用于音乐作品版权保护的数字音频水印算法

提出了一种用于音乐作品版权保护的数字音频水印嵌入算法，该算法首先将视觉可辨的二值水印图像降维成一维水印序列并进行随机置乱，再从原始数字音频信号中随机选取采样数据并进行快速傅立叶变换(FFT)，最后结合人类听觉系统(HAS)掩蔽特性选取绝对值较大的FFT系数嵌入水印信息。仿真实验表明：该数字音频水印嵌入算法不仅具有较好的透明性，而且对诸如叠加噪声、有损压缩、低通滤波、重新采样、重新量化等攻击均具有较好的鲁棒性。     

An FFT-based signal identification approach for obtaining the propagation constants of the leaky modes in layered media

We propose to find the propagation constants of modes in layered media by means of signal identification methods. To this effect we employ Cauchy's theorem, conformal mapping and Fast Fourier Transform (FFT) techniques to generate relevant Hankel moments, afterwards to be processed with selected signal identification algorithms. The method, terminated by a few Newton steps, provides a batch of highly accurate roots in appropriate disks or half-disks.     

Low threshold and tunable all-optical switch using two-photon absorption in array of nonlinear ring resonators coupled to MZI

In this paper a novel structure based on Mach-Zehnder Interferometer (MZI) and an array of nonlinear ring resonators for all-optical switching including very low threshold, fast and all-optically tunable is presented. In this proposal, an array including N ring resonators is coupled to one arm of MZI to introduce the required nonlinear phase shift to switching. Also, two-photon absorption phenomenon is used and will be proposed as another alternative for manipulation of optical switching properties. The proposed idea needs small chip area (∝1/Ntraditional cases) for implementation. We show that the switching threshold intensity can be decreased with increase of N, decrease of the coupling coefficient and increase of the two-photon absorption coefficient. In this structure with traditional optical fibers with the low nonlinear index of refractions and using an array including 15 ring resonators with 6 mm diameter for each rings only 3 mW for the switching threshold power is required. Also, using erbium-doped fiber for implementation of the rings with the high nonlinear index of refractions and five ring resonators including 0.3 mm diameter, the switching threshold power can be reduced to μW level. If the nonzero two-photon absorption coefficient is considered, the switching threshold will be very smaller than the above-mentioned values. We show that with changing the optical amplifier gain the switching threshold can be tuned. So, the proposal can be used as a functional block for the integrated optical switch with very small and tunable threshold.     

基于FPGA的简易频谱分析仪

观测信号频谱在科研中具有重大意义,在教学实验中也有利于学生更直观深入地了解信号特征。采用单片机C8051和FPGA,外加高速A／D转换器设计一种简易的频谱分析仪。该系统主要包括信号采集、频谱搬移、数字滤波、数字FFT和LCD显示。经测试,该系统能够分析信号带宽为0～5MHz,最低分辨率达到1Hz。而且信号频谱图能够很好地显示在LCD上。整个系统工作稳定,操作方便,且成本比其他频谱分析仪低很多。     

EV-DO Rev A快速寻呼接入研究

DO Rev A在前向链路采用多种包传输格式、子同步控制信道（SSCC）、动态寻呼周期等关键技术实现了前向快速寻呼;在反向链路采用高速接入信道、短接入包前导等关键技术实现了反向快速接入,从而改善了对时延敏感业务的支持。DO Rev A通过DOS协议实现了在控制信道和接入信道传送用户数据,从而支持PTT业务。本文介绍了DO Rev A上述关键技术,并分析它们对用户接入和寻呼的性能影响。     

一种任意窗函数的复数调制重叠变换的快速算法

该文提出了一种任意窗函数的复数调制重叠变换(MCLT)的快速计算方法。针对输入信号长度为2M 的MCLT,该算法将其转化为长度为2M的II型离散 Hartley 变换,然后对后者运用快速算法。与现有算法相比,该方法能够达到最少的算术运算量。     

快速轴流CO_2激光器

本文报道我们设计的快速轴流ＣＯ_２激光器和实验结果,激光器的光学谐振腔为三折Ｚ形折叠半共焦腔,输出耦合镜为ＧａＡｓ材料,透过率为７２％的,得到最大输出功率２５３０Ｗ,电光转换效率最高达到２４％。     

轧机主传动快熔的作用、选型原则及失效对策

绝缘栅双极晶体管IGBT兼有功率三极管（GTR）和场效应管（MOSFET）的优点,在电子技术、电气传动、开关电源等场合有着广泛的应用。实际使用时,由于装置设计和应用时的意外原因,IGBT可能发生短路,急剧增大的集电极电流将造成器件永久性破坏。IGBT过电流的能力极差,快熔很难起到保护作用,因此现代IGBT模块内部一般都...