Modelling PBG devices to DWDM filters design

The fibre optic transmission systems require a bandwidth of about 25 THz in telecommunications networks, for which it is necessary to resort to dense wavelength division multiplexing (DWDM) systems. These systems need optical filters to broadcast selectively or not in a given wavelength band. A new very promising technology for these applications is the photonic crystals with forbidden bandgap (photonic bandgap (PBG)). In this paper, we propose a model of PBG devices to design DWDM filters on PBG materials. Copyright © 2004 John Wiley & Sons, Ltd.     

Analytical modelling of multilayer structure electronic devices for electrothermal layout optimisation

In this paper, an analytical model for the electrothermal solution to the non‐linear 3‐D heat flow equation for multilayer structure electronic devices is proposed. Compared with previous models presented in literature, it is general and can be easily applied to a large variety of integrated devices, provided that their structure can be represented as an arbitrary number of superimposed layers with a 2‐D embedded thermal source, so as to include the effect of the package. The proposed method is independent of the specific physical properties of the layers, hence GaAs MESFETs and HEMTs as well as silicon and silicon‐on‐insulator MOSFETs and heterostructure LASERs can be analysed. Moreover, it takes into account the dependence of the thermal conductivity of all the layers on the temperature; the heat equation is solved coupled with the device current–voltage relation in order to give physical consistence to the experimental evidence that a temperature increase causes a degradation of the electrical performances and that the electrical power is not uniformly distributed. Copyright © 2001 John Wiley & Sons, Ltd.     

光电子器件封装中微位移传感器的设计与仿真

在光电子器件封装中,光纤组件和阵列波导芯片之间微小位移的检测对封装效率有很大的影响。分析了目前光电子封装存在的问题,并对几种位移测量方法进行了比较,提出了基于电阻应变式一维位移传感器结构。首先,对位移传感器结构进行了理论上的分析,得到了微位移与应变的关系式;然后,采用 ANSYS有限元分析软件对传感器的结构的进行仿真分析,得到位移与应变之间的仿真值;最后,把理论上的分析值与仿真得到的结果进行比较分析。结果表明,新型传感器能够检测微米级位移,通过优化弹性薄片的结构和改变施力点的位置,可以有效的提高传感器的灵敏度。     

Theoretical characterization of multilayer photonic crystals having a 2D periodicity

We present a new, very accurate and fast model of photonic bandgap (PBG) structure characterized by a two‐dimensional (2D) periodic change of the refractive index and finite height, therefore named quasi 3D PBG. The new model is based on the Floquet–Bloch formalism and allows to find all the propagation characteristics including the space harmonics and the total field distribution, the propagation constants, the guided and radiated power and modal loss induced by the 2D grating. A clear explanation of the physical phenomena occurring when a wave propagates inside the 2D periodic structure is presented, including the photonic bandgap formation and the radiation effects. The approach does not require any theoretical approximation, and can be applied to study rigorously any PBG‐based multilayer structures. We have applied the model to investigate several structures for both optical and microwave applications. Copyright © 2005 John Wiley & Sons, Ltd.     

一种新型的变频器件群时延特性测量方法

群时延作为衡量变频器件相位线性的主要指标,对于变频系统来说更是重中之重,对射频器件测量中具有重要地位的群时延测量问题进行了研究。首先介绍了群时延的定义及概念,然后从群时延的测量原理入手,逐步讲明了利用PNA型矢量网络分析仪的标量混频器+相位(SMC)模式测量变频器件群时延的方法及适用性,最后利用实验对该新型群时延测量方法与传统测量方法结果进行对比。结果表明,利用标量混频器+相位模式测量变频器件的变频损耗与群时延与利用矢量混频器模式测量得到的结果较为一致,变频损耗测量误差在0.5dB以内,群时延测量误差在皮秒量级,证明了该方法的正确性及准确度。且无论从测试复杂性、稳定性与溯源性上均优于传统的矢量混频器法,因此该测试方案可广泛应用于变频器件的变频损耗与群时延测量。     

用电压抽取装置检测35kV线路电压供备自投使用

介绍一种用110～220kV线路电压抽取装置检测35kV线路电压(供备自投使用)的方法。实践证明该法简单、可行、节省投资和安装空间,在老站进行综合自动化改造中,该方法尤为适用。     

功率半导体器件栅氧化层状态监测方法综述与展望

功率半导体器件栅极氧化层退化对功率器件的正常运行产生严重影响,不同偏置应力导致栅氧化层退化形式不同,故栅氧化层的状态监测研究对确保功率器件的高可靠性具有重要意义.从栅氧化层退化的微观机理出发,建立相关特征参数与栅氧化层退化的精确函数关系,在栅氧化层退化的情况下对特征参数漂移量进行检测可以实现对功率器件栅氧化层的状态监测...     

Role of the temperature distribution on the PN junction behaviour in the electro‐thermal simulation

Electro‐thermal simulations of a PIN‐diode based on the finite‐element method, show a non‐uniform temperature distribution inside the device during switching transients. Hence, the implicit assumption of a uniform temperature distribution when coupling an analytical electrical model and a thermal model yields inaccurate electro‐thermal behaviour of the PIN‐diode so far. The idea of including non‐uniform temperature distribution into power semiconductor device models is not new, as accurate electro‐thermal simulations are required for designing compact power electronic systems (as IC or MCM). Instead of using a one‐dimensional finite difference or element method, the bond graphs and the hydrodynamic method are utilized to build an electro‐thermal model of the PIN‐diode. The results obtained by this original technique are compared with those obtained by a commercial finite‐element simulator. The results are similar but the computation effort of the proposed technique is a fraction of that required by finite‐element simulators. Moreover, the proposed technique may be applied easily to other power semiconductor devices. Copyright © 2004 John Wiley & Sons, Ltd.     

电能计量装置健康度的综合评估与趋势预测方法

为有效解决电能计量装置的计划检修任务重、重复检测、针对性不强等问题,提出了一种电力计量装置健康度的综合评估方法以及电能计量装置健康度的趋势预测方法,为电能计量装置的状态在线检修优化提供辅助决策。首先,从电能计量装置的运行状态、配置方式以及运行工况等方面,提出了一种电能计量装置的健康度综合评价指标体系。并采用序关系分析法求取电能计量装置综合评估指标的赋权值,从而实现电能计量装置健康度的综合评价。其次,基于电能计量装置的综合评估结论,提出了一种基于灰色GM(1,1)模型的电能计量装置健康度预测方法,并通过天津市电力公司的实际运行进行案例验证。健康度评价和预测的结果可对电能计量装置的现场状态检修进行有效指导,并能及时发现电能计量装置的运行隐患,为电能计量装置状态检修策略优化提供理论依据。     

在生态建模中的作用

阐明可以作生态系统污染物排放环境保护以及生态平衡的总指标，进而指出生态建模通用原理，即对于一切生物都有改变本身结构以至于组成来适应环境变化本领，其能承受环境施加影响的限度称为生态学缓冲能力，为了维持这种缓冲能力，一切生态系统都趋向于自身具有最大的值，叫做“趋最大化原理”，这是以作指标分析研究生态系统一条通用的原理。     

Fast modelling of deeply and fully etched gratings based on the Bloch–Floquet theorem

A model of deeply and fully etched gratings (also identified as one‐dimensional waveguide photonic bandgap structures), based on the Bloch–Floquet theorem, has been developed to perform a complete analysis of the electromagnetic (e.m.) wave propagation in the structure, assumed of finite extension, i.e. to determine mode propagation constants, electromagnetic field harmonics and total field distribution, transmission and reflection coefficients, total forward and backward power flow in the structure, guided power and total losses. Comparisons with other accurate numerical methods confirm the accuracy of the new one, whose main advantages are the quickness and the possibility to determine a great amount of information and figures of merit in a few seconds (for each operating wavelength). Moreover, the model allows the designer a complete view of the physical and geometrical device features, so it permits to draw design rules for optimization of photonic bandgap (PBG) waveguide device design. Copyright © 2001 John Wiley & Sons, Ltd.     

电器产品快速测量、建模与设计的逆向工程系统

叙述了研发电器产品的“逆向工程”方法，针对低压电器产品的结构特点，论述了数据采集设备的选型，确定数据测量方法、数据分析及恢复方法、CAD／CAM软件的二次开发。     

智能开票系统中最大动作元件集方法的研究

通过对综合操作命令的归纳 ,提出用最大动作元件集的概念来智能分析、产生倒闸操作票的方法。在此基础上 ,给出了智能分析系统的功能模块 ,并详细讲述了求解和过滤最大动作元件集的过程     

Analysis of finite-size coated electromagnetic bandgap structure by an efficient scattering matrix method

This paper presents an efficient simulation algorithm-Scattering matrix method for investigation of the coated finite two-dimensional electromagnetic bandgap (EBG) structures. The method is derived to be capable to simulate the band properties of the coated cylinder photonic crystal with wave discontinuities. Numbers of photonic crystals with waveguide discontinuities are examined. The transmission characteristics of the EBG embedded with metal, dielectric, and various coated cylinders are analyzed. The results show that the tuned bandgap properties are able to provide an additional possibility to develop a novel device.     

微波铁氧体器件现状及新一代集成化微波铁氧体器件展望

阐述了微波铁氧体器件发展现状,指出了微波铁氧体器件当前应该发展的技术方向和亟需突破的关键技术,强调微波铁氧体器件小型化和便于IC集成要求迫在眉睫。为实现微波铁氧体器件的小型化,从微波铁氧体器件基本原理入手,论述了圆极化概念在微波铁氧体器件功能实现和性能优化方面的重要作用,提出了采用绝缘多导体磁性结构实现可满足小型化和便于集成化要求的新一代微波铁氧体器件的基本思路。绝缘多导体磁性器件结构可实现多个TEM波模式的混合传输,利用此构造关于磁化偏置方向的正负圆极化波,从而产生显著的非互易传输和电控特性。TEM模式没有低频截止问题,器件尺寸可大体不受波长比拟规则的限制,通过目前日趋成熟的磁性集成化工艺,可实现小型化和便于IC集成化的新一代微波铁氧体器件。     

Modelling of printed discontinuities on open microstrip lines by mode matching techniques

The dynamic analysis of discontinuities in printed circuits has been performed using the mode matching technique. This study concerns the open end of microstrip lines and suspended microstrip lines. The fields on either side of the discontinuity are described by means of the continuous (radiated and evanescent) and guided modes of the structure. The conditions of continuity of the electromagnetic fields are then applied in the plane of the discontinuity. By taking into account the relations of orthogonality of the modes of the same region, a system of coupled Fredholm integral equations is obtained and solved by the iterative method of Neumann's series. The study calls for the use of the continuous spectrum of microstrip lines, which can be obtained analytically only after a great amount of calculation and CPU time. Thus, the first approach consists in neglecting this continuous spectrum. This gives accurate results for the reflection coefficient but it is not sufficient for the derivation of the radiation pattern. So, two simple models for the continuous spectrum, both based on the physical behaviour of such discontinuities, are considered and discussed. © 1997 John Wiley & Sons, Ltd.     

Optimal ranking of measurements for state estimation by the gradient projection method

Optimal measurement ranking is the first and essential step in meter selection for the design of a reliable measurement system. This paper presents a computationally-efficient algorithm for the optimal ranking of measurements for state estimation. The algorithm maximizes the accuracy of estimates with respect to the measurement variances by performing a transformation on the problem formulation, and minimizing the resulting cost function subject to a set of linear constraints.

The proposed algorithm is based on the gradient projection method and includes some new computational features. Computational efficiency of the solution procedure is significantly improved by converting the constraints into a linear form through a transformation, using an analytical expression for the derivative of the cost function, employing the sparse inverse matrix technique and optimal ordering for the evaluation of the cost function and its derivatives, and simplifying the evaluation of the projected gradient vectors.

Performance of the algorithm is demonstrated on the IEEE 14, 30, and 57 bus systems.     

降低发电厂、变电所接地装置工频接地电阻的技术措施

发电厂、变电所接地装置工频接地电阻指标关系到人身设备安全。比较分析了降低发电厂、变电所接地装置工频接地电阻的方法，提出相应的技术措施。     

Modelling characteristics of the impulse transformer in a wide frequency range

In the paper, a new compact electrothermal model of the impulse transformer is proposed. This model has a form of a subcircuit dedicated for SPICE and could be used for low power impulse transformers applicable in switch-mode power supplies used in electronics. It takes into account simultaneously electric, thermal, and magnetic phenomena occurring in the considered device and describe nonidealities of the core and windings. The form of the elaborated model and analytical dependences describing all its components are presented. Correctness of this model is verified experimentally in a wide range of frequency and load resistance for selected constructions of transformers. Satisfactory agreement between the results of computations and measurements is obtained     

备用电源自动投入装置缩短投入时间的研究

在电力系统中,备用电源自动投入装置的应用,提高了供电可靠性。经研究发现,故障时甩掉的供电负荷与该装置投入的时间成正比。通过改变整定方法,明显地缩短了该装置投入时间,减少了因故障给供电客户带来的损失。该方案在实际中已得到应用,取得了预期的效果。