基于Matlab的步进频率波形与高分辨力距离像

频率步进信号是一种较常用的高距离分辨率雷达信号,常用于雷达的目标识别技术之中。首先简单介绍了一维距离像和步进频率信号,分析了步进频率雷达系统中成一维高分辨力距离像的成像原理,即采用离散傅里叶逆变换(ID-FT)信号处理方法实现距离高分辨。并通过Matlab仿真实现了各种具体情况的成像,指出了影响成像的各种因素,同时提出了相应的解决方法。     

基于0.22 THz高功率回旋管的步进频率雷达系统设计与仿真

基于0.22 THz高功率回旋管振荡器设计了频率步进成像雷达,采用收发分开的双卡塞格伦天线,发射信号形式为频率步进脉冲信号,回旋管频率调节通过调整回旋管电子束电压或者超导磁场强度来实现。给出了成像雷达设计方案,对雷达最大作用距离和步进频率雷达系统高分辨一维距离像进行了分析,开展了ISAR成像仿真。理论计算和仿真结果表明,该雷达对于散射面积为0.01 m²的目标探测距离可达到1.982 km,可分辨500 m处间距2 cm的点目标。该雷达可对低高度小目标进行高精度探测,比如对可携带武器和危险物质的无人机进行高精度探测与目标识别。     

小波谱估计用于雷达目标成像和识别

研究了小波变换谱估计用于频率步进毫米波高分辨力雷达目标一维距离像的成像方法．选用已调高斯函数作为小波基函数,进行小波变换的信号功率谱估计,获得高质量的频率步进毫米波雷达目标的一维距离像．实验结果表明这种方法对于提高目标识别率是有效的     

GPU 加速条件下基于相位补偿反投影算法的太赫兹 ISAR 成像

介绍了0.22 THz步进频率雷达系统及二维高分辨率ISAR成像方法。该雷达系统的合成带宽为12GHz,可以同时实现近场及远场成像。在近场条件下,该系统在距离向和方位向实现二维高精度成像,通过相位补偿反投影算法,太赫兹ISAR图像的分辨率可以达到厘米量级。研究结果表明,采用同样的太赫兹频率步进雷达系统,基于反投影算法的太赫兹ISAR成像可以实现更高的精度和更精细的分辨率。为了加速成像过程,采用了GPU的加速平台,该方法为进一步开展近场高分辨率雷达成像,特别是太赫兹波段雷达成像提供了研究基础。     

HPRF脉冲多普勒频率步进雷达信号处理与参数设计

频率步进雷达是一种距离高分辨雷达,传统的处理方法是采用频时转换(IDFT)获得目标的一维距离像,实际上其处理也可以采用时频转换(DFT)的方式进行,这时也可把频率步进雷达看作是一种载频跳变的脉冲多普勒(PD)雷达.采用这种分析方法的优点是,在高重复频率(HPRF)的情况下,可以通过雷达系统的参数设计和信号处理,同时获得不模糊的测速性能和距离高分辨性能,并解决HPRF PD雷达的距离模糊问题.本论文在分析频率步进雷达时频转换(DFT)处理的基础上,给出了HPRF PD频率步进雷达系统参数设计准则及频时耦合的解决方法,以及距离模糊问题的解决方案.理论分析和仿真结果证明,这种雷达体制可以同时获得不模糊测速和距离高分辨性能.     

距离高分辨测高技术

为了提高米波雷达低空探测性能,本文讨论步进频率体制下,单脉冲测角的米波雷达测高方法.首先利用步进频率信号的距离高分辨特性,得到回波的一维距离像,再对其进行前沿跟踪和单脉冲测角,进而得到目标的真实高度.仿真结果表明此种方法适用于对超低空目标的探测.     

双载频步进频率雷达精确速度测量方法

步进频率雷达中,目标的径向运动将导致合成的目标径向一维距离像产生距离徙动和波形失真,需要对目标速度进行测量以补偿其影响。该文提出基于单个步进频率脉冲串的共轭法速度测量方法,然后提出一种同时发射双载频步进频率信号的速度测量方法,并分析了其潜在测量精度。理论分析和仿真结果证明,两种方法相结合不仅具有普通步进频率信号的高距离分辨率等优点,而且具有速度测量无模糊测量范围大、测量精度高的特点,可以利用速度测量值补偿目标一维距离像的距离移动和失真,从而同时实现高速目标的速度精确测量和高分辨成像。     

基于频率步进雷达时间-距离像的宽带微动特征提取

 在详细分析频率步进雷达旋转微动点目标回波特征和一维距离像特点后,利用不同帧之间构成的慢时间一维距离像组的相关性,合成得到时间-距离像.对比分析了旋转微动目标的径向距离和距离像位置的变化规律,进而提出了一种基于频率步进雷达时间-距离像的宽带旋转微动特征提取的新方法,给出了旋转中心、旋转半径以及角速度等微动参数的理论表达式,推导得出算法的理论精度.设计并成功开展了地基毫米波频率步进雷达对称旋转目标的外场试验,验证了方法的有效性和精确性.该特征提取思想可扩展应用于振动、滚动等其他形式的微动特征提取,推广应用于线性调频信号的高分辨体制雷达系统.     

角反射器在太赫兹波段的散射特性研究

太赫兹雷达散射特性的研究对于目标识别、跟踪以及截获有重要意义.设计了0.22 THz频率步进雷达散射截面(Radar Cross section,RCS)测量系统,提出了针对频率步进太赫兹雷达信号体制下,角反射器RCS的提取方法.采用实验与仿真相结合的方式,得到了单个角反射器和角反射器组在4°范围内的太赫兹雷达散射截面.结果表明,角反射器类目标的RCS实验测量结果与理论计算结果在误差范围内一致性较好,为进一步精确测量目标在太赫兹波段的散射特性奠定了研究基础.     

基于NDFT的步进频率雷达信号处理

步进频率脉冲信号可以在发射较小瞬时带宽信号情况下，通过脉冲压缩而合成分辨率较高的距离像，因而在高分辨雷达系统中得到广泛的应用。但是，直接采用DFT方法合成距离像．其分辨性能并不理想。利用Chirp-z方法也存在一些缺点。本文提出了利用非均匀傅里叶变换(Nonuniform Discrete Fourier Transform，NDFT)方法来处理频率步进信号以改善雷达的分辨性能，解决了直接利用DFT方法和Chirp-z方法合成目标距离像时所存在的问题。文中给出了NDFT的定义及在重点观测区域内的采样方法，进行了针对多种情况的仿真实验。仿真结果显示，利用NDFT进行处理可以明显改善步进频率雷达的距离分辨性能。     

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.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

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.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks