时频双选信道OFDM系统的ICI消除与均衡

在正交频分复用（OFDM）系统中,因高速移动造成的多普勒效应导致子载波间正交性的破坏并产生载波间干扰（ICI）。为了消除ICI,本文通过分析ICI分布特性及带状矩阵特性,提出了低复杂度的迭代干扰抵消算法和基于最小均方误差准则的排序串行干扰抵消(MMSE-OSIC)算法。仿真结果表明,与传统子载波间干扰频域均衡算法相比,新算法在计算复杂度和性能之间取得了良好的平衡,且MMSE-OSIC算法可以利用时变信道的时间分集特性在高信噪比情况下有效地消除“地板效应”。      

一种时频双选信道下OFDM系统的低复杂度迭代干扰抵消算法

为了消除正交频分复用(OFDM)系统在时频双选信道条件下由于信道快时变带来的载波间干扰,本文提出了一种新的低复杂度迭代干扰抵消方法.为了消除载波间干扰,已经提出了不少方法,但这些方法要么因为矩阵求逆运算带来了高计算复杂度,要么以性能退化为代价换来低计算复杂度.利用并行迭代干扰抵消技术,本文算法可以明显改善系统性能,同时借助带状矩阵近似和最小二乘QR分解(LSQR)迭代计算的特点来降低计算复杂度.仿真结果表明,在高信噪比条件下,随着迭代次数的增加,本文所提出的算法可以有效的减少"地板效应",在系统性能和计算复杂度之间取得更好的折中.     

OFDM系统中基于软干扰抵消的Turbo均衡算法研究

针对OFDM系统中子载波间干扰带来的性能恶化问题,在最优Turbo均衡的基础上,提出了基于软干扰对消技术的MAP均衡算法。Turbo均衡部分首先利用先验信息进行干扰抵消,然后通过干扰抵消输出结果计算编码比特后验概率;同时对信道矩阵进行带状近似,提出简化算法,运算复杂度进一步降低。通过仿真分析表明,相比于传统turbo均衡算法,该算法在工程应用中更具有可行性。     

一种新颖的低复杂度MIMO—BICM迭代接收机设计

本文提出了一种用于多入多出（MIMO）比特交织编码调制（BICM）系统的低复杂度迭代接收机方案．该方案在第一次迭代中采用线性最小均方误差（MMSE）滤波，而在随后的迭代中采用一种低复杂度MMSE结合软干扰消除（SIC）的算法来抑制残余干扰和噪声．该算法通过将软干扰消除后的残余干扰和噪声的各分量近似为不相关的随机变量，使得在MMSE滤波时不必矩阵求逆，从而大大降低了计算复杂度．仿真证实该方案可以获得和传统的基于MMSE结合SIC的方案几乎相同的性能。     

一种新的OFDM系统中ICI消除算法

根据一种典型的OFDM系统模型，证明了载波间干扰（ICI）系数矩阵为酉阵，并利用其容易求逆的性质，提出了一种基于发送训练码的ICI消除方法，以较小的计算复杂度对接收信号进行处理来消除ICI。分析及仿真结果表明，与两种现有的ICI消除方法一一自消除法和加窗法相比较，该方法可以较好的消除ICI，同时，避免了自消除法和加窗法的缺陷。     

基于预编码设计的载频间干扰抑制

针对正交频分复用(OFDM)系统中归一化频偏所引起的载频间干扰(ICI)系数分布特点,设计了一种通用的OFDM预编码传输方案.可将ICI系数更好地集中在较少的子载波位置上,使接收端的干扰矩阵成为稀疏的矩阵,简化信号检测.从理论分析与系统仿真这2方面对这一算法进行了研究.与已有的基于均衡的ICI抑制算法相比,所建议的算法具有更低的计算复杂度;与ICI自身干扰抑制算法相比,具有更高的频带利用率.     

快衰落信道下OFDM系统的信道估计简化算法

在快衰落时变信道中，正交频分复用（OFDM：Orthogonal Frequency Division Multiplexing）系统子载波间的正交性会遭到破坏，由此引起的载波间干扰（ici：Inter-Carrier Interferellce）会对系统性能带来很大的影响。本文提出了一种利用时域线性模型的信道估计算法，利用随时间线性变化的模型描述信道。仿真结果表明，本算法能够有效地消除载波间干扰，降低系统的BER。与类似算法相比，当系统的BER性能相同时，算法复杂度大大的降低。     

时变信道下OFDM系统中基于载频间干扰抑制的迭代检测算法

为了有效地抑制OFDM系统载频间干扰（ICI），提出一种并行干扰消除的迭代检测算法。基于检测信号的信干噪比最大化的准则，通过对接收信号进行判决、重构、干扰抵消处理，建立了ICI抑制的迭代检测算法，给出了信号检测流程。通过对时变信道的分析，研究了时变信道中归一化频偏对系统陛能的影响，给出了性能仿真结果。仿真结果表明所建议的算法可有效地利用时变信道的时间分集特性来提高系统性能，计算复杂度从O（N^3）降低到O（N）。     

基于LSQR算法和加窗技术的判决反馈均衡器

在正交频分复用(OFDM)系统中,高速移动造成的多普勒效应破坏了子载波间的正交性并产生载波间干扰(ICI).为了消除ICI,确保快时变信道下的可靠通信,该文提出了一种低复杂度加窗LSQR(least square QR)判决反馈均衡器(Decision Feedback Equalization,DFE).借助加窗技术和时域LSQR迭代计算,该算法减少了残存的ICI,有效克服了"地板效应";此外,该算法还利用带状矩阵分解降低了计算复杂度.理论分析和仿真结果表明,在快时变信道下与已有的块状线性均衡(Block Linear Equalization,BLE)算法比较,该算法在复杂度相当的情况下可以进一步改善系统的误码率性能.     

单载波频域均衡消除符号间干扰的研究

介绍了单载波频域均衡（SC-FDE）系统以及SC-FDE所常用的频域块最小均方（FBLMS）算法。为了进一步改进单载波频域均衡系统的性能，基于抽头泄漏的思想，通过增加抽头的泄漏进一步优化了FBLMS算法，并对基于优化算法的单载波频域均衡系统进行了计算机仿真模拟。其仿真结果表明：与常用算法相比较，该优化算法能有效提高均衡器的收敛速度和显著改善均衡器消除符号间干扰（ISI）的性能。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.