基于AD7008的数字DDS信号发生器的实现

介绍DDS的基本原理和结构,DDS芯片AD7008的功能,16位单片机MSP430F435的基本使用,以及由该单片机和AD7008芯片组成的数字信号发生器的原理和结构.利用全数字频率合成技术,制作高质量低成本的信号发生器,使用单片机通过数字调节控制AD7008芯片,对信号进行放大滤波处理,提供稳定度高和失真度小,频率、相位、幅度可调的正弦波或余弦波信号.系统频率输出稳定度高、精度高,提供高质量的信号源,为高精度的计量和测试提供方便,易于控制,在实际应用中取得了明显的应用成效.     

具有50MHz时钟率的AD7008单片CMOS DDS调制器

AD7008是美国最新推出的单片CMOS DDS调制器,它把32 bit相位累加器、SIN/COS查找表、10 bit D/A变换器以及调制和控制电路集成到一起,集相位调制、频率调制、幅度调制及I/O正交调制等多种功能于一身,具有很高的性能价格比.AD7008的时钟速率可达50MHz,输出信号频率可达 20MHz,频率分辨率可达 0.02Hz.本文简要介绍了AD7008的原理、结构及使用方法.     

基于ISP技术的数字频率扫描信号发生系统

本文介绍了利用Isp芯片Lattice公司的ispLSI1032E以及DDS频率合成器AD7008构成的数字频率扫描信号发生系统，本系统可以任意设置信号的起始频率、终止频率、信号幅值以及信号在每个频率保持的时间，系统自动以一定的频率步进量完成频率扫描，频率改变不会影响波形的连续性，也不会造成的相位的突变，真正实现频率的线性连续变化。     

用DDS芯片AD9852实现MSK调制

文章介绍了最小移频键控(MSK)调制以及直接数字频率合成(DDS)的组成及工作原理,研制了基于AT89C51以及DDS芯片AD9852的MSK调制器.系统调试灵活方便,结果表明用DDS方法实现对相位要求较高的数字调制是完全可行的.     

基于DDS的线性调频信号源设计

研究并设计了一种线性调频信号源,采用直接数字频率合成(DDS)技术产生输出信号.介绍了DDS的基本结构和原理,然后对基于DDS的AD9910芯片做了简单的介绍,并在此基础上设计了一个线性调频信号源,并给出了仿真结果.     

基于AD9959的多通道信号源设计

给出了一种基于多通道DDS芯片AD9959的信号发生装置的软硬件设计,与传统信号发生装置相比,该系统结构简单,性能可靠,其输出信号易于调制,分辨率较高.     

应用DDS芯片AD9835开发的一种高精度频率信号发生器

介绍了一种DDS专用芯片AD9835,并利用该芯片设计了一种高精度频率信号发生器,讨论了DDS芯片的基本原理、应用及其与计算机、单片机的接口。并对实际结果进行了分析。     

基于DSP和DDS技术的EAS扫频信号源设计

介绍了一种基于DSP和DDS的高精度扫频信号源的软硬件实现方案.利用DSP芯片TMS320F2812控制DDS芯片AD9834,可以产生EAS系统需要的7.7～8.7MHz频率范围内周期变化的高分辨率、转换速度快、输出频谱纯的扫频信号.文中主要介绍了TMS320F2812最小系统、AD9834与DSP的硬件接口设计、整个系统的软件编程.     

基于DDS技术线性调频正弦信号发生器的设计

直接数字频率合成技术(DDS)具有频率转换速度快、分辨率高等优点,已经成为当今合成波形的主流方法.介绍了DDS芯片AD9850的基本工作原理,设计了一种线性调频正弦信号发生器,并利用单片机控制芯片AD9850使其产生的正弦信号频率连续可调,讨论了AD950与单片机的接口,并给出了按步进1HZ或1KHZ进行线性调频的具体...     

一种基于DDS芯片AD9835的多种信号发生器

本文介绍用89C51单片微机控制直接数字频率合成器(DDS)芯片AD9835设计的高精度多种信号发生器，着重讨论了AD9835基本工作原理、与89C51接口，单片微机控制系统的硬件结构及软件设计框图。     

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.     

Call for Papers The 6^th International Conference on Grid and Cooperative Computing

Recent years have seen rapid advances in various grid-related technologies, middleware, and applications. The GCC conference has become one of the largest scientific events worldwide in grid and cooperative computing. The 6th international conference on grid and cooperative computing (GCC2007) Sponsored by China Computer Federation (CCF),Institute of Computing Technology, Chinese Academy of Sciences (ICT) and Xinjiang University ,and in Cooperation with IEEE Computer Soceity ,is to be held from August 16 to 18, 2007 in Urumchi, Xinjiang, China.     

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.     

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.     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and     

Editorial:Brain-machine interface(BMI) and cyborg intelligence

正Brain-machine interfaces(BMIs)aim at building a direct communication pathway between the brain and an external device,and represent an area of research where significant progress has been made during the past decade.Based on BMIs,mind information can be read out by neural signals to control     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate     

SCIENCE CHINA Information Sciences SUBJECT INDEX TO VOLUME 57(2014)

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