一种雷达频率源的简易设计方法

针对传统多功能雷达频率源方案复杂、体积大、成本高的缺点,提出了一种雷达频率源的简易设计方法。该方法基于高频主振分频的频率合成方案,并通过信号频率的组合设计进一步简化了电路形式,成功实现了某型雷达所需的线性调频激励源、捷变频本振源、多普勒模拟源、采样时钟等多路信号的输出,X频段信号相位噪声达-106 dBc/Hz@1 kHz和-114 dBc/Hz@10 kHz,跳频时间小于2 ??s,性能指标与采用直接频率合成实现的雷达频率源相当。     

一种S频段高性能频率合成器的设计与实现

设计了一种高性能频率合成器,采用直接数字合成（DDS）与直接模拟合成相结合的方式, 实现了S频段1 Hz细步进 输出,频率捷变时间小于800 ns,并达到杂散抑制优于-65 dBc、相位噪声优于- 115 dBc/Hz偏离载频1 kHz处的高性能指标。     

8 mm脉冲磁控管测云雷达测速多普勒化

8 mm磁控管发射样本中频信号的起始相位随机分布,脉间频率抖动范围为±2 MHz ,脉内频率变化为500 kHz。为了克服这些问题,提出了一种适合于国内第一套毫米波 脉冲 磁控管测云雷达的测速多普勒化算法,幅度信息从回波数字下变频经低通滤波器后直接提取 , 相位信息由零中频回波IQ信号与发射样本IQ信号进行复卷积提取,并算法仿真结果表明多 普 勒频率误差不超过4 Hz。基于FPGA技术实现了测速多普勒化算法,利用高速缓存的设计 思想 实现了复卷器的优化,利用CORDIC算法实现了幅度与相位的高精度提取,并完成了算法在实 际 雷达系统中的测试,雷达的脉冲重复频率为1 000 Hz,多普勒频率在-496～500 H z范围内,雷 达终端显示的速度值与理论值一致;回波信号幅度值为-76～6 dBm,得到的速度值 与理论值 一致。经过该算法处理的地物杂波回波的多普勒速度在零值附近分布,云体目标的回波速度 图清晰可见。该算法已经成功应用于8 mm脉冲磁控管测云雷达系统。     

一种用于高速QPSK解调的四次方环载波恢复电路

为解决高速QPSK信号全数字解调的技术瓶颈问题,采用模拟方案 ,研制了一种四次方环载波恢复电路,重点介绍了应用混频器上变频特性的宽带平方电路以 及锁相环（PLL）载波提取电路的设计过程。测试结果表明,该载波恢复电路可以完成载频 为720 MHz、码速率100 Mbit/s～1 Gbit/s范围的QPSK信号同步载波恢复,解 决了高速信号相干解调中载波同步的关键技术问题。     

超低频通信中海洋补偿滤波器设计

分析了超低频接收机中海洋补偿滤波器的作用,分别采用1零点1极点、2零点1极点 无限脉冲响应滤波器设计超低频海洋补偿滤波器,零点和极点通过数值计算得到。分析结果 表明：在20～200 Hz频段内,实现的滤波器可以很好地逼近理论的海洋补偿滤波器;在 0～130 m范围内,实现的2零点1极点滤波器可以将幅度响应误差控制在1 dB左右, 能满足超低频接收机的设计要求。     

基于AD9361的掌上型LTE RRU设计与开发

当前小体积远端射频单元（Remote Radio Unit,RRU）主要是皮站级别的Pico-RRU，其重量和体积仍然难以满足掌上型的要求。为此，采用高集成度的AD9361芯片来实现长期演进（Long Term Evolution，LTE）宽带收发信机功能，配合时钟同步模块、放大器模块和控制接口电路等一起构建低成本的掌上型RRU。主要解决了基于AD9516的时钟同步、低相位噪声设计和高灵敏度接收机设计三个技术难点，成功实现了掌上型、高性能、低成本的设计目标。整个RRU样机尺寸为18 cm×10 cm×2 cm，质量约500 g，量产成本千元以内。测试表明，该RRU下行误差向量幅度（Error Vector Magnitude，EVM）小于3%，优于3GPP要求的8%；10 MHz带宽时上行接收机灵敏度优于3GPP要求的-93.5 dBm。     

高性能L频段频率合成器的改进设计

为了满足航天测控信道的要求,提出了一种高性能L频段频率合成器设计的改进方案,采用PLL+DDS+PLL结构实现了小步进、低杂散、低相噪的信号输出。分析了方案的可行性,设计了样品,并进行了测试,结果显示其相位噪声优于-100 dBc/Hz@10 kHz,杂散优于-75 dBc,但附加的杂散信号导致了系统同频干扰。通过分析找出引起同频干扰的机理,并提出了相应的改进措施。所提方案对测控通信、电子对抗等领域中频率合成器的研发具有一定的参考价值。     

多频段高动态信号载波频偏捕获方法研究

研究了多频段高动态信号载波频偏问题,分析了多频段给频偏捕获带来的困难 ,针对低数据率、大载波频偏的情况,讨论了抽取倍数对捕获范围和精度的影响,并提出对 于不同频段,通过改变相应的抽取倍数来满足不同的频偏和精度,再进行最大功率搜索法估计 频偏的捕获方案。仿真结果表明,与传统方法进行比较,该方案在低信噪比下条件下估计性 能更好,能够适应UHF和S频段,在数据率9.6 kb/s的条件下,估计精度在UHF频段下为 300 Hz,在S频段下为600 Hz。     

X频段高频谱纯度频率合成器设计

针对高灵敏度接收机对频率合成器的高技术指标要求，构建了一种融合了直接模拟、直接数字以及间接数字的频率合成技术方案，根据该方案，成功实现了频率合成器的工程研制。通过测试，频率合成器相位噪声达-112 dBc/Hz@5 kHz，杂散抑制优于-75 dBc，频率分辨率小于1 kHz，10 MHz跳频时间约为13 μs，满足了高灵敏度接收机对频率合成器的高技术指标要求，为高纯度频率合成器的实现提供了一条新途径。     

基于FPGA的π/4DQPSK跳频调制器的设计与实现

将π/4DQPSK调制与跳频技术相结合,设计了π/4DQPSK跳频调制器。利用FPGA实现了 π/4DQPSK基带跳频调制,并由AD9957完成正交调制、数模转换和一次上变频。设计了 乒乓 方式上变频调制器完成二次上变频及跳频调制。实测结果表明,跳频频率误差小于1 Hz ,换频时间小于2 μs, 瞄准干扰信噪比为8 dB时,误码率低于10-4。     

Brown＇s Blossom in Britain-China

The overall strategic relationship between U.K. and China is ＂better than ever＂, China- Britain relations have maintained good momentum, with increased high-level exchanges and the reinforcement of strategic mutual trust, with more room for growth in the future.     

Challenge and Opportunity Go Hand in Hand——What Global Economic Agitation Brings to the China's Economy?

Domino effects of the global finance agitation As the origin of the subprime crisis,US financial institutions lost USS45 billion last year,accounted for over half of the total US,EU & Japan loss.Since January 15th,Chtigroup released its financial statement of the 4th quarter,showing a net deficit of USS9.83 billion,which marked the hisoric high of its quarterly deficit.     

Jean-Pierre Duprieu： Willing to Be A Legate of Sino-French Business

Estaing, former French president, Valery Giscard d＇Estaing attended Sino-French Economic Seminar held in Shanghai in early April and said that the world center has shifted from the west to the east with many European and US companies entering into Asia, and China has the ability to play an important role in the world stage. Estaing, naming himself＂French Confucian＂, then said in Chinese that a cook-group includes 10 people in ancient Chinese soldier system and the cook is in charge of cooking for them. And people who belong to the same cook are actually ＂Partners＂.     

China''''s Stock Market Wave

The annual meeting of the World Economy Forum was held in Davos,a little town in Switzerland,on January 23rd to the 27th this year,with the theme"the Power fo Collaborative Innovation",over 2500 celebrates from ture political and cconomic circles of more than 80 countries and challengred logether to talk about the future of the global economy in 2008,A Forum for the problems and challenges that face whole world,some of the keywords which drew attention during the event were:the U.S.subprime mortgage crisis,soaring energy prices,the economic slowdown in the U.S.ermerging economic bodies,authority funds and the general unpredictable nature of the global economy.     

Trade Promotion from Neighborhood

If you are considering to trade with companies in Japan or expanding your .business to Japan, we are ready to help from the very beginning.＂ You will find this greeting at the first sight on the Chinese website of Japan External Trade Organization （JETRO）. JETRO has committed itself in delivering highly efficient and quality services to meet the demand of internal and external customs including Japanese companies, hence winning a good reputation in the international trade arena. In recent years, with its priority in advancing business cooperation in South and East Asia, JETRO has made great achievement in promoting trade between China and Japan. Therefore, China＇s Foreign Trade interviewed Mr. Yoichi Maine, Deputy Director General of JETRO BEIJING.     

Auto Parts Market Potential Coming into Surface

Looking at the increasingly fierce competition in the world auto market. global automobile manufacturing industry, taking Europe, the U.S. and Japan as representatives, is gradually forming a new type of relationship, mutual cooperation between whole vehicle and parts manufacturers. We can clearly see that auto parts manufacturers have become independent from the whole vehicle manufacturing companies, which means that the former structure of auto industry has greatly changed, and a new relationship,     

Domino Effect on Electricity and Coal Prices

In the middle of last December, the key purchase contracts for coal used in power generation in 2008 were signed, reflecting a demand for more than 1.085 billion tons. It is important to note that the country＇s five biggest power producers, China Huaneng Group, China Guodian Corporation, China Power Investment Corporation, China Huadian Corporation and China Datang Corporation, had settled on the prices on their purchase contracts, and they are expected to consume 290 million tons of coal for generating electricity,     

Slimmed May Day Holiday

Last November the State Council of China decided to renew its holiday system by reducing the seven-day May Day holiday to three days and introducing three new one-day public holidays, namely the Qingming Festival, Dragon Boat Festival and Moon Festival. By doing so, the three golden-week holidays that were introduced in 1999, namely the Spring Festival, May Day and National Day, could be better distributed.     

China Ranked the 7th in Global Influence Survey

The results of the Annual Global Public Opinion Survey were released by the British Broadcasting Company （BBC） on April 2,2008,the combination of 7,457 public opinion polls in 34 countries,gave Germany and Japan the No.1 and No.2 spots,respectively, while the last four went to North Korea, Pakistan,Israel,Iran.     

Figures from Government Working Report

Nine o＇clock in the morning of March 5th,2008,the first meeting of the eleventh session of National People＇s Congress was held in the Great Hall of People.As usual,the first performance of this big event in China was from the government working report made by the Premier.Five years of government＇s work in this session was counted in Premier Wen Jiabao＇s working report.