直接数字式频率合成信号的滤波处理

直接数字式频率合成信号技术广泛应用于任意波形发生器中,笔者在分析了直接数字式频率合成信号杂散的主要来源的基础上,设计了分别针对合成的正弦信号、任意信号的两种滤波器,并给出了仿真和实际设计结果.     

基于FPGA的便携式RLC参数测量仪

介绍了一种新型的数字式便携RLC参数测量仪。它采用直接频率合成(DDS)技术,由FPGA直接生成测量所需的正弦波数字信号;选择自由轴伏安法测量原理,配合五端测量法来保证测量电路简洁高效;设计了全新的数字式全波鉴相器,提高了鉴相精度;高速AD采样配合FPGA进行数据采集与处理,使整个系统体积小,运行速度快,测量精度高,满足复杂场景与功能的设计要求。     

数字合成式三相低频正弦波信号发生器的设计

采用数字合成技术制作了三相正弦波信号发生器,详细的分析了其电路工作原理和参数的选择,并将VBA的强大编程功能应用到对数据点的计算中。实验结果表明该设计所生成的三相正弦波具有频率精确度高、波形失真小、幅值稳定等优点,是各种测量和控制电路中理想的单相和三相基准正弦信号发生器。     

一种多功能信号发生器的设计与实现

本文介绍一种多功能信号发生器的设计,系统采用凌阳公司SPCE061A单片机,实现数字式正弦波、三角波、方波信号的输出,幅值和频率可调,具有液晶显示和语音播报波形种类、频率、幅度的功能.经测试验证,该信号发生器结构简单,操作方便,输出稳定,成本低廉,具有较高的实用价值.     

基于FPGA的DDS信号发生器设计

设计了一种可灵活在线调节的直接数字频率合成信号发生器,首先利用现场可编程门阵列生成各种频率、波形的信号数据,再采用LTC1821实现D/A转换,最后通过选择性滤波和功率放大电路实现信号输出,幅值范围0～10V,频率范围1Hz～100kHz,波形可设为三角波、矩形波、正弦波、锯齿波;实际测试验证了信号发生器的准确性和有效性.     

直接数字频率合成芯片AD9832原理及其典型应用设计

直接数字式频率合成技术可以提供快速的信号建立时间,纯净的信号频谱,方便地产生各种波形,实现各种调制方式,在通信与电子系统中广泛应用.笔者介绍了直接数字频率合成芯片AD9832的组成结构、转换原理和典型应用电路,分析了与80C51的接口时序,并给出了C驱动源代码.     

一种数字式移相信号发生器的设计与实现

随着现代电子测量技术的发展，能够产生各种波形信号的数字式信号发生器的应用越来越广泛。介绍了一种双通道数字式移相信号发生器的设计方法，该信号发生器以单片机和CPLD为核心，主要采用了直接数字频率合成（DDFS）、直接存储器存取（DMA）、数字移相和数字调幅等技术，可以产生幅值可变的任意波形，也可以通过改变单片机程序随意改变该信号发生器的特征。整个系统简易灵活，具有英文菜单显示和键盘输入，可作为信号源应用于科研和教学实验。     

基于FPGA的正弦信号发生器设计

设计一个基于FPGA的正弦信号发生器,该系统由FPGA、单片机和辅助电路三部分组成,能产生1kHz一10MHz范围、频率步进100Hz可调的正弦波信号。     

双定子静电微电机控制系统的信号检测研究

介绍了一种基于悬浮转子微陀螺的双定子轴向静电微电机控制系统的信号检测方法,它对实现悬浮转子旋转驱动的闭环控制尤为重要,其主要特点是采用互相关检测—锁定放大、DSP控制直接数字频率合成(DDS)产生正弦波,并通过实际正弦波发生电路和系统仿真验证其可行性,这些提供了解决微小电容检测在实际电路实现上的一些关键问题的办法,为实际电路参数选择提供重要参考。     

基于CPLD和单片机的数字频率计硬件电路设计

采用CPLD芯片和单片机相结合方法实现对正弦波和方波信号的频率测量。硬件设计方面通过施密特触发器进行信号整形,再利用CPLD进行频率计数,然后将计得的数据传输到单片机中进行处理,最后用LCD1602液晶显示器显示结果。该文试图探讨基于CPLD和单片机的数字频率计的硬件电路设计。     

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。     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。