高频数字抽取滤波器的设计

设计了采样频率为640 MHz、过采样率为64的高频数字抽取滤波器。该数字抽取滤波器由CIC(Cascaded Integrator Comb)滤波器(降16倍)、CIC补偿滤波器(降2倍)和半带滤波器(降2倍)组成。为了实现高频工作,CIC滤波器采用两级结构,第一级采用多相分解技术,使大部分结构工作在较低时钟频率下,极大地降低了CIC的功耗,第二级采用传统结构。CIC补偿滤波器使信号通带平坦,半带滤波器满足了阻带的衰减要求。为了验证数字滤波器的性能,搭建了四阶前馈—反馈结构ΣΔ调制器,作为数字抽取滤波器的输入,最终在输入信号频率为0.5 MHz时,数字抽取滤波器输出的信噪比为97.40 dB。     

用于温湿度信号采集的∑-Δ型ADC的设计与实现

为实现室内育种多通道温湿度的信号采集,采用基于过采样原理的∑-△模数转换器(ADC)及FPGA的方案更为方便简单.针对温湿度采集的低成本、低精度要求,选择了由FPGA的低压差分输入端(LVDS)及其内部的抽取型级联积分梳状(CIC)滤波器实现的一阶ADC.该ADC分辨率达到12位,转换时间约为350 μs,温湿度测量精度完全满足同类型系统指标要求,可作慢信号采集的通用ADC.通过ChipScope在线调试和改进调理电路,使得测量误差进一步减小.还可采用高阶ADC满足高精度多种类模拟信号测量,具有适用性强、成本低、功耗低,且集成度高等特点.     

一种面向Sigma Delta ADC的数字降采样滤波器的设计

近年来Sigma Delta模数转换器得益于其优异的性能,在各个领域都有广泛的应用。本文提出了一种面向Sigma Delta ADC的数字降采样滤波器,能满足多种工业、医疗测量场景应用。该应用场景下对数字滤波器提出了高精度、低功耗、线性相位的需求。本文设计的数字滤波器使用两级非递归定系数FIR滤波器对CIC滤波器进行补偿,形成平坦的通带与较窄的过渡带。同时,复用乘法器与加法器使得硬件资源消耗大大降低。所设计的数字抽取滤波器通带为0.92kHz,通带纹波为±0.02dB,阻带为1.5kHz。该设计基于TSMC 180nm CMOS工艺,工作在1.8V电源电压和128的过采样率。仿真结果显示,级联三阶一位量化的调制器后,能在1kHz带宽下实现95dB的SNDR,以及100dB的DR。     

地震勘探中高效积分梳状滤波器优化设计

在地震勘探数据采集过程中,∑-△调制器输出的信号速率较高,并含有大量的高频噪声,这给输出信号进行直接编码处理增加了难度.通过分析信号的频谱特征,设计了一种多级高效积分梳状滤波器(CIC),用来降低输出信号速率；同时,为了克服CIC滤波器通带纹波大的缺点,采用内插二阶多项式( ISoP)滤波器来补偿其通带衰减.实测数据表明,CIC与ISOP滤波器级联适用于地震勘探信号处理.     

用于Sigma—DeltaADC的数字抽取滤波器研究

该文提出了一种对数字抽取滤波器的参数进行自动优化设计的方案。针对降低数字抽取滤波器的面积和功耗,对确定合适的CIC抽取滤波器的级联数目和抽取因子以及半带滤波器的级联数目和阶数进行了讨论和分析。采用上述方案,实现了一个256倍的降频,输入信号采样频率为512kHz,输出信号频率为2kHz,输出信号的信噪比（SNR）为110dB的数字抽取滤波器。最后用Simulink软件进行了仿真验证。     

高阶∑△ADC中的抽取滤波器的设计

从电路实现和降低功耗的角度出发,优化并改进了梳状滤波器结构,同时设计了 FIR 补偿滤波器对其通带衰减进行补偿,通过合理的硬件电路安排来节省面积、提高速度,最终完成了高阶∑△ADC 中的抽取滤波器的设计。经过 Matlab 仿真,该滤波器阻带衰减为-65dB,通带纹波为±0.05dB,过渡带为0.454fs～0.583fs,经过 VerilogXL 和系统验证,该滤波器完全满足∑△ADC 的系统要求。     

基带滤波在GLONASS卫星信号仿真器中的应用

分析了GLONASS卫星信号的频谱特性,针对其频谱混叠现象,首先采用CIC滤波器对GLONASS的基带信号进行插值滤波,然后再调制到相应的中频载波上;同时完成了CIC滤波器的FPGA实现,并分析了滤波时接收机信号捕获的影响.该方法使得产生的仿真信号在理论和实际上都达到了GLONASS系统要求,并通过实验验证了基带滤波在GLONASS卫星信号仿真中的可行性和有效性.     

改进的抽取滤波器设计

在Sigma-Delta ADC芯片中,数字抽取滤波器电路占据了大部分面积。所设计的改进型Hogenauer CIC滤波器,将梳状部分进行优化,采用控制单元、加法器和寄存器代替传统Hogenauer CIC滤波器中的差分器,从而减小数字电路的面积。一个采用这种结构的4阶32倍降采样数字滤波器在Stratix Ⅱ系列2S30 FPGA芯片中实现。经过测试,耗费的硬件资源比传统Hogenauer结构滤波器减少11%。     

基于FPGA的CIC滤波器的设计

级联积分梳状(CIC)滤波器是一种被广泛应用于软件无线电中实现抽取或者插值的高效滤波器.它主要用于降低或提高采样率,同时也具有低通滤波的作用.CIC滤波器的主要特点是,仅利用加法器、减法器和寄存器(无需乘法运算),占用资源少,实现简单且速度高.针对软件无线电中的多速率信号处理技术,以降低采样率为例,首先简要总结了CIC滤波器的理论要点,重点介绍了基于FPGA的CIC滤波器具体设计方案和实现方法;然后运用VHDL语言在FPGA上进行了仿真、综合,仿真结果验证了设计的有效性和可行性.最后将其成功地运用于DDC芯片的开发中.     

一种高效灵活数字上变频FPGA设计

数字上变频器是软件无线电的核心部件之一,其基本功能是增加基带信号采样率并把其搬移到载波频率上.本文采用内插滤波器特性较好的积分梳妆滤波CIC和补偿滤波器CFIR级联的插值滤波器结构,载频可编程的数控振荡器(NCO)在Ahera FPGA EP2SGX90上实现了稳定可靠的数字上变频器.     

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.     

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.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

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.