前馈技术在改善功率放大器线性中的应用

推导并分析了存在增益和相位跟踪等误差情况下,功率放大器前馈技术对三阶线性失真的改善情况,并从原理上论述了前馈技术的工作原理.前馈技术一般可将三阶互调降低10～30 dB,在新一代的抗干扰跳/扩频电台中有广泛应用.     

802.11n高线性功率放大器的设计与实现

为了扩大802.11n无线产品的覆盖范围,设计了一款符合802.11n标准的2.4 GHz高线性功率放大器。在该功率放大器的设计中采用了双路均衡功率合成技术和差异化加速开关技术,在提供高功率输出的同时满足了802.11n的误差向量幅度（EVM）的要求,尤其是实际应用中的动态EVM。测试结果表明,该功率放大器回退7 dB后的线性输出功率为27 dBm,此时的EVM为-30 dB,合成功率输出为29.5 dBm。该功率放大器可广泛用于无线局域网中,与各种类型的无线AP直接匹配使用,提高其覆盖范围。     

一种新研制的W频段固态GaN功率放大器毫米波源

介绍了一种新研制的W频段固态GaN功率放大器毫米波源,给出了系统组成与工作原理,提供了其主要部件W频段固态Gunn驱动源、W频段波导-微带转换器、主放大器芯片基本性能及实验测试结果。该固态毫米波源工作频率94 GHz,输出连续波功率大于300 mW,线性增益10 dB,附加效率（PAE）大于16%.在W频段固态毫米波源研制过程中,其单片微波集成电路（MMIC）功率放大器半导体材料选择经历了GaAs、InP到GaN演变,结果清楚表明,W频段毫米波源的GaN MMlC功率放大器输出功率、增益、效率、高温性能要优于其他固态MMIC功率放大器性能。W频段大功率固态GaN MMlC技术将在毫米波领域带来新的技术革命和应用。     

高效率线性RF功放的研究与设计

应用EER(Envelope Elimination and Restoration)线性功放技术和高效率D类音频放大技术，实现了一个高效率线性RF功率放大器。该线性放大器为AM调制，7MHz时效率优于75％。     

前馈线性功率放大器的设计

从前馈线性功率放大器的基本原理出发,采用HP ADS仿真软件对主功放进行优化设计,并在此基础上,提出加入反馈环路的前馈线性化设计方案,在保证系统性能的同时大大降低了系统实现难度.仿真结果表明该系统在输出10 W连续波功率的同时,三阶交调失真(IMD)低于信号功率-77 dBc,取得了明显的线性度改善效果.     

大功率固态功放合成效率研究

应用散射参数理论对大功率合成器的合成效率进行了计算推导,分析了合成效率的各种影响因素,推导出合成效率所能达到的最大值,并且给出最大合成效率的条件.这对于进行S频段连续波800 W固态功放研制打下很好的理论基础.     

S频段800W固态功放的研制

采用功放管合成、电路模块合成及插箱整机合成相结合的三级合成方案，研制成功了一种S频段连续波800W固态功放，经测试在2025—2120MHz频段，功放连续波输出功率1dB压缩点大于59dBm（800W），增益大于68dB，功率附加效率25％，合成效率达到85％以上。     

第三代移动通信高线性微波功放的设计与实现

介绍了一种2.14GHz的高线性微波功率放大器,可用于第三代移动通信基站和其他通信系统。采用了功率回退法和前馈法,使本功率放大器的三阶交调优于51dBc。介绍了采用功率回退法的主功率放大器的设计方法和采用前馈法使功放的三阶交调改善10dBc的设计和实现。     

Rewriting History: the Early Sherman Act Monopolization Cases

This paper reviews two early precedent–setting US antitrust decisions and asks a series of counter–factual questions. What if the Standard Oil Company had not been broken into 34 pieces? What if the United States Steel Corporation had been fragmented? It traces the qualitative evolution of the Standard Oil fragments, following the 1911 divestiture decision, and the corresponding history of United States Steel. It then undertakes quantitative analyses of the survivors' market share trends and the comparative productivity growth, average plant sizes, price — cost margins, and net exports for petroleum refining, blast furnaces and steel from 1899 through 1939. At first, the post–divestiture performance did not differ much between the two subject industries. However, by the 1930s, competition intensified in petroleum refining and the decline of the Standard Oil fragments' market shares came to a halt. In the steel industry, however, competition continued to be mild. A lethargic United States Steel held a price um brella over its rivals and steadily lost market share. Steel companies were ill–prepared for rising import competition during the 1960s and 1970s. The paper concludes that the 1911 break–up of Standard Oil had few deleterious short–run consequences and, by shaping a more competitive environment, it had a decidedly positive long–run effect.     

Defining Markets for Ex Ante Regulation using the Hypothetical Monopoly Test

The EU is gradually systematizing its approach to ex ante regulation (notably with the publication of the recent regulatory framework for Electronic communications). Market definition is viewed as an essential first step in this, with the ‘Hypothetical Monopoly Test’ a useful conceptual tool for use in the assessment. This paper examines the use of this test for market definition when there are several differentiated goods or services under consideration. It sets out an analytic framework, discusses the pros and cons of using the test and illustrates its use in a Telecom context.     

Comparing the Impact of the September 11th Terrorist Attacks on International Airline Demand

This article compares the impact of the September 11th terrorist attacks and its after‐effects on airline demand in the Australia, Canada, Europe, Japan and the US. Using a variety of time‐series data, we compare how changes in risk perception following the attacks impacted domestic and international demand. Moreover, we decompose the terrorist attacks’ effects into their transitory and ongoing components on airline demand.     

International real business cycles with endogenous markup variability

The aggregate impact of decisions made at the level of the individual firm has recently attracted a lot of attention in both the macro and trade literatures. We adapt the benchmark international real business cycle model to a game-theoretic environment to add a channel for the strategic interaction among domestic and foreign firms. We show how the sum of strategic pricing decisions made at the level of the individual firm can have significant effects on the volatility and cross country co-movement of GDP and its components. Specifically we show that the addition of this one channel for strategic interaction leads to a significant increase in the cross-country co-movement of production and investment, as well as a significant decrease in the volatility of investment and the trade balance over the benchmark IRBC model.