单刀双掷RF MEMS开关的研究与设计

介绍了一种基于横向金属接触的DC-5GHz单刀双掷RF MEMS开关的研究与设计．横向金属接触开关包括了一套有限的共面波导（FGCPW）传输线和左右摆动的悬臂梁．为了降低开启电压,设计了一种曲折型的折叠梁结构,通过理论分析与仿真实验验证了该结构的可行性,并利用MetalMUMPs工艺加以实现．测试结果显示,该开关在5GHz处的插入损耗为0．8dB,回波损耗大于20dB,隔离度为40dB．测得最低开启电压为33V．     

掺Pt对Si(100)上形成的NiSi薄膜应力的影响

利用在线应力测试技术表征了掺入Pt后对镍硅化物薄膜应力性质的影响.通过改变NiSi薄膜中Pt含量以及控制热处理的升温、降温速率实时测量了薄膜应力,发现在Si(100)衬底上生长的纯NiSi薄膜和纯PtSi薄膜的室温应力主要是热应力,且分别为775MPa和1.31GPa,而对于Ni1-xPtxSi合金硅化物薄膜,室温应力则随着Pt含量的增加而逐渐增大.应力随温度变化曲线的分析表明,Ni1-xPtxSi合金硅化物薄膜的应力驰豫温度随Pt含量的增加,从440℃(纯NiSi薄膜)升高到620℃(纯PtSi薄膜).应力驰豫温度的变化影响了最终室温时的应力值.     

Analysis of multiple FSS screens of unequal periodicity using an efficient cascading technique

In this paper, we present an efficient cascading procedure for analyzing frequency selective surface (FSS) systems consisting of multiple FSS screens of unequal periodicity embedded in multiple dielectric layers. In this procedure, we first find a global period for the FSS system by studying the composite in its entirety. Next, we compute the scattering matrix [S] of each of the FSS subsystems for the global Floquet harmonics by applying a relationship we establish that maps the [S] matrix of the subsystem for the individual Floquet harmonics to that for the global harmonics. This mapping-cum-filling process substantially reduces the effort needed to compute the [S] matrix of a subsystem. Finally, we compute the [S] of the entire system by applying a modified cascading formulation, in which one matrix inversion step is eliminated, resulting in a reduction in the total computing resource requirement as well as time. Two numerical examples are given to illustrate the efficiency and effectiveness of the technique.     

热电耦合微执行器温度分布的节点分析法

MEMS系统设计的节点分析法已经被成功地用于机械或机电耦合器件的仿真,但其无法用于热执行器中热-电耦合问题的分析仿真.本文提出一种通过傅里叶变换使用节点分析法动态分析仿真热执行器中热电耦合问题的方法,并建立了热执行器中基本单元--梁单元的热电耦合模型.这种模型的分析计算结果与有限元软件ANSYS吻合较好.     

MS/RF CMOS工艺兼容的光电探测器

为实现光纤通信系统中的单片光电集成,采用工业标准工艺设计了硅基光电探测器,讨论了光电探测器的机理,提出了五种新的探测器结构,并采用TSMC 0.18μm MS/RF CMOS工艺进行了流片.利用半导体测试仪对芯片进行了测试,包括探测器的暗电流、响应度和结电容,并分析了深n阱、浅沟槽隔离等工艺步骤对探测器参数的影响.结果表明,利用标准MS/RF CMOS工艺实现的光电探测器具有良好的特性.     

SiC基的高性能紫外光电探测器

用宽禁带半导体n-4H-SiC和金属Au作肖特基接触,Ti,Ni,Ag合金作背底形成欧姆接触,研制出Au/n4H-SiC肖特基紫外探测器.测试分析了器件在高温高压下的光谱响应特性,响应范围在200～400nm之间,室温无偏压下,响应峰值在320nm,响应半宽为82nm.在高反压下(100V以上)探测器的光谱响应曲线出现了锐上升和锐截止,在260～380nm之间有非常平稳的光谱响应;在高温533K无偏压下,紫外响应特性仍然保持良好.     

Fabrication of 128×128 element optical switch array by micromachining technology

Polycrystalline VO₂ thin films were obtained on Si substrates by ion beam sputtering deposition and annealing in flowing Ar gas. SEM images indicate that VO₂ thin films were grown into compact surfaces. Four-probe measurements indicated that the VO₂ thin films own good electrical homogeneity. After the films' production, micromachining technology including lithography, reaction ion etching and metallization connection processes was used to produce the optical switch array. As a result, the 128×128 element optical switch array was achieved.     

Roughness of amorphous/crystalline interface in pre-amorphization implantation: Molecular dynamic simulation and modeling

Pre-amorphization implantation has been applied as a shallow junction technology. Roughness at amorphous/crystalline (a/c) interface should be controlled to improve junction characteristics. To understand and model a/c interface roughness, molecular dynamic method is applied in simulating pre-amorphization implantation. A method to reproduce roughness at a/c interface by molecular dynamic simulation is presented. A model of interface roughness is presented. Si and Ge implantation from 2-20 keV at a dose of 1 × 10¹⁵ cm⁻² is simulated. The depth of a/c interface is reproduced. Experimental results of a/c interface roughness are successfully simulated. The interface roughness is well reproduced and interpreted by the model presented.     

Bandwidth‐guaranteed QoS routing of multiple parallel paths in CDMA/TDMA ad hoc wireless networks

This paper investigates the issues of QoS routing in CDMA/TDMA ad hoc networks. Since the available bandwidth is very limited in ad hoc networks, a QoS request between two nodes will be blocked if there does not exist a path that can meet the QoS requirements, even though there is enough free bandwidth in the whole system. In this paper, we propose a new scheme of using multiple paths between two nodes as the route for a QoS call. The aggregate bandwidth of the multiple paths can meet the bandwidth requirement of the call and the delays of these paths are within the required bound of the call. We also propose three strategies by which to choose a set of paths as the route, namely, shortest path first (SPF), largest bandwidth first (LBF), and largest hop‐bandwidth first (LHBF). Extensive simulations have been conducted to evaluate the performance of the three strategies in comparison with a traditional single path routing algorithm. The simulation results show that the proposed multiple paths routing scheme significantly reduces the system blocking rates in various network environments, especially when the network load is heavy. Copyright © 2005 John Wiley & Sons, Ltd.     

Design-based texture feature fusion using Gabor filters and co-occurrence probabilities.

A design-based method to fuse Gabor filter and grey level co-occurrence probability (GLCP) features for improved texture recognition is presented. The fused feature set utilizes both the Gabor filter's capability of accurately capturing lower and mid-frequency texture information and the GLCP's capability in texture information relevant to higher frequency components. Evaluation methods include comparing feature space separability and comparing image segmentation classification rates. The fused feature sets are demonstrated to produce higher feature space separations, as well as higher segmentation accuracies relative to the individual feature sets. Fused feature sets also outperform individual feature sets for noisy images, across different noise magnitudes. The curse of dimensionality is demonstrated not to affect segmentation using the proposed the 48-dimensional fused feature set. Gabor magnitude responses produce higher segmentation accuracies than linearly normalized Gabor magnitude responses. Feature reduction using principal component analysis is acceptable for maintaining the segmentation performance, but feature reduction using the feature contrast method dramatically reduced the segmentation accuracy. Overall, the designed fused feature set is advocated as a means for improving texture segmentation performance.