Design and performance of improved lumped-distributed Wilkinsondivider topology

An improved lumped-distributed planar 3 dB Wilkinson divider is presented. The technique reduces the number of components and via-grounds. An analysis based on ideal transmission lines provides design equations for the proposed Wilkinson divider. The topology gives good results at L-band and uses less than half of the substrate area of the standard topology     

Dream Weaver4小技巧

您是否因为Dream Weaver4里面的字体、文字大小设定不能保存而大伤脑筋？笔者在此介绍一个解决的方法。先备份注册表，并且退出运行中的Dream Weaver。1运行regedit.exe。2找到HKEY_CURRENT_USER/SOFTWARE/MACROMEDIA/DREAMWEAVER 4/FONT PREFERENCES接下来有2个方案：简便方案     

Design of optical circuit devices based on topology optimization

We apply a design method based on topology optimization technique to optical waveguide devices. In our approach, after a refractive index profile in a design region is automatically generated using a topology optimization method, the obtained structure is redefined using primitive geometries with some design parameters and those parameters are optimized by a sequential linear programming. As numerical examples, we demonstrate how the method can be used for 90/spl deg/ bends and T-branching waveguides with arbitrary splitting ratio.     

Design of tree topology based Byzantine fault tolerance system

A tree topology based Byzantine fault tolerance system was designed and the calculation of the Byzantine node bound based on depth and width was given.The consistency protocol was designed through divide the tree into groups by communication and work,which guaranteed the safety of system.The access of a node was determined with joint signature mechanism.The Byzantine nodes were placed to the leaves by view change protocol,which guaranteed the liveness of the system.On the foundation of traditional protocol,the new protocol support multiple tasks operating at the same time,and communication between nodes is largely decreased,as well as the space complexity,hence the feasibility being promoted,and the gap between Byzantine fault tolerance system and the non-Byzantine systems being narrowed.     

EPON_EoC网络拓扑分层显示的设计与实现

EPON+EcC作为三网融合中双向改造的主流方案,为其构建统一网管系统是必要的,而以图形方式显示网络拓扑结构是网管系统的基本要求之一.在已实现的EPON和EoC设备统一管理方案及拓扑发现的基础上,结合Twaver SVG进行了网络拓扑多层显示的设计与实现,并完善了拓扑编辑、拓扑导出等功能.同时,在此基础上也实现拓扑显示...     

基于六端口网络的泄漏对消拓扑结构设计

设计了一种基于六端口网络的电路拓扑结构,可用来有效地抑制泄漏信号。该六端口网络主要由3个3 dB定向耦合器和一个不等分功分器组成。在与接收天线信号对应的2个输出端口,发射天线的泄漏信号经过移相后等幅且反向,使泄漏信号相互抵消,从而显著改善雷达网络收发天线之间的隔离性能。为验证该泄漏对消技术,设计并仿真验证了一种工作于22~26 GHz的电路拓扑结构。在工作频段上,该泄漏对消电路的隔离度小于-29.5 dB,并于中心频率处达到-44 dB的最大衰减。仿真结果证明,该电路可以有效提高单天线收发系统的隔离度,改善发射端到接收端的信号泄漏问题。     

维弗法在SSB调制中的应用及仿真

指出实际应用中滤波法及移相法产生SSB信号的局限性，介绍应用维弗法产生和解调SSB信号的工作原理，并基于System View软件对其进行计算机仿真分析。     

Calibration study of dual-band Weaver–Hartley receiver architecture

This paper presents a calibration study of dual-band image rejection receiver based on combined Weaver–Hartley architecture, with improved image rejection of first and second image signals. The system implementation is based on dual-band WLAN 802.11 a/g. When the desired signal is at 5.7-GHz band, the 2.4-GHz band becomes the first image signal and vice versa. The output IF frequency is at 30-MHz. The detection of the gain and phase mismatches is based on modeling, extraction of related error signals and correcting them in closed loop. Moreover, we demonstrate an open loop technique to reach the phase and gain correction signals. The correction signals can be digitally stored and applied as digital trimming control on the LO signals. Simulation showed close to 60 dB of image rejection ratio for the first image signal. Second image signal is rejected by a 4-section poly-phase filter.     

Design and optimization of color lookup tables on a simplex topology

An important computational problem in color imaging is the design of color transforms that map color between devices or from a device-dependent space (e.g., RGB/CMYK) to a device-independent space (e.g., CIELAB) and vice versa. Real-time processing constraints entail that such nonlinear color transforms be implemented using multidimensional lookup tables (LUTs). Furthermore, relatively sparse LUTs (with efficient interpolation) are employed in practice because of storage and memory constraints. This paper presents a principled design methodology rooted in constrained convex optimization to design color LUTs on a simplex topology. The use of n simplexes, i.e., simplexes in n dimensions, as opposed to traditional lattices, recently has been of great interest in color LUT design for simplex topologies that allow both more analytically tractable formulations and greater efficiency in the LUT. In this framework of n-simplex interpolation, our central contribution is to develop an elegant iterative algorithm that jointly optimizes the placement of nodes of the color LUT and the output values at those nodes to minimize interpolation error in an expected sense. This is in contrast to existing work, which exclusively designs either node locations or the output values. We also develop new analytical results for the problem of node location optimization, which reduces to constrained optimization of a large but sparse interpolation matrix in our framework. We evaluate our n -simplex color LUTs against the state-of-the-art lattice (e.g., International Color Consortium profiles) and simplex-based techniques for approximating two representative multidimensional color transforms that characterize a CMYK xerographic printer and an RGB scanner, respectively. The results show that color LUTs designed on simplexes offer very significant benefits over traditional lattice-based alternatives in improving color transform accuracy even with a much smaller number of nodes.     

新型电流源型三相逆变器的软开关拓扑设计

针对硬开关损耗大的缺陷,提出一种新型的应用于电流源型三相逆变器的软开关拓扑及其控制方法。对电流源型三相逆变器进行了系统的研究,包括数学模型的建立与分析,电流空间矢量控制技术,电流双向流动拓扑与控制,新型的软开关拓扑及其控制方法。提出了一种新型的应用于电流源型三相逆变器中的软开关拓扑,明确了其控制逻辑,分析其各个模态的电压电流特征和工作波形图。最后使用Matlab仿真软件在电流空间矢量控制下进行总体仿真,验证了拓扑及其控制方法的可行性和有效性,实现了开关的软化,降低了开关应力,并提高了效率。     

EPON_EOC统一网管拓扑发现功能的设计和实现

针对目前大部分以太网无源光网络(EPON)与以太数据通过同轴电缆传输(EOC)设备都是使用相对独立的网管方式,在研究EPON_EOC系统结构与特点的基础上,提出了一种可以实现EPON和EOC设备统一管理的方案,并进行了EPON与EOC设备的拓扑发现功能的设计与系统实现.实际测试结果表明,该方案能较好地实现EPON_EO...     

EPON网络管理系统中拓扑管理的设计与实现

阐述了拓扑管理的重要性,为了能够更加方便以太无源光网络(EPON)系统的管理,提出了一种基于B/S结构的EPON网管的拓扑管理设计方案.测试结果表明,能够快速、准确地分层显示网络拓扑图,具有Trap主动上报的功能,实现了拓扑管理的功能.     

Effect of Phase Mismatch on Image Rejection in Weaver Architecture

In a radio frequency receiver, image signals degrade the sensitivity of the receiver for receiving desired signals. This letter analyzes the effect of phase mismatch on image rejection in the Weaver architecture, which has been proposed to reject image signals. Weaver architecture requires the phase difference between the I signal and Q signal of the first and second local oscillators (LOs) to be 90deg. However, the realization of accurate 90deg phase shifters is very difficult. It is found here that an accurate 90deg phase shifter is not essential in Weaver architecture. Instead, by making the phase mismatch between the I and Q signals of the first LO be equal to that of the second LO, image rejection can be performed, being insensitive to the phase mismatch. The reason for this is mathematically analyzed and simulation results are presented     

典型网状拓扑全光网设计及配置性能分析(本期优秀论文)

基于一种结构简单、成本低廉的波长转换节点共享型光交叉连接设备建立起一个极具代表性的典型四节点四维度网状拓扑全光试验网,利用排队理论方法构建其数学模型,分析研究了光交叉连接节点配置对试验网性能的影响。数值结果表明,在网络受限波长转换条件下,合理配置的该光交叉连接节点设备具有一定的工程应用前景。     

基于稳定链路的WSNs拓扑优化算法设计及仿真研究

无线传感器网络在物联网中占有重要地位,其能够降低能耗并有效保障数据传输。然而,无线传感器网络底层拓扑结构通常存在网络链路质量低、网络能耗高、网络干扰等问题。针对现有网络链路不稳定的问题,提出具有稳定链路的幂律可调优化算法,并对其生成的拓扑动态性能进行研究。通过网络节点失效容错需求仿真和链路稳定性仿真,验证了幂律可调优化算法的准确性,为无线传感器网络拓扑优化提供参考。     

Design and implementation of a cost-effective quasi line-interactive UPS with novel topology

This paper presents an improved single-phase passive-standby uninterruptible power supply (UPS) for low cost applications. The proposed system includes an input rectifier/charger and a switching inverter. It is basically an offline UPS structure, but has nearly the performance of a line-interactive UPS. It can continuously regulate the sustained voltage swells and sags by injecting a voltage in series with the source voltage in the normal mode, and can be switched smoothly to back-up mode when the utility voltage goes outside the specified range, or fails. The regulation range is also larger than conventional offline and line-interactive UPSs. Additionally, the proposed system has no low frequency transformer, which would involve a heavy and bulky structure. Theoretical analysis has been achieved based on the power flow theory. Case study is demonstrated by means of a prototype experiment to prove its performance and effectiveness.     

Calibration of phase and gain mismatches in Weaver image-reject receiver

A modified image-reject Weaver architecture is presented. The design automatically calibrates for phase and gain mismatches that limit the performance of image-reject receivers. On-line or off-line calibrations are possible without using any calibrating tone. An experimental CMOS prototype RF front-end operating at 1.8 GHz achieves an image rejection ratio of 59 dB using on-line calibration. The design was fabricated in a 0.35-/spl mu/m CMOS process and dissipates 160 mW from a 3-V supply during on-line calibration, and 95 mW during normal receiving. The die area is 4 mm/sup 2/.     

Zero-IF topology

A new receiver topology called the double-quadrature zero-IF topology is presented. Studies have shown that with the new topology the sensitivity to phase errors of quadrature channels can be significantly decreased, and that the image-recognition ratio (IRR) against the gain mismatch characteristic is inherently superior to that for the conventional zero-IF scheme by ~6 dB     

Design and realisation of dual-band 3 dB power divider based on two-section transmission-line topology

A new dual-band 3 dB three-port power divider with arbitrary impedance terminations is proposed. The structure is composed of a two-section transmission-line transformer and an isolation resistor. Each transmission line's electrical length is /spl pi//3 at the fundamental frequency. Based on an ideal transmission line model, new design equations and graphs are given. The technique is validated by the experimental results on a 3 dB 900/1800 MHz power divider with Z/sub S/=100 /spl Omega/ and Z/sub L/=50 /spl Omega/. Good performances of the proposed power combiner/divider at both frequencies are obtained.