关于“线性无耗零状态网络的互易性和幺正性”的讨论

本文对“线性无耗零状态网络的互易性和幺正性”一文中的某些论点有不同看法,现提出讨论,说明了互易定理与互能定理的区别,指出线性无耗零状态网络不都是互易网络。     

线性无耗零状态网络的互易性和幺正性

线性无耗网络不一定同时具备互易性和幺正性,但在零状态条件下,线性无耗网络同时具有互易性和幺正性。本文从互能定理出发,证明了标量媒质和双各向异性张量媒质的线性无耗零状态网络的互易性和幺正性。     

电磁网络的无耗性与互易性

本文分析了一般电磁网络的无耗性质和互易性质，指出在各向异性媒质中从网络的无耗性质导出互易性质的所谓“证明”是错误的，文中还讨论了无论耗网络的内在对称性，深入研究了其中存在的似互易性。     

基于矢量网络分析仪的射频无源器件阻抗测量

电信运营商网络在不断布网,阻抗作为测试中的一个重要指标也是衡量整个网络布局的重要因素。本文阐述了射频无源器件阻抗和其他参量之间的关系,并举例说明了阻抗在实验室测量中的方式方法。     

电磁互易对称性和无耗对称性

本文深入探讨了两种电磁对称性:Lorentz互易对称性和Hermite无耗对称性.给出了它们在多端口网络系统中的表达形式.文中指出,非互易无耗网络的阻抗矩阵可以存在实部,即Z=R+jX,且RT=-R反对称,而网络型Foster定理则深刻的揭示了S参数的频率导数S(δ)S+/(δ)(jω)有广义惯性,不能过大.本文最后得到在辛意义下,电磁互易对称即辛内积正交,而二阶归一化电阻R矩阵正好是典型的辛矩阵.     

非合作无源探测的发展综述

非合作无源探测系统具有良好的发展前景。本文对非合作无源探测概念进行了描述,详细介绍了国内外的研究现状,分析了非合作无源探测系统的部分关键技术问题,介绍了现阶段解决这些问题所采用的相应方法,同时提出了一些可用于解决这些问题的新方法,最后结合文献分析了非合作无源探测技术的发展趋势。     

非合作C模式信号识别与无源定位仿真分析

在研究无源定位技术用于非合作C模式信号接收的基础上,分析并总结机载应答信号A/C模式脉冲编码规则与识别准则;推导基于方位、俯仰两维测角信息和高度码信息的目标单站定位方程,仿真不同种类误差对定位精度的影响,对工程应用有一定的参考价值。     

对运动辐射源单站无源定位的最大似然估计

讨论了利用测量获得的运动辐射源的方位角和到达时间差信息,通过最大似然估计实现定位的方法。文中给出了计算机模拟结果,并与模型的克拉美罗界（ＣＲＬＢ）作了比较。该方法具有定位精度高,算法稳定等优点。     

非合作无源探测中的快速测向

研究了非合作无源探测中目标方向的快速测量方法.该方法估计探测空域内的近似ARD曲面以估计目标的数目、双基地距离及多普勒频率,在此基础上利用空间扫描时目标回波在不同波束下的接收幅度估计目标的方位.证明了该测向方法是几乎无偏的、推导了该方法的估计方差范围,从理论推导了该方法的最高精度,并说明了阵列波束形成采用矩形权值时,其理论最高精度达到阵列测向的克拉美-罗界.仿真实验表明该方法是正确有效的.     

对机动目标单站无源定位的最大似然估计

研究了基于目标的信号到达方向和信号到达时问差信息，利用单个固定的无源侦察站，通过最大似然估计方法对机动目标进行定位的问题。首先建立了机动目标模型与观测方程，然后详细推导了定位算法，并进行了仿真实验。仿真结果表明，该方法具有定位精度高、算法稳定等优点。     

Broadband impedance matching via lossless unsymmetrical lattice networks

In this paper, a broadband impedance matching network (equalizer) design algorithm has been proposed. In the equalizer, a lossless unsymmetrical lattice network has been utilized. The branch impedances of the lattice network are considered as singly terminated lossless LC networks, since it is not desired to dissipate power in the equalizer. After giving the algorithm, its usage has been illustrated via an example.     

基于ARM嵌入式系统的高保真无损音乐播放器设计

介绍了1种基于ARM11嵌入式平台和嵌入式Linux内核,界面美观、操作便捷的高保真无损音乐播放器的设计。它支持WAV、FLAC和APE3种无损压缩格式音乐;还可通过触摸屏实现浏览音乐目录,控制音乐的播放、暂停和调节播放进度等控制功能;它支持外接移动硬盘、SD卡和优盘等大容量存储设备。在开发平台上已实现采样位数16或24,采样率上限48kHz的WAV、FLAC和APE高保真音乐播放。     

多光谱扫描仪（MSS）卫星遥感图象原始数据的信息保持型压缩编码

电视图象(隔行扫描)编码中采用的预测器：x^0=1/2x1′ 1/4(x3′ x4′)，同样适用于多光谱扫描仪(MSS)卫星遥感图象原始数据(逐行扫描)的信息保持型压缩编码．采用此预测器和简单的熵编码(A3码)，在两类计算机上用软件实现了典型MSS数据的信息保持型的编码／解码，压缩比略大于2．本文是课题报告及后续工作的简要报导，所提出的算法现JPEG建议中有关部分相似．     

Lossless chain code compression with an improved Binary Adaptive Sequential Coding of zero-runs

A new method for encoding a sequence of integers, named Binary Adaptive Sequential Coding with Return to Bias, is proposed in this paper. It extends the compressing pipeline for chain codes’ compression consisting of Burrows Wheeler Transform, Move-To-Front Transform, and Adaptive Arithmetic Coding. We also explain when to include the Zero-Run Transform into the above-mentioned pipeline. The Zero-Run Transform generates a sequence of integers corresponding to the number of zero-runs. This sequence is encoded by Golomb coding, Binary Adaptive Sequential Coding, and the new Binary Adaptive Sequential Coding with Return to Bias. Finally, a comparison is performed with the two state-of-the-art methods. The proposed method achieved similar compression efficiency for the Freeman chain code in eight directions. However, for the chain codes with shorter alphabets (Freeman chain code in four directions, Vertex Chain Code, and Three-OrThogonal chain code), the introduced method outperforms the referenced ones.     

Learning with handoff cost constraint for network selection in heterogeneous wireless networks

In heterogeneous wireless networks, network selection algorithms provide the user with the optimum network access choice. The optimal network is evaluated according to network parameters. Considering that the network parameters are dynamic and unavailable for the user in realistic heterogeneous wireless network environments, most existing network selection algorithms cannot work effectively. Learning‐based algorithms can address the problem of uncertain network parameters, while they commonly need considerable network handoff, resulting in unbearable handoff cost. In order to tackle the uncertainty of network parameters, we formulate the network selection problem as a multi‐armed bandit problem. Moreover, two online learning‐based network selection algorithms with a special consideration on reducing network handoff cost are proposed. By updating in a block manner, both algorithms achieve optimal logarithmic‐order regret and limited network handoff cost. The simulation indicates that the two algorithms can significantly reduce the network handoff cost and improve the transmission performance compared with existing algorithms, simultaneously. Copyright © 2014 John Wiley & Sons, Ltd.     

利用无损压缩降低循环冗余校验的错误漏检率及其电路实现

循环冗余校验(CRC)算法在很多领域都有广泛的应用。对于确定格式的CRC校验码生成多项式,其错误漏检率基本为确定值。因此待检数据的长度越大,出现错误而不会被检测到的机会也就越多。为了解决这方面存在的问题,该文利用无损压缩霍夫曼算法缩短待测数据的长度,从而降低了数据出错之后不能被检测到的概率。并设计出相应的可靠性校验电路。与单纯使用CRC校验的方法相比,该文提出的方法可以将出错的几率下降为原来的万分之一以下。设计得到的电路模块可以作为VLSI中的可靠性电路模块(IP)加以利用。     

基于分类和陪集码的高光谱图像无损压缩

在基于陪集码的高光谱图像压缩算法中,由于按照编码块的最大残差确定整块无损压缩所需的码率存在较大冗余,该文提出了基于分类和陪集码的高光谱图像压缩算法。首先利用前一波段对应位置的预测噪声对当前波段编码块的像素进行分类,将具有相似相关性的像素归于一类,然后对每一类像素分别进行陪集码编码。实验表明分类可以有效地降低码率。和基于陪集码的算法相比,该文算法无损压缩的平均码率降低了大约0.4 bpp。     

Passive optical networks for local telephony and cable TV provision

Recent proposals have been made for a passive optical local access network (PON) for telephony and cable TV applications. These are leading to the design of new telecommunications customer access equipment whose functional requirements are discussed, together with details of the system demonstrators at BTRL. Possible sccenarios for network deployment are presented.     

On the non-blocking conditions of self-routeing multistage interconnection networks

This paper studies the non-blocking conditions of a generic N × N multistage interconnection network, such as an omega network or an n-cube network, in which only one path connects any inlet to each outlet and different I/O paths can share interstage links. It is widely known that any of these networks is non-blocking for a compact and monotone pattern of k ≤ N I/O paths. Recently it has become very important to show the network non-blocking property for permutation sets, wider than the compact and monotone, which are usually encountered in broadband ATM networks. By using a new approach based on the concept of distance between I/O paths, we show here that these networks are non-blocking for a set of I/O paths obtained by shifting cyclically the inlets of a compact and monotone pattern of I/O paths by an arbitrary number of steps.     

Out of band signalling technique for passive optical networks

In this communication we present a novel means of signalling between an out-of-service RT and the CO when connected via a passive optical network which contains other RTs in-service using a TDMA protocol. A simple experiment using a non-coherent receiver is used to demonstrate the technique.