综合基带遥测单元信号同步的实现

本文介绍测控综合基带遥测单元位同步、帧同步方案及实现方法、遥测单元功能，以及位同步、帧同步的作用。     

一种采用可变同步帧的OFDM符号定时同步算法

符号定时同步是正交频分复用（Orthogonal Frequency Division Multiplexing,OFDM）系统中最为关键的同步之一。针对现有的基于数据辅助类的同步算法中帧头存在持续时间长、抗噪声性能差和对载波频偏敏感等问题，提出了一种可变长度的同步帧结构，采用滑动差分相关算法完成符号定时同步。仿真结果表明，提出的同步帧结构持续时间短于一个OFDM符号周期，并且训练序列长度可以通过估算信噪比大小而灵活控制。同时，所提算法在归一化载波频偏为12（远远超过晶振的误差范围 ±10-5）的情况下正常工作；在高斯白噪声和多径衰落信道中都有较好的性能，且其流水线结构易于硬件实现。     

帧同步电路的设计和分析

简要介绍了实现帧同步的几种方法，给出了采用置位同步法的帧同步电路的设计方案，对其状态的转变进行了阐述，并对帧同步电路参数的选择进行了分析。     

一种用于卫星通信的自适应编码调制信号接收方法

针对常规接收方法接收自适应编码调制信号时存在的接收过程易中断、数据不连续等问题，提出了一种适用于卫星信道的自适应编码调制信号接收方法。该方法通过采用统一的解调结构实现对不同调制信号的连续跟踪；利用接收端保存的帧同步字调制波形副本与接收信号中的帧同步字波形的相关结果，对解调方式切换时载波相位跳变值进行估计和补偿，解决了帧同步的连续跟踪问题。与现有方法相比，该方法不需要导频信号，可节省系统开销。     

PCM遥测帧同步技术性能分析

在分析假同步和漏同步现象的基础上,介绍了脉冲编码调制（PCM）遥测帧同步工作的三态逻辑转换过程,通过进一步简化搜索态重叠区假同步概率计算公式,重新对搜索态和校核态的帧同步工作性能指标进行理论建模和仿真,根据仿真结果对影响帧同步性能的相关因素和参数进行讨论,为帧同步参数设计提供参考。     

千兆以太网TAP卡的设计与实现

描述了一种千兆以太网TAP卡的设计与实现方法。该TAP卡可将千兆以太网上的数据帧复制到检测端口,并可在复制出的帧中插入精确的时间戳。使用FPGA完成数据帧的传输、复制及时间戳的插入,使用FPGA内的软CPU通过GPS接口实现精确的时间同步。掉电保护电路用于在TAP卡掉电或故障时保证被监测以太网链路的正常传输。本TAP卡可用于对软交换、3G网络等的维护和传输质量检测。     

一种基于局部序列匹配的跳频自同步方案

为了提高通信系统的同步信息隐蔽性和系统抗侦察能力,提出了基于局部序列匹配 的跳频自同步方案,该方案工作在跳频工作状态。本方案中,并行接收机使用很少的支路接 收具有某种特征的发送 序列L,将序列L与本地序列匹配,确定本地与发射端的跳频序列相位差,调整相位完成 同步 捕获。通过理论分析,确定了序列L唯一的条件,得到了系统复杂度和捕获时间之间的 函数 表达式,并给出了系统最优支路数。分析结果表明,该方案不需要同步引导码和勤务频率 就可以完成系统的同步保持和迟入网同步,并且捕获速度和系统复杂度均介于滑动相关法和 匹配滤波法之间。本方案结合了传统方案的优点,具有良好的隐蔽性,不易被敌方发现和干 扰 。     

TDMA信号的宽范围载波同步译码联合迭代处理

针对时分多址(Time Division Multiple Access,TDMA)信号提出了宽范围的载波同步译码联合迭代处理的方案。该方案主要分为三个部分,首先利用TDMA信号的同步码进行数据辅助同步,对信号中的大频偏和相偏进行粗估计和纠正;然后利用线性调频Z变换(Chirp-Z Transform,CZT)算法针对整突发帧进行非数据辅助同步,精确估计和纠正信号的剩余频偏;最后通过利用译码器输出的软信息进行编码辅助同步,多次迭代得到剩余相偏的精确估计,最终实现载波的精确同步并输出译码结果。实验结果表明,所提方案具有同步捕获范围宽、参数估计精度高、译码输出误比特率低等优点,在低信噪比环境下也能表现出优良性能。     

叠加共轭对称训练序列的OFDM系统时频同步方法

针对正交频分复用（OFDM）系统对同步错误率和频率偏移敏感的问题,提出了一种叠加共轭对称训练序列的OFDM系统时间和频率同步方法。该同步方法将快速傅里叶逆变换（IFFT）调制后的序列构成具有共轭对称特性的训练序列,并叠加到OFDM数据符号上;在接收端,利用叠加训练序列和融合循环前缀信息来获取OFDM系统同步信息。理论分析和仿真表明：在信噪比为5 dB时,该同步算法定时同步正确概率已接近100%;在信噪比为4 dB时,频偏估计精度可以达到10-4;该同步算法不仅具有更好的同步性能,而且节省系统的有效带宽以及降低系统的计算法复杂度。     

TDM协议实现的网型超宽带系统

超宽带系统通常使用纳秒级的超宽带脉冲，系统内所有用户实现同步是非常困难的。本文提出了一种时分多路复用(TDM)网型超宽带系统，根据系统内同步基准站提供的同步信息和每个用户分配的发送时间，实现系统内所有用户间信息交换。计算机仿真和理论计算结果表明：同步帧中使用的同步脉冲越多，同步概率越高。     

Like An Angel

The central bank of China has raised her deposit rate for 6 times,and deposit reserve rate for 16 times,since last year up to now,which resulted to a great suffer to those small and medium sized enterprises in finance collection.30 percent of China s small and medium sized enterprises have to be closed down, and 60 percent of them are because of finance problem.How to gather the fund is the biggest obstacle for China's enterprises to grow.     

Zhang Hao,Health of wealth

Contribution to the society Zhang Hao owns great opportunity to store intelligence and knowledge, in her early year.Zhang Hao was graduated from Economic Management Department of People's University in 1983 and later finished her study in Advanced Training Program of CEO of Chinese Direct Selling Enterprises in Peking University.     

Investigation on Dumpling Issue——Remarks from China''''s State Council Information Office

From the very beginning of the dumpling incident,China has pav great concernontheoroblem and moved rapidly to find the reason and take further actions.Series of investigations carried in both countries by co-organized experts'team received a primary fruit as the true picture of the incident.Each time,China IS sparing no effort responsibly to solve the products quality dilemma,which other countries face in the same.     

Beijing: Next International Financial Hub?

Beijing‘s new financial dream On May 5,the Beijing Municipal Government released a notice regarding its plans to spur the financial industry, vowing to put forth a strong effort to become the national financial decision- making center,financial management center and financial information and ser- vices center,and formally announcing its ambitious aspiration to become a financial hub with international influence.     

Universal Coverage, Pinpoint Illustration and Profound Impact HTC 2008 Intermedia Recommendation and Introduction Meeting

Holding 88 percent of train media resources across China, based on "Time Cube", on the 2008 Intermedia Recommendation and Introduction Meeting on December 19, 2007, HTC announced its high-profile strategy of tour marketing and tapping the immeasurable potentials on the train. Meanwhile, HTC officially launched its brand new product Olympic Train on the meeting, providing a fabulous platform for all the brands that are prepared to do a smart marketing on the occasion of 2008 Olympic Games.     

Market presence in China strengthened Network growth and Dual-Chinese-Hub Strategy More frequet Flyer Benefit——Air China and shanhai Airlines Join Star Alliance

In the end of 2007, Air China Limited (hereinafter "Air China") and Shanghai Airlines, formally joined Star Alliance at a ceremony held in the new Terminal Three at Beijing Capital International Airport. With the addition of the two Chinese airlines, Star Alliance now has 19 member carriers operating 17,000 daily flights to 897 destinations in 160 countries.     

Investment Guide to Qingdao

Qindao is the host city for several events of the 2008 Olympics, including the sailing competitions which will take place along the shoreline by the city. The unique architecture combination of German and Chinese in the city centre, the German demographic roots and a large Korean expat population, give Qingdao a distinct atmosphere. Too many eye-ball catching strengths turn the beautiful seashore city into an attractive place in foreign investor＇s eyes.     

A New Era for Global Business

Asia Society is the leading global organization working to .strengthen relationship and promote understanding among the people, leaders, and institutions of Asia and the U.S. Every year the Society presents a high-profile Corporate Conference in a selected city in Asia to examine the implications of macroeconomic trends and geopolitical developments for the region and the world. It provides a leading forum for executives to meet the policymakers and business leaders who shape the Asia Pacific business environment.     

China-Pakistan Strengthen Bilateral Custom Cooperation

Mr. Abdullah Yusuf, Secretary General/Chairman, Central Board of Revenue of Pakistart, arrived Shenzhen on April 22 to meet with Mr. Sheng Guangzu, the Chinese Minister for Customs Administration for discussing the bilateral customs issues. During his two-day visit, China＇s Foreign Trade Magazine interviewed to Mr. Abdullah Yusuf in Beijing, he gave the high evaluation on this visit and China＇s great development in the recent years.     

Golden South Africa,Great Development

On the occasion of the 10th panniversary of diplomatic relations between China and South Africa in 2008, China is celebrating ＂South Africa Week＂ to commemorate. H.E. Dr. Nkosazana Dlamini Zuma, the minister of South Africa,