Novel microcontacts in microwave chip carriers developed by UV-LIGA process

Design and development of novel type microcontacts in monolithic microwave integrated circuit (MMIC) chip-carriers to printed circuit board (PCB) assembly are presented in this paper. Several new concepts of microcontacts for packaging solutions of microwave and millimeter-wave MMIC are depicted. Simulation and vector network analyzer (VNA) measurement results for these microcontact transitions are discussed and conclusions for the optimal dimensions are made. Equivalent electrical circuits are extracted from the measured S-parameter data. The results show that the electrical parameters are highly dependent on the transition dimensions and substrate features. These contacts are based on male stud (bump) and female ring concept. When mating each other, there are clips effect and self-alignment features. Finally, the article discusses the technological implementation of the proposed new microcontact stud-ring through a low-cost ultraviolet electroplating, lithography, and molding (UV-LIGA) process.     

Al/SiC carriers for microwave integrated circuits by a new technique of pressureless infiltration

Materials with high thermal conductivity and thermal expansion coefficient matching with that of Si or GaAs are being used for packaging high density microcircuits due to their ability of faster heat dissipation. Al/SiC is gaining wide acceptance as electronic packaging material due to the fact that its thermal expansion coefficient can be tailored to match with that of Si or GaAs by varying the Al:SiC ratio while maintaining the thermal conductivity more or less the same. In the present work, Al/SiC microwave integrated circuit (MIC) carriers have been fabricated by pressureless infiltration of Al-alloy into porous SiC preforms in air. This new technique provides a cheaper alternative to pressure infiltration or pressureless infiltration in nitrogen in producing Al/SiC composites for electronic packaging applications. Al-alloy/65vol% SiC composite exhibited a coefficient of thermal expansion of 7/spl times/10/sup -6/ K/sup -1/ (25/spl deg/C-100/spl deg/C) and a thermal conductivity of 147 Wm/sup -1/K/sup -1/ at 30/spl deg/C. The hysteresis observed in thermal expansion coefficient of the composite in the temperature range 100/spl deg/C-400/spl deg/C has been attributed to the presence of thermal residual stresses in the composite. Thermal diffusivity of the composite measured over the temperature range from 30/spl deg/C to 400/spl deg/C showed a 55% decrease in thermal diffusivity with temperature. Such a large decrease in thermal diffusivity with temperature could be due to the presence of micropores, microcracks, and decohesion of the Al/SiC interfaces in the microstructure (all formed during cooling from the processing temperature). The carrier showed satisfactory performance after integrating it into a MIC.     

Mode analysis in microstrip resonators part II

In this contribution, the transmission line model for a printed circuit microstrip resonator is used to theoretically investigate the modes supported by simple structures. Computer analysis yields useful information on the harmonic response of resonators that is relevant to the design of printed antennas and harmonic generators.     

A new method developed in measuring the dielectric constants of metallic nanoparticles by a microwave double-cavity dielectric resonator

A microwave double dielectric resonator is implemented to measure the dielectric constants of nano-metallic powders. The metallic nanoparticles prepared by vacuum evaporation in inert gas are collected and mixed with alumina powder to fill the inner hole of a sapphire disc by which the resonant frequency and Q factor are measured at the TE/sub 011/ mode to derive the complex dielectric constant.     

芯片设计中的IP技术

从IP开发和集成两个方面入手，重点阐述了IP的基本特征，IP的设计流程及设计中的关键技术，IP集成的一般考虑及集成的关键技术，IP模块的评估与选择等，并探讨了国内IP技术发展的一些思路。     

Scheme to process arbitrary microwave devices in FDTD

An improved finite-difference time-domain (FDTD) formulation is applied to determine a microwave device's port voltage and current without solving the state equations of the equivalent circuits at each time step. This new approach has been validated by comparison with the equivalent current-source method. The results based on the proposed approach show good accuracy and computation efficiency     

半导体纳米颗粒载流子的超快弛豫过程

分析了纳米颗粒的能级结构,建立了载流子弛豫的简化模型,运用数值模拟方法讨论了激发密度、表面态密度及俘获态电子的弛豫率对弛豫过程的影响。讨论结果表明,激发密度的增大及表面态的减少都会导致表面态上电子的饱和,使导带上出现电子的积累,导带电子寿命增大;深俘获态电子的弛豫是影响材料响应速度的主要因素。最后应用此模型对近红外泵浦探测实验的结果进行分析,表明模型可望在实验结果分析上得到应用。     

超声发现脾转移性腺泡状软组织肉瘤一例并文献复习

目的:探讨转移性腺泡状软组织肉瘤的影像学表现和诊断方法.方法:对一例脾转移性腺泡状软组织肉瘤的患者的影像和随诊资料进行分析,并对相关文献进行复习.结果:本例患者无特异临床表现,彩超表现为实性肿块,边界尚清晰,内部回声不均质.CDFI示肿瘤周边及内部未见明显血流信号.CT表现为软组织肿块影,增强后略有不均匀强化.镜下组织...     

Nonlinear behavior of solutions illuminated by a ruby laser part laser: II

The simultaneous temporal and spatial equations governing the light intensity and electronic molecular level population in a laser-illuminated medium were solved numerically for the cases of metal-free and chloroaluminum phthalocyanine. An energy model, consistent with the low-intensity spectroscopic data, was constructed, and the rate constants for transitions and absorption cross sections were varied to get simultaneous agreement with several independent literature experimental data at high irradiation intensities. The results, providing a self-consistent picture of the molecular rate constants within the assumed model, are compared with other results obtained by direct experimentation (where available) and to other approximate calculation methods.     

Optic nerve signals in a neuromorphic chip II: Testing and results

Seeking to match the brain's computational efficiency, we draw inspiration from its neural circuits. To model the four main output (ganglion) cell types found in the retina, we morphed outer and inner retina circuits into a 96 x 60-photoreceptor, 3.5 x 3.3 mm2, 0.35 microm-CMOS chip. Our retinomorphic chip produces spike trains for 3600 ganglion cells (GCs), and consumes 62.7 mW at 45 spikes/s/GC. This chip, which is the first silicon retina to successfully model inner retina circuitry, approaches the spatial density of the retina. We present experimental measurements showing that the chip's subthreshold current-mode circuits realize luminance adaptation, bandpass spatiotemporal filtering, temporal adaptation and contrast gain control. The four different GC outputs produced by our chip encode light onset or offset in a sustained or transient fashion, producing a quadrature-like representation. The retinomorphic chip's circuit design is described in a companion paper [Zaghloul and Boahen (2004)].     

DC field response of hot carriers under circular polarized intense microwave fields in semiconductors limited to two-dimension

Hot carrier dynamics under intense microwave fields is investigated theoretically for the case that the dominant scattering process is optical phonon emission, and the carrier motion limited to two-dimension is intrinsic. When the microwave amplitude is appropriately large, an accumulated distribution of carriers in momentum space appears. The system of this motion is found to cause various peculiar DC fields response, e.g. strong non-linearity, negative differential conductivity, and negative response, under realistic physical conditions [J. Phys. Soc. Jpn 68 (1995) 2994]. In the proper strength of microwave and DC electric fields, especially in the case of circular polarized microwave fields, the carrier motions are converged to some trajectories in momentum space [Proceeding of 25th International Conference on the Physics of Semiconductors, 2001]. Resultantly a new type of accumulated distribution of carriers in momentum space appears. This situation is a sort of population inversion of carriers and causes various phenomena including a negative differential conductivity and/or a negative response appeared in the drift velocity vs. DC field relation not found in the case of linear polarized microwave fields. The carrier motion restricted in two-dimensional band may be essential and effective for these properties.     

A framework for misuse detection in ad hoc networks- part II

We focus on detecting intrusions in ad hoc networks using the misuse detection technique. We allow for detection modules that periodically stop functioning due to operational failure or compromise by intruders. Combining theories of stochastic coverage processes and approximation algorithms, we develop a framework to counter failure of detection modules, while minimizing the resource consumption. We show that the selection of the optimal set of nodes for executing the detection modules is an NP-hard problem. We present a distributed polynomial complexity selection algorithm that attains the best possible approximation ratio. We next consider a simple heuristic selection strategy that allows for seamless operation in time varying topologies. We obtain analytical expressions to quantify the tradeoffs between the resource consumption and detection rates attained by these algorithms. Using analysis and simulation, we identify the appropriate algorithms for different failure rates, resource limitation, and required detection rates.     

Web services in telecommunications, part II [guest editorial]

The five articles in Part II of this feature topic focus on practical articles covering web services in telecommunications. The articles are summarized here.     

Novel method of diameter control in optical-fibre drawing process

A novel method for controlling fibre diameter is devised, utilising the phenomenon that slight changes of gas flow in the fibre-drawing-machine furnace cause rapid variations in optical-fibre diameter. Resultant diameter fluctuations are reduced to ±05% for fibre lengths of over 1 km.     

An experimental method for identifying nonlinear phenomenaintervening in a FWM process developed in a semiconductor opticalamplifier

The new experimental research on the four-wave mixing (FWM) phenomena described here consists in launching three optical waves (pump, probe, and test) into a semiconductor optical amplifier and measuring the test beam transmission and the conversion efficiency of the new wave generated to one side of the test beam. It allows for an excellent identification of the nonlinear phenomena involved in the FWM process. The analysis principle is based on the modulation of the gain curve for each of the three effects considered: spectral hole burning, carrier heating, and carrier density pulsation. Experimental and theoretical results are presented     

Negative resistance in p-n junctions under avalanche breakdown conditions, part II

The small-signal impedance of the space-charge region of p-n junctions under avalanche breakdown conditions is calculated using reasonably realistic dependences of electron and hole ionization rates and drift velocities upon electric field. Two structures are analyzed: one is p⁺νn⁺structure which has a fairly uniform distribution of avalanche multiplication, and the other is a singly diffused junction which is a hybrid of an abrupt and a linear graded junction. Both structures show negative resistance when the transit time of carriers becomes appreciable. A computer program was evolved which requires, as input, the impurity profile and field dependences of ionization rates and drift velocities. The program first calculates the dc field and electron and hole currents and then solves the ac small-signal problem. Both the ac small-signal impedance and theQof the diode are calculated.     

Measurement of the mobility and concentration of charge carriers in a Gunn gallium-arsenide diode using a near-field microwave microscope

The results of local contactless measurement of the dependence of conductivity in a Gunn diode on the external electrical bias are presented. The technique of local determination of the charge-carrier concentration and mobility in a commercially produced chip Gunn diode for various values of the supply voltage is proposed.     

多晶MAPbBr_(3)薄膜中束缚载流子热发射复合过程北大核心CSCD

有机-无机卤化铅钙钛矿(organic inorganic lead halide perovskite,OLHP)半导体材料内部的陷阱是影响OLHP的光电性能的重要因素。为了理解多晶的甲胺溴基钙钛矿((Methylammonium)PbBr_(3),MAPbBr_(3))薄膜中陷阱对光生载流子复合的影响,本文采用了时间分辨微波光电导(time resolved microwave conductivity,TRMC)技术探究了多晶MAPbBr_(3)薄膜的光生载流子复合动力学过程。实验测量结果表明多晶MAPbBr_(3)薄膜的载流子复合过程包括自由载流子复合与束缚载流子的热发射复合两部分。其中,与束缚载流子热发射复合相关的能级远离连续带,且对应的能级深度约为0.6 eV,分布宽度约为89.2 meV。本文同时利用变激发波长TRMC对比实验,分析浅束缚光生电子与导带光生电子复合过程的差异。相比于导带上的电子,实验结果表明浅束缚电子跃迁到深束缚能级的概率更大。     

A novel self-aligned fabrication process for microwave static induction transistors in silicon carbide

A novel multiple-self-aligned fabrication process is developed for recessed gate microwave static induction transistors (SITs) in silicon carbide (SiC). This process is demonstrated by fabricating 4H-SiC SITs having record f/sub T/ of 7 GHz.