Ku波段宽带大功率多芯片合成设计

设计针对多个Ku波段宽带MMIC功率放大芯片进行大功率合成.对波导多路功率合成结构进行了分析,基于单个Ku波段6W功放单片,进行了16路的功率合成,研制出了工作在12～17 GHz,带宽达到6 GHz的固态功率放大器.通过测试发现该固态功率放大器的输出功率≥70 W,功率增益≥15 dB,工作电压48 V,效率≥16％...     

Delay-dependent H∞ filtering for discrete-time singular Markovian jump systems with time-varying delay and partially unknown transition probabilities

This paper is concerned with the H_∞ filtering design for a class of discrete-time singular Markovian jump systems with time-varying delay and partially unknown transition probabilities. The class of systems under consideration is more general and covers the singular Markovian delay systems with completely known and completely unknown transition probabilities as two special cases. A mode-dependent filter is constructed and by defining an appropriate stochastic Lyapunov functional combined with using the discrete Jensen inequality, a delay-dependent bounded real lemma (BRL) for the considered systems is established in terms of linear matrix inequalities (LMIs). Based on this, a sufficient condition on the existence of the desired filter which guarantees the admissibility and the H_∞ performance of the corresponding filtering error system is presented by employing the LMIs technique. Some numerical examples are provided to illustrate the effectiveness of the developed theoretical results.     

Bonding and gap states at GaAs-oxide interfaces

The nature of bonding and possible causes of Fermi level pinning at high mobility-high dielectric constant oxide GaAs:HfO₂ interfaces are discussed. It is argued that these are atoms with defective bonding, rather than states due to the bulk semiconductor of its interface. Electron-counting rules are used to define interfaces which are insulating, and which can be used in future as hosts for interfaces containing defects.     

Electrical characteristics and TDDB breakdown mechanism of N2-RTA-treated Hf-based high-κ gate dielectrics

This study investigates the effects of rapid thermal annealing (RTA) in nitrogen ambient on HfO₂ and HfSiO_x gate dielectrics, including their electrical characteristics, film properties, TDDB reliability and breakdown mechanism. The optimal temperature for N₂ RTA treatment is also investigated. The positive oxide trap charges (oxygen vacancies) in HfO₂ and HfSiO_x dielectric films can be reduced by the thermal annealing, but as the annealing temperature increased, many positive oxide trap charges (oxygen vacancies) with shallow or deep trap energy level will be formed in the grain boundaries, degrading the electrical characteristics, and changing the breakdown mechanism. We believe that variation in the number of positive oxide trap charges (oxygen vacancies) with shallow or deep trap energy levels is the main cause of the CV shift and difference in the breakdown behaviors between HfO₂ and HfSiO_x dielectrics. With respect to CV characteristics and TDDB reliability, the optimal temperature for N₂ RTA treatment is in the range 500-600 °C and 800-900 °C, respectively.     

低压高温退火对Ag掺杂ZnO薄膜性质的影响

采用电子束蒸发在n-Si(100)衬底上沉积Ag掺ZnO(ZnO:Ag)薄膜,随后在200 Pa的O<,2>气氛下分别在500、600、700和800℃退火4 h.用X射线衍射(XRD)仪、荧光光谱仪以及Van der Pauw方法测量ZnO:Ag薄膜的结构和光电学性质.结果表明,ZnO:Ag薄膜为多晶结构,且随着退火...     

GA-KBrO3-H2SO4体系化学振荡的研究

研究了GA(没食子酸)-KBrO_3-H_2SO_4体系的诱导期τ、振荡周期T_2与反应物起始浓度的依赖关系, 302 K时的经验式为τ=22.8 c~(-2.23)_(H_2SO_4) c~(-2.17)_(KBrO_3) c~(0.795)_(GA) (mol.dm~(-3))~(4.25)·sT_2=0.84 c~(-2.28)_(H_2SO-4)c~(-1.97)_(KBrO_3) exp{(0.000147(mol.dm~(-3))~2/c~2_(GA)}(mol.dm~(-3))~(4.25)·sτ及T_2都随~CGA的增加而增长, 这与B-Z反应中关于有机物的结论不同。用循环伏安法研究该体系的结果表明, GA在诱导期结束时就基本上都被氧化为中间物, GA并不象前人所认为的是维持振荡的物种, 实际参与振荡的是由GA生成的物质。本文还研究了Fe(Phen)_3~(2+)对GA-KBrO_3-H_2SO_4体系振荡的影响, 发现Br~-振荡行为随Fe(Phen)_3~(2+)的浓度而变。低~CFe(phen)_3~(2+)时,Br~-的振荡行为与GA-KBrO_3-H_2SO_4体系的基本相似, 其特征是每个振荡周期内, Br~-振荡脉冲发生前是逐渐积累的。随着~CFe(phen)_3~(2+)的增大, Br~-出现另一特征的振荡行为, 在每个振荡周期内, Br~-振荡脉冲发生前是逐渐减小。我们认为, GA-KBrO_3-H_2SO_4-Fe(Phen)_3~(2+)体系的振荡不能单一地用OKN机理加以解释, 它可能是两套振荡机理耦合的振荡。     

Calculation of the Fisher information matrix for multidimensional data sets

Data sets that are acquired in many practical systems can be described as the output of a multidimensional linear separable-denominator system with Gaussian measurement noise. An important example is nuclear magnetic resonance (NMR) spectroscopy. In NMR spectroscopy, high-accuracy parameter estimation is of central importance. A classical result on the Crame/spl acute/r-Rao lower bound states that the inverse of the Fisher information matrix (FIM) provides a lower bound for the covariance of any unbiased estimator of the parameter vector. The calculation of the FIM is therefore of central importance for an assessment of the accuracy with which parameters can be estimated. It is shown how the FIM can be expressed using the matrices that determine the system that generates the data set. For uniformly sampled data, it is shown how the FIM can be expressed through the solutions of Lyapunov equations. The novel techniques are demonstrated with an example arising from NMR spectroscopy.     

Highly reliable nitride-based LEDs with SPS+ITO upper contacts

Nitride-based blue light emitting diodes (LEDs) with an n/sup +/-short period superlattice (SPS) tunnel contact layer and an indium tin oxide (ITO) transparent contact were fabricated. Compared with conventional nitride-based LEDs with Ni/Au upper contacts, it was found that we could achieve a 60% increase in electroluminescence (EL) intensity by using ITO upper contacts. However, it was also found that the lifetime of ITO LEDs were much shorter. Furthermore, it was found that we could achieve a longer lifetime and a smaller reverse leakage current (I/sub R/) by the deposition of a SiO/sub 2/ layer on top of the ITO LEDs.     

Effect of cell-phone radiation exposure on cognitive function in humans

Several papers reporting on cognitive function and exposure to cell-phone RF fields have appeared in scientific journals. Human subjects exposed to cell-phone fields showed faster responses in simple reaction time and in choice reaction time. In addition, some investigations have found exposure to cell-phone fields has a facilitating effect on tasks that require attention and manipulation of information in working memory. Also, the same group failed to confirm their earlier findings when they repeated their experiments. On the other hand, as a follow-up, different research groups examined the relationship between the reported facilitating effect and cell-phone exposure. Their results indicated that cognitive process, such as attentional function, are differentially enhanced after exposure to the RF fields emitted by cell phones.