海底光缆余长测试新方法可行性分析

光纤余长是海底光缆的重要性能指标,目前针对光纤余长的分析主要采用解析法,尚没有进一步精确分析光纤余长分布的实验方法。文章提出两种精确分析管内光纤余长分布的实验方法:高能射线法和光纤光栅法,并从理论上分析了这两种方法的可行性。     

现场环境下设备区域电磁干扰检测与识别方法

现场环境下电磁环境复杂,设备区域电磁干扰的有效识别可为射电天文台站频谱分析提供重要依据.文章基于现场电磁干扰测量频谱,提出了一种电子设备区域干扰信号检测与识别方法.首先,针对对着设备区域和隔过设备区域两种测量状态多组频谱数据进行预处理,实现信噪分离,运用二值法检测信号边界,提取频谱中干扰信号.然后,依据一元回归算法和通道占用统计方法对多组测量频谱中干扰信号进行相关性分析,识别设备区域内电磁辐射频谱.所提方法对新疆天文台南山站内多个设备区域电磁辐射频谱检测结果与人工识别结果对比表明,本文方法94%以上的识别结果与人工识别结果相符,验证了现场环境下设备电子区域电磁干扰检测与识别方法的准确性和通用性.     

A new concept for supermodular alignment network

A technique is described for making alignment networks more reliable and cost effective. The proposed technique envisages minimizing the external links and reducing the propagation delay. The VLSI implementation of the network is based on the modularization concept, achieving a simple layout, flexible design, increased computational speed and high circuit, density. The dual tree topology which allows a smaller pin count for the chip is considered for the realization of the modularized network.     

A new concept for wireless reconfigurable receivers

In this article we present the Self-Adaptive Universal Receiver (SAUR), a novel wireless reconfigurable receiver architecture. This scheme is based on blind recognition of the system in use, operating on a new radio interface comprising two functional phases. The first phase performs a wideband analysis (WBA) on the received signal to determine its standard. The second phase corresponds to demodulation. Here we only focus on the WBA phase, which consists of an iterative process to find the bandwidth compatible with the associated signal processing techniques. The blind standard recognition performed in the last iteration step of this process uses radial basis function neural networks. This allows a strong analogy between our approach and conventional pattern recognition problems. The efficiency of this type of blind recognition is illustrated with the results of extensive simulations performed in our laboratory using true data of received signals.     

A new concept for microstrip-integrated GaAs Schottky-diodes

A new concept for integrated planar Schottky-diodes has been developed. It meets the two important requirements in the design of microwave diodes: high cutoff frequency and low parasitics. Only one epitaxial layer is needed. The Schottky contact is deposited on the slope of a mesa in order to obtain both low series resistance and low capacitance, Up to now, a Zero-bias cutoff frequency of 150 GHz has been achieved. The advantage of this type of diodes as compared to planar diodes produced by double selective epitaxy is the use of standard technology, resulting in good reproducibility and yield.     

掌握新知识提高设备检测水平

提出了在新的形势下无线电设备检测工作面临的新任务．介绍了数字蜂窝移动通信系统、无线接入系统等的几种发射设备的射频规范。检验依据和参照标准及测试项目接着介绍了检测可选择的信道．最后对未来的设备检测工作做了展望。     

A decomposition approach for testing large analog networks

This article presents an efficient method for testing large scale analog and mixed mode networks. Test equations are derived for a partitioned network from Krichhoff current law equations at the partition points. Voltages at the partition points are used to identify network parameters. The method has applications to circuit modeling, fault diagnosis, testing and calibration. The conventional testing methods for dynamic, nonlinear networks are based on the sensitivity approach, which uses incremental changes in voltages to estimate changes in network parameters. However, this conventional approach cannot handle large scale circuits because the sensitivity matrix is dense. This results in enormous requirements for memory space and computing time when the circuit size becomes large. The new method overcomes these deficiencies of the sensitivity approach. In this article, we introduce the decomposition method, describe its basic features and its algorithm, and compare this method with a conventional, sensitivity technique using testing network examples.This work was supported in part by the National Institute of Standards and Technology, U.S. Department of Commerce, Under Grant No. 70NANBGH0662.     

A new model for step-stress testing

The mathematical intractability of the Weibull cumulative exposure model (CE-M) has impeded the development of statistical procedures for step-stress accelerated life tests. Our new model (KH-M) is based on a time transformation of the exponential CE-M. The time-transformation enables the reliability engineer to use known results for multiple-step, multiple-stress models that have been developed for the exponential step-stress model. KH-M has a realistically appealing proportional-hazard property. It is as flexible as the Weibull CE-M for fitting data, but its mathematical form makes it easier to obtain parameter estimates and standard deviations. Maximum likelihood estimates are given for test plans with unknown shape parameter. The mathematical similarity to the constant-stress Weibull model is shown. Chi-square goodness of fit tests are performed on simulated data to compare the fit of the models     

A new test for whiteness

We consider the problem of testing whiteness, i.e., to say whether or not a given sequence of data is not correlated (i.i.d if Gaussian). This information could be of help when one is interested in the adequacy of a chosen model that is assumed to fit a set of data. We first introduce a new parameter or, more precisely, a “distance” to whiteness and then construct the new test for whiteness. We derive its distributions under both hypotheses: the null hypothesis (whiteness) and the non-null one. We provide the power of our new test and compare it empirically with the Portmanteau and Fisher test. Several numerical experiments are carried out in order to emphasize the performances of our new statistic for whiteness     

数字通信对称电缆生产工艺及设备探讨

主要介绍了数字通信对称电缆主要生产工艺流程、各工序主要工艺控制点,比较了国内外常用数字通信电缆生产设备性能以及设备主要技术参数。     

A test sequence selection method for protocol testing

A method for automated selection of test sequences from a protocol specification given in Estelle for the purpose of testing both control and data flow aspects of a protocol implementation is discussed. First, a flowgraph modeling the flow of both control and data expressed in the given specification is constructed. In the flowgraph, definitions and uses of each context variable, as well as each input and output interaction parameter employed in the specification, are identified. Based on this information, associations between each output and those inputs that influence the output are established. Test sequences are selected to cover each such association at least once. The resulting test sequences are shown to provide the capability of checking whether a protocol implementation under test establishes the desired flow of both control and data expressed in the protocol specification. The proposed method is illustrated by using the class 0 transport protocol as an example     

某导弹测试设备电路板智能检测系统设计

针对某型导弹测试设备电路板故障缺乏行之有效检测方法的现状，设计了某导弹测试设备电路板智能检测系统。首先简单介绍了电路板检测原理，结合该设备电路板的结构和工作特点，建立了某型导弹测试设备电路板故障检测的模型，阐述了该系统硬件各功能模块的设计方案和系统软件实现方法；以典型的光电转换电路的测试为例，对电路板智能检测系统的进行了试验；试验结果表明，该系统能解决导弹测试设备电路板检测困难、测试效率较低的问题，提高了检测的效率和故障定位的能力，其性能稳定可靠，操作使用方便，结果显示直观；结合试验积累的经验，从两个方面对下一步继续研究进行了展望。本文网络版地址：http：//www.eepw. com.cn/article/273266.htm     

新新相惜:浅谈新一代网络的高效率线路测试方式

本文用新的MELT线路测试方法揭开了对新一代网络测试的准确度和易用性。     

A new design concept for hollow-cathode white light laser

A white light laser has been constructed which employs a concentric cylinder type laser tube and embodies the novel concept of separating the functions of confining the negative glow providing for diffusion of Cd vapor. The main source preventing the white light oscillation in previous designs is not a lack of Cd vapor in lasing zone but a decrease of the hollow-cathode effect due to many holes of large diameter.     

一种新的横模选择概念与方法

提出并研究了利用腔中中空波导管选择横模的新概念和方法。基于这种方法的复合腔激光器实现了在不施行压缩振荡模体积情况下获得单横模高功率密度输出。理论分析与实验结果表明了这种新技术的诱人的应用前景。     

军用电子设备筛选与老炼

阐述军用电子设备筛选和老炼程序;电子元器件装机前筛选;部组件及设备筛选方法及注意事项。     

A microwave radar technique for dynamic testing of large structures

In this paper, the authors propose an innovative survey radar technique based on microwave holographic images for dynamic testing of large structures providing both vibration amplitude pattern and frequency. Theoretical background is provided and experimental results obtained during a dynamic test on a concrete and masonry building are reported.     

A new photoreceiver concept using InGaAs-transferred-electrondevices

A new optical receiver is proposed incorporating an InGaAs-transferred-electron device with Schottky gate-electrode (STED) and an InGaAs-metal-semiconductor-metal detector (MSM). This photoreceiver is applicable to the detection of digital, intensity modulated signals and can be integrated on an InP-substrate. The monolithically integrated circuit has been fabricated. Both the integrated STED and the MSM detector has been characterized. From the measurements the receiver can be expected to offer high current gain and inherent pulse shaping. Based on experiments the sensitivity and the gain of the photoreceiver as a function of the bit-rate has been calculated     

Multimedia multi-networking: A new concept

Recent researches in communication systems are leading to the multiplication of communication technologies. Because of this trend there is now a very wide range of different kinds of networks from copper lines for telephony to high speed fibres, as well as satellite or wireless mobile networks. It would then be very useful to be capable of using all these new communication networks all together. We call this domain related to the use by an application of several different networks “multi-networking”. But the problematic of multi-networking is two folds: (1) First, it can be really interesting to have several network access and to be able to use them in parallel. For instance, it can consist, in the case of digital and interactive tv, of using digital satellite channels for broadcasting audio and video, and using the wire Internet or anIsdn (Integrated Services Digital Network) network to send specific data to dedicated users. This is what we call “parallel multi-networking”. (2) The second folder of this problematic deals with guaranteeing Quality of Service (QoS) while connections cross several networks or domains, especially when there are firewalls orNat (Network Address Translation) servers in between that break the end to end IP model. In addition, the introduction of wireless or satellite links that have high delays and loss ratio inside the Internet can lead to important QoS degradation as wire Internet protocols are not efficient on wireless and satellite links. This aspect of the problematic is called “serial multi-networking”. This second aspect has been much more addressed in a recent past than the first one. It leads to some specific solutions, most of the time application oriented, as caching for web application for instance. To cope with other problems, as the introduction of satellite links in the Internet, proxies system have been designed to handle data flows before entering the satellite link. Proxies are, there, in charge of performing some spoofing operations. But in any case, even if there are some application specific solutions, or some network dedicated approaches, none of them is able to handle live real time traffic. Hence, this work aims to propose a new solution relying on new protocols and architecture to cope with multi-networking. The solution for parallel multi-networking is called MMPOC-MN (MultiMedia Partial Order Connection for Multi-Networking). It is based on a partially ordered and reliable communication principle that allows us to reduce the end to end delay, and to enforce synchronisation between parallel flows on separated networks. This protocol can then be tuned very precisely in order to be the optimal transmission protocol according to application requirements and network constraints. To cope also with serial multi-networking, this protocol architecture has been extended. The new general (parallel and serial) multi-networking protocol is called MNP (Multi-Network Protocol). It is based on the concept of splitting the end to end connection in several trunks, each trunk being supported by a single network domain, each domain being supported by a single technology. Then, the best suited transmission parameters are used on each trunk, and the most suited spoofing algorithms are applied on data streams depending on the application requirement model. These protocols and architecture have been developed using the opnet modeller and simulated, to evaluate the benefits of our solution. In this paper we are also focusing on how deploying such applicative protocol and architecture. The recommended solution consists in using active networking as ANTS, capable to download and run portable code on network components.