一种进位链TDC的实现及其抽头方式研究

采用Xilinx公司的Kintex-7内部的进位链,实现了时间数字转换器(Time to Digital Converter,TDC)。采用码密度校准方法 对TDC进行逐位校准,标定了TDC的码宽。码密度校准过程中发现,不同的进位链抽头位置会导致TDC的码宽不同、非线性不同,研究了2抽头、 4抽头方式下的TDC的码宽和非线性,在“0tap+3tap”的2抽头方式下,TDC可以获得较好的线性,时间分辨率为25 ps(对应最低有效位(Least Significant Bit,LSB)),微分非线性范围为-0.84～3.1 LSB,积分非线性范围为-5.2～2.2 LSB。     

一种低功耗高精度CMOS动态比较器设计与实现

设计了一种全差分动态比较器。比较器是前置放大器与动态锁存器组成的开关电容电路。在四相互不交叠时钟控制下,前置放大器完成对输入信号采样、放大,高增益提高了比较器的精度,采用正反馈结构提高了比较器的速度。文中分析了引起失调的原因,结合版图给出了减小失调的方法。分析和模拟结果表明比较器输入动态范围为2V,失调电压降低到3．5mV,达到了8bit精度要求,同时实现了0．48mW的功耗。     

基于时间累加器的二阶ΔΣ时间数字转换器

提出以一个可获得高的分辨率和宽的信号带宽的二阶ΔΣ时间数字转换器(TDC),TDC基于门控环形振荡器型TDC并结合时间差加法器构成的时间累加器实现了二阶量化噪声整形。采用SMIC 28nm工艺设计,Spectre仿真结果表明,在1 M带宽内噪声底约为-82 d Bps~2/Hz,等效到50 Ms/s奈奎斯特率型TDC的分辨率约为2 ps,功耗取决于输入时间间隔,在测量间隔1ns时功耗约为1.19 mW。受到结构限制,这种类型时间数字转换器输入范围较小。     

低失调低踢回噪声双尾动态比较器设计

对传统双尾动态比较器的预放大器的增益进行了近似分析,提出了具有高预放大器增益和低输入参考失调电压的新型比较器。所提出的比较器对踢回噪声具有低灵敏度,因为在预放大器的输入和输出之间存在一个高阻抗路径,在TSMC 0. 18μm工艺和1. 8 V的电源电压下,对比了不同的比较器并进行了仿真验证。仿真结果表明:踢回噪声为3 mV,且所提出的比较器具有低功耗和低输入参考失调电压的优势,所提出的比较器适用于低踢回噪声、低失调的应用领域。     

一种超低输入共模电压的动态比较器电路设计

为了适应物联网低功耗的应用场景,并满足低电源电压和低输入共模电压的工作要求,提出了一种适用于超低输入共模电压的双正反馈回路动态比较器。该比较器采用时序开关控制输入输出,解决了传统动态比较器在输入电压低于阈值电压时无法正常工作的问题,增大了输入动态范围;电源到地之间仅堆叠两级MOS管,降低了最小电源电压;引入两个正反馈回路,提高了分辨率。采用TSMC 180 nm CMOS工艺设计和验证,仿真结果表明,在电源电压为900 mV,差模电压为1 mV情况下,提出的比较器最低共模电压为51 m V,与传统StrongARM动态比较器和DoubleTail动态比较器相比,分别降低了374 mV和264 m V;当输入共模电压低于阈值电压时,在中等的功耗下实现了最低的延时。     

高速CMOS锁存比较器的设计

本文设计了一款用于△-∑调制器的高增益高速CMOS锁存比较器.在两相互不交叠时钟的控制下,采用四级前置放大器完成对输入信号的采样、放大,高增益提高了比较器的精度并抑制了踢回噪声,采用正反馈的锁存器提高了比较的速度.采用一种新颖的共模反馈电路实现了对输出共模电平的稳定,并采用有效的措施限制了前级放大的差分输出摆幅.设计中采用高速度、传输延时较小的推挽输出,降低了整体功耗.     

一种增益增强的折叠-共源共栅运算放大器

设计了一种适用于数字音频功放中△-∑A/D的全差分跨导运算放大器,通过采用增益增强方法,使运放具有较高的直流增益.电路采用SMIC 0.5μ CMOS混合信号双阱工艺.并在Cadence环境下用Hspice进行模拟仿真.结果表明:该运放增益可达85dB,负载电容为2.5pF时,相位裕度为68.8°,单位增益带宽为44.3MHz,共模抑制比为127dB,输入共模范围为0.3V～4.4V.     

一种降低并行ADC非线性误差的电容平均技术

提出了一种降低并行ADC中比较器失调的电容平均网络。该网络由比较器的输入失调存储电容和平均电容构成。通过理论推导和ADC系统级仿真,当平均电容与输入失调存储电容取值相等时,电容平均网络可以有效抑制70%以上的INL误差和DNL误差。     

运算放大器工作原理的深度剖析

通过引入杠杆原理深度剖析运算放大器的工作特性,给出比较器与放大器、积分与比例积分电路、微分与比例微分电路、PID调节器的电路运算本质。如比较器与放大器的本质区别是反馈形式不同,积分电路的积分过程是恒流源对电容的充电过程,比例积分比积分快及比例微分比微分慢是因为串联电容的电阻起分压作用等。将电路原理映射到杠杆原理中,获得输入与反馈电路中的电阻电容对电路增益及相位的变化规律,用Saber软件仿真,结果验证了理论分析的正确性和有效性。     

基于TDC的MVT高速采集方法研究

针对目前ADC采样存在的集成化、成本和功耗相互制约等问题，实现了一种基于TDC的多通道高速采样方法，精度不受ADC采样位宽限制，只与所用FPGA芯片的硬件参数和软件设计有关，且采样通道数只与可配置的LVDS口的数量和FPGA芯片资源大小相关。与传统ADC采样方法不同，首先，设计采集电路，用已知连续阈值信号作比较器阈值电压，TDC记录信号越过阈值时间获得采样点；其次，探究阈值信号和比较器对采样信号的影响，统计各影响因素的误差并寻找最优解；最后，总结采样规律并分析其适用性。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

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。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

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.     

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.     

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。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.