A tunable and dispersion-insensitive microwave photonic filter

A tunable and dispersion-insensitive two-tap microwave photonic filter(MPF) with a complex coefficient is proposed and demonstrated.By simply adjusting a polarization controller(PC) in one tap,the filter can be tuned over the entire free spectral range(FSR) while keeping the shape of the filter unchanged.Because the two taps are both single-sideband(SSB) modulated,the filter has high tolerance to fiber dispersion.The transmission response of a system with 25-or 40-km single-mode fiber(SMF) was measured and compared with an MPF with one double sideband(DSB) modulation tap.The proposed MPF shows much better performance for long-distance fiber transmission.     

Fast tunable and broadband microwave sweep-frequency source based on photonic technology

A high-speed broadband tunable microwave source utilizing the wavelength tunable characteristics of distributed Bragg reflector(DBR) laser is proposed and demonstrated.The wavelength tuning of the laser is achieved instantaneously by controlling the voltage of the phase section of the DBR laser.By means of optical delay self-heterodyne technology,the microwave signal with the property of frequency broadband tuning is generated.Sweep speeds of 5 and 40 μs of the sweep-frequency source prototype were achieved and the maximum tuning range was up to 38.45 GHz.     

基于FBG传感系统的可调光滤波器非线性研究

采用光纤布拉格光栅(FBG)传感系统研究压电陶瓷(PZT)驱动法布里-珀罗(F-P)型可调谐光滤波器(TOF)的非线性特性。基于多光束干涉理论建立了TOF的非线性模型,推导了透射带波长和自由光谱范围(FSR)对驱动电压的非线性响应;基于FBG传感系统测试了F-P型TOF的波长非线性,并采用多项式拟合对其进行描述,实测F-P型TOF波长的非线性误差最大为1.006 nm;基于F-P型TOF的非线性模型,研究了其波长定位误差,并提出采用参考光栅的方法降低波长定位误差。实验表明,F-P型TOF的波长随机误差可由73～81 pm降至12 pm以下。     

基于微波光子技术的混频信道化收发系统

针对雷达和电子干扰系统的射频前端对宽带多频点信号同时侦察处理的重大需求,给出了基于微波光子技术的超宽带混频信道化收发系统的设计方案,并进行了实验验证.实验结果表明,该系统能实现对频率11～15 GHz、瞬时带宽4 GHz的高频超宽带信号产生及信道化接收;与传统射频方案相比,本文方案降低了系统复杂度,为解决未来电子装备大...     

微机电可调光滤波器调谐锁定系统

针对微机电可调光滤波器调谐过程中的振荡现象,给出一种波长调谐锁定系统,利用微控制器实现对光探测器输出信号的监测和对可调光滤波器波长的反馈控制。系统中的控制算法对连续多个监测信号采样值进行平均,可解决滤波器调谐振荡引起的时间延迟问题。在4种波长偏移情况下对系统进行实验测试,波长跟踪锁定时间和误差分别小于50ms和12pm,满足光纤通信应用的要求。     

温度调谐的周期极化掺氧化镁铌酸锂振荡器

对准相位匹配周期极化掺氧化镁铌酸锂晶体的光学参量振荡器进行温度调谐实验研究,所用晶体的极化周期为30.5μm.以1.064μm的声光调QNd∶YAG激光器作为抽运源,将晶体温度控制在40～200℃,获得3.100～3.398μm的闲频光连续可调谐输出;当泵浦光功率为3.7 W时,获得输出功率约1 W的3.365μm闲频光输出,泵浦光-闲频光转换效率达27%.在谐振腔内还观察到其他激光输出,并对此进行理论分析.结果表明,它们分别是由信号光倍频、泵浦光与信号光和频,以及泵浦光与闲频光和频产生的.     

Endpoint forecasting on composite regeneration by coupling cerium-based additive and microwave for diesel particulate filter

Numerical simulation has been carried out to investigate the major factors affecting the time of composite regeneration due to coupling cerium-based additive and microwave for diesel particulate f3ilter(DPF). Effect on the composite regeneration time from various factors such as mass flow rate of exhaust gas, temperature of exhaust gas, oxygen concentration of exhaust gas, microwave power and amount of cerium-based additive are investigated. And a mathematical model based on fuzzy least squares support vector machines has been developed to forecast the endpoint of the composite regeneration. The results show that the relative error of endpoint forecasting model of composite regeneration is less than 3.5%, and the oxygen concentration of exhaust gas has the biggest effect on the endpoint of composite regeneration, followed by the mass flow rate of exhaust gas, the microwave power, the temperature of exhaust gas and the amount of cerium-based additive.     

基于热光系数互补的双折射光滤波器

设计出一种基于晶体材料热光系数互补的滤波器结构,以提高双折射光滤波器的温度稳定性。使用LiNbO3对YVO4进行补偿,根据光波两个正交偏振分量间产生恒定相位差的条件,优化晶体波片的厚度比,当温度和波长分别为20℃和1 550nm时,计算出YVO4和LiNbO3波片的最佳厚度比是6.54∶1。实验采用厚度分别为10mm和1.515mm的波片,结果表明温度在20±15℃变化时,双折射滤波器中心波长的最大偏移为0.087 5nm,满足光纤通信应用对波长稳定性的要求。     

Performance evaluation on field synergy and composite regeneration by coupling cerium-based additive and microwave for a diesel particulate filter

In order to reveal the mechanics of composite regeneration by coupling cerium-based additive and microwave for a diesel particulate filter, a composite regeneration model by coupling cerium-based additive and microwave for a diesel particulate filter was established based on field synergy theory. Performance evaluation on field synergy and composite regeneration of the diesel particulate filter was conducted by using the vortex crushing combustion and field synergy mathematical models. The results show that the peak temperature of the particulate filter body reaches 1180-1190 K when the regeneration time is 175 s, and there are optimal coordination degree between the velocity vector and temperature gradient of the filter body and the maximum ratio0.56-0.60 of the best burning regeneration region is obtained. Accordingly, the largest regeneration combustion rate inside the particulate filter body and the highest regeneration efficiency at the moment are achieved.     

一维光子晶体光开关的研究

由掺杂非线性介质的一维光子晶体形成光开关,并利用传输矩阵法对其特性进行了分析。研究发现,该结构可以很好地完成光开关的功能。     

神经元自适应滤波器谐波综合检测虚拟仪器研究

深入研究了基于单个人工神经元的自适应检测原理,建立了利用人工神经网络理论对谐波的检测方法;并以上述所建立的方法为核心,利用虚拟仪器软件开发环境LabVIEW对所接收到的谐波数据加以综合处理,完成谐波检测与分析的功能。     

基于阿尔法均值算法和马氏距离的图像自适应滤波

针对数字图像容易感染噪声的问题,提出一种基于阿尔法均值滤波算法和马氏距离的图像自适应滤波算法。该算法充分结合了阿尔法均值滤波器的优点和马氏距离的特性,首先利用阿尔法均值滤波器确定参考序列,然后计算参考序列与滤波窗口内比较序列之间的马氏距离,并根据距离的大小确定滤波窗口内各像素点的权系数,最后将加权结果作为滤波输出。实验结果表明:该算法对受到高斯噪声、椒盐噪声以及混合噪声感染的图像具有较好的滤波效果,同时可以较好地保持原始图像的细节信息。     

双抽运光子晶体光纤光学参量放大器特性研究

利用光子晶体光纤高非线性和低色散斜率的优良特性,提出了一种利用变换和缩放的四阶切比雪夫多项式计算双抽运光纤参量放大器平坦增益和带宽的方法．利用上述多项式的微小波动性,推导了放大器的增益和带宽表达式,进行了模拟分析,并与色散移位光纤参量放大器进行了比较．仿真结果表明,光子晶体光纤参量放大器具有优良的放大特性,其增益平坦度小于±0.5dB,增益带宽可达80nm．在此基础上,设计了一种新颖的可减小受激拉曼散射影响的双抽运光子晶体光纤参量放大器．     

多层图像叠加处理的低功耗自适应流水线设计

针对多层图像叠加处理技术的特点,提出低功耗自适应流水线及片上缓存架构,支持ITU-R BT.601和ITU-R BT.709标准下RGB和YCbCr格式的4层图像叠加显示.该架构根据各层图像格式,自适应调整流水线及各级逻辑工作状态以提高能效比.采用双向可控环形缓存,减少由于缓存状态导致的流水线停顿,保证流水线顺畅工作.采用像素选择性读取、色度空间转换(CSC)自适应等技术进一步降低功耗.实验结果表明:与其他相关设计相比,提出的流水线架构能够取得较好的处理效率和资源消耗比,在SMIC90工艺下硬件资源代价为136000门,工作频率达到150 MHz,能够满足3路1080p@30帧/s图像的实时叠加处理,最低动态功耗达到0.065mW.     

基于自适应小波去噪法的精密超声波测距方法

超声脉冲飞行时间的精确提取决定了超声测距的精度,因此滤除接收信号中的噪声可有效提高其测距精度。针对传统的去噪方法无法随噪声的变化而自动调整去噪阀值和小波分层数的缺点,提出了一种自适应小波去噪法,通过实时提取接收信号中的噪声特征,自动选择最优的小波参数,有效地提高了接收信号信噪比,从而提高飞行时间提取精度。实验表明,在室内环境条件下测距误差小于0.28mm,可满足大部分工业制造领域的距离测量应用。     

Towards a self-adaptive service-oriented methodology based on extended SOMA

We propose a self-adaptive process (SAP) that maintains the software architecture quality using the MAPE-K standard model. The proposed process can be plugged into various software development processe...     

Rapid satellite-to-site visibility determination based on self-adaptive interpolation technique

Rapid satellite-to-site visibility determination is of great significance to coverage analysis of satellite constellations as well as onboard mission planning of autonomous spacecraft. This paper presents a novel self-adaptive Hermite interpolation technique for rapid satellite-to-site visibility determination. Piecewise cubic curves are utilized to approximate the waveform of the visibility function versus time. The fourth-order derivative is used to control the approximation error and to optimize the time step for interpolation. The rise and set times are analytically obtained from the roots of cubic polynomials. To further increase the computational speed, an interval shrinking strategy is adopted via investigating the geometric relationship between the ground viewing cone and the orbit trajectory. Simulation results show a 98% decrease in computation time over the brute force method. The method is suitable for all orbital types and analytical orbit propagators.     

基于梯度的自适应边缘检测算法研究

对常见的边缘检测算法进行改进,基于梯度提出了一种应用于灰度图像的自适应阈值边缘检测算法.根据边界点像素灰度值的差异,分析模版中的9个像素,计算出像素的梯度幅度和梯度方向;按梯度值的不同将图像分割成若干个区域,计算每个区域的灰度平均值,确定阈值,实现边缘检测.实验表明,该方法检测出的边缘更细、更准确,可以除去虚假的边缘,是一种有效的对灰度图像进行边缘检测的方法.     

自适应Tent混沌搜索的蚁狮优化算法

针对蚁狮算法存在的早熟收敛和不易得到全局最优解等问题,借鉴混沌优化算法,提出了自适应Tent混沌搜索蚁狮算法.该算法首先使用Tent混沌映射初始化种群,然后自适应调整混沌搜索空间得到最优解,改善适应度较差个体,提高种群整体的适应度和寻优效率,同时使用锦标赛策略选择蚁狮个体.最后,利用混沌算子优化蚂蚁随机游走行为,与蚁狮觅食行为形成了全局、局部并行搜索模式.分别使用复杂高维基准函数和航迹规划问题测试算法性能.其中,6个复杂高维基准函数的寻优测试实验表明,对于30维基准函数,该算法经过约0.5秒收敛到最优值;对于50维基准函数,约2秒收敛到最优值.与标准蚁狮算法和其他优化算法相比,该算法具有较好的收敛速度和寻优精度,适合复杂高维函数寻优.航迹规划实验表明,对于包含7个威胁源的空域环境,当搜索维度为10维时,该算法经过0.939秒,迭代30次基本可以达到航迹代价的全局最优值.与标准蚁狮算法相比,能够更加快速准确地得到一条满足要求的航迹,具有实际应用价值.