用于噪声抑制的碘分子滤波瑞利散射技术研究

为了解决激光瑞利散射技术诊断燃烧场时存在的米散射和背景杂散光干扰问题,发展了基于碘分子超精细吸收凹陷的滤波技术。介绍了分子滤波的原理和碘分子的吸收光谱,设计了用于产生稳定数密度的碘分子滤波器,并采用种子注入、可调谐Nd：YAG激光器测量了碘分子的吸收谱。采用碘分子滤波器,在稳态燃烧场和瞬态燃烧场上分别进行了结构诊断的滤波瑞利散射实验,获得了清晰的燃烧场结构图像。实验表明碘分子滤波器能够有效抑制532nm激光瑞利散射实验中的米散射和背景杂散光,提高信号图像的清晰度。     

Equivalent circuit analysis of terahertz metamaterial filters

An equivalent circuit model for the analysis and design of terahertz (THz) metamaterial filters is presented.The proposed model,derived based on LMC equivalent circuits,takes into account the detailed geometrical parameters and the presence of a dielectric substrate with the existing analytic expressions for self-inductance,mutual inductance,and capacitance.The model is in good agreement with the experimental measurements and full-wave simulations.Exploiting the circuit model has made it possible to predict accurately the resonance frequency of the proposed structures and thus,quick and accurate process of designing THz device from artificial metamaterials is offered.     

10 Gb/s symmetric WDM-PON using stable multi-longitudinal mode Brillouin/SOA fiber laser as upstream colorless source

We propose a stable multi-longitudinal Brillouin/semiconductor fiber laser(BSFL) as the upstream source in a bidirectional single-fiber wavelength-division multiplexing-passive optical network(WDM-PON).The downstream wavelength serves as the pump of the BSFL.Brillouin-frequency-shifted(～10.8 GHz) upstream carrier is generated to suppress the Rayleigh backscattering and back reflection-induced crosstalk.The stable multi-longitudinal operation of the BSFL,attributed to the four-wave mixing(FWM) effect in the semiconductor optical amplifier(SOA) reduces the difficulty of generating a stable single-longitudinal fiber laser-based upstream carrier.Bidirectional symmetric transmission at 10 Gb/s over a 12.5-km single mode fiber with less than 2-dB power penalty is demonstrated.     

一种基于简化左右手复合传输线的带通滤波器

根据等效介质理论和Bloch-Floquet理论,研究了简化左右手复合传输线(SCRLH TL:Simplified Composite Right/Left Handed Transmission Line)的等效介质参量(ε,μ)、等效折射率(n)和传播参量(γB,ZB)的频响特性;设计、制作了中心频率约为7.49...     

细胞神经网络环境下偏微分方程的求解

在探索细胞神经网络新的应用时，由于低端硬件模拟非常昂贵，不可避免要使用行为仿真器．基于波数字滤波原理，本文提出了细胞神经网络的一个数字模型．将此模型用于求解泊松方程，取得满意结果．在所提的方案中，方程的解信息来自细胞的状态而非输出     

三元双正交小波滤波器的刻画

研究由三元双正交插值尺度函数构造对应的双正交小波滤波器的矩阵扩充问题.当给定的一对三元双正交尺度函数中有一个为插值函数时,利用提升思想与矩阵多相分解方法,给出一类三元双正交小波滤波器的显示构造公式和一个计算实例.讨论了三元双正交小波包的的性质.     

Compact waveguide bandpass f ilter employing two-dimensional metallic photonic crystals for millimeter to terahertz frequencies

Two-dimensional metallic photonic crystal slabs with square lattice are proposed to be used for the design of waveguide bandpass filters operating in millimeter to terahertz region. Filter characteristics are studied when rod radii and lattice constants are changed. Based on the frequency scaling technique, a series of higher frequency filters has been designed. By using laser drilling and welding processing techniques, a compact waveguide filter embedded in an EIA-WR10 waveguide with central frequency 145.5 GHz and 3-dB bandwidth of 5.26 GHz is fabricated and measured. The measurement data agree well with the simulation prediction.     

10G/40G无载波幅度相位调制系统性能研究

无载波幅度相位调制(Carrierless Amplitude and Phase,CAP)是超高速短距离光通信系统中的一种备选的方案,由于其成本低、频谱效率高、功耗小等优点,近年来越来越受到研究人员的关注。基于MATLAB与VPI联合仿真,探究10G/40G速率CAP系统中关键参数对系统性能的影响,包括数字滤波器滚降系数、滤波器抽头数,通过仿真找出最优系统参数值,同时对时钟偏移带来的影响也做了研究,以期为以后设计短距离CAP光通信系统有所帮助。     

纸币图像Gabor特征提取与识别

研究了基于Gabor滤波器组的人民币图像识别方法。针对纸币图像特点,设计了适合于其特征提取的Gabor滤波器组参数,得到了纸币图像多尺度多方向上的纹理特征,然后对纹理图像进行网格划分,并计算网格中像素灰度均值行列投影和,最后采用网格投影特征模板匹配法进行纸币识别。实验表明该法抗干扰能力较强,能够较大提高旧币和污染纸币识别率,并且耗时不长。     

全光式QEPAS系统光声信号检测方法研究

为了提高全光式石英增强型光声光谱(QEPAS)珐珀解调系统的微弱信号检测能力,设计了一种基于MAX274的有源带通滤波电路和基于AD620的前置放大电路对信号进行预处理,同时利用LabVIEW设计了正交矢量型数字锁相技术的信号处理模块。实验结果表明,该方法能从强背景噪声中获得比较微弱的光声信号,在常温常压下对空气中的水汽含量进行探测,得到其归一化噪声等效吸收系数为1.37×10-6 cm-1 W/Hz1/2。该方法具有结构简单、价格低廉、便于操作和控制、实用性强等特点。