Data/pilot combination strategies for Compass B1C signal acquisition

The new Compass B1C signal, with a power ratio of the data channel to the pilot channel of 1:3, adopts BOC(1,1) in its data channel; a new modulation, namely, a quadrature multiplexed binary offset carrier (QMBOC) in its pilot channel modulates the narrowband BOC(1,1) and the wideband BOC(6,1) components in phase quadrature with each other. To fully exploit the B1C signal and to improve the acquisition sensitivity in a degraded signal or an indoor environment, this paper proposes to combine the data and the pilot channels for B1C signal acquisition. The noncoherent, coherent, and differential coherent strategies are considered for application in the B1C signal. Considering the power inequality between the data and the pilot channels, the maximum signal‐to‐noise ratio combination (MRC) is utilized in these strategies to obtain an optimal combination. This paper also proposes to simplify the differential coherent strategy to obtain a better anti‐noise performance under stable conditions. The computer simulation results are given to verify the theoretical expressions, and some discussions with respect to the proposed strategies are provided.     

耳蜗透射电镜超薄切片样品的制备技术改进

针对耳蜗组织透射电镜样品制备难度大,不易获得质量较好的超薄切片的问题,作者通过延长锇酸后固定时间和增加树脂渗透的浓度,改善了树脂包埋组织的切割性能.电镜图片显示,明显地提高了超微切片样品制备质量.     

一种基于时间透镜的10Gb/s无色散补偿高速光纤通信系统

基于光波时空二元性理论,研究了时间透镜和光脉冲在色散介质中传输的原理,提出了一种利用光脉冲频谱包络来传输光信号的方法:利用光脉冲的频谱包络在色散介质中保持不变的原理,在发射端用基于时间透镜的全光傅里叶逆变换器件将光脉冲的频谱包络转换到时域进行表示,从而得到新的传输符号;在接收端用基于时间透镜的全光傅里叶变换器件将原始光脉冲序列恢复。该传输系统可以消除色度色散、偏振模色散、时间抖动等线性畸变对光脉冲的影响。给出了全光傅里叶变换/逆变换器件的具体实现方法和10 Gb/s-200 km无预啁啾、无任何色散补偿的传输实验,验证了该方案的正确性与可行性,为高速光纤通信提供了一种新的方案。     

一种8.75-11.2 GHz适用于802.11a/b/g零中频收发机系统低噪声分数频率综合器

介绍了一种适用于802.11a/b/g零中频接收机的超宽带分数频率综合器。文章详细推导了分数频率综合器相位噪声和杂散的数学模型,并给出了降低噪声和杂散的优化方法。实验结果表明,输出频率二分频后,在4.375GHz时积分噪声低于1度（1kHz 到100MHz);参考频率33-MHz处杂散低于-60dBc。芯片基于标准0.13微米RF CMOS工艺,电路工作电压1.2V,功耗39.6mW。     

基于改进小波包分析的导航设备故障诊断的特征提取

针对故障诊断信号特征提取问题,提出了小波包分析的改进算法,该算法通过对小波包分解系数的重新排序,解决了小波包分析的频带混叠问题,给出了应用改进小波包分析进行故障诊断特征提取的算法,并在此基础上提出了基于改进小波包分析预处理的神经网络故障字典法．通过仿真比较,该方法剔除了样本信号的冗余成分,大幅度地减少了神经网络的规模,加快了网络的收敛速度,为导航设备故障诊断的特征提取提供了行之有效的手段。     

虚拟仪器在教学中的应用

主要介绍了Multisim2001中虚拟仪器库中函数发生器、示波器的使用方法及功能；并在Multisim2001环境中仿真单管放大电路、桥式整流滤波电路。由调试结果，分析了其在教学中应用的可行性。     

Flash环境下虚拟校园浏览系统的设计

系统以虚拟校园为研究对象,用Flash制作矢量化二维电子地图,并用Cool 360及PhotoShop制作全景三维图像,来实现校园的浏览.该系统是基于浏览器/服务器模式的,用户通过Web浏览器登录到系统的界面,可以实现网络上的校园地理环境平面漫游和空间浏览.     

一种测量机载箔条云RCS时间特性的新方法

针对目前国内外场测量机载箔条云RCS时,在载机弹出箔条弹至箔条云充分展开这段时间内,测量设备无法将飞机的回波与箔条云的回波进行有效分离,导致测量精度不高的问题.文中在总结已有的国内外对机载箔条云RCS测量方法的基础上,根据雷达多普勒效应,速度不同的目标,在频谱中产生不同频移原理,提出了在外场测量机载箔条云RCS的新方法--频谱法.仿真结果说明,此方法可以更精确地测量机载箔条云的RCS时间特性.     

Three-level LLC series resonant DC/DC converter

Paper presents a three-level soft switching LLC series resonant dc/dc converter. Zero-voltage switching (ZVS) is achieved for each main switch without any auxiliary circuit. Voltage stress of each main switch is half of input voltage. Zero-current-switching (ZCS) is achieved for rectifier diodes. Wide input/output range can be achieved under low frequency range because of two-stage resonance. Only one magnetic component is required in this converter. Efficiency is higher in high line input, so this converter is a preferable candidate for power products with the requirement of hold up time. For design convenience, relationship between dc gain and switching frequency, load resistance is deduced. Its open load characteristic and short load characteristic are exposed to provide theory basis for no load operation and over current protection. Design consideration of four dead times is presented to assure that voltage stress for main switches is within half of input voltage and ZVS for each main switch is achieved. Finally the principle of operation and the characteristics of the presented converter are verified on a 500V-700V input 54V/10A output experimental prototype, whose efficiency reaches 94.7% under rating condition.     

Development of CRT＇s corner cutting repair systems

CRT Corner cutting tube is considered as a definitive reject and will be sent to reclaim at all times. It caused lots of material loss. In this paper, a novel technology used to save CRTs corner cutting tube is presented firstly. A set of repair system has been successfully developed to repair CRTs corner cutting tube. Then, the process technology for corner cutting repair has been excogitated by empirical studies. Finally, the correlative performances of repaired tube are evaluated. The experimental results show that the quality of repaired tube has no difference with that of normal product. The repair yield has reached above 97 percent. This new technology has contributed to improving the production yield, reducing the material consumption and decreasing the cost of color CRT production.