Propagation in Twisted Square Waveguide

The problem of propagation of TE modes in twisted rectangular waveguides has been solved except for the case where one of the propagating modes becomes degenerate. The purpose of this paper is to show how to obtain a solution for degenerate modes in a twisted rectangular waveguide, with emphasis on the particular case of the square waveguide, for which the lowest order mode is degerate. It is shown that the propagation constant for the twisted square waveguide can be expressed as an asymptotic series, the first term being the propagation constant for a straight square waveguide and the first order correction term being of order 1/ L where L is the distance in which the guide makes one full rotation. The propagation constant for a nondegenerate mode in a twisted rectangular waveguide, on the other hand, can be expressed in a similar manner except that the first-order correction term is of order 1/ L/sup2/. Some comments are offered on the nature of the transition when the propagating mode is almost degenerate.     

Twisted Crystalline Organic Semiconductor Photodetectors

Optoelectronic properties of anisotropic crystals vary with direction requiring that the orientation of molecular organic semiconductor crystals is controlled in optoelectronic device active layers to achieve optimal performance. Here, a generalizable strategy to introduce periodic variations in the out-of-plane orientations of 5,11-bis(triisopropylsilylethynyl)anthradithiophene (TIPS ADT) crystals is presented. TIPS ADT crystallized from the melt in the presence of 16 wt.% polyethylene (PE) forms banded spherulites of crystalline fibrils that twist in concert about the radial growth direction. These spherulites exhibit band-dependent light absorption, photoluminescence, and Raman scattering depending on the local orientation of crystals. Mueller matrix imaging reveals strong circular extinction (CE), with TIPS ADT banded spherulites exhibiting domains of positive or negative CE signal depending on the crystal twisting sense. Furthermore, orientation-dependent enhancement in charge injection and extraction in films of twisted TIPS ADT crystals compared to films of straight crystals is visualized in local conductive atomic force microscopy maps. This enhancement leads to 3.3- and 6.2-times larger photocurrents and external quantum efficiencies, respectively, in photodetectors comprising twisted crystals than those comprising straight crystals.     

Propagation Through a Twisted Medium

An explicit solution is obtained for propagation through a uniform twisted anisotropic medium subject to the conditions that propagation is along the twist axis, and that the structure is fine. The propagation constants are altered and coupling exists between the propagation modes. A parameter is defined which indicates the tendency of the radiation to adhere to the structure of the medium. The effects at boundary discontinuities are discussed, and tapers to an isotropic medium are dealt with. The particular application of the theory to cases of polarization conversion, circular to pIane, and plane to plane are discussed.     

Twisted bit-line architectures for multi-megabit DRAMs

As the memory cell array of DRAM has been scaled down, inter-bit-line coupling noise has emerged as a serious problem. The signal loss due to this noise is estimated at about 40% of the signal amplitude in a polycide-bit-line 16-Mb DRAM with a technologically attainable scaling scheme. Twisted bit-line architectures to reduce or eliminate the noise are proposed and demonstrated by the soft-error rate improvement of a 1-Mb DRAM. The effective critical charge is improved by 35%, which is attributed not only to the improvement of the signal amplitude but also to the elimination of large coupling noise during the sensing operation. The impact of these twisted bit-line architectures from a scaling viewpoint is also examined, and they are shown to be promising candidates for overcoming the scaling problems of DRAMs     

Dispersion Characteristics of Twisted Rectangular Waveguides

Based on the expressions for the dominant hybrid-mode fields in twisted rectangular waveguides, dispersion formulas with two perturbational factors have been derived theoretically. These factors correspond to the two effects of the twist on the dominant wave propagation, respectively. The one expresses a shift in the cutoff frequency while the other expresses the effect of elongation in the transmission path. A set of 20-cm-long waveguides twisted uniformly by various multiples of 90° has been manufactured by the method of electroforming. The resonant frequencies of the respective waveguides have been measured as a transmission cavity in the 10-GHz band to obtain dispersion relations. Experimental results are found to be in good agreement with the theoretically derived formulas. The results of Lewin's theory are also compared with the present ones.     

Analysis of Rapidly Twisted Hollow Waveguides

The propagation characteristics of twisted hollow waveguides are considered, and various analysis methods are proposed. It is shown that a twisted hollow waveguide can support waves that travel at a speed slower than the speed of light c. These modes are of particular interest, as slow wave structures have many potential applications in accelerators and electron traveling wave tubes. Since there is no exact closed form solution for the electromagnetic fields within a twisted waveguide or cavity, several previously proposed approximate methods are examined. It is found that the existing perturbation theory methods yield adequate results for slowly twisted structures; however, our efforts here are geared toward analyzing rapidly twisted structures using newly developed finite-difference methods. To validate the results of the theory and simulations, rapidly twisted cavity prototypes have been designed, fabricated, and measured. These measurement results are compared to simulated results, and very good agreement has been demonstrated.     

Twisted bit-line technique for multi-gigabit DRAMs

A new twisted bit-line (TBL) technique is presented to reduce bit-line coupling noise for multi-gigabit DRAMs. Sufficient noise reduction effects have been monitored through soft-error rate measurement on test chips using the proposed TBL technique. Also, the problem of excessive chip area penalty in the conventional TBL techniques can be solved in the proposed TBL technique     

Polarization Transformation in Twisted Anisotropic Media

Polarization transformation of plane waves propagating in twisted anisotropic media is studied theoretically and numerically. It is shown that rotation of linear polarization is effected by such a medium when the anisotropy is of the order of 2 to 1 and twist rates commensurate with the relative value of the dielectric constants of the medium are used (less than 15/spl deg///spl lambda//sub 0/ for low dielectric constants and up to 90/spl deg///spl lambda//sub 0/ for dielectrics in the vicinity of 1000).     

用于高对比度反射式显示的扭曲PDLC

开发了一种采用扭曲边界聚合物分散型液晶(TPDLC)的高亮度、高对比度反射式显示器。与普通的PDLC膜相比，TPDLC不依赖于偏振光，具有高的对比度和低的工作电压。还演示了一种利用染料掺杂TPDLC的黑白笔段式字母反射式显示器。     

自适应视频信号传输解决方案

目前市场上的双绞线视频传输方案大多采用外部固定均衡,但是,固定均衡不能补偿电缆差异,不同传输距离以及分立元件误差产生的影响.本文介绍的自适应均衡传输方案能够在1200米视频信号传输中获得较好的图像质量.     

Electromagnetic Wave Propagation in Twisted Anisotropic Media

The complete solution of the differential equation describing the propagation of plane uniform TEM waves along the twist axis of a twisted anisotropic medium with a constant rate of twist is shown to be of exponential type, consisting of two identical pairs of independent propagation modes, each pair being associated with a particular direction of energy flow. Knowledge of the complete solution is used to solve the boundary value problem relative to wave penetration into a twisted medium at normal incidence, a numerical example being given illustrating the polarization transformation properties of the medium near the short wavelength limit. Analysis of mode properties reveals circnlar birefringence should occur in twisted media at long wavelengths. A link power, as shown by certain crystalline substances provided by the theory.     

市话线对作为高速接入的仿真结果

讨论绞线对传输的信道模型，给出实现HDSL、VHDSL与ADSL传输的方案与仿真结果，从而说明市话线对可以作为高速数据业务的一种有效的用户接入手段。     

新型多畴扭曲向列相液晶显示器

提出在像素电极下方放置凸起物,获得具有宽视角特性的多畴扭曲向列相液晶显示器。该模式比传统的多畴TN模式摩擦过程少,工艺过程简单。在这种液晶显示器中,初始状态(未加电)时,分子排列结构和普通单畴TN模式相同,在加电压状态时,由于凸起物的存在,液晶分子沿着4个不同的方向排列形成多畴区域。文中运用专业液晶模拟软件模拟,对该液晶显示器的电光特性进行研究,结果表明,该液晶显示器具有宽视角、色散小及色彩还原性较好的特性。     

一种STN LCD驱动芯片的设计研究

介绍了一种超扭曲向列（STN）LCD驱动芯片的总体设计方案,重点讨论分析了其关键模块--接口电路、控制电路和驱动电路以及电源电路的设计,并用Verilog硬件描述语言对所设计的驱动芯片的功能进行了仿真验证。     

扭曲向列相液晶盒的制作及测试

论文介绍了一项基于高职院校实验实训平台的扭曲向列相液晶盒制作实验及其测试效果。文中详细论述了该实验的各个工艺流程,实验所用各器件及材料,各流程操作实施方法,并对实验中制作的液晶盒进行了基本特性测试。该实验在实际教学过程中使用效果较好。     

界面锚定能和扭曲向列液晶盒

向列液晶界面锚定能被认为是液晶分子与固体界面上分子相互作用势之和，据此导出了锚定能的新公式，它包含两项，因而有两个强度参量，其中第二项是由于界面诱导双轴性而引起的，倾角锚定强度Aθ和方位角锚定强度定Aφ的差别可归因于此。用新的锚定能公式详细研究了弱锚定扭曲(超扭曲)向列液晶盒，假定Aθ／Aφ=k11／k12，计算了阈值场强和饱和场强的大小。与以前我们认为的Aθ／Aφ=1情况做了比较。结果表明，倾角锚定强度Aθ与方位角锚定强度Aφ的关系对扭曲(超扭曲)向列液晶盒的阈值场强和饱和场强都有影响。     

超扭曲向列相液晶显示的优化

本文采用双膜补偿方法消除超扭曲液晶显示器中由于双折射效应在关态时带有的颜色，应用扩展琼斯矩阵方法对双膜补偿超扭曲液晶显示器进行优化，得到黑白显示和宽视角。对优化方案的具体步骤和最终结果进行了讨论。     

Deterministic Fabrication of Twisted Van Der Waals Structures

In 2D van der Waals (vdW) materials, rotational misalignment by a twist angle between adjacent layers can significantly affect their properties, referred as twistronics. Accurate tuning of twist angle of vdW materials in a controllable and efficient way is highly required. Here a thin-film assisted transfer (TAT) technique that can controllably fabricate vdW structures with deterministic twist angles (accuracy of 0.37°) is developed. The transparent and ultrathin film as transfer medium ensures the visible and intact manipulation of monolayer building blocks, thus constructing vdW architectures with multi-materials and designated position. Multilayer homo-/hetero-architectures in the geometry of series connection, spiral structure and chiral symmetry at deterministic twist angles are for the first time demonstrated. They can be located on various substrates for both structural analysis and device application. The capability of fabricating twisted homo-/hetero- vdW structures in a deterministic, high-throughput manner will serve as a powerful tool for twistronics.     

反扭曲向列相液晶的导波研究

利用全漏导波技术对反扭曲向列相负性液晶盒进行了研究,通过测量液晶盒全漏波导几何结构在不同电压作用下随内角变化的反射光强,并与理论模拟进行对比和拟合来确定液晶及液晶盒的多项参数,进而探究反扭曲向列相液晶盒内部液晶指向矢分布的信息。     

高性能透射式双稳态扭曲向列相液晶显示

我们开发了几种新型透射式双稳态扭曲向列相液晶显示（ＢＴＮ－ＬＣＤ）。与以前的模式不同，这种ＢＴＮ型不需要交叉式偏振片。实验证实，这些模式可具有较高的对比度和透过率。其中某些模式的色散特性可以和常规波导型ＴＮ模式相比。也就是说，它们可提供真实的黑／白工作模式而不需要任何进一步的色补偿。