R有源滤波器的设计与优化

仅利用运算放大器和电阻构成的Ｒ有源滤波器具有显著的优点，本文针对Ｒ有源滤波器的设计进行了推导和分析，并详细讨论了如何运用最新的ＰＳｐｉｃｅ Ｏｐｔｉｍｉ－ｚｅｒ工具对其进行优化设计，给出了相应的设计方法和步骤。     

脉冲宽度调制的直流控制——参量变化研究与电流环分析

用于直流电机驱动的脉宽调制放大器和比例式放大器相比较,已呈现出许多显著的优点。本文试图更好地弄清和利用开关调制所提供的优越性。首先,我们观察脉宽调制放大器的原理和特性,在介绍放大器的简化模型之后,将分析在稳定状态下的电流波形,并确定电机电感的影响。本文将分析围绕放大器闭合的电流环的作用,也将讨论一些其它因素,如闭环动态特性、短路保护等。     

电路设计中的相位补偿技术

在集成电路设计中,多极点响应的放大器闭环工作时很容易产生自激,因此,为了保证电路工作的稳定性,必须进行相位补偿.相位补偿的作用是利用补偿网络来改变放大器开环的频率响应特性,以增加负反馈放大器的相位裕量.     

快速设计参考图表

在测量一个放大器的噪声系数时,往往需要在被测器件与衰减器之间插入一放大级。因此,测得的噪声系数是两个放大器级联的总噪声系数。当第一级放大器的增益和第二级放大器的噪声系数为已知值时,利用图1的列线图便可确定第一级放大器的噪声系数。列线图的使用步骤1.将F_(1-2)(测得的总噪声系数) 和G_1(第一级的增益)相连并与a相交于一点;     

基于稀疏分解和混沌理论的微弱信号检测

针对数字锁定放大器中稀疏分解算法检测精度受限的缺点,结合非线性方法进行补偿,采用混沌检测联合稀疏分解的算法设计了数字锁定放大器。数字锁定放大器借助稀疏分解算法估计信号参数,根据估计得到的参数设计对应混沌系统;利用混沌系统检测信号的过程中产生间歇性混沌状态,并通过测量间歇性混沌状态的周期,精确检测信号。最终,在信号的信噪比低至-20 dB时可以成功检测信号,频率精度达到0.05 Hz,提供了一种非线性微弱信号检测方法。     

噪声影响及计算变换图表

嗓声-温度的计算1.修正第二级噪声系数列线图在测量一个放大器的噪声系数时,往往需要在被测器件与衰减器之间插入附加增益.因此,测得的噪声系数是该级联的总噪声系数.当它的增益和第二级放大器的噪声系数已知值时,利用图1的列线图便可确定第一级放大器的噪声系数.     

安德鲁3G TMA 2100双双工塔顶放大器面世

安德鲁公司针对UMTS网络需要推出塔顶放大器(TMA)。TMA 2100双双工、低噪音放大器扩大了信号覆盖面,降低了系统噪音,改善了上行灵敏度。全新的60兆赫带宽双双工放大器只需一条馈线,能降低馈线成本和塔架负载,安装便利。安德鲁TMA 2100双双工塔顶放大器,也称作杆头放大器,内置警报功能、闪电保护和紧急旁路模式。     

基于EDFA+FRA的增益平坦补偿

采用光子转换理论和数值分析方法，研究了采用DCF光纤的喇曼放大器和掺铒光纤放大器组成的混合放大器在DWDM系统中的应用。通过对喇曼光纤放大器的光纤长度、泵浦功率的选择，使得混合放大器的总增益达到一定的平坦度；并分析设计了增益均衡器，让混合放大器最后的总增益达到更高的平坦度。     

单电源测量放大器

ＯＰ2 8 4是一种低噪声双运算放大器 ,带宽为 4ＭＨｚ且为真实的 (ｒａｉｌ -ｔｏ -ｒａｉｌ)输入 输出运算。这些特性使其非常适用于低电源电压 ,如用于该图所示的 2个运算放大器测量放大器。该电路采用传统的 2个运算放大器测量拓扑结构 ,用 4个电阻器设置增益。该电路的转换方程与非变换放大器相同。电阻器Ｒ2 与Ｒ3 应该互相匹配 ,而且 (Ｒ1 +Ｐ1 )也应与Ｒ4匹配 ,保证较好的共模抑制(ＣＭＲ)性能。建议Ｒ2 和Ｒ3 采用电阻器网络 ,因为这样可得到必要的相对容差匹配。利用电压计Ｐ1 调节直流ＣＭＲ ,使其最佳 ,而用电容器Ｃ1 使交流Ｃ…     

空间用线性微波晶体管放大器设计中对辐射影响的考虑

近来表明,用于空间设备的线性微波放大器中,所用的大量的各种类型微波晶体管都是对辐射敏感的。由于晶体管的h_(FE)是对辐射非常敏感的参数,所以在空间长期工作的放大器,由于晶体管偏压条件的改变而导致其微波性能过早地下降。本文首先介绍影响线性微波晶体管放大器整个辐射灵敏度的各种因素,接着列举了对L波段和S波段前置放大器进行地面辐射试验所得的实验结果。根据估计的空间辐射剂量级进行计算所得之结果表明:在设计放大器时,若忽视辐射的影响,就可能导致放大器只有几周而不是几年的工作寿命。本文根据对元件和放大器辐照所得的实验结果,提出了使微波集成电路晶体管放大器达到耐辐射的方法。     

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.     

Sinosteel：Extraordinary Moves in Industry Chess

Among the Fortune 500 firms,more and more images from China emerge out.On the 2008 list,Sinosteel Corporation,a landmark group of China industries quietly squeezes into the candidate line.As the largest steel service ＆ trade enterprise,its sales reached at RMB 111.24 billion,with a year-on-year increase of 83.03 percent,and the profit grew by 180.03 percent.On the Sinosteel 2008 Work Meeting,the president Huang Tianwen uttered,＂In the coming year,we will work for US$20 billion sales,and look forward to getting a position in Fortune 500 firms for ourselves.＂     

Walk Through Unusual Five Years—— An Exhibitor＇s Canton Fair Course

When the 103rd Canton Fair is approaching, an old friend of Canton Fair, Li Ying from Jiangsu prov-ince recollected his past five years＇ experiences to the grand trade meeting. Each year is special, with some unforgettable memories colored by the year.     

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.