基于阵列滤波补偿装置的变频器谐波治理

本文简单分析了变频器谐波产生的机理,介绍了几种变频器谐波的抑制方法,通过比较和实践证明,介绍了一种T型结构无源滤波器,该滤波器由阵列电抗器和滤波电容器串并联组成,整体串于变频器等变流设备前端,对变频器产生的谐波有非常好的滤除效果,可以把变频器产生的电流畸变率控制到5%以内。     

Study of Intrusion Detection Systems

Modern network systems have much trouble in security vulnerabilities such as buffer overflow, bugs in Microsoft Internet, sensor network routing protocol too simple, security flaws of applications, and operating systems. Moreover, wireless devices such as smart phones, personal digital assistants （PDAs）, and sensors have become economically feasible because of technological advances in wireless communication and manufacturing of small and low-cost sensors. There are typologies of vulnerabilities to be exploited in these devices. In order to improve securities, many mechanisms are adopted, including authentication, cryptography, access control, and intrusion detection systems （IDS）. In general, intrusion detection techniques can be categorized into two groups： misuse detection and anomaly detection. The misuse detection systems use patterns of weB-known attacks or weak spots of the systems to identify intrusions. The weakness of misuse detection systems is unable to detect any future （unknown） intrusion until corresponding attack signatures are intruded into the signature database. Anomaly detection methods try to determine whether the deviation is from the established normal usage patterns or not. The critical success of anomaly detection relies on the model of normal behaviors.     

基于Talbot干涉的X射线光栅成像技术研究进展

从技术特点和研究热点的角度,综述了X射线光栅干涉成像技术与系统的国内外最新进展。介绍了具有代表性的基于Talbot-Lau干涉法的X射线光栅成像原理与系统结构,以及物质对X射线的衰减、折射与小角散射的多信息获取技术。综述了国内外对X射线光栅成像技术与系统的优化改进研究,主要包括光栅步进对高位置分辨率的松弛与大视场高分辨率光栅成像技术的实现。介绍了二维光栅与基于光栅的具有时间分辨率的四维成像技术的国内外最新发展动态。展望了X射线光栅成像技术的发展趋势。     

基于合作中继的OFDM蜂窝网络的QoS感知资源调度算法

针对基于中继的OFDM蜂窝网络,该文考虑具有不同QoS要求的混合业务场景,引入合作传输机制,提出了一种基于合作中继的QoS感知资源调度算法,解决了合作中继节点选取,子载波分配以及功率控制等问题。以最大化系统效用为目标,在考虑QoS业务的速率要求与基站功率约束的同时,针对中继结构引入了中继节点的功率约束。为降低计算复杂度,将原非线性组合优化问题分解为子载波分配与功率控制两个子问题。仿真结果表明,该文所提算法在能量节约、系统效用,吞吐量等性能方面都有显著优势。     

LTE协议解决方案及系统实现

介绍了LTE特点及现状.协议测试及重要性根现状给出了LTE协议测试解决方案并通过安立公司的MD8430A基站仿真器和MD8435A终端仿真器外加两台控制PC搭建测试平台,在平台上成功实现了LTE终端从搜索注册网络建立连接信令流程及数据传输物理层仿真.仿真速率上行达到50Mbit/s下行100Mbit/s的高速率传输,给出了各流程源程序,对于LTE移动终端的研发具有重要的作用.     

Design of an LDO with capacitor multiplier

This paper presents a low quiescent current,highly stable low-drop out(LDO) regulator.In order to reduce capacitor value and control frequency response peak,capacitor multipliers are adopted in the compensation circuit with mathematic calculations.The phase margin is adequate when the load current is 0.1 or 150 mA.Fabricated in an XFAB 0.6μm CMOS process,the LDO produces 12.2 mV(0.7%) overshoot voltage while the current changes at 770 mA/100μs with a capacitor load of 10μF.     

A tool for power and phase noise optimization in frequency synthesizers

In this paper, we present a CAD technique to design low-power and low phase noise integrated frequency synthesizers. This technique introduces a key parameter, Phase Noise per Unit Power, which correlates phase noise and power among all the sub-circuits in the frequency synthesizer. By correlating the performance of all the independent circuits together, sophisticated synthesizer design and optimization can be significantly simplified. We demonstrate a 1.8 GHz frequency synthesizer design in a 0.18 μm CMOS process achieving −132 dBc/Hz phase noise at 100 kHz offset with less than 4.3 mW power consumption.     

Using directionality in mobile routing

The increased usage of directional methods of communications has prompted research into leveraging directionality in every layer of the network stack. In this paper, we explore the use of directionality in layer 3 to facilitate routing in highly mobile environments. We introduce Mobile Orthogonal Rendezvous Routing Protocol (MORRP) for mobile ad-hoc networks (MANETs). MORRP is a lightweight, but scalable routing protocol utilizing directional communications (such as directional antennas or free-space-optical transceivers) to relax information requirements such as coordinate space embedding, node localization, and mobility. This relaxation is done by introducing a novel concept called the directional routing table (DRT) which maps a set-of-IDs to each interface direction to provide probabilistic routing information based on interface direction. We show that MORRP achieves connectivity with high probability even in highly mobile environments while maintaining only probabilistic information about destinations. Additionally, we compare MORRP with various proactive, reactive, and position-based routing protocols using single omni-directional interfaces and multiple directional interfaces and show that MORRP gains over 10–14 × additional goodput vs. traditional protocols and 15–20% additional goodput vs. traditional protocols using multiple interfaces. MORRP scales well without imposing DHT-like graph structures (eg: trees, rings, torus etc). We also show that high connectivity can be achieved without the need to frequently disseminate node position resulting increased scalability even in highly mobile environments.     

SNR wall and cooperative spectrum sensing in cognitive radio under noise uncertainty

Cooperative energy spectrum sensing has been proved effective to detect the spectrum holes in Cognitive Radio (CR). However, its performance may suffer from the noise uncertainty, which is portrayed by the SNR wall in some literatures. In this paper we analyze the spectrum sensing performance under noise uncertainty and find an alternative approach to obtain the SNR wall. Then the average SNR wall is proposed to illustrate the statistically average impact of noise uncertainty. In addition, the cooperative sensing performance under noise uncertainty with AND rule is discussed. Analyses and numerical results show that cooperative sensing can significantly improve the sensing performance under the condition of noise uncertainty.     

One-to-Many: Context-Oriented Code for Concurrent Error Detection

The paper deals with context-oriented codes for concurrent error detection. We consider a fault model for which, in the presence of a fault, the values on the circuit’s output are arbitrary. This model allows one to design an error detection code without analyzing sensitive parts or error cones in the synthesized circuit. Conventional coding schemes are based on a one-to-one mapping between an original output vector (information word) and a codeword. In this paper, we introduce a different approach, which we call one-to-many coding. In one-to-many code, each codeword comprises a predefined set of words. The functional unit is referred to as an encoder enabling each activation to map an information word to a different word. This flexible mapping system results in a lower implementation cost of the functional unit and its checker.