Characterization and performance evaluation of differentialshielded cables for multi-Gb/s data-rates

This paper compares several differential cable characteristics that were evaluated for multi-Gb/s data-rates for both data and clock paths for 1-10 m lengths. Time-domain measurements are shown for the unassembled and connectorized cables and for representative card-plus-cable signal paths and the performance limiting factors are highlighted. Techniques are shown for developing coupled-line models for odd and even excitations for all the components in a full chip-to-chip path in order to make realistic data-rate predictions     

Design of wideband circularly polarized aperture-coupled microstripantennas

Two variations of a novel feeding technique for a wideband circularly polarized aperture-coupled microstrip antenna are described. Prototype designs for wideband linearly polarized elements are first presented, and then used for circularly polarized designs. Techniques used for design of the feed network are detailed, for both series feed and parallel feed versions. Experimental results are shown for each antenna, and results for the two designs are compared. The impedance and axial ratio bandwidths for these antennas are among the best yet achieved for microstrip antenna elements. Several design variations are also discussed     

Communication over fading dispersive channels with feedback

An intermittent on-off noiseless feedback scheme for binary communication over the slow- and fast-fading Rayleigh channels is proposed and analyzed. At high energy-to-noise ratios, doubling the number of feedback iterations yields a 3-dB power saving for the slowly fading channel. Power savings ranging from 1 dB for one feedback iteration to 9 dB for 16 iterations are typical for the fast-fading model. Also for the fast-fading model, by picking the optimum number of forward transmissions for each value of energy-to-noise ratio, the best achievable performance requires approximately 7.5 dB more energy than the minimum predicted by the rate-distortion bound. Also presented is a feedback communication system for wide-sense stationary, uncorrelated-scatterer, fading, and dispersive forward and feedback channels. The model used for both forward and feedback channels is Kennedy's. Upper and lower bounds on the error probability for block orthogonalM-ary communication are presented for this system.     

ASON网络资源管理信息模型设计

自动交换光网络(ASON)作为构建下一代光网络的核心技术之一,相关的标准也正在迅速制定,但ITU-T 还没有给出其管理层面的体系结构与管理功能等相应的规范。该文从ASON网络资源管理的需求出发,提出了用于ASON跨区域端到端连接管理的网络层管理对象模型以及用于控制平面资源管理的对象模型。其中给出的控制层面管理模型可以实现控制网元以及控制通道的管理,控制层面的路由区域的划分以及控制模块的配置和性能监测管理等功能。     

Performance of a powerful error-correcting and -detecting codingscheme for the North American Basic Teletext System (NABTS) for randomindependent errors: methods, equations, calculations and results

For a powerful layered, upward- and downward-compatible error-correcting and error-detecting scheme for NABTS, various bit error rate (BER) related performance measures are derived and calculated for random independent errors. The methods, equations, calculations and results are given for the least powerful one-byte suffix codes, for the two-byte suffix code, called code C, and for the double and single bundle codes formed by using code C for each data block (i.e. horizontally) and also vertically, thus forming a product code, for a specified, but variable, number of data blocks. Performance bounds and equations for probabilities of correct decoding of error and of decoding failure are given. The weight enumerators for a number of one-byte suffix codes are calculated, and those of weight four are classified into types depending on the number of ones occurring in a byte, and in other arrangements. Performance analyses and comparisons with a code for Japanese teletext are included. Analyses used in computer simulation studies are described     

A computational methodology and results for quasistaticmultilayered magnetic shielding

A methodology for accurate calculations of shielding factors for quasistatic multilayered magnetic shields is described. “Transfer relations” for individual layers with specified magnetic permeabilities and electrical conductivities are spliced together. Specific transfer relations for four layer geometries (planar, cylindrical with transverse fields, cylindrical with axial fields, and spherical) and constraints at source and shielded surfaces for six source-shield configurations involving both externally applied fields and enclosed sources are developed. Limiting cases are extracted for magnetically permeable, nonconducting layers, and for thin, magnetically nonpermeable, conducting layers. Reciprocity conditions are identified for interchanged source and shielded regions in planar, transverse field cylindrical, and spherical geometries. Variations of magnetic field and flux density with position are shown for a specific planar example involving alternating layers of aluminum and steel, with the same total shield thickness occupied by either one or five layer pairs. Simulations with alternating layers of aluminum and steel for the four layer geometries are used to study the effects of material composition, number of layer pairs, and air gaps. An optimal number of layer pairs for a given total shield thickness is identified. Results from simulations where induced currents in the steel layers are neglected are compared with those for simulations with a realistic conductivity value for steel to assess the relative effects of flux shunting and induced current shielding     

Tables of normalized cutoff wavenumbers of elliptic cross sectionresonators

Current methods to evaluate the mode resonance of elliptic cross section resonators are cumbersome for design purposes. In this paper, tables for the cutoff wavenumbers of TE_nm and TM_nm modes for both even and odd modes are tabulated in a new way, that reveals a simple relation to the equivalent circular cross section resonator and makes interpolation results accurate. These tables range for n=0, ... 3 for even modes and n=1, ... 4 for odd modes, with m=1, ..., 5 for both. The tables cover 80 different modes for eccentricity in the range 0相似文献   

16DAPSK+OFDM及其在数字调幅广播中应用

本文提出一种新的频域16DAPSK＋OFDM。并讨论它的频域差分调制和解调,然后在白高斯信道分析它的误比特性能。同时域16DASK＋OFDM相比,频域16DAPSK＋OFDM可用于信道特性随时间变化更快的应用。最后,在典型的调幅（AM）波段信道对两者误比特性能进行了仿真。结果表明,时域和频域16DPSK＋OFDM都可用于中短波信道。在中波信道,时域16DAPSK比例域16DAPSK性能要好,在短波信道,频域16DAPSK比时域16DAPSK性能要好。另外,两者调制和解调的计算复杂度基本一样,且都不需要信息道均衡。     

Analysis of stochastic gradient tracking of time-varying polynomialWiener systems

This paper presents analytical and Monte Carlo results for a stochastic gradient adaptive scheme that tracks a time-varying polynomial Wiener (1958) system [i.e., a linear time-invariant (LTI) filter with memory followed by a time-varying memoryless polynomial nonlinearity]. The adaptive scheme consists of two phases: (1) estimation of the LTI memory using the LMS algorithm and (2) tracking the time-varying polynomial-type nonlinearity using a second coupled gradient search for the polynomial coefficients. The time-varying polynomial nonlinearity causes a time-varying scaling for the optimum Wiener filter for Phase 1. These time variations are removed for Phase 2 using a novel coupling scheme to Phase 1. The analysis for Gaussian data includes recursions for the mean behavior of the LMS algorithm for estimating and tracking the optimum Wiener filter for Phase 1 for several different time-varying polynomial nonlinearities and recursions for the mean behavior of the stochastic gradient algorithm for Phase 2. The polynomial coefficients are shown to be accurately tracked. Monte Carlo simulations confirm the theoretical predictions and support the underlying statistical assumptions     

潮湿环境对不同金属样品激光烧蚀阈值的影响

用1064nm激光辐照金属样品,通过测量金属物质烧蚀阈值附近冲击波的渡越时间的突变,确定了Cu、黄Cu、Al3种样品在干燥空气中和潮湿空气巾的烧蚀阈值。干燥空气,Cu为1．0J／cm^2,黄Cu为．9J／cm^2,Al为0．68J／cm^2;潮湿空气中,Cu为1．0J／cm^2;黄Cu为0．7J／cm^2;Al为0．38J／cm^2。结果表明,潮湿空气中的黄Cu和Al样品烧蚀阈值降低了,而Cu样品的烧蚀阈值没有变化;黄Cu和Al样品烧蚀阈值降低的程度也不同,黄Cu为22％,Al为44％。     

CE101舰船交流电源极限值的设定及其应用

对MIL-STD-461D、GJB151A CE101舰船交流电源极限值的设定进行了分析和说明,并根据MIL-STD-461D CE101 60Hz电源频率极限值的设定思路,提出了适用于我国50Hz电源频率的CE101舰船极限值。该设定方法还可用于相关极限值的剪裁。     

Modeling of control loop behavior of magamp post regulators

Small signal-control models are presented for a magnetic amplifier switching-mode post regulator for SMPS applications. Two commonly used current reset schemes are considered; an external reset scheme and a self-reset scheme. It is mathematically shown that the open-loop gain is a two-pole, single-zero transfer function for continuous-mode operation and is a single pole transfer function for discontinuous mode operation. The equations for predicting the open-loop gains for both types of reset circuits are derived and verified experimentally. It is shown that the open-loop gain characteristics of a magnetic-amplifier regulator depends on power circuit parameters, the reset-circuit parameters, and the saturable reactor parameters. Models for both continuous mode and discontinuous modes of operation that provide designers with useful tools for designing a compensation network for the feedback error amplifier are presented     

信息系统如何开展定级备案工作

信息系统定级、备案工作是开展等级保护工作的前提和基础。介绍了信息安全等级保护定级备案工作目标、内容流程和方法,为政府机关、企事业信息系统开展信息安全等级保护定级备案工作提供了借鉴。     

Crosstalk between microstrip transmission lines

Methods for prediction of crosstalk between microstrip transmission lines are reviewed and simplified for the weak-coupling case. Classical coupled transmission line theory is used for uniform lines, and potential and induced EMF methods are used for crosstalk between nonuniform lines. It is shown that the potential method is equivalent to classical coupled transmission line theory for the case of uniform lines. An experiment was performed for uniform coupled microstrip lines for frequencies from 50 MHz to 5 GHz, and good agreement between theory and measurement was obtained for both near- and far-end crosstalk     

On the performance of sequential and Viterbi decoders for high-ratepunctured convolutional codes

This paper presents new computationally efficient and accurate techniques for estimating the performance of specific high-rate punctured convolutional codes and uses these techniques to evaluate the performance of sequential and Viterbi decoders for the best known codes. In particular, it demonstrates that the disparity between sequential and Viterbi decoding increases dramatically for long memory codes with high rates and for such codes, the union bound cannot be used as a criterion for selecting good codes for sequential decoders. In contrast, it shows that the proposed methods can be used as efficient tools for performance evaluation and/or identification of good high-rate punctured convolutional codes for use with sequential decoders     

CCD成像传感器的降噪技术

系统地介绍了CCD成像传感器降噪技术的研究进展.重点介绍和分析了CCD复位噪声降噪技术和非均匀性校正技术的研究进展.特别介绍了用于克服CCD复位噪声的数字域加权双斜积分技术、基于场景的非均匀性校正技术以及多CCD成像系统的非均匀性校正技术.最后展望并讨论了CCD成像传感器降噪技术的发展趋势.     

Rain attenuation measurements over New Delhi with a microwave radiometer at 11 GHz

Rain attenuation measurements over New Delhi carried out with a microwave radiometer installed at the National Physical Laboratory (NPL), New Delhi and operating on 11 GHz for a period of more than three years are presented. For 0.01 percent of time for the period June 1977-April 1978, the attenuation exceeded for the monsoon period is 14.0 dB whereas for the whole year, it exceeds 10.4 dB. During the winter for the same percentage of time, the attenuation exceeded 1.5 dB, whereas for March-April it exceeds 0.5 dB. For the period May 1978-June 1980, it is observed that for 0.01 percent of time the attenuation for the whole year exceeds 9.0 dB. During the winter for the same percentage of time, the attenuation exceeds 1.4 dB whereas for March-April it exceeds 0.4 dB. A comparison of attenuation over New Delhi and those reported elsewhere are discussed. Yearly and worst month time ratio over New Delhi are given also as the values reported for the European region. Comparison of the attenuation distribution and the rate of surface rainfall measured with a rapid-response rain gauge are also given. The comparison shows that for the monsoon period and for 0.01 percent of time, the attenuation value exceeded for 14 dB corresponds to the surface rainfall rate of 140 mm/h. For the monsoon of 1978, 1979, comparison shows that for 0.1 percent of time, the attenuation value exceeded for 9.0 dB corresponds to the surface rainfall rate of 90 mm/h. Variation of attenuation and effective path length for various rainfall rates and elevation angles are also given.     

Contingency/disaster recovery planning for transmission systems ofthe Defense Information System Network

The paper provides recommendations for the enhancement and protection of the Defense Information System Network (DISN) for disaster recovery and contingencies. The DISN is a worldwide Defense Department network designed to serve consolidated and integrated communication requirements of the defense services and agencies. The ability to recover from disasters and allow for contingencies must be inherent in the design of this network. Basic design aspects of the DISN are described, along with several complementary programs for disaster recovery planning being implemented by the Office of the Manager, National Communications System (OMNCS). Both hostile and nonhostile threats are examined to set the stage for recommendations that follow. Techniques for disaster and contingency preparedness are described that will improve DISN survivability and disaster recovery. Specific technologies are considered for provision of independent orderwires and backup transmission systems. An interface device designed for transmission recovery is recommended for both satellite and terrestrial media. Other specific recommendations are made for network management within the various hierarchical levels of DISN management     

Analytical method of a multilayered meander-line polarizer plate with normal and oblique plane-wave incidence

Simple empirical formulas for perpendicular and parallel polarization susceptances for a meander-line grating plate are given. The numerical results compared favorably with experimental data and published data. Simple transmission-line model in terms ofE-type mode andH-type mode for multilayered meander-line polarizer plate is presented for plane wave incidence at normal and oblique angles. Numerical results for design examples are given for practical application.     

Final call: CPR's fall meeting in Boston on Oct. 25‐26

It's last call for three CPR doings: for the Fall Meeting in Boston later this month, for three trainings, and for nominations for the 2007 CPR Awards. Also, CPR member options for signing up for free electronic copies of Alternatives