面向图像差异特征融合的基于弗里德曼检验的小波基分类研究

对小波基分类是图像融合中依据不同融合需求选择小波基的基础,可以提高图像融合的智能化水平。针对现有的小波基分类方法仅根据小波自身特性进行分类,没有从统计角度有效建立小波基和图像差异特征之间的联系,本文提出了面向图像差异特征融合的基于弗里德曼检验的小波基分类方法。首先,选择典型的差异特征和小波基用于分类研究;其次,选择针对差异特征的评价指标,以评价指标结果作为标记量并进行分类实验的区组设计;然后,采用弗里德曼检验对不同区组数据进行处理及执行相应的后续检验和分类步骤,形成面向图像差异特征的小波基类集;最后,设计对比实验对分类方法的有效性进行验证和分析。试验结果表明,该分类方法能有效把对图像差异特征融合效果相近的小波基归为一类,能根据融合需求选择较好的小波基。     

一种Ka波段低相噪GaAs HBT压控振荡器

本文研究了一种采用GaAs HBT工艺实现的工作在Ka波段的压控振荡器。该振荡器采用共射级组态和对称式电容电感谐振腔结构以降低其相位噪声,采用π型反馈网络补偿180°相移。在片测试结果表明：偏离中心频率1 MHz处相位噪声为-96.47dBc/Hz,调谐范围为28.312到28.695GHz,在-6V电源电压下该振荡器直流功耗为18mA,振荡器芯片面积为0.7mm×0.7mm。     

Temperature dependent interfacial and electrical characteristics during atomic layer deposition and annealing of HfO2 films in p-GaAs metal-oxide-semiconductor capacitors

We have investigated the temperature dependent interfacial and electrical characteristics of p-GaAs metal-oxide-semiconductor capacitors during atomic layer deposition(ALD) and annealing of HfO₂ using the tetrakis(ethylmethyl) amino hafnium precursor. The leakage current decreases with the increase of the ALD temperature and the lowest current is obtained at 300℃ as a result of the Frenkel-Poole conduction induced leakage current being greatly weakened by the reduction of interfacial oxides at the higher temperature. Post deposition annealing(PDA) at 500℃ after ALD at 300℃ leads to the lowest leakage current compared with other annealing temperatures. A pronounced reduction in As oxides during PDA at 500℃ has been observed using X-ray photoelectron spectroscopy at the interface resulting in a proportional increase in Ga₂O₃. The increment of Ga₂O₃ after PDA depends on the amount of residual As oxides after ALD. Thus, the ALD temperature plays an important role in determining the high-k/GaAs interface condition. Meanwhile, an optimum PDA temperature is essential for obtaining good dielectric properties.     

220 kV智能变电站实训基地工程设计问题探讨

以220 kV智能变电站实训基地工程为例,对设计方案进行分析与探讨。在智能站的建设要求上,提出了一种针对教学特点的设计方案,既满足可靠性、经济性指标,又保证了安全性、多样化要求。     

Fabrication and characteristics of a 4H-SiC junction barrier Schottky diode

4H-SiC junction barrier Schottky(JBS)diodes with four kinds of design have been fabricated and characterized using two different processes in which one is fabricated by making the P-type ohmic contact of the anode independently,and the other is processed by depositing a Schottky metal multi-layer on the whole anode.The reverse performances are compared to find the influences of these factors.The results show that JBS diodes with field guard rings have a lower reverse current density and a higher breakdown voltage,and with independent P-type ohmic contact manufacturing,the reverse performance of 4H-SiC JBS diodes can be improved effectively. Furthermore,the P-type ohmic contact is studied in this work.     

4H-SiC MESFET的新型经验电容模型

基于器件工作机理,提出了一种新型的4H-SiC MESFET经验大信号电容模型。模型参数提取采用Lev-enberg-Marquardt优化算法,提取的模型主要参数具有一定物理意义。C-V特性的模型模拟结果与实验数据的比较表明两者符合良好。该模型还与CAD工具的通用电容模型进行了比较,结果表明新模型具有更高的精度。     

4H-SiC MESFET肖特基栅接触的界面参数提取

研究了界面态对4H-SiC MESFET的肖特基栅接触的影响.栅接触工艺主要采用Ti/Pt/Au蒸发,经过剥离后形成.基于热电子理论提出了一种参数提取方法,得到界面态密度和界面电容分别为4.386×1013cm-2·eV-1和8.394×10-6F/cm2,这与测量得到的器件端特性一致.     

4H-SiC射频功率MESFET大信号直流I-V特性解析模型

根据4H-SiC高饱和电子漂移速度和常温下杂质不完全离化的特点,对适用于Si和GaAs MESFET的直流I-V特性理论进行了分析与修正.采用高场下载流子速度饱和理论,以双曲正切函数作为表征I-V特性的函数关系,建立了室温条件下4H-SiC射频功率MESFET直流I-V特性的准解析模型,适于描述短沟道微波段4H-SiC MESFET的大信号非线性特性,计算结果与实验数据有很好的一致性.同时与MEDICI模拟器的模拟结果也进行了比较.     

4H-SiC功率MESFET的击穿特性

研究了4H-SiC MESFET器件的电学击穿特性和热学稳定性.建立了金属半导体场效应晶体管器件二维数值模型,分析了雪崩碰撞离化效应、隧穿效应和热效应在器件击穿中的作用.综合考虑了栅极偏置、自热效应等因素对击穿的影响.采用准静态方法,求解瞬态偏微分方程组,分析了器件的耐热耐压性能和可靠性.     

碳化硅混合PiN/Schottky二极管的二维模拟

利用模拟软件MEDICI对碳化硅混合PiN/Schottky二极管(MPS)的输运机理及伏安特性进行了模拟.输运机理的模拟结果表明MPS的工作原理是正向肖特基起主要作用,而反向时PN结使漏电流大大减小.伏安特性的模拟结果表明MPS的正向压降小,电流密度大,在2V正向偏压下达10-5A/μm,反向漏电流小,击穿电压高(2000V左右),可以通过改变肖特基和PN结的面积比来调整MPS的性能,与硅MPS、碳化硅PN结以及碳化硅肖特基二极管相比具有明显的优势,是理想的功率整流器.