用于测量和调控入射光偏振态的大面积阵列液晶器件

介绍了一种通过改变电极上的驱动电压来测量和调控入射光偏振态的液晶器件,同时模拟了该器件的液晶分子指向矢分布。众所周知,液晶分子的倾斜角较容易控制,却常忽视其扭曲角同样可以被调控。所以,液晶材料能够用作可变化、可转动的相位延迟器,这样就可以实现用同一器件结构测量入射光偏振态,随后调控该入射光偏振态。模拟了在十字结构电极下液晶层的指向矢分布,表明扭曲角可被电控,同时也说明将入射光偏振态调控到任意偏振态是可以实现的。     

纯位相液晶调制器的响应特性计算

液晶位相调制器在非显示领域有广泛的应用,例如自适应光学中的波前校正、大气湍流模拟、光学相控阵的光束指向等。在这些应用中液晶的响应速度、位相调制范围、色散等特性非常关键。围绕对这些特性的改进,本文总结了近年来人们在液晶器件设计、驱动方法改进以及液晶色散研究方面的理论计算方法,这为人们在提高液晶器件电光响应特性、预期其性能等方面的需求,提供了非常有价值的参考。     

Electrotunable Non‐reciprocal Laser Emission from a Liquid‐Crystal Photonic Device

A liquid crystal (LC) photonic device with an anisotropic optical heterojunction structure has been fabricated. The device has a phase‐retarding nematic LC (NLC) layer sandwiched between two polymer cholesteric LC films with right‐handed helices of different pitches. Electrotunable non‐reciprocal light transmittance and unidirectional circularly polarized (CP) lasing emission have been successfully demonstrated for this device structure. Two left CP (LCP) lasing emission peaks are observed at the edges of the overlapping region between the two photonic bands in the structure and are shifted upon the application of a voltage. In contrast, a non‐reciprocal right CP (RCP) lasing emission peak emerges at one of the band edges and diminishes upon the application of a voltage. These phenomena are interpreted based on the selective reflection of RCP light and the reorientation of the NLC molecules by the application of a voltage.     

泰曼-格林干涉仪测量液晶空间光调制器的相位调制特性

为了评价美同BNS公司反射式256 pixel×256 pixel纯相位液品空间光调制器(LC SLM)的性能,提出利用泰曼-格林干涉仪对相位调制特性进行干涉测量.实验结果表明,液晶空间光调制器的相化随灰度呈非线性分布,利用反插值法建立线性查找表,校正了器件的非线性.非线性度由原来的17.23%减小到2.85%;中心与边缘的相位调制,在同一灰度级最大相位差达到0.22π,中心相位调制均方根误差是边缘的4倍,说明该器件存在相位调制的不均匀性,中心相位误差较大,在波前控制中应给予校正.     

Reproducible analogue circuit for chaotic synchronisation

A highly reproducible analogue oscillator has been designed for chaotic synchronisation and secure communication. The oscillator contains a negative impedance converter, an LC resonance loop, an RC phase shift circuit, and a comparator chip used as a nonlinear device     

A double-element broad-band liquid crystal tunable filter-factorsaffecting contrast ratio

A double-element broad-band liquid crystal tunable filter consisting of a high-order quartz wave plate in series with a very-low-order electrooptically tunable liquid crystal phase plate and placed between crossed polarizers is described. A possible application for such a device is protection against intrusive laser radiation. The advantage of this double-element filter over a single-element low-order LC filter is that it increases the wavelength resolution of the device, which, when operated in the protect mode, allows continued sensing of the scene. Experimental and theoretical studies were made of the contrast ratios obtainable with such a filter     

Patterning Liquid Crystalline Organic Semiconductors via Inkjet Printing for High-Performance Transistor Arrays and Circuits

Liquid crystalline (LC) organic semiconductors having long-range-ordered LC phases hold great application potential in organic field-effect transistors (OFETs). However, to meet real device application requirements, it is a prerequisite to precisely pattern the LC film at desired positions. Here, a facile method that combines the technique of inkjet printing and melt processing to fabricate patterned LC film for achieving high-performance organic integrated circuits is demonstrated. Inkjet printing controls the deposition locations of the LC materials, while the melt processing implements phase transition of the LC materials to form high-quality LC films with large grain sizes. This approach enables to achieve patterned growth of high-quality 2,7-dioctyl[1]-benzothieno[3,2-b][1]benzothiophene (C₈-BTBT) LC films. The patterned C₈-BTBT LC film-based 7 × 7 OFET array has 100% die yield and shows high average mobility of 6.31 cm² V⁻¹ s⁻¹, along with maximum mobility up to 9.33 cm² V⁻¹ s⁻¹. As a result, the inverters based on the patterned LC films reach a high gain up to 23.75 as well as an ultrahigh noise margin over 81.3%. Given the good generality of the patterning process and the high quality of the resulting films, the proposed method paves the way for high-performance organic integrated devices.     

Analysis and design of an optimally coupled 5-GHz quadrature LCoscillator

A 5-GHz quadrature LC oscillator has been realized, in which the two LC stages are coupled with phase shifters. Analysis on the behavioral level shows that an N-stage LC oscillator is optimally coupled when each stage is connected with phase shifters providing ±180°/N phase shift. Simulation of the 5-GHz two-stage quadrature LC oscillator reveals a 4.3-dB reduction in phase noise compared to a quadrature LC oscillator without phase shifters. Measurements of the 5-GHz quadrature LC oscillator, made in a 30-GHz f _T process, show a phase noise lower than -113 dBc/Hz, with a resonator quality factor of only 4 and an oscillator core power dissipation of 21.2 mW     

液晶损耗对可调谐液晶光学滤波器性能的影响

F- P型可调谐液晶光学滤波器是一种小体积窄带宽低压调谐滤波器。液晶作为腔内工作物质,其损耗对器件的性能有重要的影响。文章以F- P干涉仪为基础,分析了液晶损耗对这类滤波器的半强度带宽(FWHM) 和峰值透过率的影响,以利于不同要求的滤波器的设计制作。     

CMOS LC-oscillator phase-noise analysis using nonlinear models

In this paper, a second-order stochastic differential equation is used as a tool for the analysis of phase noise in a submicron CMOS LC oscillator. A cross-coupled topology typical of integrated CMOS designs is considered. Nonlinear limiting and mobility degradation effects in the circuit are modeled and used to predict the statistics of the random amplitude and phase deviations in terms of design variables. Assuming Gaussian noise disturbances and describing the phase noise as a random diffusion process, the average phase-noise power spectrum is derived and its accuracy verified with measurement and simulation results. Calculations for phase noise arising from stationary tank noise, nonstationary channel thermal noise, and flicker noise are discussed. The analysis is used to emphasize the fundamental power/performance tradeoff associated with compensation of tank losses via adjustments in the power supply and device size.     

Theoretical analysis of low phase noise design of CMOS VCO

A theoretical analysis on low phase noise of voltage-controlled oscillators (VCOs) based on complementary cross-coupled LC VCO by 0.35-/spl mu/m complementary metal oxide semiconductor technology is demonstrated. From the procedure of optimization steps, the excess noise factor of the amplifier coming from the active device has been determined. The proposed VCO operates at 2 GHz with phase noise of -116 dBc/Hz at offset frequency 600 kHz. The power consumption is 22.62 mW under 3 V bias with 9.1% frequency tuning. The achievement of low phase noise is also matched with prediction by formula in the frequency domain.     

基于开关电容阵列的5.8GHz全集成LC压控振荡器设计

采用TSMC 0.18μm 1P6M RF CMOS工艺,完成了一种基于开关电容阵列的全集成LC压控振荡器的设计.版图后仿真结果表明,在1.8V电源电压下,电路核心功耗约为7.2mW,中心振荡频率为5.8GHz,在偏离中心频率1MHz处,该VCO的相位噪声为-121.8dBc/Hz,调谐范围为10.2%,满足交通专用短程通信系统的频段要求.     

A 50 MHz phase- and frequency-locked loop

A monolithic phase/frequency-locked loop has been developed for operation at up to 50 MHz. The loop combines wide capture range and narrow bandwidth, making it ideal for timing recovery in digital transmission systems. The 24-pin device features an electronically-tuned voltage-controlled LC oscillator and includes the input differentiation and full-wave rectification circuitry required for clock recovery from unipolar nonreturn-to-zero (NRZ) data.     

Electronically tunable external-cavity laser diode using a liquid crystal deflector

A novel external-cavity wavelength tunable laser based on a liquid crystal (LC) deflector is proposed. This device consists of a gain chip, collimating lens, LC deflector, and diffraction grating. By controlling the voltage applied to the LC deflector, a maximum wavelength variation of 12 nm and a sidemode suppression ratio higher than 30 dB are obtained.     

叉指换能器新的等效电路模型及其PSPICE仿真

声表面波器件PSPICE仿真是包含声表面波器件电子系统设计的难点,文章提出了适于PSPICE仿真的叉指换能器新等效电路模型,它应用LC网络等效Mason等效电路模型的复阻抗,由Y导纳矩阵推导计算声表面波器件的二阶效应频率特性,根据电路理论综合出与Y矩阵得到的声表面波器件二阶特性相同的等效电路,并与主信号叉指换能器等效电路模型叠加,PSPICE仿真结果与实验结果在中心频率处插入损耗和带宽相符.     

The impact of device type and sizing on phase noise mechanisms

Phase noise mechanisms in integrated LC voltage-controlled oscillators (VCOs) using MOS transistors are investigated. The degradation in phase noise due to low-frequency bias noise is shown to be a function of AM-PM conversion in the MOS switching transistors. By exploiting this dependence, bias noise contributions to phase noise are minimized through MOS device sizing rather than through filtering. NMOS and PMOS VCO designs are compared in terms of thermal noise. Short-channel MOS considerations explain why 0.18-/spl mu/m PMOS devices can attain better phase noise than 0.18-/spl mu/m NMOS devices in the 1/f/sup 2/ region. Phase noise in the 1/f/sup 3/ region is primarily dependent upon the upconversion of flicker noise from the MOS switching transistors rather than from the bias circuit, and can be improved by decreasing MOS switching device size. Measured results on an experimental set of VCOs confirm the dependencies predicted by analysis. A 5.3-GHz all-PMOS VCO topology demonstrates measured phase noise of -124 dBc/Hz at 1-MHz offset and -100dBc/Hz at 100-kHz offset while dissipating 13.5 mW from a 1.8-V supply using a 0.18-/spl mu/m SiGe BiCMOS process.     

Analysis and Design of a CMOS Phase-Tunable Injection-Coupled LC Quadrature VCO (PTIC-QVCO)

This paper presents the design, analysis, and characterization of a low-power, low-phase-noise, phase-tunable injection-coupled LC quadrature oscillator (PTIC-QVCO). Two LC VCOs are superharmonically coupled in quadrature phase via a frequency doubler that injects a synchronizing signal at the common source node of the negative transconductor stage. Conceptual and analytical models of the circuit are introduced to derive the conditions for quadrature operation and examine the circuit parameters affecting the phase imbalance due to mismatched VCOs. Additionally, a tunable tail filter (TTF) is incorporated to calibrate the residual quadrature imbalance in presence of a 3-$sigma $ variation in the device parameters and drive the oscillator to its optimum phase noise performance. To validate the proposed approach, measurements have been carried out on a 9 GHz prototype implemented in a 0.18 $muhbox{m}$ RF CMOS process. With core current consumption of 5 mA at 1.8 V supply voltage, the circuit achieves a measured phase noise figure-of-merit ranging from 177.3 to 182.6 dBc/Hz at 3 MHz offset along the 9.0 to 9.6 GHz frequency tuning range. Quadrature phase correction of $pm 11 ^{0}$ at 9 GHz is demonstrated.      

低电压CMOS压控振荡器设计

设计和分析了一种低电压CMOS压控振荡器,对设计的电路进行理论分析和模型建立,并使用仿真工具对电路进行验证和优化。设计中主要考虑相位噪声和调谐宽度等指标,通过采用电感电容滤波技术以及合理调整电路结构和元器件参数,使相位噪声和调谐宽度均达到了较高的性能指标。结果表明,在1.2 V工作电压下,设计的VCO的尾电流为3 mA,输出振荡频率为2.24~2.57 GHz,中心频率约为2.4 GHz,调谐范围达到13.7%。     

A High-Speed Measurement Method for Reflective Liquid Crystal Cells Using a Liquid Crystal Polarization-Converting Device

We propose a novel measurement method for determining cell parameters, such as a cell thickness and twist angle in reflective liquid crystal (LC) cells, by using a unique polarization-converting device prepared with a circularly and homogeneously aligned LC (CH-LC) cell. The light intensity distributions from the reflective LC cell transmitted twice through the CH-LC cell are measured by a charge-coupled device array camera. Cell thickness can be derived by using coordinate values of local minimum spot in the spatial light intensity distribution measured at one wavelength, where the pretilt angle is assumed to be the designed value. Both cell thickness and twist angle can also be determined by two local minimum positions of the light intensity at two different wavelengths and the effects of a quarter-wave plate are discussed     

A Stimuli‐Responsive,Photoluminescent, Anthracene‐Based Liquid Crystal: Emission Color Determined by Thermal and Mechanical Processes

Here, a photoluminescent liquid crystal that exhibits a change of emission color on the metastable–stable phase transition induced by external stimuli is prepared. A 2,6‐diethynylanthracene derivative with amide groups and dendritic side chains exhibits a columnar phase on slow cooling from the isotropic phase and shows blue emission in this columnar phase. In contrast, a cubic phase is obtained by rapid cooling from the isotropic phase. In the cubic phase, the 2,6‐diethynylanthracene cores form excimers, resulting in yellow emission. While the columnar phase is a stable liquid‐crystalline (LC) phase, the cubic phase is a metastable LC phase. It is found that a change of the photoluminescent color from yellow to blue is observed on the cubic‐columnar phase transition induced by heating or mechanical shearing for this 2,6‐diethynylanthracene derivative in the cubic phase. This change of photoluminescent color is ascribed to the inhibition of excimer formation on the metastable–stable LC phase transition.