Analysis of finite-differencing errors to determine cell size when modeling ferrites and other lossy electric and magnetic materials using FDTD

The focus of this paper is the modeling of materials that have both significant electric and magnetic losses, such as ferrites, using finite-difference time domain (FDTD). The primary contribution is identifying appropriate cell sizes when modeling these types of materials. It is shown that finite-differencing errors increase in lossy media compared to lossless media when sampling at the same number of cells per wavelength. Losses in a medium are defined by the ratio of the attenuation constant, /spl alpha/, to the phase constant, /spl beta/, since that ratio accounts for all losses, whether they be electric or magnetic. In addition to a detailed finite-differencing error analysis, a simple approximation is given for selecting a cell size in a lossy material that will give the same finite-differencing error as ten cells per wavelength in a lossless material. This paper also presents a means for deriving pure real constitutive parameters from complex constitutive parameters. Being able to make such calculations is useful in cases where complex constitutive parameters are given for a material, and the FDTD model being used only accepts pure real constitutive parameters, as is the case for several contemporary models. Comparisons of theoretical and FDTD-modeled reflection and transmission show that the derived, real constitutive parameters are valid.     

以PZT薄膜为驱动和传感的微型陀螺研制

利用压电陶瓷PZT的正反压电位效应,将PZT薄膜同时作为驱动及传感材料,设计并制造了两种新颖的以IC兼容技术制作在硅片上的压电薄膜微型陀螺。高质量的PZT薄膜是在Pt/Ti/SiO2/Si基底上以溶胶－凝胶技术铺设的。基于反压电效应,微型陀螺在其谐振频率上被输入的交流信号驱动,由其正压电效应,可检测到与转动角速度成正比的输出信号。文章分别介绍了两种微型陀螺的设计原理,详述了制作方法,并对制出的压电微型陀螺进行了检测,得到了的结果与预测结果相符。     

Plasma circular cylindrical waveguide in lossy material

The surface modes in the plasma circular cylindrical waveguide in a lossy material are analyzed, particularly for the variations of their propagation properties with plasma parameters and surrounding material. The characteristic equations of surface modes are derived, and their relevant approximate solutions are given. The limit results of this paper are consistent with that given in literature’s. The analysis show that it can be used to improve the properties of mode suppressors and fabricat cut-off attenuators.     

Neural Network Signal Processing Approach for Damage Assessment in Fiberoptic Smart Material Systems and Sructures^①②

An approach by using neural network signal processing in associate with embedded fiberoptic sensing array for the newly developed“smart material systems and structures” is discussed in this paper.The principle,structure of this approach and suitable neural network algorithms are described.The results of simulation experiments are also given.     

国内外多晶硅发展现状

叙述了国内外多晶硅的发展概况，讨论了多晶硅生产过程中改良西门子法的几项关键技术，并对我国多晶硅材料的研究提出了几点建议。     

Glass fibers for optical communications

Glass optical waveguides with attenuations below 20 dB/km have made possible a new approach to optical communications. These glass fibers satisfy requirements for transmission over kilometer lengths with experimental systems utilizing existing devices for sources and detectors. The realization of material and fabrication advances necessary for this accomplishment are the topic of this paper. Basic theoretical principles are introduced in a review fashion. The application of these principles in choice of materials and fabrication is described. Results in fiber performance following this framework are given in a section on evaluation, which includes information capacity, attenuation, and some environmental requirements. Preliminary experiments in bundling and cabling are discussed, followed by concluding remarks.     

一种新型铁电体移相器

介绍了一种用于相控阵雷达的新型铁电体移相器,利用有限元方法对铁电体材料加载波导移相器进行了分析,给出了计算结果。最后讨论了铁电体移相器设计中几个值得关注的重要问题。     

我国半导体硅材料的发展现状

叙述了我国半导体硅材料的发展现状及与国外相比存在的差距 ,提出了发展我国硅材料的一些建议     

双负异构材料——一种新型射频/微波人工合成材料

双负异构材料（即同时具有负介电常数和负导磁率的人工材料）是近期有关学者较感兴趣的课题。本文简要地介绍了双负异构材料的特性及几种不同合成方法所组成的双负异构材料，并对材料名称提出了一点想法。     

InAs/InP Quantum-Dash Lasers and Amplifiers

InAs quantum-dash structures fabricated by self-assembly growth techniques and based on compound semiconductors lattice matched to InP substrates were used to realize long wavelength lasers and amplifiers for telecom applications. With this new type of laser material special properties of low-dimensional electronic systems can be utilized for device applications, which allow to realize new device features not possible by conventional device designs. In this paper a brief overview is given about application oriented material and device research on this wire/dot-like material system by highlighting laser and high-speed optical amplifiers. Broadband laser material with a gain bandwidth of more than 300 nm could be obtained to cover the extended telecommunication wavelength range between 1.4 and 1.65 . High-speed optical amplifiers could be realized by using this quantum-dash laser material with unique device performance, like multiwavelength amplification without any cross-talk at data rates of 10 Gbit/s and pattern-free and noise reduced signal amplification at saturation condition demonstrated up to 40 Gbit/s.     

高折射率长波红外材料PbTe的研究现状

本文综述PbTe材料及其薄膜的当前研究进展,并针对PbTe薄膜的不同制备方法及特点进行了探讨,得出了PbTe薄膜的化学组成、组织结构、形态、光学特性与材料自身性质、基底特性、沉积温度、制备方法有直接关系的结论.上述结论对今后的PbTe薄膜研究具有重要意义。     

微波腔体微扰方法测量非电量技术

本文简述微波腔体微扰方法测量湿度、厚度等非电量的原理.根据电磁场理论,导出分辨率公式.计算及实验均表明,用微波腔体微扰方法测量非电量具有高的分辨率.文中还介绍几种检测腔体失谐的方法,着重讨论了鉴相方法和实验结果.     

基于物理的GaAs MESFET模型参数计算

根据材料性能和物理结构参数近似计算 Ga As MESF ET等效电路模型参数 ,并给出等效电路参数随物理参数的变化曲线。     

Nonlinear properties of IMPATT devices

The basic principles of IMPATT diodes as microwave devices are reviewed and the current status of these devices concerning power output and efficiency is given. The main purpose of this paper, however, is to discuss the nonlinear properties of these diodes which are useful in the design of amplifiers, oscillators, and other microwave devices. The main results of this paper are obtained from a digital computer analysis where an approximate, but realistic, diode model is employed. A detailed comparison of complementary silicon diodes as well as GaAs diodes concerning power output and efficiency is given. The effects of doping profile, current density, temperature, and material parameters on the performance of these devices have been investigated and are summarized. Saturation effects which limit the efficiency and power output of these devices are described and optimum efficiencies which can be achieved for various doping profiles are given. A comparison between single-sided and double-drift diodes in both silicon and GaAs is also presented.     

纳米吸波材料的物理实质及研究进展

吸波材料是隐身技术的关键材料,纳米材料由于其特殊的量子尺寸效应和隧道效应等产生的优良的电磁波吸收性能而受到世界各国的重视．本文简单介绍了吸波材料的工作原理,进而阐述了纳米吸波材料吸收电磁波的物理实质．详细介绍了纳米涂敷型吸波材料和纳米结构型吸波材料的研究现状,并对纳米吸波材料的发展趋势进行了展望．     

光纤连接器反射特性的研究

主要研究常用的垂直端面连接器的光反射特性。通过测量光纤垂直端面的光反射分析光纤抛光端面上的高折射层厚度与反射比的关系,环境温度与反射比的关系特性;光纤端面不抛光而直接连接时的反射比与温度、空气隙度等的关系特性,给出垂直端面上的高折射率层的折射率和厚度计算与测量方法。实验结果与分析相吻合。     

纳米半导体材料的评价技术

简要地介绍了纳米半导体材料表面形貌、位错缺陷的观测手段与方法以及研究量子点的发光行为和光学性质的手段与方法。     

用UV激光加工高密度印制板

在本文中,讨论激光技术的几个基本概念和激光加工材料的机理及其加工实例。     

MOCVD生长GaAs/Si材料及其在MESFET中的应用

本文研究了MOCVD生长GaAs/Si复合材料的生长工艺及材料特性,并生长出用于MESFET的多层结构材料。讨论了影响外延层电阻率的因素,并给出了GaAs/Si材料在MESFET中的应用结果。     

Gain and bandwidth of fast near-infrared photodetectors: A comparison of diodes, phototransistors, and photoconductive devices

Different materials and different types of detectors are used for optical data communication in the wavelength range oflambda sim 0.8µmlambda sim 1.7µm. In this paper the behavior of p-n diodes, Mn and Mp Schottky diodes is evaluated as well as that of bipolar transistors, n-p-n and p-n-p, and of photoconductive detectors using n-type or p-type material. The different behavior of lateral and coaxial versions is shown taking into account contact and surface recombination. The gain, the bandwidth, the gain bandwidth product, and the rise time of all these types of fast detectors are given in terms of material and technological data, including the discussion of the different rise and fall times of some detector versions. Finally, a theoretical comparison is made between the detectors showing their different behavior and ultimate performance limit. For practical GaAs planar devices as a photoconductive detector, a p-n diode, a heterojunction n-p-n and a lateral n-p-n transistor, a Mn Schottky diode, and a totally depleted MnM structure (symmetrical Mott barrier) experimental data are given. They verify the theoretical prediction that with all types of detectors rise times of <100 ps can be achieved.