A circular crossed-field amplifier for in situ measurements, studyof reentrant beam effects, and comparison with numerical simulation

A low frequency, injected beam, circular format crossed-field amplifier has been designed and constructed for the purpose of studying electron-radio frequency wave interaction in reentrant devices. The device has been designed to allow in situ diagnostic probe measurements in the space between the anode and sole. The device has been operated in nonreentrant, fully reentrant, and reentrancy controlled configurations. Details of the design and operating parameters are described. Device characteristics are examined with respect to the amount of circulating charge or degree of reentrancy. A large increase in gain has been achieved from nonreentrant to the fully reentrant format. A gain of 7.2 dB has been obtained for the latter whereas only 3.8 dB has been obtained for the former with 30 mA of injected beam current. A maximum gain of 14.4 dB has been achieved for the fully reentrant configuration. Electron beam and noise measurements versus the degree of reentrancy have also been examined. Results from the nonreentrant amplifier performance have been directly compared with the MASK simulation code and good agreement has been obtained. These experiments will provide the basis for more detailed investigations on the effect of reentrancy on CFA operation and will also allow for the development of more accurate computer models of the reentrant system for numerical simulation of CFA operation     

Design Envelopes and Optical Feature Extraction Techniques for Survivability of SnAg Lead-free Packaging Architectures Under Shock and Vibration

In this paper, a design-envelope approach based on optical feature extraction techniques has been investigated for drop and shock survivability of electronic packaging has been presented for 6-lead-free solder alloy systems. Solder alloy systems investigated include, Sn1Ag0.5Cu, Sn3Ag0.5Cu, Sn0.3Ag0.7Cu, Sn0.3Ag0.7Cu0.1Bi, Sn0.2Ag0.7Cu0.1Bi-0.1Ni, 96.5Sn 3.5Ag. Previously, digital image correlation (DIC) has been used for measurement of thermally induced deformation and material-characterization. In this paper, DIC has been used for transient dynamic measurements, and optical feature extraction. Board assemblies have been subjected to shock-impact in various orientations including the JEDEC zero-degree drop and the vertical free-drop. Transient deformation has been measured using both digital image correlation and the strain gages. Measurements have been taken on both the package and the board side of the assemblies. Accuracy of high-speed optical measurement has been compared with that from discrete strain gages. Package architectures examined include-flex ball-grid arrays, tape-array ball-grid arrays, and metal lead-frame packages. Explicit finite-element models have been developed and correlated with experimental data. Models developed include, smeared property models, and Timoshenko-beam models. The potential of damage identification and tracking for various solder alloys has been investigated. Data on identification of damage proxies for competing failure mechanisms at the copper-to-solder, solder-to-printed circuit board, and copper-to-package substrate has been presented. Design envelopes have been developed based on statistical pattern recognition. The design-envelope is intended for component integration to ensure survivability in shock and vibration environments at a user-specified confidence level.     

Optimized cooling systems for high-power semiconductor devices

Straightforward air cooling of semiconductor devices has gradually been replaced by methods using liquid coolants, especially water cooling. In this paper, more advanced cooling devices for hockey-puck-type and module-type semiconductors are suggested. An established heat sink made of aluminum nitride for the water cooling of hockey-puck-type semiconductors has been used as a basis for the development of high-performance heat sinks for increased heat flux densities. By means of thermal and fluid dynamics simulation tools the internal geometry has been optimized with regard to improved heat transfer and reduced pressure drop. The simulation results have been confirmed by a number of experiments using various measuring techniques. As an alternative cooling method for semiconductor modules, a modified baseplate comprising a number of fins for direct water cooling has been suggested. For an intelligent temperature management control algorithms have been developed, resulting in a prototype application-specific integrated circuit which has been implemented for test purposes     

Process technology for radiation-hardened CMOS integrated circuits

A process technology for radiation-hardened CMOS integrated circuits has been defined. Process parameters for the SiO/SUB 2/ gate insulator have been optimized for radiation hardness, and circuit latch-up due to parasitic p-n-p-n structures on the integrated circuits has been prevented by gold-doping the silicon substrate to reduce carrier lifetime. The device yields for the hardened technology have been evaluated and the reliability has been characterized by bias-temperature life testing.     

Assimilation of altimeter significant wave height into a third-generation global spectral wave model

Data from three different altimeters (Topex/Poseidon, Jason-1, and European Remote Sensing Satellite 2) have been assimilated in a third-generation global spectral wave model forced by winds observed by scatterometer onboard QuikSCAT. Two different approaches of assimilation have been discussed. In the first approach, a simple scaling has been used to generate wave spectrum from altimeter-derived significant wave heights for assimilation in the model. In the second approach, the influence of altimeter observation has been spread to nearby grid points. Assimilation has been carried out every 6 h for five days. After the expiry of the assimilation phase, the model has been run in pure hindcast mode. Assimilation experiments have been carried out for the months of September and December 2002. Impact of assimilation has been found to be quite high in the Indian Ocean. It has been also found that the model is able to retain the memory of assimilation for a period of two and a half days as far as global ocean is concerned. This memory is more for the Indian Ocean. The wave spectrum generated by the model in the hindcast mode has been validated against the buoy-observed wave spectrum in the high sea conditions. The more significant impact has been seen in the case of altimeter track in the vicinity of the buoy.     

我校"信号与系统"课程的改革与建设

信号与系统是电气信息类专业重要的技术基础课程。近年来,课程组对“信号与系统”课程进行了全面的改革与建设,造就了一支高素质的教师队伍,提出了具有鲜明时代特征的教育教学思想,重构了课程体系,更新了教学内容,出版了高水平教材,改革了教学方法与手段,取得了丰硕成果,2003年被评为国家精品课程。     

Quantum Transport Simulation of Experimentally Fabricated Nano-FinFET

We have utilized the contact-block-reduction (CBR) method, which we extended to allow a charge self-consistent scheme, to simulate experimentally fabricated 10-nm-FinFET device. The self-consistent CBR simulator has been modified to simulate devices with channels along arbitrary crystallographic orientation. A series of fully quantum-mechanical transport simulations has been performed. First, the fin extension length and doping profile have been calibrated to match the experimental data. The process control window for the threshold voltage as a function of fin extension has been extracted for the considered device. Then, a set of transfer characteristics and gate leakage currents have been calculated for different drain voltages. The simulation results have been found to be in good agreement with the experimental data in the subthreshold regime. The device turn-off and turn-on behavior has been examined for different fin widths: 12 (experimental), 10, 8, and 6 nm. Finally, the subthreshold slope degradation at high temperatures has been studied     

Analytical modeling of flicker and thermal noise in n-channel DG FinFETs

A compact physics-based thermal and flicker noise model has been developed for n-channel Double Gate FinFETs with varying structural parameters. The effects of mobility degradation due to velocity saturation, carrier heating and channel length modulation have been incorporated for an accurate modeling of noise. The mobility fluctuations dependent on the inversion carrier density have been considered and a characteristic of the flicker noise different from that of Bulk MOSFETs was observed. This has been validated by the experimental results. Based on the proposed thermal and flicker noise model, a compact expression of the corner frequency has been derived and the effects of the structural parameters such as the length and the thickness of the channel have been analyzed. Finally, the model has been applied for p-channel devices and noise behavior in accordance with experimental data has been obtained.     

AOTF成像光谱仪及其在青藏高原多尺度遥感中的试验应用

简要阐述了AOTF的光学滤波机理和AOTF成像光谱仪的系统架构,研制了一套基于AOTF的地面成像光谱试验系统,将其应用于青藏高原多尺度遥感试验,针对高原植被试验区获取了不同尺度的成像光谱数据,为多尺度遥感试验提供了更为丰富的地面支持及比对数据。通过对数据的处理分析,证明了该技术在工程上的可行性,并为遥感图像混合像元分解等问题提供了新的解决方案。     

AOTF成像光谱仪及其在青藏高原多尺度遥感中的试验应用

简要阐述了AOTF的光学滤波机理和AOTF成像光谱仪的系统架构,研制了一套基于AOTF的地面成像光谱试验系统,将其应用于青藏高原多尺度遥感试验,针对高原植被试验区获取了不同尺度的成像光谱数据,为多尺度遥感试验提供了更为丰富的地面支持及比对数据.通过对数据的处理分析,证明了该技术在工程上的可行性,并为遥感图像混合像元分解等问题提供了新的解决方案.     

空时二维自适应处理的统一理论,模型与局域处理方法

本文提出了机载相控阵雷达空时二维自适应处理的统一理论，并建立了空时二维处理器系统设计的统一数学模型，根据信号处理域的不同类型，本文把处理器系统分为四大类。本文对这四大类局域处理系统进行了深入研究与分析，给出与提出多种可能的降维变。     

High-performance VLSI architectures for turbo decoders with QPP interleaver

This paper analyses different VLSI architectures for 3GPP LTE/LTE-advanced turbo decoders for trade-offs in terms of throughput and area requirement. Data flow graphs for standard SISO MAP (maximum a posteriori) turbo decoder, SW – SISO MAP turbo decoder, PW SISO MAP turbo decoder have been presented, thus analysing their performance. Two variants of quadratic permutation polynomial (QPP) interleaver have been proposed which tend to simplify the complexity of ‘mod’ operator implementation and provide best compromise between area, delay and power dissipation. Implementation of decoder using one variant of QPP interleaver has also been discussed. A novel approach for area optimisation has been proposed to reduce required number of interleavers for parallel window turbo decoder. Multi-port memory has also been used for parallel turbo decoder. To increase the throughput without any effective increase in area complexity, circuit-level pipelining and retiming have been used. Proposed architectures have been synthesised using Synopsys Design Compiler using 45-nm CMOS technology.     

LTE-Advanced中的多用户MIMO的标准化进展

下行增强MIMO是LTE-Advanced的关键技术之一,文章讨论了LTER8和R9的多用户MIMO的传输模式,并且就LTE-Advanced中的多用户MIMO的主要问题进行了讨论。比较了各种可能的导频设计,下行控制信令、反馈及增强的码本设计方法,探讨了多用户MIMO适用的场景以及每个用户支持多于两个layer的可能性,并介绍了标准化进展情况。     

Schottky diode for bipolar LSI's consisting of an impurity-controlled Si substrate and Al(2%Si) electrode

Circuit design conditions of Schottky diodes have been investigated and the fabrication method for diodes suitable for the conditions has been proposed for applications to bipolar LSI's, such as ECL RAM and Schottky TTL. It has been found that the desired Schottky diode for bipolar LSI's is not an ideal device from the theoretical point of view. Desired built-in voltage, ideal factor, series resistance, and junction capacitance for the Schottky diode have been estimated, respectively, for the bipolar RAM and Schottky TTL. A proposed Schottky diode consists of an impurity-concentration-controlled     

Effects of the inversion layer centroid on MOSFET behavior

The effects of the average inversion-layer penetration, the inversion-layer centroid, on the inversion-charge density and the gate-to-channel capacitance have been analyzed. The quantum model has been used, and a variety of data have been obtained by self-consistently solving the Poisson and Schrodinger equations. An empirical expression for the centroid position that is valid for a wide range of electrical and technological variables has been obtained and has been applied to accurately model the inversion-layer density and capacitance     

多波段图像融合算法研究及其新发展(Ⅰ)

对多通道、特别针对可见光与长波红外图像像素级融合的各种算法进行了深入的研究,针对工作实际需要,对其均进行了一定的改造和编程调试,对某些算法做了较重大改进,在若干方面提出了自己的具有特色的算法与思想。在此基础上编制了大型程序软件包。     

浅谈语音实验室建设与管理

近年来,语音实验室在我国高等院校得到迅速发展.南京邮电大学经过近四年的努力,已经建设成用于语音信号分析和处理的各种设备,开发了语音分析、编码、识别、消噪等各种软件.本文从我校语音实验室建设与管理上进行探索,详细介绍了语音实验室建设的概况和内容,讨论了语音实验室对学生和教师全方位开放的必要性,以及如何为教学和科研服务等问题.     

Metal wave-guide to dielectric image guide transition using exponential taper

A unique metal wave guide to dielectric image guide transition has been developed using exponential taper in dielectric wave guide. The propagation characteristics have been computed theoretically and taper impedance for the different cross-sections have been evaluated, so as to match it with the metal wave guide for efficient mode conversion. Transmission loss and return loss for triangular and exponentail taper with frequency for same dimensional parameters have been measured.     

A tutorial on computer-aided analysis of switched-capacitor circuits

In this paper, various formulation techniques for analyzing switched-capacitor circuits have been described and compared. Some basic pcoperties of the time-, z-, and frequency-domain solutions have been presented. Analysis techniques for handling nonideal op-amps, switch resistances, and noise and distortion effects are discussed. Methods for sensitivity analysis have been briefly mentioned and, finally, an overview of computer-aided analysis techniques has been given.     

Queueing-Delay Formula for Common-Channel Signaling Systems

An approximate queueing model for common-channel signaling systems has been developed and the queueing-delay distribution has been obtained. As a special case, the approximate average queueing-delay formula for common-channel signaling systems has been derived. By simulation, it has been ascertained that this formula is reasonably accurate.