Low-loss inductors built on PECVD intrinsic amorphous silicon for RF integrated circuits

The quality factor (Q) of inductors on silicon (Si) is limited by the series resistance of the metal at low frequency and by the substrate resistivity at high frequency. Oxide is generally used to isolate the useful signal of the inductor from the lossy substrate. However, stoichiometric silica (SiO2) is processed at a high temperature, which eliminates the possibility of post-CMOS integration. By contrast, plasma enhanced chemical vapour deposition (PECVD) amorphous Si can be deposited at a low temperature and is easily integrated with most Si-based processes. Intrinsic amorphous hydrogenated silicon (i-a-Si:H) also displays low conductivity. In this work, i-a-Si:H deposited at a low temperature (250?) is used in a novel approach as the isolation material for planar inductors on Si for RF integrated circuits. An improvementof more than 50% in Q is measured when 1.5 μm i-a-Si:H film is deposited on the Si substrate prior to fabrication of the inductor. This result demonstrates the influence of i-a-Si:H film on the RF performance of an inductor. Intrinsic a-Si:H is shown to be a promising material for the isolation of RF devices on low-resistivity Si.     

非晶硅太阳电池作为空间能源的性能特点

总结了非晶硅太阳电池在器件物理、制造工艺、大规模生产和应用方面所取得的重大进展。文章分析了非晶硅太阳电池作为空间能源系统技术上的主要优势;很高的质量比功率和可弯曲特性;极好的抗辐照性能;良好的高温性能;较高的空间效率和低的制造成本,这是其它太阳电池不具有的优势,使得非晶硅太阳电池能源系统在低成本通信卫星、平流层气球通讯平台,以及空间太阳能电站应用领域内具有较强的竞争力。     

Simulation of hydrogenated amorphous silicon: temperature dependence of nonequilibrium distribution functions for trap states

Journal of Computational Electronics - Nonequilibrium distribution functions (NDFs) for trap states in the mobility gap under photoillumination and zero bias voltage are derived by a constructed...     

Equivalence checking for digital circuits

Integrated circuit technology has made it possible to produce chips with several millions of transistors. However, the increasingly more complex digital circuit designs and limited time constraints only add to the pressure during the implementation process. Traditional functional verification based on simulation has, during the design creation phase, reached its limits. Thus alternatives to simulation are being used. The most important alternative is equivalence checking, known also as formal verification. With equivalence checking, the highly automated analysis of the different levels of digital circuit design is performed. A comprehensive formal verification solution at every stage in the design-flow is the main approach for today's digital circuit design. Equivalence checking uses mathematical proof algorithms, then verifies every node in the design. Thus, equivalence checking guarantees 100% verification coverage without the need for test vectors. This is the big advantage over the traditional practice of functional verification by simulation that is directed by a set of test vectors.     

Computer assisted diagnosis for digital mammography

This article describes the application of wavelet transform for image enhancement in medical imaging. The initial clinical application is the enhancement of microcalcification clusters (MCCs) in digitized mammograms to improve both their visualization and their detection using computer assisted diagnostic (CAD) methods. The potential universal application for improved visual interpretation of medical images using a computer monitor is also demonstrated. The early detection of MCCs is important in screening programs since their presence is often associated with a high incidence of breast cancer. The enhancement of MCCs is an excellent model for real world evaluation of the wavelet transform. The detection of MCCs presents a significant challenge to the performance characteristics of X-ray imaging sensors and image display monitors since microcalcifications vary in size, shape, signal intensity, and contrast and may be located in areas of very dense parenchymal tissue, making their detection difficult. The classification of MCCs, in turn, as benign or malignant, requires their morphology and detail to be preserved     

QE测量在晶体硅太阳电池研究中的应用

介绍了量子效率测量的原理以及此项技术在太阳电池研究中的应用。通过对晶硅太阳电池量子效率的测量,分析了不同设备和工艺参数对太阳电池量子效率的影响,为优化生产工艺,提高电池性能提供有力的依据。     

Wavelets for contrast enhancement of digital mammography

Multiresolution representations provided an adaptive mechanism for the local emphasis of features of importance to mammography. In general, improvements in image contrast for multiscale image processing algorithms were superior to those obtained using existing competitive algorithms. These initial results are encouraging and suggest that wavelet based image processing algorithms could play an important role in improving the imaging performance of digital mammography. In part 2, features blended into the mammograms were "idealized" representations of the types of objects that are of primary interest to mammographers. The resultant mammographic images were appropriate for the purpose of demonstrating improved image contrast made possible by wavelet based image processing algorithms. These images were also useful for comparing multiscale wavelet based algorithms with existing image processing algorithms. The test results obtained in this study, however, cannot be directly extrapolated to clinical mammography. In addition, it is also important to study possible image artifacts introduced by new wavelet filters, which may increase the false positive rate     

Envelope compensation for high speed digital protection

The time delay compensation method as presented previously by B.S. Ashok Kumar (1986) attempts to reduce the delay introduced by different components of a relaying system. The method uses the transient fault signal, the prefault signal, and a predetermined system time constant to estimate the postfault steady-state signal. While the results were encouraging from the viewpoint of delay reduction, a number of difficulties such as overreaching, singularity at the origin, and oscillations were encountered. Among these, the overreach problem was severe enough to warrant a search for new methods. The authors report the results of a variety of methods that have been tried for reducing the overreach problem. A better convergence function has been identified which gives faster fault detection without increased overreaching. Other problems mentioned above are also reduced by the new method. The method is verified using computed transients of a transmission line     

全数字化继电保护测试系统设计

介绍了基于IEC61850规约的全数字化继电保护测试系统的设计思路和实现方案.该测试系统基于CPU+DSP模式的高速双处理器硬件平台,在硬实时多任务操作系统μC/OS的基础上,针对IEC61850通信及全数字化保护测试相关需求,通过合理分配任务优先级和任务间调度与通信,可很好地实现以太网链路层通信、模拟量电流和电压信号的采样与转换、符合IEC61850要求的采样值数据组帧与发送等强实时性功能.为了完成闭环试验,按照IEC61850的要求,该测试系统还具备接收、解析保护设备所发出的GOOSE跳闸信号,并将断路器位置接点信号编码、组帧、发送GOOSE开关量报文给全数字化继电保护装置等的功能.在上述基础上,通过人机接口软件配合,还可以实现全数字化保护的动态模拟试验、静态测试、暂态仿真闭环测试、定值校验等功能.     

Error detection and correction templates for digital courses

Error detection and correction [EDC] is normally considered an advanced topic, and therefore it is not usually covered in an introductory digital electronic book, with an exception of Mano and Kime. This lack of discussion is unfortunate, because not only is error detection and correction an increasingly important topic in digital design, but it is fairly easily injected into digital logic courses. A spreadsheet “template” based methodology is proposed, which will assist the students to visualize the error detection and correction. An additional benefit to this methodology is that the templates utilized are analogous to the familiar digital design methodologies such as Karnaugh maps and Quine-McCluskey methods     

机车姿态仿真系统横向数学模型及其数字仿真

通过对系统的分析 ,建立机车模拟驾驶装置横向的数学模型 ,通过数字仿真分析系统的动态特性。     

交流数字伺服系统的智能力矩控制

本文提出了一种交流永磁同步伺服电机的数字式交流伺服系统的高性能电流控制方案。该方案采用数字式智能力矩控制和滑模变结构力矩控制器，得到了平稳的直轴电流响应和快速且平稳的交轴电流响应，减少了交轴电流的脉动，因而可改善系统的速度和位置控制性能。数字仿真和实验结果证明了该方案的有效性和实用性。     

Fault impedance estimation algorithm for digital distance relaying

Fault impedance is one of the major parameters that must be estimated accurately in digital distance relaying application. In this paper, a new algorithm is proposed based on symmetrical components theory. The proposed algorithm has computational advantage over previously suggested symmetrical components based algorithms. A procedure for applying shunt fault conditions to the sequence equations to estimate fault impedance of the protected transmission line is discussed. The Alternative Transient Program (ATP) that is available on personal computers was used in evaluating the proposed algorithm. ATP models a power system and simulates many fault conditions on a selected transmission line. Fault data obtained were used in calculating fault impedance using the proposed algorithm. Fault impedance estimates were inserted in relay characteristics to determine suitability of the proposed algorithm for first zone distance protection. Sample results of these studies which show stable fault distance estimates are presented and discussed in the paper     

A modified sensitivity measure for linear digital systems

In this paper a new sensitivity measure for state space systems is proposed. This new measure is a modified form of Tavsanoglu and Thiele's measure but has three advantages: (1) it is more precise than Tavsanoglu and Thiele's measure when the parameters of the state space realizations contain 0 and ±1; (2) it can be used to explain why the sparse Schur and Hessenberg realizations can give better actual sensitivity performance than the corresponding fully parametrized optimal realizations; (3) it is identical with the global round-off noise gain G = tr(QW) + y obtained by Hwang under a dynamic constraint.     

数字化变电站的几个关键技术问题

以非常规互感器和支持IEC61850标准的变电站自动化系统为应用标志的数字化变电站将构成数字化电网发展的基础,分析了数字化变电站具有的特点,对数据采集共享、电子式互感器可靠性、系统的网络选型、IED的互操作性实现、状态检修的在线监测技术的开发应用等实现数字化变电站的关健技术问题进行了分析讨论,对数字化变电站技术的研究与发展具有一定的指导意义.     

A digital soft-start circuit for buck DC-DC converter

In this paper, a soft-start circuit is present to prevent the large surge current and overshoot voltage to improve the reliability of the DC-DC converter. The proposed structure generates the step-shaped soft-start voltage through 7 bits DAC. Combining with the PWM comparator, the soft-start circuit controls the system duty cycle directly. The mechanism of the soft-start acts as the high clamp function, which eliminates the need of the clamp circuit. A DC-DC buck converter with the proposed soft-start circuit is based on a 0.4 μm BCD process for verification Hspice simulation shows that under the condition with 3.6 V input voltage, 1.8 V output voltage and 600 mA load current, the soft-start is achieved. After 1.2 ms of the soft-start time, the operation turns to stable.     

Wavelet transform based digital protection for transmission lines

This paper presents a high speed, computationally efficient scheme for protection of transmission lines. The relay logic consists of three parts: directional protection, fault classification and fault location. Wavelet transform is used for extracting information from the fault transients and only the first level high frequency details of the voltages and currents are used. Proposed protection logic compares the directional signals from both terminals to discriminate between faults inside and outside the zone of interest. Fault classification is achieved using local terminal current information. An estimate of the location of the faults is obtained utilizing single faulted phase current information from both terminals. The logic is deterministic and can work reliably in the presence of fault resistance, load variation and CT saturation. The validity of the proposed logic was exhaustively tested by simulating various types of faults on a four bus meshed system modeled in EMTP/ATP.     

一种便携式天气雷达数字中频测试系统

雷达数字中频系统是雷达接收系统的核心部件,其性能直接影响到整个雷达系统的工作效率.介绍了一种可行的便携式数字中频测试系统的硬件测试平台和软件控制程序,通过对天气雷达数字中频的A/D信号数据采集测试和I/Q数据测试,分别实现了分析数字中频A/D信号和I/Q数据的FFT频域分析界面和Time Data时域分析界面的图形,能够快速地分析、处理和显示,可以准确、高效的完成对天气雷达数字中频的测试和维护;解决了雷达台站无法配置频谱仪等昂贵设备的条件限制,缩短了技术支援的时间和实效性,可提高对天气雷达的业务保障时效,为天气雷达的现场测试保障体系提供一种新的解决方案.     

数字视频信号测量与基带传输的研究

针对数字视频信号与基带传输测量专业设备昂贵的问题,提出了使用标准示波器、频谱分析仪和矢量网络分析对数字视频信号在时域的眼图和频域的频谱进行分析及测量方法,给出了具体仪器进行实际的测试结果和分析图形。具体对数字基带信号在同轴电缆传输的设计冗余量处理进行了研究分析,根据具体的同轴电缆均衡芯片指标计算出比电缆厂家提供数据更长的同轴电缆传输距离,实际测试数据验证了用均衡芯片指标计算的同轴电缆传输长度更准确。