Indoor multisource channel characteristic for visible light communication

In this paper, we present a wavelength depended ray-tracing algorithm to model the indoor multisource channel impulse response for visible light communication （VLC）. We compare the multipath loss difference between multisource and unisource channel. We also analyze the root mean square （RMS） delay spread and average time delay of three typical wavelengths as VLC holds a wide spectrum from 380 nm to 780 nm, the spectral reflectance of walls is wavelength-dependent. And the result shows that the blue light emitting diode （LED） owns a larger communication bandwidth than other wavelengths in the room with plastic walls. Also, the path loss of three different wavelengths is compared.     

一种倾斜波束双极化天线

提出了一种具有倾斜波束辐射特性的新型双极化天线。该双极化天线由两个正交的纺锤形偶极子 组成,根据准八木天线原理,在偶极子两侧加载寄生振子作为反射器和引向器,用以实现倾斜波束辐射。这种纺锤 形偶极子可以增加电流长度从而减小天线的整体尺寸。同时在每个偶极子贴片上蚀刻两个梯形槽,以实现良好的 阻抗匹配。另外,通过连接到同轴线的金属短截线对纺锤形偶极子进行激励,简化了天线馈电结构。测试结果表 明,天线的阻抗带宽为3. 36~3. 69 GHz(S11 <-10 dB),两个极化端口之间的隔离度大于16 dB,波束倾斜度为30°,波 瓣宽度约为85°,可适用于单侧大角度扫描阵列。     

基于海天线提取和混合灰度差的船舶检测方法

为了快速、准确检测海天背景下远距离水平观测的船舶目标,提出了一种基于海天线提取和混合灰度差的船舶检测方法.首先,利用边缘检测算法将图像分为天空、海天线和海面三个区域,并根据海天区域连接点,采用直线拟合方法确定海天线的直线参数;然后提取海天线区域作为目标感兴趣区域,并在去除海面杂波和噪声等干扰后利用混合灰度差水平投影和垂...     

Conduction cooled narrow linewidth sub-nanosecond multi-beam laser

A conduction cooled high peak power, narrow linewidth, and sub-nanosecond multi-beam laser as an excellent candidate for non-scanning lidar is demonstrated. This laser is based on master oscillator power amplifier (MOPA) scheme which consists of a pulse pumped Nd:YAG/Cr4+:YAG microchip laser as the master oscillator and a high efficient grazing incidence Nd:YVO4 slab amplifier, and the output beam is expanded to 100 mm diameter by a 50× low aberration Galileo beam expander and then divided into a 50×2 staggered arrangement multi-beam array by a diffractive laser splitter. The laser operates at 1 064.28 nm with a spectral linewidth about 20 pm, which generates 1 mJ, 0.78 ns pulses at 7 kHz rate. The fluctuation of output power is less than ±2% when it works continuously for 1 h. The energy uniformity of the 100 sub-beams is up to 90%, the divergence of each sub-beam is about 20 μrad, and the total transmission efficiency of the diffractive laser splitter is more than 85%.     

一种GaN半桥驱动器电平移位电路设计

GaN半桥输出点电压在死区时间为负值,给GaN功率器件栅极驱动电路信号通信带来了挑战.通过研究驱动器电平移位锁存电路工作状态与半桥功率级输出节点电压跳变、死区时间负压之间的相互影响,设计了一种新型的零静态功耗电平移位电路及其误触发消除电路.电路采用100 V BCD 0.18μm工艺设计,在输入电压100V、开关频率5...     

一种基于相同标准的评价图像质量的新方法

设计了一种新的实验方法,使主观实验者能同时对两块液晶屏的图像质量进行评价,使他们有一个相同的标准来评价不同的液晶屏,解决了以往实验方法中缺乏统一的评价标准的问题.统计分析表明,实验图片的不同并不影响观察者对图像质量的评价,主观实验者认为的不可接受的视角不仅仅是取决此角度下图像的总体质量,还与图像的质量随着视角的变化有关.     

基于卡尔曼预测采样与空域图描述的稳健红外目标跟踪

目标状态采样策略和观测概率模型是影响粒子滤波理论框架下红外目标跟踪性能的主要因素.为了提高红外目标跟踪性能,介绍了一种基于卡尔曼预测采样与空域图描述的红外目标跟踪方法.目标状态采样采用卡尔曼预测采样策略,通过卡尔曼预测过程将目标的观测信息组合到重要性建议分布;采用空域图技术实现红外目标的稳健描述,通过计算参考目标的空域图与目标样本的空域图之间的Bhattacharyya距离,建立观测概率模型.传感器自运动场景、辐射不稳定场景及海杂波背景下的红外目标跟踪实验证明:该方法是有效的和稳健的.     

EPDM基红外隐身涂层耐热性及使用寿命预测研究

从发射率变化的角度建立了红外隐身涂层失效的评价标准.根据Arrhenius公式研究了涂层寿命的估算方法.采用IR-2型发射率测试仪,测试了低红外发射率EPDM/Cu涂层在不同温度下发射率的变化,得出了涂层的最高耐受温度,并预测了涂层在不同Ma数的飞机蒙皮上的使用寿命.结果表明:涂层的最高耐受温度为523 K;涂层在1 Ma和1.5 Ma的蒙皮上的寿命分别可以达到4.91×103h和3.78×104h.理论计算结果与实验结论比较符合,这表明此预测方法在实际应用中有一定的普遍性,能够比较准确地预测红外隐身涂层的使用寿命.     

激光诱导光纤损伤可持续利用技术

研究了光纤损伤对光纤传能特性的影响.由小到大注入激光能量时,光纤端面偶尔会产生微弱火花并出现微小坑状损伤,但并不影响光纤的注入耦合效率.当光纤端面发生等离子闪光后出现了比较严重的灾难性损伤,光纤输出端激光能量明显下降.光纤端面损伤降低了激光注入耦合效率,从而导致光纤传输效率下降.建立光纤端面损伤理论模型,由于光纤端面损伤引起的注入激光能量损失与损伤面积的对应关系,当注入激光光斑能量为高斯分布时,注入激光能量损失率与损伤面积成负指数关系.实验结果还表明光纤端面损伤存在增长效应.通过实验研究和理论分析证明了提出的光纤损伤后仍可持续利用设想的可行性,它为高功率光纤传输系统设计,特别是单脉冲激光点火或起爆系统的设计提供了新的思路.     

Parallel Image Processing Technology of Surface Detection System

To improve image processing speed and detection precision of a surface detection system on a strip surface, based on the analysis of the characteristics of image data and image processing in detection system on the strip surface, the design of parallel image processing system and the methods of algorithm implementation have been studied. By using field programmable gate array（FPGA） as hardware platform of implementation and considering the characteristic of detection system on the strip surface, a parallel image processing system implemented by using multi IP kernel is designed. According to different computing tasks and the load balancing capability of parallel processing system, the system could set different calculating numbers of nodes to meet the system＇s demand and save the hardware cost.