基于DDS的扫频信号发生器

直接数字频率合成技术 (DirectDigitalSynthesis ,简单DDS)是近年来发展起来的一种新型信号合成技术。由于采用了全数字结构 ,它具有合成信号相对频带宽、频率转换时间短、频率分辨率高及合成信号相位连接等优点。介绍了DDS的基本原理 ,详细描述了DDS芯片AD70 0 8特点 ,并给出了基于AD70 0 8芯片的 5MHz扫频信号发生器。     

调频信号的数字合成方法

调频信号作为一种常见信号在电子技术的各个领域，特别是通信领域有着广泛的应用。因此调频信号的合成就成为了其中关键性的一项技术。传统的调频信号通常是通过模拟方法合成的。但是模拟合成有频率不稳定、参数设置不可量化等缺点，而用数字合成的方法就可以解决这些问题。数字频率合成通常采用DDS技术，调频信号的数字合成也基于这项技术。本文首先介绍了DDS的基本原理。然后提出用双DDS结构实现调频信号数字合成的方法。由于把调制波形的幅度量化成了频率字，构成了一个输出频率字的DDS。因此只要改变这个DDS波形RAM中的数据。就可以产生任意以周期信号为调制波形的调频信号，并且调制频率和深度都精确可调。     

一种基于DDS技术的通信信号的调制方法与设计

直接数字频率合成（DDS）技术在无线通信等领域得到越来越广泛的应用。基于DDS技术,本文介绍一种用FPGA实现的信号调制方法。设计并实现了对FM、FSK、AM、ASK、PSK等数字、模拟信号的调制。该系统的基波频率在100Hz～70MHz内可调,可以输出较理想的各种调制信号。     

基于FPGA的QPSK信号源的设计与实现

调相脉冲信号可以获得较大的压缩比,它作为一种常用的脉冲压缩信号,在现代雷达及通信系统中获得了广泛应用。随着近年来软件无线电技术和电子技术的发展,DDS（直接数字频率合成）用于实现信号产生的应用越来越广。DDS技术从相位的概念出发进行频率合成,它采用数字采样存储技术,可以产生点频、线性调频、ASK、PSK及FSK等各种形式的信号,其幅度和相位一致性好,具有电路控制简单、相位精确、频率分辨率高、频率切换速度快、输出信号相位噪声低、易于实现全数字化设计等突出优点。     

VHDL实现的基于DDS技术的干扰信号

VHDL作为一种硬件描述语言,用于描述硬件电路的功能、信号连接关系及定时关系,在电子工程领域得到了广泛的应用。DDS（直接数字频率合成）是将先进的数字处理理论与方法引入频率合成的一项新技术。介绍了DDS的基本原理及其调制特性,并利用VHDL语言编程实现了DDS;介绍了基于DDS技术的噪声调频干扰信号的产生,给出了其主要部分的仿真结果,验证了其正确性。     

一种基于AD9959的频率合成器的设计

直接数字频率合成(Direct Digital Synthesizer,DDS)利用了全数字的结构,通过DAC把数字量的信号转换为模拟量的信号,从而合成所需的模拟频率。DDS拥有直接频率合成技术与间接式频率合成技术的优势。AD9959是一个内置了4个10 bit速度最高可达500 MS/s采样率的DAC的DDS芯片。以DDS原理为依据,采用AD9959芯片,以STC10L08XE单片机为MCU,设计了一种产生高频本振信号的频率合成器,有效应用在音频信号接收机中。     

基于Verilog HDL的DDS信号发生器的设计与实现

基于数字频率合成(DDS)技术,采用分频方法,设计了一种可输出任意起始相位和一定频率范围的正弦波、方波、锯齿波、三角波的信号发生器.在QuartusII软件上进行仿真,结果表明,设计的DDS信号发生器达到预期要求,系统集成度高、扩展性好、控制灵活.     

短波发射机DDS型频率合成器的工作原理

频率合成器又简称频综,是高精密的专用频率信号源。在短波机上由它产生频率为3.9~22MHz的高稳定、高纯度的频率基准信号,作为高频放大系统的载波信号源。随着现代通信技术的发展,低相噪、高纯度、高捷变速率及高分辨率的频率合成器已经成为当今发展的主要趋势。直接数字频率合成(DDS)技术是近年来随着数字集成电路和计算机的发展而迅速发展起来的一种新的频率合成技术。其特点是:极高的频率分辨率、频率变化速度快、频率变化时相位连续、易于实现各种数字调制、集成度高。本文从论述DDS频率合成器的工作原理入手,介绍其特点。     

基于DDS的短波射频频率源设计与实现

介绍了直接数字频率合成（DDS）的结构和原理,并将DDS技术应用于短波射频通信频率源中。实现了一种基于单片机＋DDS可编程低噪声频率源,输出信号范围46.5～75 MHz。实验结果表明,该频率源具有频率分辨率高、相位噪声低等优点,满足短波射频通信系统对频率源的设计要求。     

基于DDS的毫米波汽车防撞雷达扫频源设计

利用直接数字频率合成(DDS)分辨率高、转换速度快的特点,设计了一种基于DDS芯片AD9910的毫米波汽车防撞雷达扫频信号源.通过DDS芯片产生调频、调幅、调相等各种调制信号,实现了在短距离内快速捕捉目标、处理信息、发出告警的功能.所设计的扫频源输出信号中心频率为8.6 GHz,幅度为-16 dBm,相噪为-70 dBc/Hz@1 kHz,满足了在多目标检测时对信号源的幅度、稳定度和相噪的要求,从而使DDS技术得以在微波检测领域获得应用.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks