一种低功耗低噪声8相位输出环形振荡器

针对环形振荡器的功耗大、噪声大、线性度差等问题,基于TSMC 55 nm工艺,提出了一种新型交叉前馈结构环形振荡器电路。深入分析了器件自身热噪声、闪烁噪声对环形振荡器输出相噪贡献百分比,利用电容滤波技术来降低振荡器输出相噪,采用源极负反馈电路得到线性电流来改善调频线性度,并提供了宽调谐范围。Spectre RF仿真结果表明,设计的环形振荡器频率覆盖范围为0.2 GHz~3.8 GHz,产生8相位,相位噪声为-91.34 d Bc/Hz@1 MHz,在1.2 V电源电压下消耗电流为4.6 m A,线性度良好。     

一种低相噪CMOS环形振荡器设计

设计了一种带有正交输出,频率为900MHz的两级低相噪环形振荡器,电路设计采用0.18μm CMOS工艺,电源电压为1.8V.环形振荡器的调谐范围随控制电压从0V的1460MHz到电源电压1.8V的720MHz发生变化,并且具有较好的线性度.在频率为900MHz、偏移载波频率为600kHz的情况下,环形振荡器的相位噪声为-108dBc/Hz,功耗为18mW.在与其它环形振荡器的比较中,yynw环形振荡器显示了较好的性能参数.     

低相位噪声宽带LC压控振荡器设计

基于0.13μm CMOS工艺,设计了一款低相位噪声宽带LC压控振荡器。采用开关电容阵列使VCO在达到宽调谐范围的同时保持了低相位噪声。采用可变容阵列提高了VCO频率调谐曲线的线性度。仿真结果表明,在1.2 V电源电压下,电路功耗为3.6 m W。频率调谐范围4.58 GHz-5.35 GHz,中心频率5 GHz,在偏离中心频率1 MHz处相位噪声为-125d Bc/Hz。     

基于环形振荡器的压控振荡器的频率设计

文章分析了环形振荡器中延迟环节内与延迟时间(即振荡频率)有关的MOS管参数问题,结合一个中心频率为600MHz,0.18-μmCOMS制造工艺,1.8-V电源电压的VCO设计,做了仿真验证。最后文章总结出对于一般的基于环形振荡器的压控振荡器的频率调解的方法。     

DSP内嵌PLL中的CMOS压控环形振荡器设计

介绍了一种用于DSP内嵌锁相环的低功耗、高线性CMOS压控环形振荡器.电路采用四级延迟单元来获得相位相差90.的正交输出时钟,每级采用调节电流源大小,改变电容放电速度的方式.基于SMIC 0.35μm CMOS工艺模型的仿真结果表明,电路可实现2MHz至90MHz的频率调节范围,在中心频率附近具有很高的调节线性度,且总功耗仅为3.5mW.     

适用于频率综合器的宽带低相噪VCO设计

针对频率综合器在宽调谐范围下相位噪声变差的问题,设计了一款适用于频率综合器的宽调谐范围低相位噪声的压控振荡器;采用180nm BiCMOS工艺,运用可变电容阵列和开关电容阵列实现宽调谐范围;通过加入降噪模块,滤除压控振荡器产生的二次谐波和三次谐波,增大输出振幅,降低相位噪声;并在压控振荡器输出端加入输出缓冲器,降低频率综合器其他器件对压控振荡器的影响;通过Cadence软件对压控振荡器进行仿真,仿真结果表明：调谐电压为0.3~3V,压控振荡器的输出频率范围为2.3~3.5GHz;当压控振荡器的中心频率为3.31GHz时,在偏离中心频率10kHz、100kHz和1MHz处的相位噪声分别为-93.21dBc/Hz,-117.03dBc/Hz,-137.41dBc/Hz,功耗7.66mW;在较宽的频率范围内,取得良好的相位噪声抑制,提高压控振荡器的噪声性能,满足宽带低相噪频率综合器的应用需求。     

低功耗宽调谐范围锁相环设计

针对传统锁相环输出频率范围有限、功耗大的缺陷,通过对压控振荡器震荡机理进行理论分析,设计了一款用于时钟发生器的低功耗、宽调谐范围、低相位噪声锁相环。该锁相环采用了新型可编程、低调谐增益、低功耗的环形振荡器,达到了宽频率输出范围、低相位噪声、低功耗的目的,采用SMIC公司0.18um混合信号工艺,用Cadenced的Hspice仿真工具进行仿真,在1.8V电源电压供电情况下获得了50MHz~1.7GHz的频率锁定范围和1.8mW~2.3mW的较低功耗。单边带相位噪声在10KHz频偏处为-104dBc/Hz.。     

一种用于GPS波段的低相噪VCO设计

设计了一种工作频率为1.8 GHz的低相噪频率可调的LC压控振荡器电路。该压控振荡器采用AMOS管作为变容二极管,提高了频率的调谐范围。为了降低电路的相位噪声,设计中采用了PMOS顶部偏置电路代替底部的NMOS偏置电路,并在电路中串联了一个大电容以滤除电路中的高频噪声。仿真测试结果表明,该电路在1 MHz频偏时其相位噪声为-116.5 dBc/Hz。     

恒定压控增益的宽带CMOS LC VCO的设计

采用SMIC 0.18μm Mixed Signal CMOS工艺设计了恒定压控增益的宽带LC压控振荡器。采用模拟式振幅负反馈的方式,通过模拟电路实现对偏置电流的负反馈控制,同时采用了通过数字控制的单刀双掷开关控制可变电容阵列的调谐,并且对固定电容单元进行开关的方法,从而实现恒定的压控增益且相邻频带之间的频率间隔近似相等。后仿真结果表明,本设计的LC VCO调谐频率范围2.15~3.03 GHz,压控增益在全部频率调谐范围内为70~80 MHz/V,相位噪声在全部频率调谐范围内低于-120.0 d Bc/Hz@1 MHz。     

应用于网络安全协处理器的真随机数产生器

介绍一款基于环形振荡器的真随机数产生器。电路使用固定频率时钟采样可控频率振荡器的输出,使用级间反馈随机改变可控频率振荡器的振荡频率。设计启动电路来保证环形振荡器快速起振,在使能信号无效时断开振荡电路以节省功耗。电路采用CMOS 0．18μm标准工艺实现,使用Hspice-RF仿真环形振荡电路的相位抖动以获得最优设计参数。仿真结果表明,电路在输出速率为1Gb／s时产生的随机序列具有良好的随机性,该设计可用于网络安全协处理器中。     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。