减小SC滤波器中GB效应的新结构

本文讨论了在开关电容(SC)滤波器中如何减少增益带宽积(GB)效应的问题,提出了一个减少GB效应的新的双二次拓扑结构,此结构对寄生电容不敏感,并且具有很低的无源W0,Q灵敏度。以低通SC滤波器为例,给出了减小GB效应的具体设计方法。并用设计实例和实验结果证明了所得结论的正确性。     

Compact formulation for exact analysis of nonideal SC circuits

A systematic analysis procedure to obtain closed-form expressions for the z-domain transfer functions of SC circuits with finite GB product op-amps is presented. This method allows exact frequential analysis of a general class of SC circuits, without imposing any restriction in the ratio between GB and clock frequencies.     

HIGH SELECTIVITY SC BANDPASS FILTERS WITH LESS CAPACITOR SPREAD

Two novel switched-capacitor(SC)bandpass filters using a single operational am-plifier(op amp)are presented.Optimal designs for minimizing capacitor spread are also given.Gain-bandwidth product(GB)effects of op amps on the proposed SC circuits are taken intoconsideration.Comparisons with the proposed circuits and the circuits given by the literatureshow that the new circuits require less chip area in monolithic integration and are less sensitiveto the GB effects.     

单一单位增益放大器的Q增强SC滤波器

本文阐述了采用单位增益放大器的SC滤波器的设计方法。基于无源Q增强技术,由Sallew Key有源RC电路导出了一系列Q增强的二阶SC低通、高通和带通滤波器。设计表明,本文提出的Q增强SC电路比文献给出的电路需要小得多的电容分散度。本文考察了这些电路灵敏度和有限GB对SC电路的影响。用分立元件做了实验,实验结果与理论计算相吻合。     

New analogue four-quadrant voltage divider

A new circuit structure for the realisation of an analogue four-quadrant voltage divider with improved dynamic performance is proposed. The structure was developed on the basis of the augmented Lagrangian method and the gradient optimisation approach. The circuit is especially suited for monolithic IC implementation by employing the CMOS switched-capacitor (SC) techniques. The device has been built using SC discrete components and also simulated on computer. Experimental test and computer simulation results have confirmed the theoretical predictions, especially the dynamic error reduction of the device.<>     

Generation of Flat Supercontinuum in a Single-mode Optical Fiber with a Convex Chromatic Dispersion Profile

A single-mode optical fiber with a convex chromatic dispersion profile is proposed for generating a flat supercontinuum(SC).The fiber has normal dispersion and the dispersion parameter D(λ,z) is a convex function of wavelengths.It is shown from the numerical results that the chromatic dispersion,the flatness of the dispersion curve and the pump conditions have significant effect on SC generation.A flat and broad SC without strong residual pump component can be obtained when the pump wavelength is set in the...     

3D Modelling of Superconductor Enabled Magnetic Induction Transmitter and Relay Coil for Non-conventional Media Communication

The well established way of communication using radio frequency (RF) waves do not perform well in Non-Conventional (Non-Con) media viz. underground and underwater. Herein, the medium of soil or water is dynamic thus the use of RF technique is unusable. To establish a more effective communication in Non-Con media, researches showed that Magnetic Induction (MI) communication to be more suitable. In MI communication, parameters like number of turns, size and coil orientation have a significant effect on transceiver coil model. In this paper, a novel MI transmitter model using superconductor (SC) in one directional (1D) and in three directional (3D) is proposed. The model provides an enhanced magnetic field strength over a given distance. Further, SC based relay coils which collectively known as waveguide structure is also proposed to increase the MI communication range with intensified field strength. The performance evaluations are quantified in terms of communication range and received power for Non-Con medias. The frequency response for SC based transmitter model is given for maximum power transfer. Besides, the performance of traditional MI systems and waveguide are quantitatively compared with our improved SC based MI system and waveguide. The results show that the system has stronger magnetic field strength and greater communication range than the traditional ones.

     

基于训练序列的OFDM系统定时同步改进算法

本文从OFDM系统模型和同步技术作为切入点重点分析研究了基于训练序列的OFDM系统定时同步算法,针对基于SC算法构造的训练序列帧结构及所采用的定时估计算法会造成定时同步位置具有峰值平台、定位点模糊、定时同步不够精确的缺点,提出了一种基于SC算法的改进型训练序列帧结构及改进算法。该算法对SC算法中训练序列前后两部分的搬移重复结构进行改进,构造了前后两部分呈中心对称的训练序列帧结构。改进算法不再采用SC算法中训练序列的后半部分来定义能量函数,而是采用整个训练序列长度来定义能量函数,从而构建同步度量函数,找到最佳定时同步估计点并完成定时同步。理论分析和仿真结果表明,改进算法解决了SC算法定时同步估计位置模糊、定时同步不精确的问题,改进后的算法能够确保定时同步的精确性。      

Delta-doped avalanche photodiodes for high bit-rate lightwavereceivers

The authors estimate the GB (grain bandwidth) product limits and the noise performance of a new SAGM-APD (separate avalanche, grating, and multiplication avalanche photodiode) structure: the δ-doped SAGM-APD. It is shown that GB products in excess of 140 GHz for a 0.2-μm-thick multiplication layer and possibly larger GB products for smaller widths can be obtained. While recent calculations have predicted increased GB products for this δ-doped SAGM-APD structure, the authors explicitly prove using conventional theory that this is possible only with a concomitant increase in the multiplication noise. It is further demonstrated that it is essential to optimize the width of the multiplication layer for a given bit-rate to achieve minimum multiplication noise consistent with a GB product high enough to accommodate the requisite frequency response at the optimum gain. It is shown that the δ-doped SAGM-APD structure is a very good candidate for high bit-rate receiver applications     

Optimum design of δ-doped InGaAs avalanche photodiode byusing quasi-ionization rates

An avalanche photodiode (APD) designed by using quasi-ionization rates in InP and InGaAs is described. The structure has a δ-doped layer in an InP window layer. The heterointerface electric field is investigated and determined to prevent the tunneling current and carrier multiplication in InGaAs. The gain bandwidth (GB) product of the δ-doped APD is analyzed by R.B. Emmons's (1967) p-i-n electric field method. The highest GB product is 160 GHz     

High-power supercontinuum generation in a nested linear cavity involving a CW Raman fiber laser

We construct a novel nested linear cavity configuration to generate supercontinuum (SC) under continuous-wave pump. With this structure, stimulated Raman scattering and four-wave mixing can affect the whole region of the SC spectrum while the pump line is removed outside of the continuum, and a symmetrical spectrum can be obtained. The properties of the structure are demonstrated by using 3.5-km single-mode fiber, and an SC centered at 1315 nm with the bandwith of 102 nm and the output power of 1.3 W is achieved. By tuning the feedback fiber Bragg grating, we can easily adjust the spectral shape of SC to fit different requirement.     

n-Si bifacial concentrator solar cell

Various approaches have been developed for reducing the cost of the photoelectricity produced by silicon solar cells (SCs). Of highest priority among these approaches are improvement of the efficiency of the SCs, transition from p-Si to n-Si, light concentration, and use of bifacial SCs. In the present study, an SC combining all these approaches has been developed. In this SC, transparent conducting oxides serve as antireflection and passivating electrodes in an indium-tin-oxide/(p ⁺ nn ⁺)-Si/indium-fluorine-oxide structure fabricated from Cz-Si with wire contacts (Laminated Grid Cell design). The SC has front/rear efficiencies of 16.5?C16.7/15.1?C15.3% X (under 1?C3 suns). This result is unique because the combination of bifaciality and concentrator operation has no analogs and the SC compares well with the world standard among both bifacial and concentrator SCs.     

Programmable switched-capacitor bump equalizer architecture

A versatile and economical switched-capacitor (SC) equalizing structure to compensate attenuation characteristics is presented. The monolithic SC bump equalizer has three operational amplifiers and six capacitor banks to independently control the center frequency, bandwidth, and peak voltage gain steps for the bump (and dip) frequency response. The bump equalizer has been integrated using 3-μm CMOS (p-well) technology and occupies an area of 3.36 mm², including an additional test amplifier and test buffer. The circuit operating from ±5-V power supplies typically dissipates 60 mW when sampled at 75 kHz     

Photonic Crystal Palette of Binary Block Copolymer Blends for Full Visible Structural Color Encryption

Structural color (SC) arising from a periodically ordered self-assembled block copolymer (BCP) photonic crystal (PC) is useful for reflective-mode sensing displays owing to its capability of stimuli-responsive structure alteration. However, a set of PC inks, each providing a precisely addressable SC in the full visible range, has rarely been demonstrated. Here, a strategy for developing BCP PC inks with tunable structures is presented. This involves solution-blending of two lamellar-forming BCPs with different molecular weights. By controlling the mixing ratio of the two BCPs, a thin 1D BCP PC film is developed with alternating in-plane lamellae whose periodicity varies linearly from ≈46 to ≈91 nm. Subsequent preferential swelling of one-type lamellae with either solvent or non-volatile ionic liquid causes the photonic band gap of the films to red-shift, giving rise to full-visible-range SC correlated with the pristine nanostructures of the blended films in both liquid and solid states. The BCP PC palette of solution-blended binary solutions is conveniently employed in various coating processes, allowing facile development of BCP SC on the targeted surface. Furthermore, full-color SC paintings are realized with their transparent PC inks, facilitating low-power pattern encryption.     

开关电容Q倍增带通结构

高Q值的开关电容带通双二次节需要很高的电容比和较大的芯片面积。本文从理论和设计两方面说明采用Q倍增结构可以使这个问题得到较好的解决。     

硫系化物悬吊芯光纤产生温控可调谐超连续谱

设计了一种以高非线性三硫化二砷(As2Se3)作为纤芯、以温敏材料甲苯填充包层的悬吊芯光纤,并提出了一种产生可调谐超连续谱(SC)的方法。通过全矢量有限元法数值模拟了光纤中传输光的色散和非线性特性,利用非线性薛定谔方程和分步傅里叶算法分析了在甲苯临界温度为-90~110℃范围内产生的SC,并进行了结构参数和泵浦参量的优化;引入光谱平坦度(SFM)的概念,对模拟产生的SC进行定量分析。研究发现,当光纤纤芯直径为3μm时,利用中心波长为3.1μm、峰值功率为20 kW、脉冲宽度为300 fs的泵浦源可在临界温度下实现1.20μm光谱宽度的调谐;随着可调谐光谱宽度的增大,SFM略有下降,SFM的取值范围为0.89~0.92,这说明SC保持平坦。产生的可调谐SC在物质探测、光谱学和环境分析等领域具有广阔的应用前景。     

千兆以太网端口自协商分析

在以太网发展到快速以太网时,为了实现不同速率的以太网设备混合通信,在介绍以太网自协商的概念以及基本原理的基础上,较详细地说明了千兆以太网自协商的三种page帧结构.重点阐述了千兆以太网端口的自协商基本过程,并以1000BASE-T为例分别介绍了千兆以太网端口的自协商接收与发送流程.     

典型室内电磁环境防护控制分析研究

超过一定阈值的电磁辐射会对生物体造成潜在的不良影响,这是无线设施电磁环境研究中的重要问题之一。为评估该电磁效应与辐射源空间相对构型以及室内辐射特征受建筑设施结构影响的关联,文中探究了典型辐射源在代表性建筑结构中不同位置所产生的辐射特征分布,并基于《电磁辐射防护规定》(GB8702-88)探讨电磁辐射对生物体的潜在影响。文中分析了以窗户为室内显著电磁环境调节要素对室内的辐射强度的控制作用,并在此基础上提出了针对性的防护控制规则。     

量子点-腔系统耦合强度对非相干抽运的响应

用量子主方程理论研究了量子点-腔耦合系统。为了说明理论模型,分析了一个量子点微柱腔强耦合(SC)实验。经研究发现耦合系统在稳态时抽运产生一个新的强耦合标准,抽运可以抑制或者增强强耦合;腔发射谱双峰结构并不是强耦合的明确特征,它还依赖于非相干抽运。研究表明,强耦合经常出现变相的单峰而弱耦合(WC)出现双峰结构与系统所控制的参数值密切相关。激子抽运增加时,腔发射谱由双峰逐渐变成增宽的单峰最后变成窄的单峰;腔衰减率增加时,均为双峰结构的腔发射光谱经历了从强耦合到弱耦合的转变。量子点腔失谐系统有效耦合强度与非相干抽运密切相关。     

三维空间多天线相关性及互耦影响研究

针对三维传播环境下多天线系统空域相关性评估问题,首先将达波信号二维角度谱建模为更为通用的von Mises-Fisher（vMF）分布,并推导了不同阵列流型天线空域相关系数的解析式和近似表达式;然后分析互耦机理及其对接收信号矢量的影响,据此推导了互耦效应下天线空域相关性的闭式表达式,并给出了存在互耦的相关性与无互耦相关性之间的内在关系.仿真结果表明,本文推导的天线相关性表达式与数值计算结果非常吻合.另外,小角度扩展时,考虑互耦效应的天线空域相关曲线围绕着无互耦时的相关性曲线上下波动,且面型阵列具有更好的抗互耦能力.