一种改进的CPFSK信号频率估计方法

针对突发信号解调中多普勒频偏大的问题,提出了一种改进的连续相位移频键控信号(CPFSK)频率估计方法.首先接收信号平方运算使信号的调制指数加倍,再通过一次离散傅里叶变换(DFT),用搜索信号平方谱谱峰的方法实现突发信号频率估计.仿真实验表明,在低信噪比条件下,该算法的频率估计精度比经典的相位差频率估计算法提高了20%;该算法与广泛用于高动态突发信号的频率插值估计算法相比,同道干扰信道下信干比改善可达4 dB,DFT长度缩短约1/3.     

基于LTE技术的车地无线通信传输方案在城市轨道交通中的应用

在无线通信技术高速发展的背景下,基于LTE技术的车地无线通信传输方案正广泛应用于城市轨道交通.王岩和陈序(2014)通过郑州地铁1号线工程案例证明了TD-LTE技术在车地无线通信中的应用稳定可靠,为其他地铁同行提供了可以参考的方案.本文基于工程实例介绍了地下区间选用1785MHz-1805MHz频段作为城市轨道交通车-地无线通信综合承载方案的频率规划及频率覆盖方案.     

一种利用相位跟踪的星载AIS 信号单通道分离算法

针对星载船舶自动识别系统(AIS)中无法避免的信号混叠问题,研究了突发混叠信号单通道分离中广泛应用的逐幸存路径处理(PSP)与最大似然接收解调,提出了一种基于相位跟踪的AIS 信号单通道分离算法。该算法通过最小化混叠信号状态转移表中的欧氏距离,解决了信道估计与跟踪中由频偏和调制系数估计误差导致的相位畸变问题。仿真表明,该算法相位跟踪性能在归一化频偏误差(相对符号速率)大于2×10-2时仍然能收敛,该算法的解调误码率与抗频偏的PSP 算法及线性联合检测算法相比,当误码率等于10-3时,同道干扰信道下具有2 dB ～4 dB 的信干比性能优势。     

多径瑞利衰落信道条件下射频干扰抵消误差对CCFD系统中OFDM性能的影响

针对同时同频全双工无线通信系统,考虑远端到近端的无线信道为多径瑞利衰落信道,近端发射天线到接收天线的自干扰信道为加性白高斯噪声信道,分析了同时同频全双工传输场景中,自干扰射频抵消幅度及载波相位误差对OFDM误码率的影响。结果表明,在相同信干比和信噪比条件下,幅度和载波相位估计误差的绝对值越小,误码率越低;针对载波频率2.3 GHz, OFDM子载波个数4096,子载波间隔15 kHz的同时同频全双工传输方式,在信干比为-70 dB,误码率为10-2时,若期望信噪比损失小于0.8 dB,则需要射频干扰抵消的载波相位估计误差的绝对值小于610-6,幅度估计相对误差的绝对值小于310-5;若期望获得40 dB的射频自干扰抑制效果,则射频干扰抵消的载波相位估计误差的绝对值小于0.5,幅度估计相对误差绝对值小于1%。     

自干扰幅度及相位误差对全双工系统的影响

在加性白高斯噪声无线传播信道和自干扰信道中,分析了自干扰射频抵消幅度及载波相位估计误差对二进制相位调制同时同频全双工系统误码率的影响.分析结果表明:相同信干比条件下,误码率随幅度估计相对误差、载波相位估计数值误差的绝对值减小而减小;当载波频率为1.9 GHz、信干比为-120 dB、误码率为10-2,自干扰载波相位估计数值误差为10-5度时,同时同频全双工系统损失发射功率0.2 dB.     

噪声跟踪干扰检测算法性能分析

基于认知无线电中协作频谱感知的思想,提出了一种跳频通信中噪声跟踪干扰的检测算法。首先采用能量检测算法,研究了干扰条件下单跳信号的检测性能。在此基础上,应用“k out of n”准则,在决策融合模块实现对噪声跟踪干扰的检测,推导了AWGN信道下噪声跟踪干扰的检测性能。理论分析和仿真结果表明,随着信干噪比的逐渐减小,对于单跳信号和噪声跟踪干扰的检测概率均逐渐增大;而在相同信干噪比情况下,噪声跟踪干扰的检测概率较单跳信号的检测概率得到了提高。      

基于局部自适应阈值的跳频信号提取和检测

针对通信对抗中跳频(FH)信号的提取和检测问题,考虑存在定频干扰的情况下,提出了一种基于局部自适应阈值的跳频信号提取和检测方法。在短时傅里叶变换(STFT)的基础上,通过求解合适的局部自适应阈值,消除定频干扰的影响,实现对跳频信号的提取。然后,根据跳频信号在驻留时间上的连续性对提取结果进行检测。仿真结果表明,当干信比(ISR)为10 dB时,无论是否发生频率碰撞(跳频信号的频率与干扰频率相同),算法均可以实现对跳频信号的有效检测,且算法复杂度低、可靠性高。     

城市轨道交通车地无线通信的应用

伴随城市交通压力的增加,城市轨道交通的应用日渐广泛,成为许多城市人群的出行首选,这在推动城市轨道交通发展的同时,也对车地无线通信系统提出严峻的挑战,应该借助先进的无线通信技术满足快速行驶的轨道列车的对地通信需要,为人们提供安全、舒适、信息化的乘车环境,实现地铁的平稳运营.本文就此展开论述,探讨城市轨道交通车地无线通信的具体应用.     

单音干扰下OFDM系统中频域迭代干扰消除算法

针对正交频分复用（OFDM,Orthogonal Frequency Division Multiplexing）系统受单音干扰问题,提出了一种有效的频域迭代干扰消除算法。所提算法首先在频域对干扰进行准确估计和重构,然后进行干扰消除。为实现更准确的干扰频率粗估计,提出了新的结合补零内插的频谱波峰搜索方法,有效地避免了干扰位于两子载波之间时频谱泄露导致的谱峰错判。干扰频率精确估计综合采用频率转化、低通滤波、加权相位平均算法迭代实现,估计误差在每一次迭代中减小。仿真结果表明:对于-20dB以上的干信比,所提算法能保证干扰参数的精确估计,使系统达到没有干扰时的误码率性能。      

基于测速误差的雷达间电磁干扰判决方法

为了更好地判定雷达间电磁干扰对雷达性能的影响程度,分析了传统干扰余量判决方法的不足,在雷达受到干扰的情况下建立了雷达测速误差的计算模型,并以3种典型雷达信号为例推导了测速误差与信干比的定量关系.仿真实验结果表明:随着信干比的不断增大3种信号的测速误差逐渐降低,当信干比由0 dB增加到20 dB时,矩形脉冲信号和线性调频...     

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.     

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.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

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.