一种新的PSWF调制信号PAPR抑制方法

针对椭圆球面波(Prolate Spheroidal Wave Function,PSWF)时域正交调制信号峰均功率比(Peak-to-Average Power Ratio,PAPR)过高,易受功率放大器非线性特性影响,造成PSWF脉冲间良好正交性下降,导致系统解调性能下降的问题,引入A律压缩,提出了一种基于A律压缩的PSWF调制信号PAPR抑制方法。该方法能够有效抑制PSWF调制信号PAPR,改善经过功放后调制信号的功率谱和系统误码性能。     

基于PSWF框架的非正交脉冲波形调制方法

现有调制方法主要基于正弦函数,并利用其正交性传输信息.本文突破对调制信号的正弦函数约束和正交性限定,从椭圆球面波函数(Prolate Spheroidal Wave Function,PSWF)的高能量聚集性和框架函数系的过完备特性入手,提出基于PSWF框架的非正交脉冲波形调制方法(Nonorthogonal Pulse Shape Modulation,NPSM).该方法利用频谱交叠的非正交PSWF获得了优良的功率谱特性,同时利用框架函数的过完备特性,在提高系统频带利用率的同时,有效消除码间串扰.与目前广泛应用的QAM-OFDM方法进行性能相比,在相同调制幅度数和误码率的情况下有2dB的优势,且该优势随调制进制数增加而扩大,同时其调制信号具有良好的功率谱特性,PAPR性能比相同频带利用率的QAM-OFDM有3dB的优势.     

基于Householder变换的正交PSWF脉冲设计

传统的Schmidt方法对椭圆球面波函数（PSWF）脉冲组进行正交化时,脉冲组的最大互相关值受脉冲个数的影响,同时还存在计算复杂度高的问题。针对上述问题,提出了基于Householder变换的正交化方法,通过将PSWF脉冲离散化,再依次对各离散的PSWF脉冲进行Householder变换,实现了对PSWF脉冲组进行QR分解,并得到新的正交PSWF脉冲组。仿真结果表明,与传统Schmidt方法相比,基于Householder变换的正交化方法使得脉冲组的最大互相关值从10-4降低到10-11,改善了脉冲组的正交性能,突破了脉冲组在脉冲个数的限制,并降低了计算复杂度,同时能够保持PSWF脉冲带内能量集中度高的优势。     

基于Karhunen-Loeve变换的正交椭圆球面波脉冲波形设计

针对正交椭圆球面波函数(PSWF)脉冲硬件实现复杂度高和难以实时产生的问题,通过对PSWF脉冲求解和正交化两个过程的优化整合,该文提出了一种基于Karhunen-Loeve变换的正交PSWF脉冲波形设计方法。该方法首先将PSWF脉冲表示为Legendre多项式加权求和的形式,通过对原脉冲互相关矩阵进行Karhunen-Loeve变换,得到正交系数矩阵,从而实现PSWF脉冲的正交化。以此为基础,设计了一种高效快捷的正交PSWF脉冲实现方案,建立了正交PSWF脉冲与Legendre多项式系数向量的对应关系,能够通过改变特征多项式的系数来快速设计正交PSWF脉冲,同时具有实时性好和实现复杂度低的优点,为正交PSWF脉冲的工程化实现提供了一种高效快捷的新方案。     

关于降低OFDM系统中峰均功率比技术的研究

主要围绕降低OFDM（正交频分复用）系统中峰均功率比（PAPR）展开研究.先对目前降低OFDM峰均功率比的各种技术进行了分析总结.然后,对信号畸变技术中的加权信号调制技术进行深入的研究和分析,通过仿真证明该技术可以有效地降低PAPR.本文所研究的内容均利用Matlab软件进行仿真.     

一种抑制PAPR信号峰均功率比的有效方法

OFDM技术的应用越来越广泛,但是其发送信号功率的峰均功率比（PAPR）比较大是其主要的缺陷之一。本文提出了一个降低OFDM信号PAPR的有效灵活的技术。该方法是通过恰当的选择OFDM调制中各个子载波的时域脉冲波形。仿真结果表明该方法能够大大降低OFDM信号的PAPR值。该技术与现有的其他方法相比实现复杂度也更低。     

降低LWT-OFDM系统PAPR的联合算法

针对小波提升变换的正交频分复用( LWT-OFDM)系统峰均功率比( PAPR)过高的问 题,采用了部分传输序列( PTS)与指数压扩变换的联合算法?首先由PTS算法选出 系统中峰值最小的一组信号,再通过指数压扩变换来降低峰均功率比?仿真结果表明,相对于其它的限幅类技术,本文所提联合算法在该系统中能更有效的降低峰均功率比,并且误码率相对较低?     

OFDM技术及其峰均功率比降低的一种有效方法的研究

正交频分复用（OFDM）是一种多载波调制技术，其特有的调制特性决定了它有较高的峰均功率比值。高峰均功率比信号会对实际放大器提出很高的线性要求，因此它是限制OFDM技术实用化的主要障碍。目前虽然有很多降低OFDM信号的峰均功率比（PAPR）的方案，但大多是以增加系统的复杂程度为代价的。本文提出了一种降低OFDM信号PAPR的方法，可以在不过分增加系统复杂性的基础上解决其PAPR在一定程度上降低的问题。     

基于改进Nyquist脉冲成形的降低PAPR方法

OFDM（正交频分复用）信号的主要缺点之一是存在较高的峰均功率比（PAPR）,阻碍了OFDM技术的实际应用。在分析脉冲成形（PS）技术降低PAPR的原理基础上,提出一种改进的Nyqu ist脉冲成形降低PAPR方法。该方法引入子载波波形间的相关性,即采用有效的Nyqu ist成形脉冲集合对各子载波进行脉冲成形。实验结果表明,该方法能增强各子载波间的相关性,显著地降低了PAPR值,而且算法实现简单。     

一种基于信号分组平均降低OFDM系统PAPR的方法

介绍了OFDM是一多载波调制技术,具有抗多径信道干扰和频谱利用率高等特点根据OFDM信号的统计特性提出一种降低OFDM系统PAPR(峰均功率比)值的方法,即将IFFT变换后的个信号按一定的规律分成V组,计算分组平均值,用分组平均值代替相应的原信号值。仿真结果表明信号分组平均方法可非常有效地降低系统的峰均功率比值。     

聚对苯撑苯并双(口恶)唑发光及其器件制备

采用光谱技术,研究了聚对苯撑苯并双(口恶)唑(PBO)溶液的光敏发光特性,并用相对法估算出溶液发光效率在50%范围.结合光谱技术、半导体电学和电化学等研究手段,具体研究了以PBO为发光层的单层电致发光器件,研究结果显示,电致发光与薄膜的光致发光有具有相同的发光中心,峰值位于510 nm左右.同时发现,由于存制备过程中不同处理条件使得不同厚度薄膜残留的掺杂物质浓度不同,从而引起薄膜的导电性的不同.使得器件的阈值场强随PBO厚度的减小而逐渐增加.     

系统级封装新型埋入式电源滤波结构的研究

在高密度小尺寸的系统级封装(SiP)中,对供电系统的完整性要求越来越高,多芯片共用一个电源网路所产生的电压抖动除了会影响到芯片的正常工作,还会通过供电网路干扰到临近电路和其他敏感电路,导致芯片误动作,以及信号完整性和其他电磁干扰问题.这种电压抖动所占频带相当宽,几百MHz到几个GHz的中频电源噪声普通方法很难去除.结合埋入式电容和电源分割方法的特点,提出一种新型高性能埋入式电源低通滤波结构直接替代电源/地平面.研究表明,在0.65～4GHz的频带内隔离深度可达-40～75 dB,电源阻抗均在0.25ohm以下,实现了宽频高隔离度的高性能滤波作用.分别用电磁场和广义传输线两种仿真器模拟,高频等效电路模型分析这种低通滤波器的工作原理以及结构对隔离性能的影响,并进行了实验验证.     

Emerging interconnects: a state-of-the-art review and emerging solutions

Aluminium was a primary material for interconnection in integrated circuits (ICs) since their inception. Later, copper was introduced as interconnect material which has better metallic conductivity and resistance to electromigration. As the aggressive technology scaling continues, the copper resistivity increased because of size effects, which causes increase in delay, power dissipation and electromigration. The need to reduce the resistor-capacitor??????? delay, dynamic power utilisation and the crosstalk commotion is as of now the fundamental main impetus behind the presentation of new materials. The purpose of this paper is to do a survey of interconnect material used in IC from introduction of ICs to till date. This paper studies and reviews new materials available for interconnect application which are optical interconnects, carbon nanotube (CNT), graphene nanoribbons (GNRs) and silicon nanowires which are alternatives to copper. While doing a survey of interconnect material, it is found that multiwalled CNTs, multilayer GNR and mixed CNT bundles are promising candidates and are ultimate choice that can strongly address the problems faced by copper but on integration basis copper would last for coming years.     

Arsenic deposition as a precursor layer on silicon (211) and (311) surfaces

We investigate the properties of arsenic (As) covered Si(211) and Si(311) surfaces by analyzing data from x-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) images. We then create a model using total surface energy calculations. It was found that both Si(211) and Si(311) had 0.68±0.08 surface As coverage. Si(211) had 0.28±0.04 Te coverage and Si(311) had 0.24±0.04 Te coverage. The Si(211) surface replaces the terrace and trench Si atoms with As for a lower surface energy, while the Si edge atoms form dimers. The Si(311) surface replaces all terrace atoms and adsorbs an As dimer every other edge site. These configurations imply an improvement in the mean migration path from the bare silicon surface by allowing the impinging atoms for the next epitaxial layer, tellurium (Te), to bind at every other pair of edge atoms, and not the step terrace sites. This would ensure a nonpolar, B-face growth.     

光子晶体微腔发光二极管

光子晶体微腔因其具有增强自发辐射、定向输出和单模工作的能力而受到广泛关注。介绍了光子晶体微腔发光二极管的基本原理、设计、特性、制作及其典型器件。     

Comparative study of maximum power point tracking techniques for hybrid renewable energy system

The power generation demand is increasing day-by-day throughout the world, therefore, the use of hybrid systems becomes a significant solution. The hybrid renewable energy system (HRES) is used for delivering power in various regions in order to overcome intermittence of wind and solar resources. Because of increasing environmental problems, for example, greenhouse gas emission and energy cost have interested novel research into substitute methods in favour of electrical power generation. Maximum Power Point Tracking (MPPT) control method is a vast deal of novel research used for enhancing the efficiency of HRES. The authors have revealed that the hybrid techniques i.e. Global MPPT, fuzzy-neuro systems, Adaptive Neuro-Fuzzy Inference System (ANFIS), Perturbed and Observe (P&O) + Adaptive Neural Network (ANN) etc. can provide best results as compared to other MPPT control methods. This paper offering a state of art review of MPPT control techniques for HRES.     

用于单光子TOF测量的时间-幅度变换器

基于新型共源共栅电流源的积分方法,设计了一种用于单光子飞行时间(TOF)测量的时间-幅度变换器(TAC).该方法有效简化了 TAC电路结构,减小了 TAC占用面积,显著提高了TOF的满量程范围(FSR).采用0.18 μm标准CMOS工艺设计.集成TAC的单光子探测器像素单元的填充因子可达到26.8％.后仿真结果表明,...     

Joint estimation of TOA and DOA in IR-UWB system using a successive propagator method

Impulse radio ultra-wideband (IR-UWB) ranging and positioning require accurate estimation of time-of-arrival (TOA) and direction-of-arrival (DOA). With receiver of two antennas, both of the TOA and DOA parameters can be estimated via two-dimensional (2D) propagator method (PM), in which the 2D spectral peak searching, however, renders much higher computational complexity. This paper proposes a successive PM algorithm for joint TOA and DOA estimation in IR-UWB system to avoid 2D spectral peak searching. The proposed algorithm firstly gets the initial TOA estimates in the two antennas from the propagation matrix, then utilises successively one-dimensional (1D) local searches to achieve the estimation of TOAs in the two antennas, and finally obtains the DOA estimates via the difference in the TOAs between the two antennas. The proposed algorithm, which only requires 1D local searches, can avoid the high computational cost in 2D-PM algorithm. Furthermore, the proposed algorithm can obtain automatically paired parameters and has better joint TOA and DOA estimation performance than conventional PM algorithm, estimation of signal parameters via rotational invariance techniques algorithm and matrix pencil algorithm. Meanwhile, it has very close parameter estimation to that of 2D-PM algorithm. We have also derived the mean square error of TOA and DOA estimation of the proposed algorithm and the Cramer-Rao bound of TOA and DOA estimation in this paper. The simulation results verify the usefulness of the proposed algorithm.     

超宽带脉冲信号的光学生成方法研究

近年来超宽带(UWB)通信技术迅猛发展,在测量、雷达技术、民用和军事无线通信中有着重要的应用,UWB-over-fiber技术已经成为目前研究的热点,其中就包括UWB脉冲信号的产生方法。区别于传统的电子学方法,光子学产生方法不受电子瓶颈制约,可以实现很高的带宽,并且具有抗电磁干扰、重量轻、结构紧凑的优点。通过对比国内外本领域研究成果,讨论及总结了以下三种原理的UWB脉冲信号的光学生成方法:1)相位调制-强度调制转换(PM-IM);2)半导体光放大器(SOA)的非线性效应;3)频谱塑形和色散所致频域-时域映射,然后对各种方案进行了对比分析。     

多孔硅发光机制的分析

从量子力学的基本理论出发讨论了量子限制效应，推导出多孔硅有效禁带宽度增量并用量子限制效应和表面态及其物质在发光中作用的理论解释了ＰＳ光致发光的实验现象。