A wide-band multiport planar power-divider design using matchedsectorial components in radial arrangement

This paper proposes a new multiport planar power-divider design by radially combining the sectorial components and the input and output matching networks. This design can achieve good input match over a wide bandwidth without resorting to transformer sections of high-impedance lines, which are difficult to realize. This approach is applied to the design of 4-and 14-way center-fed power dividers in microstrip structures with good input match (voltage standing-wave ratio (VSWR) <1.5) over a bandwidth of 30% and 15%, respectively. The return loss of output ports and the isolation among them in the 14-way divider are less than -13 dB. A simple analysis method using the radial transmission-line theory to model the microstrip sectorial components is employed to characterize the power dividers. The calculated scattering parameters are found to be in good agreement with the measured data     

Adaptive coding scheme for wireless LANs with CSMA/CA MAC protocol

The generalised type II hybrid automatic repeat-request scheme based on rate-compatible convolutional codes is used to achieve adaptive error protection in wireless local access networks (LANs) with the CSMA/CA protocol. Simulation results show that this coding scheme is a suitable error control method for wireless LANs where the channel state is unpredictable     

On determination of the number of signals in spatially correlatednoise

A method for determining the number of signals in a correlated noise field using two well-separated linear arrays of receivers was given by Zhang and Wong (1993). In this paper, we improve on this method with the use of new penalty functions. Three criteria are given, and it is proved that for a large class of penalty functions, the probability of incorrect detections by each of the new criteria is exponentially decreasing when the moment-generating function of the squared Euclidean norm of the observation vector is finite at some point. It is also proved that with these new criteria, the estimates of the number of signals are strongly consistent. Randomized penalty functions for the three criteria, based on samples, are presented, and their uses are then shown to give consistent estimation of the number of signals. The finite sample behavior of the proposed approaches are studied by Monte Carte simulation     

添加Y2O3的自蔓延高温合成β-Sialon粉的微波烧结

采纳合理的保温结构，利用TE103单模腔微波烧结系统对添加6wt％Y2O3的自蔓延高温合成β-Sialon粉末的微波烧结行为、烧结样品的微观结构和力学性能进行了研究，SEM和TEM、HREM观察表明，烧结样品晶粒细小，微观结构均匀，力学性能测试表明在1600℃保温5min时烧结样品具有抗弯强度为470MPa，断裂韧性为5．0MPa·m－2，洛氏硬度为89．5；在1650℃保温5min时烧结样品具有抗弯强度为630MPa，断裂韧性为5．8MPa·m-2，洛氏硬度为91．6．     

激光实际大气传输湍流效应相位校正一些实验结果

进行了近地面水平大气中激光传输湍流效应及其自适应光学相位校正实验，对光束振幅起伏、到达角起伏及其远场Strehl比进行了测量分析。实验结果表明，光束到达角起伏功率谱在低频段（f＜0．4υ／d）近似地满足-2/3次幂关系，而在高频段（f＞0．4υ／d）则近似满足-8／3次幂关系。在较弱湍流效应情况下时数振幅起伏方差小于0．3），相位补偿是有效的，而在较强湍流效应树数振福起伏饱和）时，自适应光学系统常常不能实现稳定闭环。由于传输场景地形复杂，湍流效应及其相位校正效果定量规律的描述还需进一步研究。     

聚焦光束稳态热晕补偿实验

进行了聚焦光束稳态热晕效应及自适应光学补偿的室内模拟实验观测，获得了在不同热畸变参数情况下，自适应光学系统开闭环时光束远场Strehl比和信标光波前方差的测量结果。测量结果表明自适应光学对聚焦光束整束热晕的补偿效果是显著的。在热畸变参数Nd大于170时，校正剩余波前大差呈非线性增长。在热畸变参数N_d与光束菲涅耳数N_f的比值大于1时，校正后的远场光斑峰值强度随入射功率的增加开始呈下降趋势。     

Flash存储器技术与应用

本文主要介绍了Ｆｌａｓｈ存储器的特性及其存储技术，并探讨了Ｆｌａｓｈ存储器的应用领域。     

低气压下制备金刚石薄膜的研究

利用我们自己研制的磁约束直流等离子体设备，在低气压（＜１Ｔｏｒｒ）下。用Ａｒ＋Ｈ２＋ＣＨ４的混合气体在基片上进行了沉积金刚石薄膜的工艺研究。利用扫描电镜和拉曼光谱对不同的进气方式所制备出的金刚石薄膜的形貌和质量进行了比较。结果表明。当在基片表面附近引入碳源气体和大约５０％氢气时，可以大大提高薄膜质量。     

同轴环形螺旋谐振腔设计分析

提出了一种适用于同轴环形放电结构气体激光器的环形螺旋谐振腔,并给出了理论分析。该谐振腔由一螺旋面反射镜和一球面反射镜构成,可充分提取激活区的能量并输出单束激光。该结构易于实现同轴环形放电激活区中的功率萃取。     

WDM光传输系统2.5Gbit／s光发送模块研究

本文介绍了作者设计，调试的２．５Ｇｂｉｔ／ｓ光发送模块的工作原理、关键技术、典型性能参数，该模块通过控制激光器温度来稳定其中心波长，为波分复用系统的应用提供了具备稳定中心波长特性的光源。