用于空间聚光结构的折展机构设计与分析

针对空间太阳能电站大口径聚光结构的应用需求与运载条件相矛盾的情况,以离轴式聚光系统为研究基础,设计了一种具有折叠展开功能的次镜支撑机构。机构采用三关节串联结构为主,两组平行四杆机构为辅,可实现水平、竖直的两次展开,并能保证次镜组件在展开过程中始终保持平动状态。通过建立机构折展的运动学方程,对机构的工作空间进行了求解,规划了展开方案;对机构展开的位置、姿态精度进行了研究,分析了展开精度对机构各结构参数的敏感度;最后,在ADAMS软件中建立了折展机构的虚拟样机,对展开过程进行了仿真,验证了机构设计的正确性与合理性。     

Cross‐Layer Resource Allocation Scheme for WLANs with Multipacket Reception

Tailored for wireless local area networks, the present paper proposes a cross‐layer resource allocation scheme for multiple‐input multiple‐output orthogonal frequency‐division multiplexing systems. Our cross‐layer resource allocation scheme consists of three stages. Firstly, the condition of sharing the subchannel by more than one user is studied. Secondly, the subchannel allocation policy which depends on the data packets’ lengths and the admissible combination of users per subchannel is proposed. Finally, the bits and corresponding power are allocated to users based on a greedy algorithm and the data packets’ lengths. The analysis and simulation results demonstrate that our proposed scheme not only achieves significant improvement in system throughput and average packet delay compared with conventional schemes but also has low computational complexity.     

A novel simplified tone reservation combined with cross antenna rotation and inversion to reduce PAPR for MIMO‐OFDM system

In this paper, we first propose a simplified tone reservation (STR) method with low computational complexity which is based on the Fourier series expansion. Then, we analyze how to combine the STR method with the cross antenna rotation and inversion method to reduce the peak‐to‐average power ratio (PAPR) for multi‐input multi‐output orthogonal frequency division multiplexing (MIMO‐OFDM) system. To validate the analytical results, extensive simulations are conducted and the numerical results show the efficiency of the proposed schemes including the PAPR reduction and low computational complexity for MIMO‐OFDM system. Copyright © 2010 John Wiley & Sons, Ltd.     

宽带雷达微弱目标信号的积累方法

利用长时间信号积累来提高信噪比（SNR）是微弱目标检测的一种常规方法。针对宽带雷达目标运动引起跨距离单元走动以及目标回波能量分散而无法有效积累问题,通过对宽带雷达目标模型与回波特性的分析,利用相邻脉冲重复周期目标一维像的相似性,提出了一种基于互相关技术的多周期回波信号的频域积累方法。仿真结果表明,该方法适用于低信噪比下的信号提取,为宽带雷达微弱目标检测提供一种有效的积累方法。     

Performance of ATM traffic in optical CDMA

An ATM transit switch is proposed based on direct sequence optical code division multiple access technique. No buffering is necessary to facilitate the switching. Code conversion is used instead to emulate the switching function. The switch not only provides asynchronous access to the users but also has a limited capability of dynamic bandwidth allocation. It is free from timing jitters and switching delay is significantly reduced. A look‐up table is employed in the switching and updated through network management functions. The switch provides a new approach to asynchronous cross‐connection in the ATM core network. The performance of the new switch is evaluated by a set of prime codes and modified prime codes. Copyright © 2001 John Wiley & Sons, Ltd.     

GDB RSP协议与USB通信在嵌入式调试系统中的应用

对于嵌入式系统开发来说,远程调试器非常重要,而GDB RSP协议与USB通信一般在嵌入式调试系统中占有重要位置。文章在研究GDB RSP协议与USB通信的基础上,针对ZW100 DSP处理器的体系架构,给出了一种基于RSP命令交互与USB数据通信实现硬件仿真器与PC端调试软件进行调试信息交互的开发与实现方法。该设计实现了GDB通过硬件仿真器下载程序到目标板进行开发调试的功能,使得开发简洁便利,缩短了研发周期。     

双向对称WDM光网络中光交叉连接器复杂度的降低

随着波分复用波长数量的增多及传输容量的快速增长 ,光交叉连接器的端口数目也相应地增加。利用低维光交叉连接器构建高复杂度的光交叉连接器 ,具有很大实用价值。文中针对波分复用传输系统中的双向对称系统 ,提出了一种降低 N× N光交叉连接器复杂度的方案 ,能实现完全连接的可重构无阻塞交换 ,与传统的 Benes交换模型相比 ,更为经济有效     

基于衬底注入技术的交叉耦合式QVCO设计

提出了一种基于衬底注入技术的正交压控振荡器(QVCO)。此QVCO的实现是基于两个电感电容压控振荡器的耦合作用,并没有任何额外的耦合器件。在相位噪声、正交相位误差、调谐范围以及功耗方面,对所提出的QVCO与传统的QVCO进行了比较。仿真表明:该QVCO在4.1 GHz处取得了0.62°的正交相位误差,采用标准的0.13 μm 互补金属氧化物半导体(CMOS)工艺对该QVCO进行流片实现,芯片面积为0.51 mm×0.87 mm。测试结果表明:在3.95 GHz处的相位误差为-118.5 dBc/ Hz@1 MHz,在0.5 V 电源电压供电下,消耗的功耗为0.41 mW,适用于低功耗需求场合。     

基于方位向互相干因子的建筑物布局成像

针对超宽带MIMO穿墙雷达建筑物布局成像中墙体位置偏移以及稀疏阵列引起的旁瓣和栅瓣问题,利用方位向上距离向轮廓在主瓣周围相似而在旁瓣/栅瓣周围不同的特性,提出一种基于方位向互相干因子加权的建筑物布局成像方法。首先计算方位向互相干因子,加权消除图像的旁瓣/栅瓣;然后结合Hough变换检测墙体位置并计算未知墙体的厚度,分别按墙体位置和墙体厚度划分子图像和补偿时延,获得墙体位置校正后的子图像;最后融合子图像得到最终的建筑物布局成像。仿真实验和实测数据处理结果表明,该方法在抑制旁瓣/栅瓣的同时也校正了墙体位置并实现聚焦成像。     

一种基于等效间距法的低散射阵列设计

针对阵列天线在某些角域出现强散射的现象,提出了一种等效间距法并分析了强散射点的产生机理,给出了抑制散射峰值同时满足辐射要求的最佳折中阵列间距确定准则。运用该方法对8单元贴片阵列进行了实例验证,结果表明:设计的贴片阵列可以在满足辐射性能的基础上,带内和带外单站雷达散射截面的强散射点得到了有效抑制,使其在绝大多数入射角处于低散射状态,从而证明了该方法可以快速、有效地指导兼顾辐射性能的低散射阵列设计。