国内尾流光学检测研究进展

以检测参量为主线,综述了国内尾流光学检测近15年的发展历程。归纳了已有的连续激光散射强度检测、成像检测、脉冲回波检测和偏振检测等四大类不同的尾流光学检测方法,介绍了不同检测方法的基本原理、发展以及存在的问题。结合检测的新方法、信号处理与抗干扰技术、建立尾流特性数据库和拓展相关应用对尾流光学检测的进一步研究进行了展望。     

入侵检测相关技术的研究

首先对入侵检测技术的研究背景进行阐述,然后对入侵检测系统的有关技术、网络入侵检测技术、评价入侵检测系统的指标和CIDF标准框架进行了深入研究。其中对于入侵检测系统详细地讲解了基于主机的入侵检测系统和基于网络的入侵检测系统;对于入侵检测技术深入讲解了误用检测技术、异常检测技术和混合检测技术;对于入侵检测性能指标详细讲解了漏报和误报、系统负荷、检测延迟时间和抗攻击能力。最后对网络入侵检测技术的未来发展方向进行了展望。     

基于机器视觉的电子连接器检测系统的设计

介绍了电子连接器检测的方法及原理,研究开发了基于机器视觉的电子连接器检测系统。针对实际的目标图像通过图像滤波、图像分割、图像匹配、边缘提取、纹理变换、颜色识别等多种方法处理,得到电子连接器缺陷完整的几何特征,从而实现自动化检测。实验证明,系统的检测结果与人眼检测结果相符,不仅保证了检测的准确性,而且大大提高了电子连接器检测的效率。     

电磁兼容检测信息管理系统的设计与实现

为提高电磁兼容检测信息的管理水平,基于Microsoft Office Access数据库,通过Visual Studio.NET开发环境建立了电磁兼容检测信息管理系统,实现电磁兼容检测各要素的有效管控、电磁兼容检测报告自动生成、检测仪器设备的管理、查询统计等功能。电磁兼容检测信息管理系统在实际使用过程中大大提高了工作效率,提升了电磁兼容检测的管理水平。     

移动机器人视觉目标检测与跟踪方法研究综述

针对移动机器人视觉目标检测与跟踪任务,首先,阐述了其研究背景及意义,分析了当前目标检测与跟踪方法研究中存在的难点;其次,结合特征表达的类型和检测步骤对传统目标检测算法、基于候选区域的目标检测算法、基于回归的目标检测算法与基于增强学习的目标检测算法等4种目标检测算法的优缺点进行了分析比较;接着,分析比较了传统跟踪算法、基...     

红外无损检测的数值模拟及其对比性研究

红外无损检测技术是一种新型的无损检测技术,具有非接触、检测面积大、检测速度快等优点,现已发展出许多有不同的检测方法,为了研究不同检测方法的优缺点,根据传热学的理论,对比分析红外无损检测的不同检测方法,建立了一个二维导热模型;并利用建立的模型,模拟计算出了试件在不同热激励条件下的温度场,在此基础上实现了对红外无损检测中的脉冲检测法、锁相检测法和脉冲相位检测法的数值模拟,从理论计算的角度比较了这三种红外无损检测方法的优缺点,得出了这三种红外检测技术的最佳使用范围,为红外无损检测的检测方法的选取提供了理论依据。     

SMT生产线多环节质量检测与控制技术

在电路板贴片安装生产过程中,进行多环节质量检测和控制可以大大降低返修成本、提高产品的合格率。文章讨论了贴片生产线多个不同生产环节的各种质量缺陷、自动检测技术和统计过程控制,比较了焊膏检测、自动光学检测、在线检测和功能检测及X射线检测等各种检测技术,分析了多环节质量检测和控制策略。     

基于ARM7TDMI核的工业洗衣机智能控制系统硬件设计

为了实现工业洗衣机的智能化、Internet远程监控的功能,本文深入分析了工业洗衣机智能控制系统的人机接口、电机控制、电磁阀控制、洗衣机状态检测、温度检测、布质布量检测、浑浊度检测、智能控制、Internet通信等功能模块,在此基础上完成了基于ARM7TDMI核的系统硬件设计。着重研究了水位、布量、水量和转速脉冲检测原理,给出了详细的水位检测、重量检测电路。实践表明,系统硬件运行稳定,在进行模糊推理及神经网络学习时具有更快的速度。     

毫米波雷达高压线检测技术的研究进展

高压线是威胁飞行器低空安全飞行的主要障碍,高压线的准确检测和有效预警是毫米波低空防撞雷达最重要的功能需求之一。首先介绍了毫米波雷达高压线检测技术的研究现状,其次重点分析了高压线的电磁散射特性、检测算法和检测系统三个主要方面的研究进展,提出了毫米波防撞雷达应具备大空域扫描、高数据更新率、高分辨率、小目标检测和抗杂波干扰等特点,最后指出了高压线检测技术的未来发展趋势,即基于多传感器信息融合检测、自主学习的智能化检测和深度信息检测。     

采用信息融合的红外目标检测算法

针对空中红外目标检测过程中存在的检测精度不高、易受干扰等问题,本文提出了一种信息融合的目标检测算法。首先,针对单一滤波模式的不足,采用降采样方式将多种模式的滤波方法进行融合,有效提高了滤波后的图像信噪比,减少了预处理时间。然后,对质心检测选定的检测区域进行显著性检测和边缘检测,并将结果进行融合,增强了目标区域的信号强度,改善了算法的检测精度。文中从理论上介绍和分析了该算法对红外目标检测的有效性,并通过Matlab仿真实验与其他单一检测算法进行了对比。实验结果表明,信息融合的检测算法能够在多种复杂情况下有效检测出空中红外目标,证明融合检测算法的抗干扰性和适应性上更强、检测精度更高、算法的鲁棒性更好。     

Timing Synchronization in Ultra-Wideband Systems with Delay Line Combination Receivers

This paper proposes a novel non-data aided timing synchronization algorithm designated as "timing with delay line combination" (TDLC), to improve the synchronization speed of differential impulse radio ultra-wideband systems. Continuously integrating the combinative output signal provided by the proposed "frame-differential delay line" (FDL), it is found that the integration output exhibits a sharp rising or falling transition at the moment that the first signal per symbol arrives. By accurately detecting the time of the rising or falling edge, the symbol boundary can be simply derived. The proposed scheme achieves timing synchronization within a single symbol duration     

MSK信号的参数估计

针对通信侦察中MSK信号参数估计的实际应用,提出构造延迟相乘自混频辅助信号获取与原信号同码速率的基带脉冲,对该脉冲采用小波变换提取边沿信息并进行谱分析实现信号码速率的估计;提出采用平方律和一阶循环矩子集相结合,通过检测循环频率位置的方法实现MSK信号的载波估计.这些算法无需MSK信号的任何先验信息,从而有利于通信侦察机...     

A new edge detector for CMI optical fiber transmission withimproved jitter tolerance

An edge detecting scheme for coded mark inversion (CMI) line codes which can reject wrong slot errors is proposed. This scheme looks at data transitions over one-and-a-half symbol durations and makes a binary decision based on the most likely transition pattern. An analysis and measurement results for the bit-error-rate performance of this scheme over an optical fiber link which show improvements in the detector tolerance against symbol timing jitters are presented     

Joint synchronization in Eureka 147 DAB system based on abruptphase change detection

We present a joint symbol, frame, and carrier synchronization method for the Eureka 147 DAB signal. Symbol timing is determined first by detecting an abrupt change in the phase angle of the complex product between the last quarter of a useful symbol and its cyclic extension in the guard interval. The detection of this abrupt change is based an the maximal likelihood (hit) principle. Frequency offset of fractional carrier spacing is estimated from the phase angle of the autocorrelation after symbol timing is estimated. Coarse frame synchronization and null symbol detection can also be achieved through this correlation information. Frequency offset of integral carrier spacing is determined from the convolution outputs between a received phase reference symbol and several locally generated but frequency-shifted phase reference symbols. We found the length of a guard interval is the most important parameter for the synchronization algorithm to work. Simulation results show that the performance of this synchronization method approaches to the ideal synchronization case in both an additive white Gaussian noise (AWGN) channel and a two-path Rayleigh fading channel     

Multiple symbol differentially detected multilevel codes for theRayleigh-fading channel

Conventional differential detection is known to perform poorly on the fast-fading Rayleigh-fading channel due to the rapid variation of the channel state. The technique of multiple symbol differential detection (MSDD) improves the error performance by detecting over a sequence of symbols and exploiting the inherent correlation of the fading process. To further reduce the error rate, we need to introduce some form of coding. Successful coding for the Rayleigh-fading channel requires interleaving to decorrelate the channel-a conflicting requirement to MSDD. We propose a solution consisting of interleaving blocks of L M-ary phase-shift keying (MPSK) symbols that are multiple symbol differentially detected. The blocks are treated as elements of an M^L symbol alphabet over which a multilevel code based on geometrically uniform partitions is defined     

一种用于信号侦测的码元速率估计方法

提出了一种数字通信信号码元速率的估计算法。对截获接收机输出的调制信号提取基带信号,利用此基带信号小波变换系数的模值,构造与原调制信号码速率一致的单极性脉冲序列。通过对此单极性脉冲序列的功率谱分析可知,在基带信号码元速率的整数倍处存在离散谱线,检测这些离散谱线即实现了信号码元速率的估计。这种算法能在低信噪比下估计信号的码元速率。理论分析和实际信号处理证明了本文提出算法的可行性。     

瑞利衰落信道下差分跳频通信系统的性能分析

介绍了一种新型的短波跳频通信技术--差分跳频,频率转移函数设计和信号的检测方法是差分跳频中的关键技术.针对逐符号检测和按序列检测两种信号检测方法,分别就差分跳频通信系统在瑞利衰落信道条件下的性能进行了理论分析,同时做出相应的计算机仿真.结果证实了,差分跳频通信技术和按序列检测方法的结合,使通信系统在瑞利衰落信道条件下的性能得到了比较显著的提升.     

Comparison of four FFT-based frequency acquisition techniques forCostas loop BPSK signal demodulation

This paper discussed four open-loop frequency acquisition techniques for suppressed-carrier BPSK signals. The techniques, which do not require accurate symbol timing nor a data preamble sequence, employ fast Fourier transforms (FFT's) on the Costas loop phase detector output to detect the Doppler frequency offset. Performance of the full-, half-, and staggered-symbol integration techniques as well as the low-pass filter technique are compared in terms of the error signal output SNR's. Then, the probability of detecting the frequency offset is computed for the special case when the frequency of the tone to be detected coincides with one of the FFT-bin center frequencies. It is shown that the performance of the integration techniques depends strongly on the symbol timing offset. On the other hand, the detection probability for the one-pole arm filter technique depends directly on the filter bandwidth. The staggered integration technique is shown to have comparable performance to the low-pass filter technique for low-to-medium symbol SNR's but the latter is superior at high symbol SNR's     

有限字符集下采用空间调制的物理层网络编码方案

空间调制(Spatial Modulation)通过利用天线索引承载数据信息,可以提升复用增益,实现更高速传输。利用这一特性,可针对协同多址接入信道模型设计一种基于空间调制的物理层网络编码方案。在协同节点,将其中一个源信息映射成传统调制符号,而将另一个源信息映射到协同节点的天线序号上。在目的节点,通过最大似然检测,判决接收到的传统调制符号和发射天线序号,分别恢复两个源节点发送的信息。研究结果表明,由于两个源信息载体相互独立,基于空间调制的多址接入方案可以获得优于传统方案的容量区域。仿真结果表明,在高信噪比条件下,系统和速率近提高1倍,同时两路信息误码性能均较好。此外,考虑到实际系统中使用的并非理想的高斯信源,文中分析均基于有限字符集展开。     

Hexagonal Multiple Phase-and-Amplitude-Shift-Keyed Signal Sets

Selection of a particular signal set array for a bandwidthConstrained multiple phase-and-amplitude-shift-keyed (MPASK) communication system for a linear additive Gaussian noise channel requires consideration of factors such as average and/or peak power versus symbol error probability, signal amplitude dynamic range, simplicity of generation and detection, and number of bit errors per symbol error (Gray code properties). A simple technique is presented for generating and optimally detecting the honeycomb (hexagonal.) signal set, i.e., the signal set that has the tightest sphere-packing properties. The symbol and bit error probability performance of this set is compared to other two-dimensional signal sets that have been investigated in the literature, and is shown to be slightly superior from an average power standpoint. The paper concludes with a comparison of all of these signal sets from the standpoint of the factors listed above.