础上,提出电(磁)介质参数插值的新思路,详细阐述了线性电(磁)介质参数插值法的基本思想,并推导了一维线性插值的计算公式.仿真实验结果表明,该计算方法具有易实现、速度快、效率高的特点.     

Rediscovering William Stanley, Jr. Part I

William Stanley, Jr. pioneered the development and use of ac for electric light and power applications. He conceived solutions before others recognized the problems. He contributed in a major way to a major invention: the transformer, the key to large-scale exploitation of ac electricity. This article deals with Stanley's contributions to electrical transmission and distribution.     

Impasse points. Part I: Numerical aspects

Impasse point is an important phenomenon found in many non-linear circuits and systems. Among other things, the presence of an impasse point Q implies that the circuit model is defective and must be remodelled by augmenting it with parasitic inductances and/or capacitances at appropriate locations in order to predict the bifurcation from slow to rapid motions (jump phenomenon) widely observed in practice. the presence of an impasse point Q also implies that a numerical simulation of the associated system of implicit differential-algebraic equations would give rise to an extraneous and random small-amplitude oscillation in the vicinity of Q. the wave-form associated with this ‘fake’ oscillatory phenomenon depends on the error-controlled mechanism of the integration routine and can be detected using the results from this paper. Impasse points in high-order circuits (n > 2) need not be isolated. In fact, they often form an impasse set made of impasse curves, impasse surfaces, impasse manifolds, etc. In order to detect the impasse set associated with the implicit differential-algebraic system. An analytical characterization of an impasse point (X₀,y₀) is derived and proved to be equivalent to that of solving for the limit-points of an associated static bifurcation problem. Interpreting this as the parametric equation of a space curve in the y-space, an impasse point (X₀,y₀) is simply a ‘turning point’ of this curve.     

Transient modeling of electromechanical relays. Part I: armaturetype overcurrent relay

An electromechanical, armature type 50 relay is modelled in EMTP/ATP using TACS. Mechanical, magnetic, and electrical characteristics are represented in the form of simple mathematical models that can provide a useful tool for studying the dynamic responses of the armature type 50 devices and incorporating them into a power system transient analysis. This paper is the first part of a summary report by the Rensselaer Polytechnic Institute (RPI) of work on relay modeling sponsored by the Bonneville Power Administration (BPA). It presents the Electro-Magnetic Transient Program/Alternative Transient Program (EMTP/ATP) model for armature type 50 instantaneous overcurrent relays that compares with actual tests performed on the devices on a power system simulator (PSS)     

The overdamped double-scroll family. Part I: Piecewise-linear geometry and normal form

This paper is the first part of a two part work that aims to introduce a new family of piecewise-linear differential equations that exhibit chaotic behaviour in numerical simulations and to provide a rigorous mathematical proof of its chaotic nature. The new family presented here has the same eigenvalue distribution as the well-known Lorenz equations in its chaotic regime but has a different symmetry. It is a derivative of the recently investigated double-scroll family of piecewise-linear differential equations.¹ It differs, however, from the double-scroll family in that its members have all real eigenvalues at the origin. In particular, since the associated eigenspace E^s(0) is similar to that of an overdamped linear circuit, we will henceforth refer to this family as the overdamped double-scroll family. We establish Chua's circuit² as a member of this family under appropriate conditions. Preliminary numerical simulations exhibit some interesting phenomena such as period-doubling, periodic windows between chaotic behaviour, and strange attractors of differing geometric structure. Our approach in the rigorous analysis will be that employed for the double-scroll family in Reference 1. We derive a linearly equivalent class of piecewise-linear differential equations which includes the family simulated numerically as a special case. the necessary and sufficient condition for two piecewise-linear vector fields belonging to this new overdamped double-scroll family to be linearly equivalent is that their respective eigenvalues at respective equilibrium points be scalar multiples of each other. If the scalars are all identity, then we have linear conjugacy of the vector fields. an explicit normal form equation, in the sense of global bifurcation, is presented that is parametrized by its own eigenvalues. We find that linearly equivalent vector fields associated with the overdamped double-scroll family exhibit the same global behaviour even though their equivalence is based on the local concept of normalized eigenvalues. In addition, the piecewise-linear differential equations associated with these equivalent vector fields can be quite different from each other.     

The thermal rating of overhead-line conductors Part I. The steady-state thermal model

The stead-state current rating of short transmission and distribution lines is often determined by the maximum permissible temperature of the conductors to avoid excessive sag or long-term annealing of the conductors. A thermal model to calculate the relationship between the current and the conductor temperature is proposed, and the parameters in the model are examined in detail.     

Electrification of a major steel mill. Part I. early use of direct current power

This paper discusses the shift of Bethlehem Steel Company from steam to electrical power for its process machinery. Part I of this article covers the early use of direct current (DC). Subsequent parts will cover the development of the 25-Hz power system and the electrification of the rolling mill drives.     

Polymer outdoor insulating materials. Part I: Comparison ofporcelain and polymer electrical insulation

It is the objective of this series of articles, beginning in this issue, to review for users the benefits of polymer insulating materials. Material science, design, and processing conditions all influence performance and must be considered. Using silicone as an example, we will discuss performance considerations and present data on performance counter to common industry perceptions. The series goal is to acquaint the user with relevant topics so that more informed decisions can be made in the evaluation, selection, and use of outdoor polymer material insulation. In Part I, a comparison of porcelain and polymer properties is presented, including the relative advantages of each     

Effects of direct currents in power transformers Part I. A general theoretical approach

The DC component of current circulating in power transformers produces a certain degree of core saturation. The waveshape of the excitation current displays a pulse of high magnitude at each cycle. The width of the pulse depends on the period of the cycle under saturation. This excitation current induces a drop of potential across the primary winding impedance thus reducing the magnetizing voltage and injecting harmonics into the network. Moreover, it is demonstrated that this condition of operation will increase copper and stray losses but will tend to decrease iron losses.In order to study the detrimental effect of direct current, the equivalent circuit of a power transformer has been reviewed to confirm its applicability under partial saturation of the core. For single-phase transformers, the mathematical model developed allows calculation of rms and crest values of magnetizing current, core flux and magnetizing voltage, along with copper and core losses.