面向功放-整流一体化设计的逆F类功率放大器

针对微波无线功率传输对于高功率处理能力的高效整流器需求,提出一种基于高效率功率放大器的功放-整流一体化设计思路。文章首先使用型号为CG2H40010F的氮化镓高电子迁移率晶体管(GaN HEMT),通过谐波控制、负载牵引等方法,设计出一款工作在2.45GHz逆F类高效率功率放大器。在高效率功率放大器的基础上基于时间反转对偶理论,通过改变逆F类功率放大器电流方向,同时结合耦合器和移相器实现了高功率容量整流电路的设计。仿真结果表明,在245GHz工作频率下,功率放大器的输入功率为28dBm时,功率附加效率达到76%,输出功率40dBm;整流电路的输入功率为41dBm时,RF-DC转换效率可达到79%,整流最佳效率大于80%,显示了整流器的高功率处理能力。引入了两个单刀双掷开关实现功率放大器和整流器的功能切换,文章对核心电路功率放大器进行了实物测试,测试结果与仿真重合较好,验证了功放-整流一体化设计的可行性。     

PIC16F627编程器的设计与实现

PIC16F627是集成片上闪存(1k～2kbits)和在线编程接口(ICSP)的单片机,性价比很高。但目前的编程器主要是多功能编程器,价格昂贵。笔者提出了一个基于ICSP的简易编程器方案,它以AT89C2051为控制核心,通过RS232接口与计算机相连,计算机中的软件用Delphi5.0实现,价格低廉,适合个人制作、使用。     

结构分析程序中几个问题的处理方法

JY851程序是一个复合材料、金属混合结构应力分析及强度校核程序。从1986年投入使用以来,已推广到几个厂、所使用,计算了几个型号的机翼、垂尾、方向舵等复合材料结构。现就编写元素刚度矩阵中所遇到的几个问题的处理方法作一简单的介绍。 1.复合材料板弹性模量阵的计算 复合材料板弹性模量阵A、B、D的计算中,关键是求偏轴模量阵[ō],层压板中第     

涡轮叶栅端壁二次流动与换热的V2F模拟

针对低展弦比涡轮叶栅端壁区亚声速流动及换热,采用基于线性涡黏假设的V2F模型开展了数值模拟.结果表明：涡轮叶栅流动中存在马蹄涡、通道涡、压力侧角涡、吸力侧角涡等多种复杂涡系结构,其中马蹄涡与通道涡是涡轮叶栅二次损失的主要来源.端壁换热与马蹄涡及通道涡强度及位置直接相关,并呈现明显的分区特征.端壁极限流线结果显示,V2F模型模拟的端壁单马蹄涡分离线与实验结果吻合,优于SST （shear stress transport）k-ω模型模拟的端壁双马蹄涡分离线.V2F模型引入了新的湍流尺度,在马蹄涡及通道涡位置、端壁静压损失系数分布、叶栅出口总压损失分布及端壁Standon数分布等方面均与实验结果吻合较好,对叶栅气动损失及端壁换热有良好的预测能力.     

C8051F023在自动售货机网络管理系统中的应用

介绍自动售货机网络管理系统的整体构成和工作原理,分析C8051F023与接口模块设计相关的一些功能,讨论接口模块中与C8051F023有关的设计要点,得出了基于C8051F023设计的接口模块结构紧凑、性能优越且实用性强的结论。     

4F富里叶变换透镜系统的三维变换特性

本文从理论和实验上应用4F富里叶变换透镜系统,把三维物场转换为三维象场。象的空间位置和光场振幅的变化与透镜系统的焦距以及物体距焦平面的位置有关。根据4F系统的三维变换特性,本文还讨论了该系统对三维粒子场全息记录、再现的影响。     

一种电离层物理模型及其在F1谷区形成讨论中的应用

在电离层F区考虑了三种中性成分的4种离子(O~+、No~+、N_2~+和O_2~+),从严格的电子和离子密度连续方程出发,由中性风所满足的动力学方程和离子运动方程解出水平中性风,从而得到离子垂直漂移速度,由此建立了一种电离层的物理模式;并用此模式,针对我国中、低纬(116°E,30°N)地区,讨论了光化学作用对F_1层的影响和动力学效应在F层中的作用。着重讨论由水平中性风引起的离子垂直漂移运动对F_1谷区的影响。结果表明:在光化平衡模式下,E区明显形成。在太阳活动低年夏季可产生明显的F_1“凸缘”。但仅靠光化平衡作用不能产生深的F_1谷区,也不能解释F_2层的形成;双极扩散是F_2层形成的主要机制;中性风的因素对E层影响不大,却可以在太阳活动低年夏季产生谷深在0.05—0.1的深F_1谷区。用此模式还计算了F_1谷区日变化,结果表明:中性风影响模式能较好地反映我国中低纬地区F_1谷区变化的地域特征。     

An update global model of hmF2 from values estimated from ionosonde and COSMIC/FORMOSAT-3 radio occultation

In this paper, we present our recent work on developing an updated global model of the ionospheric F2 peak height hmF2 parameter by combining data from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC/FORMOSAT-3) radio occultation (RO) measurements and from the extended global ionosonde stations. In particular, 10 Chinese ionosonde stations’ data are newly introduced into this study. The modeling technique used is based on a two-layer empirical orthogonal function (EOF) expansion. Global distributions of hmF2 maps calculated using the newly constructed global model and the one provided by the International Reference Ionosphere model (IRI-ITU-R) are compared with the global distributions of hmF2 obtained by the COSMIC RO measurements and quantitative statistical analysis of the differences between the model results and those of the COSMIC RO measurements is made for the low (2008) and high (2012) solar activity years. The obtained average root-mean-square differences (RMSEs) for our model are 27.7 km (11.1%) and 31.0 km (9.8%), respectively for the years 2008 and 2012, whereas those for the IRI-ITU-R model are 39.9 km (16.9%) and 35.0 km (11.6%), respectively. Comparison of the results calculated both by our model and the IRI-ITU-R model with the digisonde observation is also made. The comparisons show that the newly constructed global hmF2 model can reproduce reasonably well the observations and perform better than IRI-ITU-R model.     

Dynamics of global electron content in 1998–2005 derived from global GPS data and IRI modeling

We analyzed the dynamics of global electron content (GEC) for the period 1998–2005 and compared the estimated GEC with variations of the 10.7-cm solar radio emission and with and with GEC values obtained with IRI-2001. We found a strong resemblance between the curves’ shapes for the experimental and modeled GEC: strong semiannual variations are discernible in these series and both curves tend to increase the absolute GEC value during the period of maximum of solar activity. However, there are some significant distinctions, such as absence of 27-day fluctuations in the series of GEC computed by the IRI-2001. On the contrary, observational GEC reflects well dynamics of solar activity: 27-day variations of GEC are very similar to the ones of the index F10.7, but GEC undergoes a lagging of about of 30–60 h as compared to value of the F10.7 index. The relative amplitude of 27-day variations decreases from 8% at the rising and falling solar activity to 2% at the period of its maximum.     

Evaluation of global modeling of M(3000)F2 and hmF2 based on alternative empirical orthogonal function expansions

Global modeling of M(3000)F2 and hmF2 based on three alternative EOF (empirical orthogonal function) expansion methods is described briefly. Data used for the model construction is the monthly median hourly values of M(3000)F2 from the ionosonde/digisonde stations distributed around the world for the period of 1975–1985 and the hmF2 data of the same period converted from the measured M(3000)F2 based on the strong anti-correlation existing between them. Independent data of a low (1965) and a high (1970) solar activity year are used to validate the three alternative models based on different EOF expansion methods. Comparisons between the modeled results and observed data for both the low (1965) and high (1970) solar activity years showed good agreement for both M(3000)F2 and hmF2 parameters. Statistical analysis on the differences between model values and observed data showed that all the three alternative models (Model A, B and C) based on the different EOF expansion methods have better agreement with the observed data than the models currently used in IRI. All three alternative EOF based models have almost the same accuracy. Discussion on the preference of the three alternative EOF based models is given.