基于FPGA的三相函数信号发生器设计

基于FPGA的三相函数信号发生器以DDS为核心,在Altera公司CycloneⅡ系列EP2C8T144C8上实现正弦波、方波、三角波和锯齿波信号的产生,利用单片机PIC18F4550控制波形的频率及相位差。同时单片机通过DAC0832控制波形数据转换DAC902参考电压实现在波形幅度的控制,D/A输出的波形经过放大、滤波后输出。波形参数的输入输出通过触摸屏和液晶屏实现,测试结果显示该系统具有较高的精度和稳定性。     

一种基于DDS技术的2FSK铁道信号发生器

目前,我国铁道通信频率调制信号仍以二进制键控频移(2FSK)为主,为能够方便地产生2FSK调制信号,文中采用直接数字频率合成(DDS)技术研究设计了一种铁路专用的2FSK信号发生器。该信号发生器以FPGA为开发平台实现DDS模块功能,其输出离散电压信号经AD9708进行D/A转换,最后通过一个7阶椭圆低通滤波器输出正弦信号,同时单片机MSP430149作为整个系统的控制单元,控制信号的发送。所设计系统结构稳定,频率可调,相位连续,操作简单。     

基于AD9858定时信号源模块设计

定时及DDS信号源模块是将定时器和DDS信号源两个功能集成在一个模块中实现,能够完成定时信号和DDS信号的产生,并对DDS信号8倍频后,输出中心频率2.4GHz调频/调相信号。本设计采用多种方法较好的解决了模拟信号和数字信号相互影响的问题,保证了DDS输出稳定的调频信号,在实际工作中取得了良好的效果。     

基于AD9850 DDS芯片的宽频信号源

提出了一种基于单片机控制的DDS方式的高速宽频信号源系统,并对其中的LCD显示、输出运算放大模块、D/A转换模块、幅度控制模块等进行了介绍。该系统可以产生任意频率的正弦、方波、三角波信号及其各种模拟和数字调制信号功能,并且具有频率范围宽、步进小、幅度和频率的精度高等优点。     

基于ARM、DDS和蓝牙技术的信号发生器设计

提出了一种基于ARM、高精度直接数字频率合成器DDS和蓝牙技术的信号发生器的设计方案,在该方案中,ARM核心处理器通过蓝牙模块接收蓝牙终端发送的信号频率和相位控制字并将其发送到DDS模块,从而生成所需的正弦波信号。经测试,该系统能输出0⁴0 MHz频带内的正弦波和方波,可生成调频和调相等多种调制方式的调制信号,以及实现高速扫频功能。     

基于DDS的高精度频率信号源的实现

介绍了一种基于DDS（直接数字频率合成器）和单片机的高精度频率信号源的硬件实现方案。利用51单片机STC12LEC5A32S2控制DDS芯片AD9852,可以产生一个分辨率高,转换速度快,波形良好,输出频谱纯的信号。具有调幅、调频、数字调幅、数字调相、数字调频、跳频等功能。通过LabWindows上位机软件可以控制DDS的工作模式,以及工作频率。上位机和信号源通过485总线连接,可以实现远程控制。从实验数据可以得到较好的信号指标,如频率准确度,杂散和谐波。文中主要介绍了单片机与AD9852的硬件接口设计和系统设计,及注意事项。     

基于DSP和DDS的数字立体声调频发射系统

介绍了计算机控制的数字立体声调频发射机的设计。该系统利用DSP实现数字立体声调制,并通过AD9852DDS芯片将数字信号转换成射频信号。系统采用计算机控制,接收S／PDIF接口的数字音频输出,适合校园数字调频广播和外语听力训练。     

正弦信号发生器的设计与实现

为精确地输出正弦波、调幅波、调频波、PSK,ASK等信号及保证信号的高可靠性,设计出一种新型的正弦信号发生器.该正弦信号发生器以可编程逻辑器件CPLD和单片机AT89S52为基础,采用数字频率合成DDS技术实现频率合成功能,结合高速D/A器件AD9713使得输出频率维持在1k～10MHz范围内,步进为100Hz,且通过对CPLD采用相应的数字控制算法实现调频FM,调幅AM和健控PSK,ASK数字调制功能.测试结果表明,设计的正弦信号发生器输出信号稳定度优于10~-4,在频率范围内50Ω的负载上输出正弦波电压幅度稳定在6±0.6V,波形无明显失真,系统的整体性能良好.     

基于DDS的调制信号发生器的设计

DDS原理与AD9852 的结构基本的DDS是在高速存储器中放入正弦函数-相位数据表格,经过查表操作,将读出的数据送到高速 DAC产生正弦波。常用的可编程 DDS系统如图1所示。 DDS系统由频率控制字、相位累加器、正弦查询表、D/A转换器和低通滤波器组成。参考时钟一般为高稳定度的晶体振荡器,其输出用于同步DDS各组成部分的工作。     

基于MSP430的红外光通信装置的研究

MSP430系列单片机目前已广泛应用于许多数字电子控制领域。红外光通信装置将语音信号与室温的温度信号经过MSP430采样、A/D转换、编码从而实现将模拟信号转换为数字信号,再将两种数字信号调制在红外光上发射,在收发部分均辅助以光学透镜以汇聚红外光,减少信号能量的损失。接收模块对信号进行放大、滤波、整形等处理,并将得到的数字信号在控制器MSP430中进行解码与D/A转换,发送至相关模块输出,进而实现利用红外光为传输载体完成红外无线通信。该系统可以较为准确地还原原始语音信号,单片机以5.3k Hz的采样频率对语音信号进行采样,可听到喇叭播放的混有少量噪声的原始语音,同时液晶显示屏显示的室温每秒更新一次。     

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.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

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.     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.