Wide bandgap semiconductor transistors for microwave poweramplifiers

Explores the RF power performance of microwave amplifiers fabricated from wide bandgap semiconductor transistors and demonstrates that microwave power amplifiers fabricated from 4H-SiC and AlGaN/GaN transistors offer superior RF power performance, particularly at elevated temperatures. Theoretical models predict room temperature RF output power on the order of 4-6 W/mm and 10-12 W/mm, with power-added efficiency (PAE) approaching the ideal values for class A and B operation, available from 4H-SiC MESFETs and AlGaN/GaN HFETs, respectively. All calculations were thoroughly calibrated against dc and RF experimental data. The simulations indicate operation at elevated temperature at least up to 5000°C is possible. The RF output power capability of these devices compares very favorably with the 1 W/mm available from GaAs MESFETs. The wide bandgap semiconductor devices will find application in power amplifiers for base station transmitters for wireless telephone systems, HDTV transmitters, power modules for phased-array radars, and other applications. The devices are particularly attractive for applications that require operation at elevated temperature     

Tests on self-healing metallized polypropylene capacitors for powerapplications

Results of research carried out at the Institute of Industrial Electrical Engineering of the University of Bologna on self-healing metallized polypropylene (MPP) power capacitors are presented. The aim of the tests is to characterize the degradation of these capacitors when employed in automatic power factor correction systems or in power electronic applications with special reference to the disconnection of the `sprayed ends' from the electrode-edges, one of the main reasons for failure of MPP capacitors employed in the above systems. The research is carried out also in view of the definition of adequate type-test standards, presently not yet available for this kind of application     

宽带大动态范围自动电平控制技术研究

简要介绍了自动电平控制的作用及工作原理,深入分析了自动电平控制电路设计中的关键技术及难点,提出了一种应用于宽带大动态范围信号源中的自动电平控制技术方案,针对检波中根据输入信号的大小呈现的平方律线性特性,设计了双斜率对数放大电路,使对数放大器输出电压在大信号和小信号时始终与输入功率成线性比例关系,并对该电路进行了详细的理论分析,通过实验对设计的电路进行了验证,结果表明该设计稳定可靠,性能优良。     

Sr-Ca-La-Co型六角铁氧体微波与传统预烧工艺比较研究

在实验室采用微波预烧(MC)和传统马弗炉预烧(CC)两种方法制备了M型六角铁氧体预烧料,然后制备出烧结磁体。采用XRD、SEM和VSM分析样品的结构特征、微观形貌及磁特性。研究表明,MC技术能快速有效地生成六角铁氧体永磁材料,且能提升材料的Br和Hc J。对于配方Sr0.22La0.38Ca0.4Fe11.6Co0.24O19,当预烧温度和烧结温度分别为1250℃和1170℃时,对应MC预烧料的烧结样品的Br=444m T和Hc J=415k A/m,与相同温度下的CC预烧料的烧结样品指标相比分别提高1.6%和5%。     

Development of a microwave clothes dryer

A laboratory test model of a microwave clothes dryer was constructed and tested over a wide range of test variables, including number of magnetrons and use of auxiliary heat. The tests identified three distinct operating modes: (1) cool drying, which uses only microwave energy and drying occurs at less than 105°F; (2) fast drying, where microwave drying is superimposed on conventional drying; and (3) efficient drying, where the use of microwave energy with waste heat recovery from the power supply results in significant efficiency improvements compared to conventional dryers     

微波通信工程中天线系统的校准技术

在微波通信中,天线方位角的校准通常采用经纬仪法,存在误差大、效率低的缺点。为此,提出重锤线法,使天线－天线系统角度的校准变得简易。在天线－反射板－天线系统校准中,提出采用分段调整法,简化了系统的调整过程。     

微波通信站本地监控系统研制

阐述通信网络管理系统的结构,研制了一种微波通信站本地监控系统.该系统可作为通信站的本地监控独立运行,也可作为网元层而构成全网的TMN系统.     

贵州电网微波通信系统再利用及最新微波技术展望

微波通信为无线电通信,电力光纤通信是在跟着电力线路架设,应对自然灾害时,与光纤通信形成互补。微波通信是按地理位置建设,在物理构架上与光通信形成互补。光纤通信是环网结构,微波是树枝型结构,微波与光环网互联,就能形成更为强大的通信网络。技术接口上微波通信接口与光纤通信接口是一致的,都是同步网链路接口。     

GaN基MSM结构紫外探测器及其研究发展

本文主要介绍了GaN基紫外探测器,尤其是GaN基金属-半导体-金属(MSM)结构紫外探测器的工作机制、结构、特点及其应用,并且对GaN基MSM结构紫外探测器的研究进展进行回顾,并对目前较为热门的紫外焦平面阵列探测器的研究进展进行简单的介绍。     

电动车用蓄电池充电技术的进展

综述了电动车用蓄电池充电技术的历史、发展现状,总结了现代充电技术几个特点并展望了其未来的发展方向。     

数字实时补偿技术在现代微波合成扫频信号源中的应用

本文在介绍锁相扫频技术的基础上,论述了现代微波合成扫频信号源中针对振荡器预置非线性进行补偿的必要性,探索了一种数字实时补偿的实现方法,着重描述了补偿的原理框图、主要硬件电路及在同步时序的控制下补偿的过程,这种补偿方法已成功应用于宽带微波合成扫频信号源的设计中,经验证能够产生较好的补偿效果。     

Space solar power programs and microwave wireless power transmission technology

Future large-scale space solar power (SSP) will form a very complex integrated system of systems requiring numerous significant advances in current technology and capabilities. Ongoing technology developments have narrowed many of the gaps, but major technical, regulatory, and conceptual hurdles remain. Continuing systems concept studies and analyses will be critical to success, as will following a clear strategic R&T road map. This road map must assure both an incremental and evolutionary approach to developing needed technologies and systems is followed, with significant and broadly applicable advances with each increment. In particular, the technologies and systems needed for SPS must support highly leveraged applicability to needs in space science, robotic and human exploration, and the development of space. Considerable progress has been made in the critical area of microwave power transmission. At 5.8 GHz, DC-RF converters with efficiencies over 80% are achievable today. Rectennas developed at 5.8 GHz have also been measured with efficiencies greater than 80%. With optimized components in both the transmitter and rectenna, an SPS system has the potential of a DC-to-DC efficiency of 45%.     

微波仪器中即插即用技术的设计和应用

微波仪器由于频率高,分布参数影响严重,难于批量生产,为方便电路板的生产调试和维护,提高微波仪器的生产效率,本文设计了一种适用于微波测量仪器的即插即用技术包括电路单元和软件协议.该技术采用标准I2C总线实现,结构简单、可靠便于使用,对仪器EMC效果不会产生影响.采用该技术后微波仪器的应用软件能够自动识别电路板配置,加载特征数据,并实现软件功能组件的装载,使电路板在微波仪器中能够即插即用.该技术已成功应用于高灵敏度宽带EMI接收机中.     

基于GaN的3.5 kVA单相逆变电源研制

为了满足动车组列车对车辆设备轻量化的要求,研制一种容量为3.5 kVA的自然散热型车载单相逆变电源,并对其散热器的散热性能进行系统分析以提高该电源的散热效率从而降低工作温度以保证系统的可靠性.首先,基于热损耗理论、计算器件的功率损耗;然后,运用热分析软件ICEPAK对散热器翅片的厚度、高度、间距和基板厚度进行参数化仿真...     

电力系统IP宽带综合业务网络平台技术的探讨

考虑到未来的电力系统宽带综合业务网应定位为“电力通信综合业务平台”,提出了电力宽带综合业务网的三层体系结构,和组网技术的选择应遵循的原则,其中,业务支撑网络是关键,建议采用ＩＰ技术,结合ＭＰＬＳ。对应地网管也分为三个层次。并就宽带网络平台上综合业务的开展,以及相关的ＩＰｖ６、ＩＰＱｏＳ进行了简述。     

Theory of GaN Quantum Dots for Optical Applications

The optical properties of III-N wurtzite heterostructures are dominated by the built-in polarization potential. We first review the dependence of III-N bulk valence band structure on strain and the key factors determining the polarization vector in polar and nonpolar quantum wells, including electromechanical effects. We then present a surface integral technique to determine the built-in potential in quantum dots (QDs) of arbitrary shape. We show for polar QDs how the polarization potential spatially separates electrons and holes vertically but confines them laterally, causing the radiative recombination rate to decrease rapidly with increasing dot height and a strong blueshift with increasing carrier density. Finally, we show that although the polarization potential can be much reduced in nonpolar GaN/AlN QDs, it is likely to remain significant in nonpolar InN/GaN QD structures.      

水轮发电机组推力轴承技术的发展

本文介绍了水轮发电机组推力轴承瓦面材料、支撑结构和循环冷却系统,推力轴承设计技术和试验技术及推力轴承的发展.     

Load modeling for wide area power system

The electrical loads have significant impacts on the dynamic performances of the wide area power system, and the dynamic behaviors of the power system can not be reproduced by the simulation system, unless the electrical load was modeled accurately. In the previous load modeling, the dynamics of the electrical load itself is of concern. Using such load models, the satisfied dynamic behaviors of the wide area power system can not be obtained by simulation. In this paper, a system-wide load modeling strategy is proposed. The electrical loads are firstly classified into a few categories using the component based load modeling method. According to the problems studied, the output variables of the power system are selected, and the objective function is constructed using the data from Wide Area Measurement System (WAMS). The trajectory sensitivities of the load model parameters with respect to the output variables are analyzed. Based on which, the key parameters playing important roles on dynamics of the power system are identified and included in further parameter estimation. The load models for the wide area power system are built simultaneously, and the system-wide load modeling method is implemented on the IEEE 39-bus system to evaluate its effectiveness.     

第三代核电技术及发展

我国第三代核电发展历史在CPR1000体系的形成和运用过程中,共经历了中国核电工业制度变迁的三个阶段,如表1。1977年到1986年,是中国对核电行业深入探索的阶段。中国政府并没有因为先前苏南核电的失败放弃发展核电的信心,促成了中国与法国的第一次技术和商业合作,我国引入了法国的核电技术路线M310,     

微网标准和技术发展

集成分布式电源和负荷的微网技术,为改善分布式电源应用中的电网电压和电能质量提供了途径,介绍了微电网的概念和特点、微网标准和技术发展概况,重点介绍了微网标准IEEE P1547.4,并讨论了现阶段微电网研究中的关键和研究方向.