铁电液晶显示的交流稳态技术与等效电路模型改进

针对交流稳态技术提出了一种改进的能体现铁电液晶电学、光学各向异性的等效电路模型.通过将介电张量与电场的耦合作用和由表面定向层引起的锚定能量以等效源的形式表达在电路模型中,成功地将模型拓展到介电各向异性情况下.分别就正、负性介电各向异性及应用交流稳态技术时的光响应特性和动力学机制进行了模拟,并给出了对应的介电扭矩、铁电扭矩和极化反转电流.模拟结果吻合于理论分析及文献报道的结果,表明了电路模型的有效性.     

硬脂酸凝胶法制备的BaTiO3超微粉和陶瓷

用硬脂酸凝胶法制备了BaTiO_3超微粉.并通过XRD、介电和热释电等方法研究了这种超微粉以及由其制备的陶瓷的结构和其它物性.发现它们的性质与常规的BaTiO_3陶瓷极为不同.只有一个铁电一顺电相变、而且铁电相的结构为准立方结构.它可能是由于这种超微粉表面包裹一层偏离BaTiO_3化学配比的非铁电材料,使BaTiO_3微晶机械受夹,不能自由产生铁电畸变所致.     

不同介电层对HfxZr1-xO2薄膜铁电性能影响的研究进展

近年来,铁电Hf_xZr_1-xO₂(HZO)薄膜受到越来越多的关注,但是铁电层与电极材料层以及铁电层与半导体衬底层之间的界面问题并没有得到解决,阻碍了HZO薄膜的进一步应用。总结了通过引入不同介电层材料,如Al₂O₃、ZrO₂、HfO₂、Ta₂O₅等,调节HZO薄膜铁电性能的方法及其机理;详细介绍了各种介电层材料作为封盖层对HZO薄膜铁电性能的影响,如对HZO薄膜提供平面内应力、控制铁电层的晶粒尺寸及作为铁电层形核核心的作用;最后,总结并展望了利用介电层调控HZO薄膜铁电性能的一般规律,为后续相关研究的开展提供了指导。     

钛酸钡微晶粉粒的热刺激电流

研究了铁电微晶粉粒的热刺激电流及其铁电相变。对三种不同化学成分的钛酸钡粉料与硅油的混合物进行了热刺激电流测量。钛酸钡粉粒与硅油的混合物有很明显的热刺激电流(TSC)且表现出和铁电相变有关的明显的峰,显示出与粒径存在一定的关系;得出了样品的表观极化强度曲线。证明了当粉料与硅油混合后,用介电谱观测不到的粉料的铁电–顺电相变,用 TSC 方法可以观察到。     

用于功率MOSFET的新型栅电荷测试电路

栅电荷是用于衡量功率MOSFET开关性能的重要参数,通常采用在栅极输入电流阶跃信号的方法来测量。一种新型的栅电荷测试电路被提出,该测试电路使控制信号从MOSFET的源极输入,从而消除了控制信号对栅极输入电流的影响。因为输入电流太小不能直接测量,测试时采用测量电压阶跃信号的方法来衡量电流阶跃信号的性能。与以往的测试电路对比结果表明,该电路可以使MOSFET栅极输入的电流更接近于理想的电流阶跃信号,该信号上升时间小于100 ns,并且上升后稳定,因此提高了栅电荷测量的准确度。     

铁电（Ba,Sr）TiO3及介电Bi2O3-ZnO-Nb2O5薄膜材料应用于电调谐微波器件研究进展

铁电钛酸锶钡BaxSr1-xTiO3(BST)是一种拥有十分优越铁电/介电性能的材料,在可调谐微波器件方面具有很好的应用前景。本文概括介绍了BST薄膜的研究意义、基本结构、薄膜的制备方法,并针对可调谐微波器件应用需求,详细探讨了通过掺杂、组分梯度变化、纳米铁电多层薄膜以及将铁电BST与新型介电Bi2O3-ZnO-Nb2O5(BZN)薄膜相结合等对铁电薄膜性能进行优化的手段,最后对该领域的前沿问题从材料研究层面作了小结与展望。     

铁电材料相变温度自动测试仪

铁电材料相变温度的测量一般采用电桥法,即测量铁电材料介电系数随温度的变化,由介电系数的转折温度来确定相变温度。但电桥法测量常常碰到一些困难:第一,有些铁电材料相变温度较高,在高温时电导较大;有些铁电材料在接近相变温度时损耗已超出电桥测量范围,使电桥无法平衡,不能确定其相变温度。第二,大部分手控电桥不备有线性电压输出,     

PZT铁电薄膜介电性能测试研究

运用数字锁相技术研究了Pb(Zr,Ti)O_3(PZT)铁电薄膜的介电性能测试技术,随着薄膜微图形化尺寸的缩小,电路寄生参数的影响将逐渐变大并成为主导因素,从而严重影响薄膜介电性能测试的准确性.通过补偿方法,消除了电路寄生参数的影响,准确测量了薄膜的介电常数.通过对溶胶-凝胶制备的PZT薄膜样品的介电性能测试表明,上述补偿法可满足PZT铁电薄膜制备技术及微机电系统中器件设计对PZT微图形性能测试的要求.     

铁电薄膜材料I-V特性的测量

介绍了测量铁电材料Ｉ－Ｖ特性的原理和电路,并对ＰＹＺＴ铁电薄膜试样进行了电滞回线和Ｉ－Ｖ特性的测量,指出铁电材料具有其特有的Ｉ－Ｖ特性曲线。因此,有无铁电体Ｉ－Ｖ特性曲线不仅可以判断该材料是否为铁电体,还可判断铁电材料性能的好坏,如极化强度和矫元场大小,对称性等。     

用于MFIS的ZrO_2薄膜的制备及特性研究

新型不挥发非破坏性读出铁电存储器金属 /铁电 /半导体器件结构中 ,存在着铁电薄膜与半导体衬底之间相互扩散、离子陷阱密度高、铁电薄膜难于直接淀积在硅衬底上、电荷注入等问题 ,因此在铁电薄膜与半导体之间增加一层合适的介质材料作为阻挡层是制备不挥发非破坏性读出铁电存储器的关键。文中研究了运用 SOL- GEL方法制备 Zr O2 介质层的方法 ,并且对制备的介质层的成份、结构、电特性进行了分析 ,为研制 MFIS作了准备。     

改进的RF-LDMOS小信号模型参数提取方法

准确地提取RF-LDMOS小信号模型参数对LDMOS大信号模型建模十分重要,而且好的小信号模型能很好地反映微波器件的性能。针对LDMOS提出了一种改进的小信号模型参数提取方法,此方法增加了测试结构的建模和参数提取,极大地方便了S参数曲线的拟合,而且对于测试版图的研究有一定的指导意义。由此方法提取的小信号模型与实验测试数据在0.1～8 GHz拟合的很好,并且准确地预测了器件的特征频率。该模型和方法能够很好的适用于LDMOS的L,S波段小信号建模和参数提取。     

基于信号流程的电子装备机理建模方法

针对面向电子装备战斗操作训练和技术维修训练的模拟器,研究机理模型建模问题。首先总结了当前主要的建模方法,进而根据模块化思想,提出了基于信号流程建立电子装备的机理模型,共分为装备分解,提取信号流程图、建立子模型、建立完整机理模型等四个步骤。阐明了建模过程,重点介绍了如何构建子模型和完整模型。讨论了模型的时间管理机制,多分辨率建模等问题,分析了该方法在故障建模中的应用,并提出了一个三级分辨率的机理模型体系。该方法的创新点包括：通过调整模型分辨率,可以兼容其他主要建模方法;同时能有效解决故障装备机理建模的问题。分析表明,该方法可以满足当前模拟器在各个层次上对机理模型的需求。     

Parametric modeling of somatosensory evoked potentials usingdiscrete cosine transform

This paper introduces a parametric method for identifying the somatosensory evoked potentials (SEPs). The identification was carried out by using pole-zero modeling of the SEPs in the discrete cosine transform (DCT) domain. It was found that the DCT coefficients of a monophasic signal can be sufficiently approximated by a second-order transfer function with a conjugate pole pair. The averaged SEP signal was modeled by the sum of several second-order transfer functions with appropriate zeros and poles estimated using the least square method in the DCT domain. Results of the estimation demonstrated that the model output was in an excellent agreement with the raw SEPs both qualitatively and quantitatively. Comparing with the common autoregressive model with exogenous input modeling in the time domain, the DCT domain modeling achieves a high goodness of fitting with a very low model order. Applications of the proposed method are possible in clinical practice for feature extraction, noise cancellation and individual component decomposition of the SEPs as well as other evoked potentials.     

PARAFAC-based unified tensor modeling for wireless communication systems with application to blind multiuser equalization

In some antenna array-based wireless communication systems the received signal is multidimensional and can be treated as a tensor (3D array) instead of a matrix (2D array). In this paper, we make use of a generalized tensor decomposition known as constrained Block-PARAFAC and propose a tensor (3D) model for the signal received by three types of wireless communication systems. The considered wireless communication systems are multiuser systems subject to frequency-selective multipath and employing multiple receiver antennas together with (i) oversampling or (ii) direct-sequence spreading or (iii) multicarrier modulation. The proposed modeling approach aims at unifying the received signal model of these systems into a single PARAFAC model. We show that the proposed model has a constrained structure, where model constraints and associated dimensions depend on each particular system. The proposed constrained Block-PARAFAC model is demonstrated by expanding the tensor using Kronecker products of canonical vectors. As an application of this model to tensor signal processing, a new tensor-based receiver is proposed for blind multiuser equalization, which combines PARAFAC-based modeling with a subspace method. Simulation results are presented to illustrate the performance of the proposed blind receiver.     

Dynamic Modeling and Analysis of Z Source Converter—Derivation of AC Small Signal Model and Design-Oriented Analysis

This paper contributes to the AC small signal modeling and analysis of Z source converter (ZSC) in continuous conduction mode. The AC small signal model considers the dynamics introduced by Z network uniquely contained in ZSC. AC small signal model of ZSC is derived and computer simulation results are used to validate the small signal modeling method. Various applications of the AC small signal models to ZSC design and experimental verifications are presented.     

Programmable polymer light emitting transistors with ferroelectric polarization-enhanced channel current and light emission

We present a voltage programmable polymer light emitting field-effect transistor (LEFET), consisting of a green emitting polymer (F8BT), and a ferroelectric polymer, P(VDF-TrFE), as the gate dielectric. We show by both experimental observations and numerical modeling that, when the ferroelectric gate dielectric is polarized in opposite directions at the drain and source sides of the channel, respectively, both electron and hole currents are enhanced, resulting in more charge recombination and ～10 times higher light emission in a ferroelectric LEFET, compared to the device with non-ferroelectric gate. As a result of the ferroelectric poling, our ferroelectric LEFETs exhibit repeated programmability in light emission, and an external quantum efficiency (EQE) of up to 1.06%. Numerical modeling reveals that the remnant polarization charge of the ferroelectric layer tends to ‘pin’ the position of the recombination zone, paving the way to integrate specific optical out-coupling structures in the channel of these devices to further increase the brightness.     

An approach for handling the nonlinearities of HVDC system forstability analysis

An approach for linearizing the nonlinearities of the high voltage direct current (HVDC) system for analyzing the system stability over wide range of operation is presented. The nonlinearities can be linearized with ±5% error over a wide range of system operation. It is shown that the nonlinearities introduced by the converter, real power, and reactive power equations can be linearized over a wide range by using the integral square error (ISE) method. The results are compared with standard techniques called small signal analysis. It is shown that the stability margin of the system predicted by the new technique is relatively smaller than what is predicted by small signal analysis. The system stability boundaries are determined by the AC voltage and the reactive current control. These two control schemes may provide the same stability margin, provided appropriate controller gains are selected. The power factor control modeling is discussed     

Modeling ferroelectric capacitors for memory applications

The ferroelectric capacitor model is the foundation for accurate simulation of ferroelectric hysteresis loops and minor loops, transitions between the loops under arbitrary voltage patterns, transient responses of ferroelectric capacitors to short voltage pulses with widths in the nano-second range, and temperature behaviors of ferroelectric capacitors. The simulation speed is the same as that for a typical nonlinear capacitor. To the circuit designers, a ferroelectric capacitor is represented as a two-port device like a capacitor. The parameters are extracted easily and reliably by curve fitting the measured hysteresis loops. The model is applicable to fast circuit simulations for large ferroelectric memory designs.     

舰载相控阵雷达信号处理的建模与仿真

本文介绍了一种利用组件化建模的思想的舰载相控阵雷达信号处理的仿真建模方法。 首先,按照功能对舰载相控阵雷达信号处理进行了功能组件划分,介绍了基于 C++语言的舰载相控阵信号处理仿真系统的构建方法,使其具备可复用性、可重构性与可扩展性。接着对舰载相控阵雷达的信号处理进行了信号级仿真,通过对仿真的结果进行精度分析与性能评估,验证了模型的准确性。建立的舰载相控阵雷达信号处理模型为舰载相控阵雷达的仿真与应用提供了良好的基础,在工程上具有一定的参考意义。     

MBi_4Ti_4O_(15)基陶瓷的研究现状与发展趋势

铋层状结构无铅铁电陶瓷具有良好的抗疲劳性能和较高的居里温度,在铁电存储以及高温压电器件方面具有广阔的应用前景。介绍了MBi4Ti4O15基铋层状陶瓷的结构特点,综述了微量元素掺杂、粉体制备方法和晶粒定向技术对该陶瓷铁电压电性能的影响。并展望了MBi4Ti4O15基铋层状无铅铁电陶瓷未来的发展趋势。