一种无线局域网传输短消息的加密算法

对于目前局域网中短消息加密算法的安全性漏洞,采用一种经典的加密算法,即Playfair加密法与RC4相结合的算法,为无线局域网络中短消息的传递提供了一种可靠的加密方法。运用该复合的加密算法可以有效地避免RC4密钥的静态安全性问题,还能避免密钥被窃取而导致的加密算法被破解。     

认知无线电系统中基于量子粒子群算法的PHY层及MAC层决策优化

认知无线电技术是下一代通信发展的方向和趋势,同时也是目前通信研究中的热点问题。针对认知无线电系统中,在某一信道条件下其通信系统的物理层（PHY）和媒体链路层（MAC）的基于多个目标来实现优化的问题,基于量子粒子群算法的基本思想,把量子粒子群算法引入认知无线电系统中,并对该算法进行适当的改进,最后基于WSGA控制对电台优化问题进行了仿真,通过仿真证明了其有效性。     

负载牵引法在开关类功率放大器设计中的应用

为提高开关类功率放大器设计的准确性,找出功放管的最优输出阻抗值,采用负载牵引法设计开关类功率放大器,得到最佳输出阻抗值,然后设计输出及输入匹配网络及谐波抑制网络,仿真结果输入功率为28dBm时,功率附加效率达到69．352％,表明功率负载牵引方法为改进开关类放大器设计,优化开关类功放管性能提供了快速而有效的方法,提高了大信号下模型的准确性。     

利用空域滤波虚光栅叠栅法提取干涉图波面

虚光栅叠栅条纹法是一种利用单幅干涉图提取波面信息的方法,为了解决叠栅条纹的滤波问题,提出了一种基于高斯函数的空域滤波法。利用高斯函数在空域中对叠栅条纹图进行模糊处理,滤除不需要的高频分量,仅保留包含波面相位信息的低频分量。重点研究了高斯函数滤波窗口的选择和干涉图的载频之间的对应关系。该方法具有计算量小、易于选取滤波窗口的优点。对一光学平面的面形测量结果表明,利用空域滤波虚光栅叠栅法提取的波面[峰谷(PV)值为0.080λ,均方根(RMS)值为0.020λ,λ=632.8nm]与利用Zygo GPI干涉仪的四步移相法得到的波面(PV值为0.079λ,RMS值为0.017λ)相吻合。     

Investigation of X-ray fluorescence computed tomography (XFCT) and K-edge imaging

This work provides a comprehensive Monte Carlo study of X-ray fluorescence computed tomography (XFCT) and K-edge imaging system, including the system design, the influence of various imaging components, the sensitivity and resolution under various conditions. We modified the widely used EGSnrc/DOSXYZnrc code to simulate XFCT images of two acrylic phantoms loaded with various concentrations of gold nanoparticles and Cisplatin for a number of XFCT geometries. In particular, reconstructed signal as a function of the width of the detector ring, its angular coverage and energy resolution were studied. We found that XFCT imaging sensitivity of the modeled systems consisting of a conventional X-ray tube and a full 2-cm-wide energy-resolving detector ring was 0.061% and 0.042% for gold nanoparticles and Cisplatin, respectively, for a dose of ～ 10 cGy. Contrast-to-noise ratio (CNR) of XFCT images of the simulated acrylic phantoms was higher than that of transmission K-edge images for contrast concentrations below 0.4%.     

ADC Multi-Site Test Based on a Pre-test with Digital Input Stimulus

This paper describes two novel algorithms based on the time-modulo reconstruction method intended for detection of the parametric faults in analogue-to-digital converters (ADC). In both algorithms, a pulse signal, in its slightly adapted form to allow sufficient time for converter settling, is taken as the test stimulus relieving the burden placed on the accuracy requirement of the excitation source. Instead of calculating the accurate conventional dynamic and static parameters, a signature result is obtained through the analysis of the output data in the time domain. The basic concept of the algorithms is the evaluation on the performance of ADCs by the comparison of the similarity of the output waveforms. The multi-site test is expensive for traditional specification-based tests of ADCs, as high quality analogue data generators are required. Based on these two algorithms, this paper proposes a solution for this problem. The objective of the test scheme is not to completely replace traditional specification-based tests, but to provide a reliable method for early identification of excessive parameter variations in production test that allows quickly discarding of most of the faulty circuits before performing a conventional test. The efficiency of the methods is validated on an industrial 12-bit pipelined ADC both in simulations and in measurements.     

啁啾超高斯脉冲半导体激光器频谱的补偿修正研究

利用一段色散位移光纤(DSF)对半导体激光器产生的皮秒啁啾超高斯脉冲的频谱补偿修正,获得了较好的修正结果。适当的压缩脉冲频谱可以减小码间干扰,防止频谱因过度展宽而导致信号脉冲失真,从而在一定程度上有利于超高斯脉冲的稳定传输,提高光纤系统的传输距离。研究时,采用对称分步傅里叶法(SSFM),数值模拟了初始啁啾为-3,初始脉宽为10ps,峰值功率为30W的啁啾超高斯脉冲,在DSF中传输时消啁啾的频谱演变过程。模拟结果表明,利用长度为0.5m的DSF可以在最大程度上消除该初始脉冲的“红移”啁啾。     

一种基于Femto的GSM网关设计与实现

GSM网络用户众多,在GSM接入网中引入Femto架构,符合移动通信网络扁平化发展趋势。在此研究基于Femto架构的GSM网关,作为用户端数据接入核心网的接口,将移动、宽带和固定业务融合在一起,在GSM网络中将发挥重要的作用。采用IP化承栽方式,Abis接口完全IP化,用模块化设计方法,基于Femto架构,在ATCA的平台上设计实现了具有信令处理、数据转换、编码转换及速率适配、路由等4功能的GSM网关,通过该网关已打通电话,语音质量达到商用,具有重要的实际应用价值。     

多路UART总线与CAN总线通讯系统设计

主要利用TI公司的多路异步收发器,TLl6C554和PHILIPS公司的SJAl000设计一个多路总线协议转换通讯系统。为了实现4路UART总线与CAN总线之间的相互转换过程,采用微控制器AT89S51来控制通讯数据转换,通过硬件电路实验和软件调试算法,得到了4路串行总线与CAN总线之间的相互透明转换过程。该电路系统大大方便了具有UART接13的设备进行远距离、多节点传输,增强了系统的通讯可靠性。     

四边形单端带电线路开关的导电回路电阻测试

介绍了福建水口发电集团有限公司的500 kV升压站,采用特殊四边形接线方式,共安装有4台高压开关,由于在高负荷用电环境下,无法全站停电检修,多数情况是单条线路停电,开关一端带电、致使开关不能正常进行预防性试验。而采用新型的测试计算法,检测HGIS内部开关及刀闸的接触电阻,便于和出厂数据进行对比。既确保了试验过程中设备和检修人员的人身安全,也缩短了线路停役时间,提高了社会效益。在当前新的用电环境下具有一定的推广意义。