楔形光纤探针传输效率的研究

用实验方法测量了楔形光纤探针的传输效率随光纤楔角的变化关系,作出传输效率曲线,通过测定楔形光纤探针传输效率的实验可知,楔体角度越大,过渡区越短,泄漏光就越少,传输效率会提高.在楔角由20.2° 增大到33.6°以及楔角由55.8°增大到83.6°时,传输效率曲线呈较快的上升趋势;在楔角由33.6° 增大到55.8°,传输效率曲线上升趋势较缓.在相同的条件下,楔形光纤探针的传输效率随入射光波长的增大而快速地下降.     

基于空时联合约束的机载雷达STAP单脉冲角度估计方法

对现有STAP(Space-Time Adaptive Processing)单脉冲角度估计方法存在单脉冲比失真及目标多普勒失配时角度估计性能严重下降的问题,本文从数学上分析了常规STAP单脉冲方法的失效机理,并基于机载雷达杂波的空时耦合特性,将差波束约束条件扩展到空时二维空间,提出了基于空时联合约束的STAP单脉冲角度估计方法,将单脉冲曲线延伸为单脉冲曲面,通过空时联合约束显著提高了目标角度估计的精度和稳健性.计算机仿真结果验证了本文方法的有效性.     

雷达模拟器与雷达的接口电路设计

提高雷达模拟器生成回波信号的真实性和可靠性,需要实时采集一些重要的雷达工作状态参数,如雷达工作时的天线方位角和高低角信号、主脉冲信号、锥扫基准信号和载波频率信号等。这些信号分别为模拟回波信号的生成提供了天线增益大小、时间基准、相位基准和载波频率大小等重要的参考信息。通过对这些信号性能参数的分析和研究,提出模拟器与雷达系统接口电路设计方案。雷达实验可以证明该设计性能稳定、可靠、成本较低,很好地实现了接口电路的功能要求。     

半导体激光器单管准直实验研究

利用高斯光束的ABCD传输矩阵理论分析了LD与自聚焦透镜之间的距离与出射光束远场光斑尺寸之间的关系.通过理论计算可以方便地得到最佳距离,获得较高亮度输出,并进行了实验验证.对平面自聚焦透镜、球面自聚焦透镜和圆柱透镜的准直效果进行了实验比较,最后将自聚焦透镜与LD固定,制做了实用的器件,该器件可以将LD椭圆形光斑转变成线形光斑,快轴、慢轴远场发散角分别为0.1°和2.50°耦合效率86%.     

Surface modification of silicon by laser surface treatment: Improvement of adhesion and copper deposition

We have studied the use of lasers for modifying the surface properties of silicon to improve its wettability and adhesion characteristics. Using a 4th harmonic Nd:YAG (λ = 266 nm, pulse) laser, the wettability and adhesion characteristics of the silicon surfaces have been enhanced by laser irradiation. It was found that laser surface treatment of silicon modified the surface energy. By the contact angle measurement, using distilled water, the wetting characteristics of silicon after the laser irradiation show a decrease in the contact angle and a change in the surface chemical composition. In the case of the laser-treated silicon surface, laser direct writing of copper lines has been achieved through pyrolytic decomposition of copper formate by using a focused Ar⁺ laser beam (λ = 514.5 nm, continuous wave (CW)) on the silicon substrates. The deposited lines and surface chemical compositions were measured by energy dispersive x-ray (EDX), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and surface profiler (Alpha Step 500, San Jose, CA) to examine the cross section of deposited copper lines.     

空间交会激光雷达信息测量技术

为了测量目标飞行器的位置及速度等信息,提出采用模拟插入脉冲计数法测距,最小二乘曲线拟合微分法测速,四象限(QD)光斑定位法测角。并在MATLAB/SIMULINK环境下,对采用该方法的脉冲激光雷达信息测量系统进行了计算机仿真。结果表明,距离测量精度高,误差小于0.01m,速度精度也高,误差小于0.02m/s。采用该测量技术的脉冲激光雷达是可靠的。     

基于深度神经网络的自适应波束形成算法

阵列天线接收到的期望信号和干扰信号,其入射的到达角度(Angle of Arrival,AOA)总是快速变化的,而传统波束形成算法计算量大,无法实时计算。针对这一问题,提出了一种基于深度神经网络的自适应波束形成(Deep Neural Network Adaptive Beamforming,DNNABF)算法,用入射信号AOA组成的向量作为网络输入,网络输出逼近最小方差无失真响应(Minimum Variance Distortionless Response,MVDR)算法求得的权矢量。仿真结果表明,卷积神经网络(Convolutional Neural Network,CNN)与DNNABF方法都能准确拟合MVDR算法权矢量,可在入射信号AOA快速变化时自适应地形成波束和零陷,但DNN计算速度相对MVDR有将近6.5倍的提升,训练模型时间也远低于CNN。     

基于霍夫变换和相位相关的图像配准方法

本文结合霍夫变换和相位相关技术来处理图像配准问题.根据1D相位相关技术,提出了一种通过搜索角度脊来得到旋转参数的方法;将待处理图像去旋转后,再采用2D相位相关来得到平移参数.本文方法可以充分利用FFT 的高效运算.实验结果表明此方法能准确有效地处理具有旋转和平移的图像配准问题.     

Novel angle estimation for bistatic MIMO radar using an improved MUSIC

In this article, we study the problem of angle estimation for bistatic multiple-input multiple-output (MIMO) radar and propose an improved multiple signal classification (MUSIC) algorithm for joint direction of departure (DOD) and direction of arrival (DOA) estimation. The proposed algorithm obtains initial estimations of angles obtained from the signal subspace and uses the local one-dimensional peak searches to achieve the joint estimations of DOD and DOA. The angle estimation performance of the proposed algorithm is better than that of estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm, and is almost the same as that of two-dimensional MUSIC. Furthermore, the proposed algorithm can be suitable for irregular array geometry, obtain automatically paired DOD and DOA estimations, and avoid two-dimensional peak searching. The simulation results verify the effectiveness and improvement of the algorithm.     

Wollaston棱镜分束角的光谱特性

提要:为了了解Wollaston棱镜分束角随入射光波长的变化规律,我们对其分束角的光谱特性从理论上进行了分析,并进行了实验测试,结果表明:入射光波长对Wollaston棱镜的分束角有一定的影响,其规律为:棱镜的结构角越大,入射光波长对分束角的影响越大:紫外光谱区的影响大于可见和红外光谱区。对于Wollaston棱镜分束角的对称性,其特点为:棱镜结构角越大,入射光波长越短,对称性越差。