Telecommunication, satellite links and set-top boxes allrequire tuning a high frequency oscillator. The actualtuning element is a varactor diode, a 2-terminal device thatchanges capacitance as a function of reverse bias voltage.1 The oscillator is part of a frequency synthesizingloop, as detailed in Figure 1. A phase locked loop (PLL)compares a divided down representation of the oscillatorwith a frequency reference. The PLL’s output is levelshifted to provide the high voltage necessary to bias thevaractor, which closes a feedback loop by voltage tuningthe oscillator. This loop forces the voltage controlledoscillator (VCO) to operate at a frequency determined bythe frequency reference and the divider’s division ratio.
上传时间： 2013-12-20
上传用户：ABCDE
阐述了一个由上位PC机和AT89C52下位单片机组成的主从分布式温度巡回检测系统。主从机采用RS-485 串行通讯标准进行通信，可在下位单片机实现基本的温度数据巡回检测基础上，由上位PC机实现综合处理功能或扩展为远程操作。整个系统具有巡检速度快，扩展性好的特点。 Abstract: In this paper,a top PC and AT89C52 under-bit microcontrollers from the main component of the tour distributed temperature detection system is presented. Master and slave can use RS-485 serial communication standards for communications.Based on next-bit machine for basic goods temperature detected data Tour, the top can achieve the integrated treatment of PC functions or for the expansion of long-distance operation. The entire inspection system is fast, expansion.
上传时间： 2013-10-13
上传用户：zhoujunzhen
我采用XC4VSX35或XC4VLX25 FPGA来连接DDR2 SODIMM和元件。SODIMM内存条选用MT16HTS51264HY-667(4GB)，分立器件选用8片MT47H512M8。设计目标：当客户使用内存条时，8片分立器件不焊接；当使用直接贴片分立内存颗粒时，SODIMM内存条不安装。请问专家：1、在设计中，先用Xilinx MIG工具生成DDR2的Core后，管脚约束文件是否还可更改？若能更改，则必须要满足什么条件下更改？生成的约束文件中，ADDR，data之间是否能调换？ 2、对DDR2数据、地址和控制线路的匹配要注意些什么？通过两只100欧的电阻分别连接到1.8V和GND进行匹配 和 通过一只49.9欧的电阻连接到0.9V进行匹配，哪种匹配方式更好？ 3、V4中，PCB LayOut时，DDR2线路阻抗单端为50欧，差分为100欧？Hyperlynx仿真时，那些参数必须要达到那些指标DDR2-667才能正常工作？ 4、 若使用DDR2-667的SODIMM内存条，能否降速使用？比如降速到DDR2-400或更低频率使用？ 5、板卡上有SODIMM的插座，又有8片内存颗粒，则物理上两部分是连在一起的，若实际使用时，只安装内存条或只安装8片内存颗粒，是否会造成信号完成性的影响？若有影响，如何控制？ 6、SODIMM内存条(max:4GB)能否和8片分立器件(max:4GB)组合同时使用，构成一个(max:8GB)的DDR2单元？若能，则布线阻抗和FPGA的DCI如何控制？地址和控制线的TOP图应该怎样？ 7、DDR2和FPGA（VREF pin）的参考电压0.9V的实际工作电流有多大？工作时候，DDR2芯片是否很烫，一般如何考虑散热？ 8、由于多层板叠层的问题，可能顶层和中间层的铜箔不一样后，中间的夹层后度不一样时，也可能造成阻抗的不同。请教DDR2-667的SODIMM在8层板上的推进叠层？
上传时间： 2013-10-12
上传用户：han_zh
UART 4 UART参考设计，Xilinx提供VHDL代码 uart_vhdl This zip file contains the following folders: \vhdl_source -- Source VHDL files: uart.vhd - top level file txmit.vhd - transmit portion of uart rcvr.vhd - - receive portion of uart \vhdl_testfixture -- VHDL Testbench files. This files only include the testbench behavior, they do not instantiate the DUT. This can easily be done in a top-level VHDL file or a schematic. This folder contains the following files: txmit_tb.vhd -- Test bench for txmit.vhd. rcvr_tf.vhd -- Test bench for rcvr.vhd.
上传时间： 2013-11-07
上传用户：jasson5678
针对当前国内外网站内容管理系统（CMS）的背景以及发展的现状，并对网站内容管理系统以及相关理论和设计思想进行了探究，在此基础上基于J2EE架构平台下，研究了基于Struts架构的多层web应用体系，选用目前最流行的框架组合Struts2、Spring和Hibernate分层架构技术，提出了构建一个基于JAVAEE平台的网站后台管理系统的方法，并给出了系统的框架设计，包括持久层、业务逻辑层和视图层的设计。
上传时间： 2013-10-13
上传用户：lty6899826
The #1 Step-by-Step Guide to labviewNow Completely Updated for labview 8! Master labview 8 with the industry's friendliest, most intuitive tutorial: labview for Everyone, Third Edition. Top labview experts Jeffrey Travis and Jim Kring teach labview the easy way: through carefully explained, step-by-step examples that give you reusable code for your own projects! This brand-new Third Edition has been fully revamped and expanded to reflect new features and techniques introduced in labview 8. You'll find two new chapters, plus dozens of new topics, including Project Explorer, AutoTool, XML, event-driven programming, error handling, regular expressions, polymorphic VIs, timed structures, advanced reporting, and much more. Certified labview Developer (CLD) candidates will find callouts linking to key objectives on NI's newest exam, making this book a more valuable study tool than ever. Not just what to d why to do it! Use labview to build your own virtual workbench Master labview's foundations: wiring, creating, editing, and debugging VIs; using controls and indicators; working with data structures; and much more Learn the "art" and best practices of effective labview development NEW: Streamline development with labview Express VIs NEW: Acquire data with NI-DAQmx and the labview DAQmx VIs NEW: Discover design patterns for error handling, control structures, state machines, queued messaging, and more NEW: Create sophisticated user interfaces with tree and tab controls, drag and drop, subpanels, and more Whatever your application, whatever your role, whether you've used labview or not, labview for Everyone, Third Edition is the fastest, easiest way to get the results you're after!
上传时间： 2013-10-14
上传用户：shawvi
1．实验要求 l 实验目的： （1）进一步掌握指针、异常处理的使用； （2）掌握栈的操作的实现方法； （3）培养使用栈解决实际问题的能力 l 实验内容：利用栈实现迷宫求解问题，具体要求如下： （1）可以使用递归或非递归两种方法实现； （2）老鼠能够记住自己的路，不会反复走重复的路径； （3）可以自己任意设置起点； （4）必须要有异常处理，比如输入参数错误时应抛出异常 2. 程序分析 2.1 存储结构 该程序采用栈的顺序存储结构，利用一组地址连续的存储单元依次存放老鼠在迷宫中的每一步路径，由于栈的插入和删除只能在栈顶实现，因此，每前进一步，表示该点的数组元素入栈，栈顶指针top+1；每后退一步，表示原来点的数组元素出栈，top-1。栈的操作示意如图(a)所示： 图(a) 栈的操作示意图
上传时间： 2013-11-08
上传用户：jasonheung
ExpressPCB 是一款免费的PCB设计软件，简单实使。可以画双层板。 Our Free PCB software is a snap to learn and use. For the first time, designing circuit boards is simple for the beginner and efficient for the professional. Our board manufacturing service makes top quality two and four layer PCBs. Use our MiniBoard service and pay only $51 for three boards (plus $8 shipping).
标签： ExpressPCB PCB 设计软件
上传时间： 2013-11-15
上传用户：lchjng
superpro 3000u 驱动 PIC16C65B@QFP44 [SA245] PIC16C65B: Part number QFP44: Package in QFP44 SA245: Adapter purchase number AM29DL320GT@FBGA48 [SA642+B026] AM29DL320GT: Part number FBGA48: Package in FBGA48 SA642: Adapter purchase number (Top board with socket) B026: Adapter purchase number (Bottom board, exchangable for different parts) 87C196CA@PLCC68(universal adapter) [PEP+S414T] 87C196CA: Part number PLCC68: Package in PLCC68 universal adapter: this adapter is valid for all parts in this package PEP: The PEP (Pin-driver Expansion Pack necessary to work with the adapter S414T) S414T: Adapter purchase number (Universal for all parts in this package) S71PL127J80B@FBGA64(special adapter) [(SA642A-B079A-Y096AF001)] S71PL127J80B: Part number FBGA64: Package in FBGA64 special adapter: this adapter is valid for this
上传时间： 2013-10-23
上传用户：Avoid98
ExpressPCB 是一款免费的PCB设计软件，简单实使。可以画双层板。 Our Free PCB software is a snap to learn and use. For the first time, designing circuit boards is simple for the beginner and efficient for the professional. Our board manufacturing service makes top quality two and four layer PCBs. Use our MiniBoard service and pay only $51 for three boards (plus $8 shipping).
标签： ExpressPCB PCB 设计软件
上传时间： 2013-10-09
上传用户：1047385479
