共查询到20条相似文献,搜索用时 15 毫秒
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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 相似文献
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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 相似文献
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Design of optical circuit devices based on topology optimization 总被引:1,自引:0,他引:1
Y. Tsuji K. Hirayama T. Nomura K. Sato S. Nishiwaki 《Photonics Technology Letters, IEEE》2006,18(7):850-852
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. 相似文献
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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. 相似文献
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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。 相似文献
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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。 相似文献
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《Microelectronics Journal》2015,46(6):439-446
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. 相似文献
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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. 相似文献
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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 相似文献
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Ming Tsung Tsai Chia Hung Liu 《Power Electronics, IEEE Transactions on》2003,18(4):1002-1011
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. 相似文献
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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/. 相似文献
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Zero-IF topology 总被引:3,自引:0,他引:3
Da-You Sun Jian Xu 《Electronics letters》2000,36(12):1009-1010
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 相似文献
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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. 相似文献