基于FPGA与Matlab的数字正交解调器的设计

为有效提取测控系统输入信号的幅度和相位信息,设计了基于FPGA与Matlab的信号数字正交解调器;在Matlab/Simulink 环境中产生一路调幅信号,并在此环境下利用5个直接I型的4阶FIR滤波器节搭建了20阶FIR滤波器;利用FPGA查表法实现数控振荡器(NCO),并控制1路调幅信号与正交的正、余弦信号分别进行数字混频处理;对经FPGA数字混频处理后的两路倍频分量和基频分量信号进行滤波处理,经处理后的信号在FPGA的控制下进行相加处理;最后在硬件平台上进行了仿真测试实验,验证了该方案的正确性和可行性.     

基于正交混频的数字下变频技术研究

数字下变频(DDC)是软件无线电的关键技术之一,可以将宽带大数据流信号变成窄带低数据流信号,以便后端DSP实时处理;讨论了基于正交混频的数字下变频实现技术.并将它与直接抽取的数字下变频进行对比,显示出其优势,详细给出了数字振荡控制器(NCO)、信号频谱搬移、抽取前的抗混叠滤波器及整数倍抽取的设计方法;通过对一中频信号进行基于正交混频的数字下变频的仿真试验,结果正确解调出了原始信号;表明这种技术简单可行,有较高的实用价值.     

基于高速采样的实时DDC架构技术

近年来,随着混合域示波器技术的发展,示波器既要实现传统示波器的功能,又要实现频域、调制域功能,这样在数字域信号处理中需要实现实时数字下变频（DDC）功能,实时DDC技术是实现示波器向频域和调制域功能扩展的基础,可以实现示波器的增值应用,大大扩大示波器的应用领域。本文根据高速信号采样的特点,给出了实时DDC技术架构,该架构由数字正交混频、FIR1-FIR3滤波器、HB1-HB10滤波器组成,对于20GSa/s采样数据流而言,最高支持1.25GSa/s I/Q数据流输出,最低305 kSa/s I/Q数据流输出,可满足绝大多数应用场景。对数字正交混频、FIR1滤波器、FIR2滤波器、FIR3滤波器、HB滤波器进行详细设计分析,给出了实现架构,对于FIR和HB滤波器,还给出了最佳滤波器阶数及其幅频响应曲线。对于数字正交混频、FIR1-FIR3滤波器,由于其数字速率超过了FPGA正常工作时钟范围,通过多路并行处理的手段实现信号处理。最后使用矢量信号分析软件对DDC的13种I/Q速率下的EVM性能进行了评估,分别评估了载波频率1.5GHz和3GHz的EVM性能,通过评估,EVM值大部分集中在0.5%以下,可满足使用需求。     

综合孔径辐射计的接收机结构及单双边带选择

根据I/Q解调实现方式的不同,将综合孔径辐射计接收机的结构分为I/Q下变频及先下变频再I/Q解调两种。分析了综合孔径辐射计在这两种接收机结构下分别选择单、双边带工作模式反演成像时是否会产生镜像干扰。结果表明,只有在综合孔径辐射计接收机为先下变频再I/Q解调结构且选择双边带模式时,系统反演成像会产生镜像干扰,在其它3种情况下皆不会产生;通过频域分析得到镜像干扰产生的原因是接收机在信号处理过程中将射频输入信号的负频分量混叠到中频输出解析信号中。最后,对综合孔径辐射计的单双边带两种工作模式进行了比较,并通过仿真验证了镜像干扰分析结果。     

I~2形MEMS谐振器的电阻差分检测方法

为克服I2形MEMS谐振器输入端(热执行)与输出端(压阻敏感)直接耦合所造成的输出信号品质较差的缺点,设计并制作了一种电阻差分检测电路。该电路通过外接电阻的方法,产生与输出信号中耦合成分幅值相同、相位相反的差分信号。将差分信号与谐振器输出信号相组合,从而实现解耦的目的。实验结果表明,电阻差分检测可有效消除了输出信号中的耦合成分,使频谱响应曲线得到更直观的体现。与其他消除耦合信号的技术方案相比(混频检测电路、惰性谐振器等),电阻差分检测法电路设计简单,无需改动器件的加工工艺,有利于满足未来器件小型化要求。     

OFDM系统中联合抑制ICI的算法

针对正交频分复用（OFDM）系统中由频率偏移引起的子载波间干扰（ICI）的问题,提出了一种基于对称子载波的ICI自消除算法。该算法将互为相反数的发送符号映射到对称的子载波上,并在接收端将解调信号进行线性组合。为了进一步降低ICI,将基于对称子载波的ICI自消除算法与时域加窗相结合,即在发送数据符号之前,与升余弦函数相乘。对算法进行仿真实验,相对于相邻符号自消除算法,该算法减小了子载波间的干扰系数;加窗后OFDM符号频谱的边瓣衰减速度快,最大可衰减至－40 dB;对于系统的信号干扰比性能（SIR）,加窗后的算法同相邻符号自消除算法相比可提高8 dB左右;在信噪比较大的情况下,改善了系统的误码率。仿真结果表明,所提算法能够抑制ICI,提高系统抗干扰性能。     

基于温度自动补偿的直接上变频发射机中IQ不平衡校准方案

本文针对信号发射过程中，由基带信号经过正交调制后的正交 (in phase-path and quadrature-path, IQ)信号不完全正交且具有不同的幅度增益而产生的镜像干扰问题，提出了一种新的对IQ不平衡信号的校准参数进行估计的算法。通过建立不理想的信道模型，基于信号的二阶统计特性，计算发射信号和接收信号的相关矩阵，用所提算法估算出补偿参数，结合温度传感技术，对信号进行数字预校准，并对该算法的有效性进行验证。经过测试，不同温度环境下IQ不平衡信号经过校准后在理想接收端一侧的镜像抑制比(image rejection ratio, IRR)能稳定在50dB左右。     

基于FPGA的多路I2C总线设计与实现

介绍了一种基于FPGA的多路I2C总线设计与实现.主要包括系统处理器、局部总线、FPGA逻辑模块、负载设备几部分,实现了从处理器局部总线到I2C协议的转换及其多路扩展,使系统具有多个I2C总线通道,且每一路I2C总线上能挂载多个不同的主设备或从设备.该系统中各路I2C总线相互独立工作,没有干扰和影响.     

基于决策理论的模拟数字混合信号调制识别

提出一种基于决策理论的模拟数字混合调制信号自动识别算法,采用基于I/Q正交双路的信号处理架构,利用扩展收敛域的CORDIC算法提取信号的瞬时幅度、瞬时相位和瞬时频率,结合软件无线电中具体的工程实现方法,修改部分识别特征参数,介绍基于判决树的识别流程。仿真结果表明,在信噪比不小于6 dB时,采用该算法的平均正确识别率在94%以上。     

I形MEMS谐振器的电阻差分检测方法

为克服Ｉ2形MEMS谐振器输入端（热执行）与输出端（压阻敏感）直接耦合所造成的输出信号品质较差的缺点,设计并制作了一种电阻差分检测电路。该电路通过外接电阻的方法,产生与输出信号中耦合成分幅值相同、相位相反的差分信号。将差分信号与谐振器输出信号相组合,从而实现解耦的目的。实验结果表明,电阻差分检测可有效消除了输出信号中的耦合成分,使频谱响应曲线得到更直观的体现。与其他消除耦合信号的技术方案相比（混频检测电路、惰性谐振器等）,电阻差分检测法电路设计简单,无需改动器件的加工工艺,有利于满足未来器件小型化要求。     

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.