Estimation of High-Frequency Currents From Near-Field Scan Measurements

High-frequency currents on the pins of integrated circuits (ICs) and on printed circuit board (PCB) traces are needed to predict and analyze electromagnetic interference in high-speed devices. These currents can, however, be difficult to measure when traces are buried within the PCB or chip-package, especially when several current-carrying traces are in close proximity. Techniques for estimating high-frequency currents from near-field scan data are proposed in this paper. These techniques are applied to find currents on the pins of an IC, on traces buried beneath other traces in a PCB, and on traces over a slot in the ground plane. Methods of dealing with the ill-posed nature of the current-estimation problem are discussed, as are applications to electrically large structures. A study of the sensitivity of the technique to errors in the measured fields, errors in the circuit geometry, and errors in the estimated dielectric constant of the PCB or chip package show that, for reasonable errors in these parameters, currents can be estimated to within an average of 20% (1.6 dB) or less of their correct values.     

A Graph-Theoretic Approach to Constrained Floor Plan Estimation From Radar Measurements

This paper proposes an approach to deducing the floor plan of a building using only a set of noisy room dimension measurements that have been obtained indirectly through radar probes. It is not assumed that the set of measurements is complete. The key feature of this approach is a method of relating, via a graph-theoretical construction, a given floor plan topology to a model that depends linearly on a minimal set of parameters. Given a list of floor-plan topologies and a system of realizability constraints, it is possible to formulate this problem as a constrained least-squares optimization problem. An algorithm for generating all floor plan topologies with a specified number of rooms is presented, as well as an algorithm for deciding if two floor plan representations are isomorphic. The techniques in this paper are intended to serve as an exploration into the theoretical performance bounds on the floor plan estimation problem.     

基于精密测距测角的相对定位方法

本文介绍了一种基于舰船间精密测距、测角的相对定位方法,以克服现有导航定位模式存在的缺点和不足,减小多舰船协同作战系统中由定位、航向误差引起的目标位置报告差异。 误差分析与仿真试验说明,该方法在一定条件下是有效的。     

Geometric-Polar Tracking From Bearings-Only and Doppler-Bearing Measurements

Bearings-only tracking (BOT) and Doppler-bearing tracking (DBT) perform target motion analysis from measurements of bearings, Doppler and bearings, respectively. The state equations are simple for both the target and observer in the rectangular coordinates. Hence, BOT and DBT mostly work in that coordinate. By developing the trigonometric relations between target and observer postions over time, this paper first derives the pseudolinear equations for direct range and bearing estimation. It then provides a generalized total least squares (GTLS), and a maximum likelihood solution. Polar tracking has two advantages over rectangular. First, for applications that require range and bearing, polar output avoids a coordinate conversion at every output instant. Second, polar equations often have a smaller bias than rectangular. Consequently, polar estimates can give a closer (to the optimum) initialization for iterative algorithms. Simulation results have validated the theoretical development, confirming the near optimality of the GTLS and maximum likelihood solutions.      

Test Rig for High-Temperature Thermopower and Electrical Conductivity Measurements

A high-temperature test rig to simultaneously measure electrical conductivity and thermopower is described. The apparatus allows to perform measurements in a controlled atmosphere or vacuum to protect oxygen-sensitive materials. A spring-loaded mounting placed in the cold zone reduces the thermal contact resistance between the sample and two metallic blocks (the hot side and the heat sink) even at high temperatures. The hot-side metal block is periodically heated to obtain the thermopower from the slope of ΔV versus ΔT. Conductivity is measured before each thermopower measurement by a linear four-wire method. The automatic data acquisition and analysis are controlled by a LabView-based interface. Two interchangeable setups are possible. The first one uses silver blocks and K-type thermocouples and is suitable for temperatures from 300 K to about 1000 K. The second one uses W blocks and S-type thermocouples to allow higher-temperature measurements since all the hot-zone parts are made of Al₂O₃, Pt or W. The device was tested using PdAg alloy and Ni rods and, for the low-temperature range, the NIST standard reference material 3451 (bismuth telluride), strictly confirming the reference data.     

半导体激光器的光谱及参数测量

半导体激光器的输出光谱,反映了激光器本身的基本工作特性。本文从实验上研究了半导体激光器的输出光谱特性随偏置电流而变化的关系,并对其进行了理论分析。在此基础上,进一步测得了半导体激光器的热阻,增益峰值波长和纵模波长对载流子密度的相对变化率等基本参量。     

Microwave Emission and Scattering From Deserts: Theory Compared With Satellite Measurements

The emission and scattering from desert surfaces are analyzed using simulations and measurements from the Special Sensor Microwave/Imager (SSM/I) and the Advanced Microwave Sounding Unit (AMSU) microwave satellite instruments. Deserts are virtually free of vegetation, so the satellite radiometers are able to observe the emissivities of different minerals, such as limestone and quartz. Moreover, since deserts contain little moisture, the thermal emission originates below the surface at a depth of many wavelengths. At high frequencies, where the penetration depth of radiation is smallest, the radiometric measurements display the large diurnal variation in surface temperature, which reaches its maximum at around 1 P.M. Conversely, at low frequencies, where the penetration depth is largest, the radiation measurements display the small diurnal variation of subsurface temperature, which reaches a minimum at around 6 A.M. In addition to these emission signals, sand particles also scatter microwave radiation. Volume scattering causes the measurements to decrease as the frequency increases; although compared to other scattering media (snow cover and precipitation), the larger absorption and fractional volume (i.e., solidity) of sand reduce the scattering. Although the scattering effect is small, SSM/I measurements between 19 and 85 GHz show that deserts scatter the upwelling microwave radiation in a manner similar to light precipitation, which makes it difficult to uniquely identify precipitation over arid regions. Interestingly, the higher frequency AMSU measurement at 150 GHz is nearly the same as at 89 GHz for deserts, whereas the 150-GHz measurement is much lower than at 89 GHz for precipitation. These different spectral features at high frequencies can provide a means of separating the scattering from desert surfaces from that of precipitation.     

Pseudo-Codeword Analysis of Tanner Graphs From Projective and Euclidean Planes

We consider coded data transmission over a binary-input output-symmetric memoryless channel using a binary linear code. In order to understand the performance of maximum-likelihood (ML) decoding, one studies the codewords, in particular the minimal codewords, and their Hamming weights. In the context of linear programming (LP) decoding, one's attention needs to be shifted to the pseudo-codewords, in particular, to the minimal pseudo-codewords and their pseudo-weights. In this paper, we investigate some families of codes that have good properties under LP decoding, namely certain families of low-density parity-check (LDPC) codes that are derived from projective and Euclidean planes: we study the structure of their minimal pseudo-codewords and give lower bounds on their pseudo-weight. Besides this main focus, we also present some results that hold for pseudo-codewords and minimal pseudo-codewords of any Tanner graph, and we highlight how the importance of minimal pseudo-codewords under LP decoding varies depending on which binary-input output-symmetric memoryless channel is used.     

航迹关联和相对系统误差估计

航迹关联是多传感器多目标跟踪系统中的关键问题。当存在系统误差时航迹关联问题变得更复杂。该文将最优Bayes联合决策估计(JDE)法应用于存在系统误差的航迹关联中,并提出了简化的JDE法。最优Bayes JDE,通过在航迹关联时考虑传感器相对系统误差的估计误差,在相对系统误差估计时考虑航迹关联误差,来提高航迹关联的正确率和相对系统误差的估计精度。提出的简化JDE法可减少了计算量,其性能比最优JDE稍差。并给出了matlab仿真结果来验证方法的有效性。     

卷积窗及其在电力系统参量估计中的应用

利用矩形窗的多重卷积,导出一类新的窗函数,称其为卷积窗,并研究其在电力系统的参数估计中的应用.误差分析和数值模拟表明: 若采用k阶矩形卷积窗(矩形窗的k重卷积),各电气参量测量值的误差正比于相对频偏的k次方.在电力系统中,只需取4阶窗函数,便可将因非同步采样引起的测量误差降低到10^-7的量级,而不必采用任何同步采样措施.     

IDES: An Internet Distance Estimation Service for Large Networks

The responsiveness of networked applications is limited by communications delays, making network distance an important parameter in optimizing the choice of communications peers. Since accurate global snapshots are difficult and expensive to gather and maintain, it is desirable to use sampling techniques in the Internet to predict unknown network distances from a set of partially observed measurements. This paper makes three contributions. First, we present a model for representing and predicting distances in large-scale networks by matrix factorization which can model suboptimal and asymmetric routing policies, an improvement on previous approaches. Second, we describe two algorithms-singular value decomposition and non-negative matrix factorization-for representing a matrix of network distances as the product of two smaller matrices. Third, based on our model and algorithms, we have designed and implemented a scalable system-Internet Distance Estimation Service (IDES)-that predicts large numbers of network distances from limited samples of Internet measurements. Extensive simulations on real-world data sets show that IDES leads to more accurate, efficient and robust predictions of latencies in large-scale networks than existing approaches     

细长型高功率脉冲氙灯

高功率脉冲氙灯主要在惯性约束聚变(ICF)研究中用作高功率激光驱动器的抽运光源,其各项性能和使用寿命对高功率激光驱动器的整体工作性能影响很大。在改进制灯材料和管壁结构的基础上,研制了两种不同规格的细长型高功率脉冲氙灯:一种是in16 mm,放电弧长为1140 mm;另一种是in17 mm,放电弧长为1270 mm。研制的细长型高功率脉冲氙灯,其极限负载能量大、工作寿命长、辐射效率高,工作性能较原先脉冲氙灯有很大的改进和提高。     

Accurate Bluetooth Positioning Using Weighting and Large Number of Devices Measurements

One of the most efficient methods to reduce the dropping and blocking probabilities of the secondary users (SUs) in cognitive radio networks is channel sub-banding strategy. This means that when all the channels are occupied by the primary and secondary users, then the SUs’ channels can be divided into two sub-bands, and two SUs can use a sub-band, simultaneously. In this paper, we propose an opportunistic spectrum sharing system in cognitive radio networks in which, the channel sub-banding strategy is implemented. Furthermore, we describe the problem of channel sub-banding considering the spectrum sensing errors such as false alarm and miss-detection events for both initial and on-going SUs’ calls. Due to unreliable spectrum sensing by the SUs and subsequently possible interference with the primary users, we assume that both primary and secondary users may lose the channel due to the collision. The proposed model is analyzed by a two-dimensional Markov chain model and for performance evaluation, metrics such as blocking and dropping probabilities and channel utilization are derived. Numerical and simulation results show the accuracy of the proposed model which can be used in the evaluation of future cognitive radio networks’ performance.     

网络分析仪的工作原理及在测量领域的应用

介绍了矢量网络分析仪的基本原理、应用范围,通过对矢量网络分析仪原理的介绍和误差修正,帮助理解和改进使用矢量网络分析仪进行测量的各种方法。同时详细介绍了矢量网络分析仪在部分测量领域的使用。包括：如何解决高功率放大器在测量中大功率电平的问题;如何解决电缆测量中延迟时间的问题;如何改进反射测量;如何利用频偏方式来测量混频器、变频器和调谐器等频率转换器件;如何提高非插入式器件测量的精度。     

DisHAP:基于层次亲和聚类的分布式大图划分算法

平衡图划分是改善并行图计算性能的关键.一个良好的划分算法应保证划分后的子图在负载均衡的前提下,减少子图之间的交互边(切割边)规模,从而减少网络通信.对此,本文设计一种基于层次亲和聚类的分布式大图划分算法(DisHAP).该算法采用亲和聚类的思想,将图初始划分为规模相等的k个子图;再将结果映射成顶点序列,以线性嵌入顺序处理节点,通过局部交换策略优化割边率;最后将DisHAP应用在MapReduce框架中,使用多种真实及理论图数据,与现有的大图划分算法做比较分析.以Twitter图为例,划分2,4,8,16,32个子区,相较于现有的大图划分算法(LDG,BLP,Spinner,Fennel,ParMetis及PSA-MIR算法),割边率减少1.7％～30.2％,说明了该算法的优越性.同时该算法具有良好的可扩展性,划分的子区数量及图的规模对划分时间具有较低的影响.     

Use of Flow Graphs to Evaluate Mistermination Errors in Loss and Phase Measurements (Correspondence)

Epprecht calculated the scattering matrix of two cascaded two-ports. Redheffer does the same for the 2n-port using non-standard notation. This note will comment on the physical interpretation of the constituents of the resultant-scattering matrix.     

基于量测预测联合估计的单站只测角跟踪

提出用于单站只测角系统的修正最佳线性无偏估计(BLUE)滤波器。针对BLUE 滤波器用于雷达目标跟踪时需要完备的非线性观测集合来构建转换量测及单站只测角系统只提供方位观测,无法直接应用普通BLUE滤波器跟踪目标的问题,构造了基于目标状态预测的预测斜距,并在分析预测斜距误差统计特性后,用斜距预测和方位观测组成转换量测,推导出可应用于单站只测角系统的BLUE滤波模型。所提改进算法在性能和运算量上有明显优势,有很好的应用潜力。     

卫星地面站干扰环境电测及采取的抗干扰措施

本文介绍海峡之声广播电台广播卫星地球站微波干扰环境电测的理论根据，测试方法，以及在大功率中短波发射台建广播卫星地球站采取的抗干扰措施。     

Radio Signals with Large Relative Bandwidth for Over-the-Horizon Radar and Spread-Spectrum Communications

It is known that radio signals must have a small relative frequency bandwidth if structures and circuits resonating with sinusoidal functions are to be used for radiation and reception. This paper develops concepts showing that a small relative frequency bandwidth is also required for the use of amplitude or frequency modulation of sinusoidal radio carriers in the usual form. However, it is easy to modify the usual methods of amplitude and frequency modulation for signals with large relative frequency bandwidth. The primary application of such methods is for over-the-horizon radar and spread-spectrum communications in the short-wave region where the desired relative frequency bandwidths are neither small (in the order of 0.01 or less) nor close to 1.