频率选择性信道下Turbo码和SC-FDE的联合方案

针对频率选择性信道下宽带数据传输存在符号间干扰(ISI),提出了一种频率选择性信道下联合Turbo码和单载波频域均衡(SC-FDE)的宽带传输方案.通过改进传统SC-FDE结构,设计了一种SC-FDE软信息提取方法,提高了进入Turbo码译码器先验信息的精确性,从而改善了系统整体性能.仿真结果表明,相比较于硬信息输出,采用SC-FDE软信息输出能够改善输出信噪比,提高系统性能.     

星载自适应调零天线在LEO卫星中的应用研究

分析了LEO卫星系统对自适应调零天线的需求,针对地基干扰站对LEO卫星实施大功率阻塞式干扰的可行性进行了量化分析。在星载多波束天线的应用背景下,提出了适合LEO卫星的自适应调零天线的构架,给出了系统框图,并对相关问题进行了分析讨论。在此基础上,提出了凝视干扰波束的概念,极大地简化了LEO卫星调零天线在干扰调零后的波束重组的过程,并给出了波束重组过程的示意图。     

嵌入式系统

英特尔扩展凌动处理器平台应用 英特尔公司发布首款针对连网的家庭、小型办公以及家庭办公（SOHO）存储设备而优化的凌动处理器平台,英特尔凌动处理器D410单核或D510双核与英特尔82801IR I／O控制器组成,其处理性能和输入／输出（I／O）连接能力可充分满足LaCie、LG Electronics、QNAP、Synology和Thecus等领先存储厂商对于吞吐量方面的需求。     

要闻

蓝牙联盟启动4.0版本资格认证计划蓝牙技术联盟日前宣布,正式采用以低耗能技术为代表优势的蓝牙核心规格4.0版本。这对会员而言,也标志着蓝牙技术联盟的资格认证计划现已向所有蓝牙4.0规格产品开放。由于     

毫米波低副瓣赋形介质透镜天线设计

通过对介质透镜赋形,把初级馈源方向图转变为透镜口径面上所需的场分布函数,便可获得所需要的各种波束。本文给出了一种基于几何光学的简单而实用的透镜赋形方法,通过赋形能实现介质透镜天线低副瓣的要求。     

速调管矩形波导加载输出腔的粒子模拟

利用三维PIC 软件,首次建立与速调管输出腔外接矩形波导耦合装置几何尺寸完全一致的计算模型,对S 波段矩形波导输出腔加载做了设计和优化,在工作电压80 kV,束流45 A,工作中心频率为2.85 GHz 条件下,得到了1.43 MW的输出功率,3 dB 带宽达到了6%,经过实验证明,理论仿真计算与实测结果是吻合的。     

C 波段连续波速调管的研制

本文介绍一个C 波段连续波速调管的设计计算和测试情况。通过对电子枪、聚焦系统、输出电路、互作用段的计算,获得了连续波输出功率15kW,带宽2.3%的输出特性,研制的第一支样管获得了7.4～13.8kW 的连续波输出功率。     

多注速调管TM410 模同轴输出腔的研究

研究了多注速调管TM₄₁₀ 模同轴输出腔中出现的外观品质因数高,模式频率间隔小以及工作模式场分布的均匀性差等问题,提出了一种设置短路杆和金属环的输出腔结构,从而改善了TM₄₁₀ 模输出腔上述三个方面的性能。通过分析发现,适当设置短路杆和重入环不仅可以使外观品质因数降低,还可以改善工作模式的场分布;设置重入环还可以增大工作模式和邻近模式的频率间隔。利用CST-MWS 软件,对X 波段具有短路杆和金属环的多注速调管TM₄₁₀模同轴输出腔进行了模拟计算,其工作模式（TM₄₁₀模）的外观品质因数降低了42.7%（从540.4 降至309.6）,TM₄₁₀ 模与邻近模式的频率间隔均达到了1.3 GHz 以上,工作模式的场分布也变得均匀。     

Research on the low complexity adaptive power allocation algorithm in cooperative systems

Cooperative diversity is a new technology to improve bit error rate(BER)performance in wireless communications.A new power allocation algorithm to improve BER performance in cellular uplink has been proposed in this paper.Some existing power allocation schemes were proposed for the purpose of maximizing the channel capacity or minimizing the outage probability.Different from these schemes,the proposed algorithm aims at minimizing the BER of the systems under the constraint of total transmission power.Besides this characteristic,the proposed algorithm can realize a low complexity real-time power allocation according to the fluctuation of channels.Simulation results show that the proposed algorithm can decrease the BER performance of the systems effectively.     

SNR-based weighted cooperative spectrum sensing in cognitive radio networks

Cooperative spectrum sensing (CSS) is an approach to confront fading environment. However, in conventional cooperative spectrum sensing (CCSS), the difference among the secondary users (SUS) is ignored when SUS suffer from different fading. In this article, a signal-to-noise ratio (SNR)-based weighted spectrum sensing scheme is proposed to improve the sensing performance. The sensing performance of the weighted spectrum sensing scheme is then derived. Considering the minor contribution of the SUS with small weighted factor, a selective CSS scheme is proposed, where SUS with low SNR are not selected into cooperative spectrum sensing. The simulation results confirm the analytical results. And the performance of weighted scheme is better than that of conventional schemes. In the case where the SNR of SUS are randomly distributed, the performance of selective scheme is almost the same as the weighted scheme while the number of cooperative SUS is reduced to save the consumption of system resource in cooperation with little additional complexity.