Automatic generation of accurate low-order models for magnetic devices

A method to automatically create low order state-space models for magnetic devices is set forth. The method begins with geometrical and materials data from which the finite element analysis (FEA) is used to build a high order state-space model. It is shown that this model contains far more state variables than are necessary to achieve the nearly the same results in the frequency band of interest. It is shown that the full-order model can be reduced methodically without additional physical assumptions. The reduction method is applicable directly to magnetically linear systems, but applies to a wide range of power electronics applications and can be a basis for future nonlinear device modeling. The method reduced an example inductor model from 882 state variables to two. To confirm correct model derivation, the full-order model is checked against and agrees with experimental data to the extent that the FEA and materials data are accurate. The reduced-order model agrees very well with the full-order model, particularly in computing impedance.     

Fiber attachment for guided wave devices

Reviews the status of fiber attachment to guided wave devices. Current methods for achieving low fiber-waveguide-fiber insertion loss are discussed and techniques for aligning and permanently attaching fibers are described     

My generation [third generation wireless mobile communication]

As the introduction of third generation (3G) mobile communications systems is expected to be evolutionary rather than revolutionary it is vital to establish a solid business case for 3G. The old business model of `coverage, coverage, coverage' will evolve to one of `capacity, capability and content' and a thorough evaluation will have to be made of the volume of expected usage, the value that customers will expect for their money and the variety of services that can be offered. The author discusses the business case for 3G and concludes that it will have to embrace `my generation' thinking, i.e. the need for equipment and services to be personalised     

Resonant-tunneling devices for millimeter-wave generation

Oscillations from resonant-tunneling diodes have been observed up to 200 GHz, and theoretical estimates predict that device performance should extend into the THz range. This paper addresses the issue of the ultimate frequency response and power generation capability of these devices. Techniques recently developed to solve the time-dependent Schrödinger equation are used to predict the rf power vs. frequency obtainable from resonant-tunneling diode oscillators, based on the calculated small-signal response. Factors limiting the rf power output from these devices are presented. Also, recently obtained dc experimental results for the In_.53Ga_.47As-In_xAl_1-xAs heterostructure material system grown on InP are presented. Using a quasi-static approximation, the rf power available from these devices under large-signal conditions is estimated.     

Race-UMTS for third generation wireless communications

Universal mobile telecommunication system (umts) is a projected European standard of the ccir defined future public land mobile telecommunication systems (fplmts) for third generation mobile communications. Race mobile project is studying issues related to umts. Race is the European Commission’s programme on research and development in advanced communications in Europe. The main purpose of this programme is to introduce an integrated broadband communications network (ibcn) so that it provides an universal standard telecommunications system across Europe, with the capacity to meet demand in the early 21st. century. The purpose of this paper is two fold. The first one is to make the reader familiar with the Race mobile project which is partially funded by Commission of European Community (cec). The second one is devoted to the activities in the project since its start in 1988 and major results up to now. Further, the paper describes many techniques investigated within the project with respect to umts requirements.     

第三代TrenchMOS技术开发成功

位于美国加州Sunnyvale的Philips半导体公司是皇家Philips电子公司的一个分部,它所推出的第三代TrenchMOS（深槽MOS）工艺技术,可以将以MOSFET为基础的电路单元的尺寸进一步缩小。这项工艺技术是针对奔腾4甚至更新一代微处理器的技术要求而开发的。采用此项工艺技术以后,器件的单元密度可以达到50M单元/平方英寸。 此项工艺可以制成200V以下的MOS器件,可以广泛应用于dc/dc变换器,电压调节器,和syncFET等器件之中。现在推出的产品是属于这类器件中25到30V这一档的器件。 第三代工艺技术的特点包括:低阻的特殊导电层,方块电阻可达22mΩ/mm2-比现在一代工艺制成的电阻低40％。亚微米的槽宽降低了栅漏电容,减少了栅极电     

Thermal carrier generation in charge-coupled devices

The build-up of thermally generated carriers in a charge-coupled device shift register is characterized by constructing a model for the generation inside a single shift-register bit. Using the model, theoretical response curves are constructed for two practical modes of operation where the contribution from the generation of carriers can be substantial. Experiments are presented which confirm all aspects of the theoretical response curves, including the presence of an initial period of reduced generation in one of the two modes. Procedures for determining generation parameters directly from observed CCD characteristics are presented and implemented. One generation parameter, the minority carrier lifetime τ, is determined by employing the CCD connected in a gate-controlled diode configuration; two others, the depleted surface generation velocity s0, and the general shape of the depletion layer, are determined utilizing a curve fitting procedure. The spatial variation in generation rates is also investigated and found to possess a distribution which is skewed positively and not Gaussian.     

A generation of microwave ferrite devices

The development of microwave ferrite materials and devices over the last thirty years is traced. The status of materials, devices, and theoretical understanding prevalent in the mid-1950s is first reviewed. Developments in materials engineering of garnets and lithium ferrites in the 1960s and 1970s are described, along with the evolution of circulators and phase shifters. Current levels of performance achievable in circulators and phase shifters are described, and future challenges and opportunities are discussed     

Self-alignment technique for fiber attachment to guided wave devices

We propose and demonstrate a new multiple fiber-waveguide alignment technique suitable for single-mode and multimode guided wave devices. The method uses an overlap between a precision-etched silicon substrate and the top surface of the waveguide substrate to align all but one of the six degrees of freedom automatically. We have attached six arrays, each with twelve single mode fibers, and have measured an average excess loss of 0.9 dB atlambda = 1.3 mum. The lowest loss array had an average excess loss of 0.4 dB.     

Harmonization of global third generation mobile systems

The International Telecommunication Union launched the third-generation project in 1986 with the aim to provide global personal communication using an inexpensive mobile terminal that can truly facilitate communication "anywhere, anytime". In previous years, standardization activities toward IMT-2000 have accelerated toward concrete specifications. By June 1998, a total of 15 proposals from around the world had been submitted to the ITU as radio transmission technology candidates. Since then, the 3G standardization landscape has seen many changes-a steady progression of the convergence process. This article provides a comprehensive overview of the worldwide harmonization efforts on the standardization of third-generation terrestrial mobile communication systems. The status, as of October 1999 when this article was written, of the technical specifications within 3G partnership projects are also summarized.     

Optimum conditions for nonresonant third harmonic generation

A detailed theoretical analysis of nonresonant third harmonic generation (THG) is given which includes the intensity dependent refractive indices of the nonlinear medium as an integral part. According to the third-order analytic solution, the maximum attainable conversion efficiency is only limited by a nonlinear parameter β which is essentially the ratio of the Kerr-constants and the third harmonic coefficient. Only for|beta| < 1intensity (energy) conversion efficiencies in excess of 90 percent (40 percent) are possible. The influence of the intensity distribution of the input beam is discussed. Diagrams are given from which the optimum experimental conditions can be deduced in order to get the optimum harmonic output. Limiting processes, such as fifth-order effects or self-focusing, are analyzed. As an example, the optimum conditions for efficient frequency tripling of powerful Nd:glass laser radiation are evaluated.     

3G中的STTD发送分集技术

空时发送分集(STTD)方案已经被选做第三代移动通信系统WCDMA的一种标准。STTD是基于空时分组码(STBC)的一种发送分集技术[1],在详细分析了空时分组码的基础上,研究STTD发送分集技术。针对STTD需要很好的估计信道参数,利用导频信号对信道参数估计,最后进行仿真并给出结论。     

Theory of multichannel magnetic stimulation: toward functionalneuromuscular rehabilitation

Human excitable cells can be stimulated noninvasively with externally applied time-varying electromagnetic fields. The stimulation can be achieved either by directly driving current into the tissue (electrical stimulation) or by means of electro-magnetic induction (magnetic stimulation). While the electrical stimulation of the peripheral neuromuscular system has many beneficial applications, peripheral magnetic stimulation has so far only a few. This paper analyzes theoretically the use of multiple magnetic stimulation coils to better control the excitation and also to eventually mimic electrical stimulation. Multiple coils allow electronic spatial adjustment of the shape and location of the stimulus without moving the coils. The new properties may enable unforeseen uses for peripheral magnetic stimulation, e.g., in rehabilitation of patients with neuromuscular impairment.     

Intelligent paging strategies for third generation mobiletelecommunication systems

Location management procedures, in conjunction with the millions of users expected to subscribe to third generation mobile telecommunication systems, will generate a huge signaling load. In this paper, we propose a method which aims at the reduction of signaling overhead on the radio link produced by the paging procedure. The key idea is the application of a multiple step paging strategy which operates as follows: at the instance of a call terminating to a mobile user who roams within a certain location area, paging is initially performed in a portion of the location area (the paging area) that the so-called “paging related information” indicates. On no paging response, the mobile user is paged in the complementary portion of the location area-this phase can be completed in more than one (paging) step. Various “paging related information” elements (e.g. recent interaction information, high mobility flag, etc.) can be used and several “intelligent” paging strategies can be defined. Representative paging strategies are analyzed in terms of network performance and quality of service (paging signaling, paging delay, processing power requirements), via a simulation tool which models a realistic city area environment     

Access network evolution beyond third generation mobile communications

Second-generation mobile radio systems have been deployed successfully worldwide. These systems have evolved to higher data rates and packet transmission. Third-generation mobile radio systems are currently being standardized worldwide to be initially deployed in 2001 and 2002 in different regions of the world. New advanced multimedia services are under development, and first services are already being offered in second-generation systems, which will provide new business opportunities. Already today discussion is starting on the development of systems beyond third-generation mobile radio systems due to the long timeframe for system specification and international standardization. However, today there is no clear vision available on such systems. This discussion takes into account the new deregulated and liberalized communication environment. This article presents a concept for a system beyond third-generation mobile radio systems, which comprises a combination of several optimized access systems in a common IP-based medium access and core network platform. These different access systems will interwork through horizontal and vertical handover, service negotiation, and global roaming. The different access systems are allocated to different mutually complementing cell layers in the sense of hierarchical cells with respect to cell size, coverage, and mobility to provide globally optimized seamless services to users. This vision requires extensive international research and standardization activities to solve many technical challenges. Key issues are the global interworking of different access systems on a common platform, advanced antenna concepts, and the implementation of multimode and multiband terminals and base stations through software-defined radio concepts.     

Radio resource allocation in third generation mobile communicationsystems

Code-division multiple access has been widely accepted as the major multiple access scheme in third-generation mobile communication systems. Wide-band CDMA and its hybrid associate time-division CDMA are key elements of the IMT2000 framework of standards. Since the beginning of the 1990s there has been enormous research activity in analysis of the soft (i.e., interference limited) capacity of these CDMA-based systems. Optimal usage of the soft capacity to provide, maintain, and guarantee QoS for different service classes is now becoming a very important issue. Therefore, interest in radio resource allocation has recently. This article presents an overview of RRA schemes (primarily for CDMA-based systems) that are flexible, support traffic services with various QoS requirements, minimize call/session blocking and dropping probabilities, and have acceptable radio resource utilization     

Millimeter-wave generation with plasma devices: The state of the art

The electron beam-plasma interaction and the plasma multiplier have been investigated during the last decade in the hope that one or the other might have some application at millimeter wavelengths. So far the expectations for these devices have not been realized because of many unresolved engineering problems. Major difficulties are described here, and an attempt is made to evaluate the potential of both devices.