一种低抖动、宽调节范围的带宽自适应CMOS锁相环

提出了一种低抖动、宽调节范围的带宽自适应CMOS锁相环.由于环路带宽可根据输入频率进行自动调节,电路性能可在整个工作频率范围内得到优化.为了进一步提高电路的抖动特性,在电荷泵电路中采用匹配技术,并在压控振荡器中应用电压-电压转换电路以减小压控振荡器的增益.芯片采用SMIC 0.35μm CMOS工艺加工.测试结果表明该锁相环电路可在200MHz～1.1GHz的输出频率范围内保持良好的抖动性能.     

某办公楼中央空调节能措施的经济效益分析

通过对具体工程实例分析和论述,得出中央空调的节能可以通过提高制冷主机冷凝器的换热效率来提高主机在常年运行时高效节能,并利用冷凝热回收技术来回收原来冷却塔带走的热量,这样既可得到免费热水,又可以减少冷却塔的排放热量,利用新风全热换热器来回收排风中的冷量,并通过空调自动控制系统,在中央空调各种不同工况时,进行优化控制,实现整个系统的节能运行,从而达到降低整个中央空调系统能耗的目的。     

基于IBM SiGe BiCMOS工艺5PAe的2GHz功率放大器设计

采用IBM公司刚刚推出试用的0.35μm SiGe BiCMOS开发性工艺5PAe设计并实现了一个2GHz功率放大器. 该放大器采用两级单端结构,除集电极扼流电感外,其余元件全部片上实现,具有集成度高、结构简单的特点. 通过在管子基极和匹配电感中串联电阻,实现了全频段稳定. 键合测试表明,在所有电源电压下电路均能稳定工作. 在VC=3.5V, VB=6V, f=2.0GHz时,小信号增益为20.8dB,输入输出反射系数分别小于-17和-16dB, Pout-2dB约为24dBm. 而在输出功率为25.1dBm时,功率附加效率达到21.5%,二次和三次谐波分别小于-45和-52dBc,因而具有较好的线性度.     

虚拟网络的服务迁移技术研究

提出了一种面向单域环境的虚拟网络迁移算法。基于动态服务质量计算,定义了迁移判定因子,量化迁移代价与收益参数,动态评判迁移的时机,并选择判定因子最小的虚拟节点作为服务迁移节点。该算法可以有效地减少服务延迟,提高用户的服务体验质量,实现网络高效的资源管理和降低能耗的目标。     

一种8VSB Turbo格状编码调制方案

本文阐述这了一种适用于带限信道的８ＶＳＢ Ｔｕｒｂｏ格状编码制方案,它把纠错极强的Ｔｕｒｔｏ码和频带效率极高的格状编码调制结合,具有极强的信道传输能力。同时给出了相应的迭代译码算法及其误码率曲线。     

多次辐照条件下YAG脉冲激光熔敷层开裂敏感性研究

采用Nd:YAG固体脉冲激光器,在镍基高温合金上激光熔敷镍基自熔合金,对激光多次辐照条件下熔敷层的开裂问题进行了探索性研究。试验结果表明:脉冲激光多次辐照,对熔敷层的组织及硬度影响不大;激光辐照次数的增多,促进了熔敷层裂纹萌生,其裂纹形态为沿晶高温液化裂纹;对基材热输入的增多,促进了基材再热裂纹的萌生     

基于中断概率的多跳混合协作地理路由算法

为了减小无线传感器网络中路由的路径长度,该文提出基于中断概率的多跳混合协作地理路由(MHCGR)算法。首先对不同协作机制的链路进行分析,理论分析表明,在一定中断概率要求下,采用译码放大转发混合协作机制可以进一步扩大传输距离,并推导了每跳协作链路的理想最大协作传输距离和理想中继的位置。在无信标地理路由(BLGR)算法的基础上,MHCGR算法结合节点位置信息为每跳选择最佳的中继节点和转发节点,建立从源节点到目的节点的多跳协作路由。仿真表明,与ENBGCR算法和基于DF协作机制的MPCR算法两种协作地理路由算法相比,MHCGR算法可明显减少路由的跳数,改善路由的整体发射功率。     

深空通信网络协议的发展与展望

分析了发展深空通信网络的需求,结合深空通信网络的特点,对深空通信网络协议体系和路由策略等的技术现状进行了综述,对其中的关键技术进行了分析,并对深空通信网络的未来发展进行了展望。     

End-to-end differentiation of congestion and wireless losses

In this paper, we explore end-to-end loss differentiation algorithms (LDAs) for use with congestion-sensitive video transport protocols for networks with either backbone or last-hop wireless links. As our basic video transport protocol, we use UDP in conjunction with a congestion control mechanism extended with an LDA. For congestion control, we use the TCP-Friendly Rate Control (TFRC) algorithm. We extend TFRC to use an LDA when a connection uses at least one wireless link in the path between the sender and receiver. We then evaluate various LDAs under different wireless network topologies, competing traffic, and fairness scenarios to determine their effectiveness. In addition to evaluating LDAs derived from previous work, we also propose and evaluate a new LDA, ZigZag, and a hybrid LDA, ZBS, that selects among base LDAs depending upon observed network conditions. We evaluate these LDAs via simulation, and find that no single base algorithm performs well across all topologies and competition. However, the hybrid algorithm performs well across topologies and competition, and in some cases exceeds the performance of the best base LDA for a given scenario. All of the LDAs are reasonably fair when competing with TCP, and their fairness among flows using the same LDA depends on the network topology. In general, ZigZag and the hybrid algorithm are the fairest among all LDAs.     

Magnetic tunnel junctions with doubly-plasma oxidized AlOx insulation layer

Magnetic tunnel junctions (MTJ), with the tunnel barrier plasma oxidized in two steps, were fabricated in order to obtain structurally uniform AlO_x insulator. The doubly oxidized junctions exhibited the magnetoresistance (MR) ratio of 27-31% without showing any noticeable drop in the MR ratio even after oxidation time was extended well beyond the optimal oxidation time for the normal junctions. Transmission electron microscopy of the junctions confirmed that the AlO_x thickness was thinner for the doubly oxidized junctions compared to the singly oxidized MTJ. X-ray photoelectron spectroscopy of the doubly oxidized junction also strongly suggested that the initial oxide layer prevents the over-oxidation of the bottom electrode. The AlO_x tunnel barrier oxidized in two steps improved the junction performance and widened the processing window.