Advanced spectrum estimation methods for signal analysis in power electronics

Modern frequency power converters generate a wide spectrum of harmonic components. Large converters systems can also generate noncharacteristic harmonics and interharmonics. Standard tools of harmonic analysis based on the Fourier transform assume that only harmonics are present and the periodicity intervals are fixed, while periodicity intervals in the presence of interharmonics are variable and very long. A novel approach to harmonic and interharmonic analysis, based on the "subspace" methods, is proposed. Min-norm harmonic retrieval method is an example of high-resolution eigenstructure-based methods. The Prony method as applied for signal analysis was also tested for this purpose. Both high-resolution methods do not show the disadvantages of the traditional tools and allow exact estimation of the interharmonics frequencies. To investigate the methods several experiments were performed using simulated signals, current waveforms at the output of a simulated frequency converter, and current waveforms at the output of an industrial frequency converter. For comparison, similar experiments were repeated using the fast Fourier transform (FFT). The comparison proved the superiority of the new methods. However, their computation is much more complex than FFT.     

Advanced thermal architecture for cooling of high power electronics

This paper presents a thermal architecture concept for analysis of thermal problems and solutions existing in electronics systems. The thermal problems are categorized into a total of seven levels from chip to system. Advanced thermal technologies for addressing the thermal problems at all seven levels are discussed. Integrating the thermal architecture with the electronic architecture can significantly improve the effectiveness of the thermal management.     

A century of electronics [the evolution of vacuum tubes]

This article traces the evolution of vacuum tubes (thermionic valves) from their origins in incandescent filament lamps. It details the use of diodes and triodes in early radio transmission and detection, being the building blocks of rectifiers, amplifiers and oscillators. It also mentions the later developments of tetrodes and pentodes and concludes that the end of the vacuum tube era began with the introduction of the point contact transistor.     

UWB在生物医学电子中的应用研究进展

在介绍UWB技术在植入式和体外生物医学电子系统中的应用研究成果及进展的基础上,分析其在生物医学电子系统中广泛应用所面临关键技术、难点以及可能的解决方法;最后讨论了生物医学电子系统的发展方向,使UWB在生物医学中所需要研究的问题和方向更加具体化和明确化。     

Effect of side groups on the vacuum thermal evaporation of polythiophenes for organic electronics

The vacuum thermal evaporation of poly(3-hexylthiophene) (P3HT) and poly(thiophene) (PTh) conductive polymers with and without side groups is reported. The role of side groups in relation to structural and electronic properties is examined. FT-IR and GPC analysis is used to study the effect deposition has on conjugation of the polymer. Topography and grain structure of the polymer films are studied using MicroXAM, AFM and TEM. XRD and TEM data reveal enhanced molecular packing and crystallinity of PTh. This results in significantly improved charge transport properties with relatively high hole mobilities (10⁻⁴ cm²/Vs). Evaluation of PTh and P3HT electronic properties is performed on simple geometry planar C₆₀ heterojunction solar cells. PTh/C₆₀ devices exhibit almost a 70% increase in efficiency as compared to P3HT/C₆₀ devices, demonstrating enhanced charge collection in PTh films through improved molecular order.     

面向毫米波遥感成像的双极化毫米波探测器

针对多极化毫米波遥感成像重大需求,报道了一种高集成度双极化毫米波探测器。探测器采用固态电子学方案,通过喇叭天线接收毫米波信号,利用正交模耦合器进行极化信号分离,采用两级低噪放芯片放大信号,通过肖特基二极管实现功率检测。每支探测器集成两路接收通道,每个接收通道可同时探测水平与竖直两个极化方向信号。经测量,探测器探测频段为W波段(75～110 GHz),平均等效噪声温差达到0.3 K(@10 ms),尺寸不足155 mm×15 mm×20 mm,质量<0.3 kg。利用该探测器实现城市环境双极化毫米波遥感成像,成像结果表明,相比于单极化遥感成像,双极化遥感成像可以获得更多极化信息,可对城市环境下常见物品进行突出显示,这有助于今后进行自动物品识别、轮廓提取与远程物质成分识别。     

Integrated electronics and change in the electronics industry

Those who use electronics to solve problems for customers must exercise science, engineering, art, and business sense, and work with four generations of electronics based on vacuum tubes, discrete semiconductor devices, integrated circuits, and integrated electronic components, respectively. This paper includes forecasts of the growing applications and economic impact of integrated electronics. The concept of Active Element Groups (AEGs) is used to analyze the growth of the market from 1963 to 1973 and to emphasize the increasing integration of electronics. Despite dramatic trends now emerging in product mix and technology, the electronics industry will not be radically changed in structure. Bigger organizations are likely to get still bigger and stronger; smaller organizations are likely to consolidate; integrated electronics will make electronics pervasive. Integrated electronics makes the inward-looking science, engineering, and art of electronics more usable and allows the outward-looking practitioners who use electronics to solve problems for customers to move up their skills and concentrate on more effective and more sophisticated solutions-to those problems. It does not decrease their ability to serve their customers. It does require that they upgrade and change the emphasis of that ability to serve their customers more effectively.     

分子尺寸器件与单分子器件

未来的计算机可以小到什么程度?迄今无人可以做详尽的回答。但毫无疑问,硅基集成电路由于光刻技术的限制和生产成本随尺寸变小作指数增长,将很快达到它的极限(最小线宽100nm)。目前国际上已提出未来的纳米电子器件的各种方案,其中最小的器件有可能由单个分子所构成。扼要讨论了当前最“热门”的分子尺寸电子器件以及将要进一步发展的单分子电子器件。其中具有电双稳性能的分子是最可期许的材料。初步的研究结果表明能得到构成逻辑门用的单分子开关、超高密度存贮器和单分子整流器等功能器件的原型。最后还讨论了分子电子学进一步发展的前景和问题。     

基于毫米波传输的光纤无线融合架构研究

通过对毫米波生成技术的研究以及光纤/无线融合方案主流架构的分析,提出基于毫米波传输的光纤/无线融合架构设计。相比以往的网络融合方案,它可以实现一种在垂直方向从上往下依次包括业务层、控制层、媒体传输层和接入层,在水平方向覆盖核心网和接入网乃至用户驻地网的新型网络融合。     

Emerging trends in millimeter-wave CAD

This paper discusses three emerging trends in the area of millimeter-wave (mm-wave) electromagnetic (EM) simulation and computer-aided design (CAD). Diakoptics techniques for frequency- and time-domain EM-simulation methods are needed for mm-wave circuit design. Development of artificial neural network (ANN) models is likely to result in an efficient use of EM simulators. Possible applications of knowledge-based tools are suggested for initial stages of the design process     

Two-terminal millimeter-wave sources

Basic principles of operation, fundamental power-generation capabilities, and fabrication technologies are reviewed for three groups of two-terminal devices, i.e., resonant-tunneling diodes (RTDs), transferred-electron devices (TEDs), and transit-time diodes. The paper focuses on devices for frequencies above 30 GHz, and an overview of recent research in this area and of various state-of-the-art laboratory results is given. As an outlook, the potential of some new material systems for high-power devices is discussed     

Printed millimeter-wave reflectarrays

Periodic and quasi-periodic structures printed on a dielectric substrate can be employed to control reflection and transmission properties of incident waves as a function of structure geometry. This can be done mostly independently for both polarizations. These structures thus allow the realization of different kinds of filters and polarizers. Local variation of the element geometry on a substrate with backside metallization — resulting in respective variations of the reflection phase angle — can be employed to design printed reflectarray antennas. Including the dual polarization properties of such antennas, dual function or dual frequency antennas can be built, or these properties can be exploited for the realization of compact, low-profile folded reflector antennas. Examples for a number of antennas are presented, including dual radiation characteristics, dual frequency operation, and very compact, low loss folded reflector antennas     

我国电子信息产业技术效率的实证研究

采用随机前沿生产函数方法对1996-2006年我国电子信息产业技术效率的变化状况进行了实证分析.结果表明:1996-2006年期间我国电子信息产业技术效率呈逐步上升的趋势,且东中西部三大地区的电子信息产业技术效率也表现出逐渐上升的趋势,但中西部地区电子信息产业技术效率要低于东部地区.     

Tuneable millimeter-wave gyrotrons

In the course of developing a low-power, tuneable millimeter-wave source, two gyrotrons have been constructed. Gyrotron I was a fixed-frequency device operating at 120 GHz while Gyrotron II produced more than 20 lines in the frequency range 130 to 260 GHz. The design of tuneable gyrotrons is discussed with reference to the Gyrotron II results.