基于压缩感知的分数阶Fourier 域LFM 信号检测

提出一种新的基于压缩感知CS（Compressed Sensing）理论的LFM 信号检测算法。利用LFM 信号在分数阶 Fourier 变换（Fractional Fourier Transform,FrFT）域稀疏的特点,构造FrFT 矩阵作为LFM 信号的稀疏变换基,通过少量待检测 LFM 信号的随机投影,求解信号在FrFT 域的系数向量,然后对该系数向量进行检测判决,进而达到对感兴趣信号检测的目 的。理论分析和仿真实验表明,随机投影点数低至奈奎斯特采样点数的1/10、信噪比低至-8 dB 时,该算法对感兴趣的LFM 信号检测的成功率可达到95%以上,并且对强窄带干扰不敏感;与波形一致算法相比,该算法在相同信噪比条件下,可以获得 更高的信号检测概率。     

基于FRFT的线性调频信号欠采样快速检测方法

采用分数阶Fourier变换对线性调频信号(Linear Frequency Modulation,LFM)进行检测与参数估计时,由于信号的特征未知,需要运用二维搜索方法确定分数阶Fourier变换的最佳旋转角度.该方法运算量巨大.为减少运算量,本文推导了欠采样前后LFM信号的分数阶Fourier变换最佳能量聚集旋转角度关系,证明了无噪LFM信号的调频率估计可以完全不受Nyquist采样定理的限制;通过推导分析欠采样含噪LFM信号在最佳分数阶Fourier域的信噪比,给出了欠采样倍数M对LFM信号检测的影响及其选取原则;最终提出一种基于欠采样理论的LFM信号快速检测方法.实验结果表明,当M选取合适时,利用原始信号的欠采样样本即可对LFM信号实现有效检测,快速确定其调频率.     

基于FrFT的LFM信号检测与参数估计算法

针对线性调频(Linear Frequency Modem,LFM)信号的快速检测和高精度参数估计问题,在分析LFM信号特征和分数阶傅里叶变换(FrFT)原理的基础上,基于快速解线性调频技术,提出了一种LFM信号检测和参数估计算法,该算法将LFM信号检测由二维搜索转换为一维搜索,从而有效地减少了运算量。仿真结果表明,算法在低信噪比下具有良好的参数估计性能。     

一种chirp信号快速参数估计算法

针对目前线性调频(chirp,LFM)信号参数估计算法运算量较大且估计参数较少的问题,在分析Radon-Wigner变换(RWT)和分数阶傅里叶变换(FrFT)应用于chirp信号参数估计的基础上,提出了一种基于Wigner-Ville分布(WVD)切片和FrFT的chirp信号参数估计新算法。该算法首先通过对观测信号两个WVD切片的计算估计出调频斜率,然后得到相应的FrFT阶数,最后利用一次FrFT估计出chirp信号的初始频率、初始相位和幅度等参数。整个算法只需三次FFT的计算量即可估计出chirp信号的四个参数。仿真实验表明了该算法能在低信噪比下实现chirp信号参数的快速有效估计。     

基于FrFT的伪码-线性调频信号参数估计算法

伪码-线性调频(PRBC-LFM)信号是近些年来应用于低截获概率(LPI)雷达的一种常用复合调制信号。针对PRBC-LFM信号的特点提出了一种基于分数阶Fourier变换(FrFT)的参数估计算法,算法首先通过二维分数阶Fourier域峰值搜索找到最佳旋转角,估计调频斜率;然后对信号做相应阶数的FrFT,利用FrFT峰值点之间距离与调频信号参数的相互关系估计信号的调频带宽、起始频率、码元时宽、载波频率等参数;最后根据估计出的调频参数重构线性调频信号,与原信号每个码元共轭相乘去载波,通过对基带信号幅度符号的辨别识别出二相编码信号的编码规律。仿真实验表明,本文方法能在较低信噪比下实现PRBC-LFM信号参数有效估计。      

用FrFT插值实现LFM信号的参数估计

分数阶傅立叶域的分辨率由信号时宽带宽积决定,有限的分辨率影响了利用FrFT(分数阶傅立叶变换)估计LFM(线性调频)信号参数的精度.针对此问题,提出了一种利用FrFT插值的LFM信号参数估计方法.在分析引起峰值点偏差的因素后,得到FrFT在峰值点的分数阶傅立叶域的函数表达式,基于此,在分数阶傅立叶域进行插值计算,突破了原有分辨率的限制,提高了参数估计的精度.仿真实验结果验证了算法的有效性.     

低信噪比强窄带干扰条件下的LFM信号检测技术的比较与分析

研究了低信噪比强窄带干扰条件下的LFM信号检测技术,提出了基于短时傅里叶变换(STFT)的线性调频(LFM)信号增强技术、基于时频峰值滤波的强窄带干扰抑制技术和基于一维搜索的宽带LFM信号检测技术.试验结果表明,采用以上这些方法在低信噪比强窄带干扰情况下,对于LFM信号具有较高的正确检测概率及参数测量精度.     

基于改进的FrFT的LFM最佳u域点滤波

分数阶傅里叶变换（Fractional Fourier Transform,FrFT）能够对线性调频信号（Linear Frequency Modulation,LFM）起到很好的能量聚焦效果，因此常用FrFT来对LFM信号进行未知参数估计以及滤波。基于此，提出了一种基于改进的FrFT的最佳u域滤波算法。仿真结果表明，相较于传统的在FrFT u域下的滤波而言，所提的滤波算法信号幅度谱损失更少，信息保留更完整，输出信噪比提升了3 dB，运算量减少了25%。     

基于FRFT模最大值的LFM信号参数估计方法

提出了一种基于分数阶Fourier变换模最大值的LFM信号参数估计方法,先对线性调频信号以较大的间隔先进行FRFT模变换,寻找次次最大值和次最大值点.在这两点之间以较小的间隔再进行FRFT模变换,此时寻找最大值点所对应的变换阶数即是最佳变换阶数,由量纲归一化即可得到LFM信号的调频斜率.提出的两次搜索最佳变换阶数法相比于传统方法不需要二维搜索,在相同的计算精度条件下大大降低了计算量,提高了效率.     

一种基于分数阶Fourier变换的雷达运动目标检测算法

针对雷达回波为多分量LFM信号时,时频分析存在的交叉项干扰问题,提出了一种基于分数阶Fourier变换(Fractional Fourier Transform,FRFT)的伪Wigner分布(PWD).该方法通过在参数平面按阈值进行峰值搜索确定变换域阶次,再在相应的分数阶Fourier域计算PWD,有效地抑制了交叉项的干扰,有利于更好地提取信号的时频信息.仿真实验证明了在强背景噪声下该算法的有效性.     

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.     

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.     

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.     

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.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

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.     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.