针对UHF读写器设计中，在符合EPC Gen2标准的情况下，对标签返回的高速数据进行正确解码以达到正确读取标签的要求，提出了一种新的在ARM平台下采用边沿捕获统计定时器数判断数据的方法，并对FM0编码进行解码。与传统的使用定时器定时采样高低电平的FM0解码方法相比，该解码方法可以减少定时器定时误差累积的影响；可以将捕获定时器数中断与数据判断解码相对分隔开，使得中断对解码影响很小，实现捕获与解码的同步。通过实验表明，这种方法提高了解码的效率，在160 Kb/s的接收速度下，读取一张标签的时间约为30次/s。 Abstract: Aiming at the requirement of receiving correctly decoded data from the tag under high-speed communication which complied with EPC Gen2 standard in the design of UHF interrogator， the article introduced a new technology for FM0 decoding which counted the timer counter to judge data by using the edge interval of signal capture based on the ARM7 platform. Compared with the traditional FM0 decoding method which used the timer timed to sample the high and low level， the method could reduce the accumulation of timing error and could relatively separate capture timer interrupt and the data judgment for decoding， so that the disruption effect on the decoding was small and realizd synchronization of capture and decoding. Testing result shows that the method improves the efficiency of decoding， at 160 Kb/s receiving speed， the time of the interrogator to read a tag is about 30 times/s.
上传时间： 2013-11-10
上传用户：liufei
通过比较各种隔离数字通信的特点和应用范围，指出塑料光纤在隔离数字通信中的优势。使用已经标准化的TOSLINK接口，有利于节省硬件开发成本和简化设计难度。给出了塑料光纤的硬件驱动电路，说明设计过程中的注意事项，对光收发模块的电压特性和频率特性进行全面试验，并给出SPI口使用塑料光纤隔离通信的典型应用电路图。试验结果表明，该设计可为电力现场、电力电子及仪器仪表的设计提供参考。 Abstract: y comparing characteristics and applications area of various isolated digital communications， this article indicates advantages of plastic optical fiber in isolated digital communications. Using the standardized TOSLINK interface， it helps to control costs and difficulty in hardware development and design. Then it gives the hardware driver circuit of plastic optical fiber module， explains the noticed details in design process， gives results on the basis of the optical transceiver module voltage characteristics and frequency characteristics tests. Finally，it gives typical application circuit of the SPI communication port by using plastic optical fiber isolation .The results show that this design can be referenced for the power field， power electronics and instrumentation design.
上传时间： 2014-01-10
上传用户：gundan
同步技术是跳频通信系统的关键技术之一，尤其是在快速跳频通信系统中，常规跳频通信通过同步字头携带相关码的方法来实现同步，但对于快跳频来说，由于是一跳或者多跳传输一个调制符号，难以携带相关码。对此引入双跳频图案方法，提出了一种适用于快速跳频通信系统的同步方案。采用短码携带同步信息，克服了快速跳频难以携带相关码的困难。分析了同步性能，仿真结果表明该方案同步时间短、虚警概率低、捕获概率高，同步性能可靠。 Abstract: Synchronization is one of the key techniques to frequency-hopping communication system， especially in the fast frequency hopping communication system. In conventional frequency hopping communication systems， synchronization can be achieved by synchronization-head which can be used to carry the synchronization information， but for the fast frequency hopping， Because modulation symbol is transmitted by per hop or multi-hop， it is difficult to carry the correlation code. For the limitation of fast frequency hopping in carrying correlation code， a fast frequency-hopping synchronization scheme with two hopping patterns is proposed. The synchronization information is carried by short code， which overcomes the difficulty of correlation code transmission in fast frequency-hopping. The performance of the scheme is analyzed， and simulation results show that the scheme has the advantages of shorter synchronization time， lower probability of false alarm， higher probability of capture and more reliable of synchronization.
上传时间： 2013-11-23
上传用户：mpquest
影响无线通讯可靠性和距离的几个因素无线通信距离的主要性能指标有四个：一是发射机的射频输出功率；二是接收机的接收灵敏度；三是系统的抗干扰能力；四是发射/接收天线的类型及增益。而在这四个主要指标中，各国电磁兼容性标准（如北美的FCC、欧洲的EN 规范）均只限制发射功率，只要对接收灵敏度及系统的抗干扰能力两项指标进行优化，即可在符合FCC或CE 标准的前提下扩大系统的通信距离。一影响无线通信距离的因素1、地理环境通信距离最远的是海平面及陆地无障碍的平直开阔地， 这也是通常用来评估无线通信设备的通信距离时使用的地理条件。其次是郊区农村、丘陵、河床等半障碍、半开阔环境，通信距离最近的是城市楼群中或群山中，总之，障碍物越密集，对无线通信距离的影响就越大，特别是金属物体的影响最大。一些常见的环境对无线信号的损耗见下表根据路径损耗公式:Ld=32.4+20logf +20logd f=MHZ d=Km 可知信号每损耗6dB，通讯距离就会减少一半!另一个因素就是多路径影响， 所以如果无线模块附近的障碍物较多时也会影响通讯的距离和可靠性。2、电磁环境直流电机、高压电网、开关电源、电焊机、高频电子设备、电脑、单片机等设备对无线通信设备的通信距离均有不同程度的影响。3、气侯条件空气干燥时通信距离较远，空气潮湿（特别是雨、雪天气）通信距离较近，在产品容许的环境工作温度范围内，温度升高会导致发射功率减小及接收灵敏度降低，从而减小了通信距离。
上传时间： 2013-11-13
上传用户：bvdragon
提出了一种以ARM微处理器为控制核心的远程无线视频监控终端的设计方案，其监控终端的硬件设计包括视频采集处理、中央管理控制、无线传输3个模块。并给出了监控终端的软件开发平台和开发模式的系统启动代码、嵌入式Linux系统移植以及驱动程序和应用程序。测试结果表明，该监控终端设计方案合理、有效，基本满足监控需求。 Abstract: A remote wireless video monitoring terminal design， which uses ARM microprocessor as its core control， is proposed in this paper.The hardware design of monitoring terminal system is composed of the video acquisition and processing module， the central management and control module， wireless transmission module.Meanwhile the monitoring terminal-s software development platform and development patterns are designed. Also the design of the system-s start codes， embedded Linux system-s transplantation process， driver and the corresponding applications are given. The results showed that the monitoring terminal design is reasonable， effective， basically meet monitoring requirements.
上传时间： 2013-11-13
上传用户：wanqunsheng
3变压器在电力系统中的主要作用是什么? 答：变压器在电力系统中的作用是变换电压，以利于功率的传输。电压经升压变压器升压后，可以减少线路损耗，提高送电的经济性，达到远距离送电的目的。而降压变压器则能把高电压变为用户所需要的各级使用电压，满足用户需要。 4套管裂纹有什么危害性? 答：套管出现裂纹会使绝缘强度降低，能造成绝缘的进一步损坏，直至全部击穿。裂缝中的水结冰时也可能将套管胀裂。可见套管裂纹对变压器的安全运行是很有威胁的。 5高压断路器有什么作用? 答：高压断路器不仅可以切断和接通正常情况下高压电路中的空载电流和负荷电流，还可以在系统发生故障时与保护装置及自动装置相配合，迅速世断故障电源，防止事故扩大，保证系统的安全运行。
上传时间： 2013-11-07
上传用户：wayne595
中文版详情浏览：http://www.elecfans.com/emb/fpga/20130715324029.html Xilinx UltraScale:The Next-Generation Architecture for Your Next-Generation Architecture The Xilinx® UltraScale™ architecture delivers unprecedented levels of integration and capability with ASIC-class system- level performance for the most demanding applications. The UltraScale architecture is the industr y's f irst application of leading-edge ASIC architectural enhancements in an All Programmable architecture that scales from 20 nm planar through 16 nm FinFET technologies and beyond, in addition to scaling from monolithic through 3D ICs. Through analytical co-optimization with the X ilinx V ivado® Design Suite, the UltraScale architecture provides massive routing capacity while intelligently resolving typical bottlenecks in ways never before possible. This design synergy achieves greater than 90% utilization with no performance degradation. Some of the UltraScale architecture breakthroughs include: • Strategic placement (virtually anywhere on the die) of ASIC-like system clocks, reducing clock skew by up to 50% • Latency-producing pipelining is virtually unnecessary in systems with massively parallel bus architecture, increasing system speed and capability • Potential timing-closure problems and interconnect bottlenecks are eliminated, even in systems requiring 90% or more resource utilization • 3D IC integration makes it possible to build larger devices one process generation ahead of the current industr y standard • Greatly increased system performance, including multi-gigabit serial transceivers, I/O, and memor y bandwidth is available within even smaller system power budgets • Greatly enhanced DSP and packet handling The Xilinx UltraScale architecture opens up whole new dimensions for designers of ultra-high-capacity solutions.
标签： UltraScale Xilinx 架构
上传时间： 2013-11-21
上传用户：wxqman
本教程内容力求以详细的步骤和讲解让读者以最快的方式学会 MC8051 IP core 的应用以及相关设计软件的使用，并激起读者对 SOPC 技术的兴趣。本实验重点讲 8051Core 的应用，并通过一个简单 C51 程序对51Core 进行硬件测试。 本实验教程的内容编排如下： 第 1 章简单的描述了 MC8051 IP core的基本结构及一些应用说明。 第 2 章详细的介绍 8051Core 综合、编译应用。包括 Quartus II、Synplify Pro 软件的基本应用，ROM、RAM 模块的生成，8051Core 的封装及应用测试。 附录 A为 MC8051 IP Core 的指令集。 在阅读本教程的过程中，请读者注意以下几点： 本教程在写作过程中遵循“宁可啰唆一点，也不放过细节”的方针。在教程中的某些地方，有些读者可能觉得很“简单” ，甚至显得有些啰唆，但对大多数初学者可能并非如此。因为作者认为，足够简单甚至可以跳过的内容，对某些读者来说，未必能一下子就弄清楚，所以，本教程很 多地方将尽量阐述清楚，以节省读者理解的时间。但在后面的章节中，如果涉及的细节在前面章节中已经提及，这些内容就会省略。 最 后作者要强调的是，本教程旨在引路，不会带领读者掌握更深层次的开发，更高级的应用希望读者自己去挖掘。
上传时间： 2013-10-26
上传用户：归海惜雪
This white paper discusses how market trends, the need for increased productivity, and new legislation have accelerated the use of safety systems in industrial machinery. This TÜV-qualified FPGA design methodology is changing the paradigms of safety designs and will greatly reduce development effort, system complexity, and time to market. This allows FPGA users to design their own customized safety controllers and provides a significant competitive advantage over traditional microcontroller or ASIC-based designs. Introduction The basic motivation of deploying functional safety systems is to ensure safe operation as well as safe behavior in cases of failure. Examples of functional safety systems include train brakes, proximity sensors for hazardous areas around machines such as fast-moving robots, and distributed control systems in process automation equipment such as those used in petrochemical plants. The International Electrotechnical Commission’s standard, IEC 61508: “Functional safety of electrical/electronic/programmable electronic safety-related systems,” is understood as the standard for designing safety systems for electrical, electronic, and programmable electronic (E/E/PE) equipment. This standard was developed in the mid-1980s and has been revised several times to cover the technical advances in various industries. In addition, derivative standards have been developed for specific markets and applications that prescribe the particular requirements on functional safety systems in these industry applications. Example applications include process automation (IEC 61511), machine automation (IEC 62061), transportation (railway EN 50128), medical (IEC 62304), automotive (ISO 26262), power generation, distribution, and transportation. 图Figure 1. Local Safety System
上传时间： 2013-11-14
上传用户：zoudejile
学会不画电路图，不用网络表，用手工布线。从而加深对PCB电路版图设计的理解。
标签： PCB
上传时间： 2013-11-06
上传用户：lyson
