基于复杂网络的雷达辐射源信号脉内特征提取算法

针对现代电子战环境下雷达辐射源信号的高度密集、复杂调制、交叠概率大等特点,基于时域、频域、时频域以及其他数学变换域的信号分析方法仍然不能满足雷达辐射源信号分选识别的要求,结合雷达辐射源信号具有可分辨性的确定数据结构表示,受时间序列的复杂网络分析启发,提出一种基于复杂网络的雷达辐射源信号脉内特征提取算法。该特征提取算法首先采用相空间重构方法对信号频谱序列数据进行预处理,将重构后的信号序列转换至复杂网络域进行表征;其次,通过复杂网络建模及其统计特征分析,研究雷达脉内信号时间序列动力学微观特性,从而挖掘信号的有效特征参数;最后,在不同噪声环境下,实现雷达辐射源信号序列的特征参数的分类性能及其准确性分析。仿真结果表明,所提取的特征参数在低信噪比环境下具有良好的抗噪能力和不错的聚类质量,验证了基于复杂网络时间序列分析的信号特征提取方法的可行性,为进一步丰富刻画雷达辐射源信号提供了有效的技术支持和手段。     

基于BSResSKGRU的雷达信号调制样式识别

针对基于图像识别的雷达信号调制样式识别方法生成图像耗时长,收敛速度慢,且在低信噪比条件下识别准确率低的问题,提出了一种新的雷达信号调制样式识别模型。此模型将雷达信号时间序列经简单预处理后直接作为网络输入,避免了将信号转换为图像的复杂过程;网络能够自主提取雷达信号空间和时间两个方面特征,完善了特征提取的方式;同时,对网络结构进行了优化,并引入了选择性核网络,以获取特征在不同尺度上的重要信息。实验结果表明,此模型在低信噪比条件下具有较快的训练速度和较高的识别准确率。     

基于扩张残差网络的雷达辐射源信号识别

针对低信噪比条件下,复杂多类雷达辐射源信号识别存在特征提取困难,识别正确率低的问题,本文提出了一种基于时频分析和扩张残差网络的辐射源信号自动识别方法.首先通过时频分析将信号时域波形转换成二维时频图像以反映信号本质特征;然后进行时频图像预处理以保留时频图像完备信息,适应深度学习模型输入;最后构建扩张残差网络以自动提取信号时频图像特征,实现雷达辐射源信号分类识别.实验结果表明,信噪比为-6dB时,该方法对16类雷达辐射源信号的整体识别正确率能够达到98.2%,对时频图像特征相似的类LFM（Linear Frequency Modulation）信号的整体识别正确率超过95%.本文提供了一种新的雷达辐射源信号智能识别方法,具有较好的工程应用前景.     

基于改进相像系数和奇异谱熵的雷达信号分选

脉内特征提取是新体制雷达辐射源信号分选的关键问题,文中针对现有方法分选准确率不高和对噪声敏感的问题,提出了一种基于高次频谱相像系数和频域奇异谱熵特征的分选新方法,实现了低信噪比下雷达辐射源信号的高准确率分选。对接收到的信号提取高次频谱相像系数特征以及奇异谱熵特征,并将两者作为分选的联合特征向量,运用K means聚类算法实现对不同调制方式的雷达辐射源信号的分选。仿真结果表明：改进后提取的信号特征类间的分离度大且受噪声影响程度小,在信噪比为-2 dB的情况下,该算法的总体平均分选准确率在85％左右,不同调制类型信号间的分选准确率最低为80％。与现有方法相比,文中提出的算法具有更好的信号识别效果。     

低信噪比下基于分裂EfficientNet网络的雷达信号调制方式识别

针对低信噪比条件下复杂多类雷达信号调制方式识别率低的问题，本文提出了一种基于时频分析和深度学习的雷达信号调制方式识别方法 .利用CTFD(Cohen class Time-Frequency Distribution)时频分析将信号时域波形变换为二维时频图像，更清晰地表征信号特征；采用灰度化和双三次插值运算等方法对时频图预处理，实现图像通道数和尺寸的减少，以降低深度学习模型数据输入量；进一步调整输入输出通道数构建小型EfficientNet网络，再由多个小型网络并行处理构建分裂网络EfficientNet-B0-Split3，将时频图像输入网络实现雷达信号调制方式识别.实验结果表明，在信噪比为-8 dB时，新方法对17类不同调制方式的雷达信号整体识别率可达97.1%，相对于扩张残差网络提高约2.4个百分点；在信噪比为-10 dB时，识别率可达92.1%，相对于EfficientNet提高约0.7个百分点，提升了低信噪比条件下复杂多类雷达信号调制方式识别率.     

一种适应低信噪比的脉内识别算法

针对传统的雷达信号脉内调制类型在低信噪比下识别能力不高的局限性,提出一种改进的适应低信噪比的信号调制类型分类识别算法。该算法对雷达脉冲信号流进行时间和脉宽格子划分,对同一格子中脉冲信号采用一阶差分自相关函数法计算特征向量,根据特征向量值进行聚类统计分类。分类后对每组内脉冲信号进行平方处理,再次计算特征向量并进行聚类统计分类,选择每组内质量较好的脉冲信号进行调制类型识别,提高了信号分类识别正确率,通过仿真实验验证了该方法的有效性。     

基于改进残差网络的雷达辐射源多标签识别北大核心CSCD

针对现有的雷达辐射源识别方法具有低信噪比情形下识别精度低、无法识辩多个辐射源等缺点,文中提出融入注意力机制的残差网络用于雷达辐射源多标签识别。首先,利用残差网络学习过程数据的时序特征并提取相应的深层特征;然后,引入注意力机制对提取的特征进一步地分类和识别;最后,在雷达辐射源数据集上进行仿真实验。结果表明所提的Atten-Resnet模型不但可以在多标签条件下进行雷达辐射源的准备识别,而且在信噪比为6 dB时仍然可以保持95%以上的准确率。Atten-Resnet模型具有较高的实用性和较强的鲁棒性。     

基于多尺度残差网络和小波变换的LPI雷达信号识别

针对复杂战场电磁环境下的低截获概率（Low Probability of Intercept,LPI）雷达信号识别问题,提出了一种基于小波变换和多尺度残差网络的识别方法。首先利用离散小波变换提取LPI雷达信号的时频特征;然后利用多尺度残差网络的多层特征提取网络对输入信号进行深层自主学习,以获取原信号时频数据的分布式特征,从而实现对雷达信号的识别预测。在不同信噪比条件下对不同调制样式信号进行实验,证明了所提方法的可行性与有效性,以及较高的识别率和泛化能力。     

一种雷达辐射源智能个体识别的方法

针对使用传统的卷积神经网络及低信噪比环境下雷达辐射源智能个体识别研究中识别性能不够的问题,提出了一种基于短时傅里叶变换(STFT)和EfficientNet的雷达辐射源个体识别方法。首先对雷达信号进行短时傅里叶变换,提取时频特征,然后利用EfficientNet中多个MBconv模块对不同时频特征图像的叠加,挖掘出信号图像隐含的更加复杂和抽象的深层次时频特征,包括信号强度的分布、时频模式、周期性变化等,从而完成个体分类识别。EfficientNet可以同时改变网络深度、宽度、图像分辨率3个参数,解决了梯度消失、梯度爆炸等问题。实验结果表明,基于STFT和EfficientNet的雷达辐射源智能个体识别的方法,相比于传统卷积神经网络在低信噪比环境下具有更好的识别性能。     

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.     

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.     

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.     

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     

Call for Papers—Feature Topic,Vol.12,No.7,2015

正Information Centric Networking Information-Centric Networking(ICN) is an emerging direction in Future Internet architecture research,gaining significant tractions among academia and industry.Aiming to replace the conventional host-to-host communication model by a data-centric model,ICN treats data content as the first