不变性测试方程法在开边界多导体静电系统分析中的应用

在"测试环"概念的基础上,提出了两种确定MEI系数的方法.数值结果表明,利用电偶极子层激励作为测试子和自由空间格林函数作为积分核确定MEI系数的方法,比之其它方法具有更高的精度和明显的优点.分析并总结了数值实验中出现的一些问题,使得对MEI方法的理解更深入了一步.另外,对MEI方法的不稳定性和有效性也做了理论分析.最后,利用本文方法计算了一个较为复杂的微带线参数,得到了满意的结果.     

基于最小覆盖的多点中继集及其选择算法

多点中继广播机制是无线mesh网络中一种高效的广播方法.但由于不同1跳邻居节点对相同2跳邻居节点的重叠覆盖,当前基于图论最小控制集理论的多点中继集易造成无线资源的浪费.定义一种使网络中重叠覆盖数量最少的多点中继集,并提出选取这样的多点中继集的快速启发式算法.通过仿真结果证明使用重叠覆盖数量最少的多点中继集能够有效利用无...     

时域MEI方法在矩形导体柱散射问题中的应用

本文用时域有限差分法（FDTD）模拟二维矩形导体柱的电磁散射场，采用时域不变性测试方程（MEI）作为吸收边界条件对该散射场进行求解。将所得计算结果与截断边界网格点采用Mur二阶吸收边界条件所得的数值结果相比较，两者吻合很好。结果表明使用时域MEI方法作为吸收边界条件能有效缩短截断边界与物体边界的距离，且能得到足够精确的解。     

利用锁频环路的快速跳频合成信号发生器

介绍一种高性能快速跳频合成信号发生器,利用锁相环路和锁频环路相结合的原理和跳频校准控制技术而实现的。着重介绍了延迟线鉴频器锁频环路的工作原理、低噪声特性和宽带特性,仪器实现低相噪和快速频率转换的机理。介绍了通过信道、序列设置,每个频率点的环路增益参数和预调电压的校准和存储,实现快速跳频的方法。     

传输线与延迟线

0102204时域 MEI 方法初探[刊]/廖成//电波科学学报.—2000,15(3).—323～327(K)对时域 MEI 方法进行了初步探索,根据 MEI 方法的基本原理.建立起时域 MEI 方法的一阶吸收边界条件.应用该条件对线源辐射问题的数值实验和研究表明.它可使截断边界离源更近。同时也证实了时域MEI方法的可行性和精确性。参13Y2000-62483-45 0102205嵌入式自定时系统的芯片级动态再校准延迟线=Anon-chip dynamically recalibrated delay line for embeddedself-timed systems[会,英]//2000 IEEE 6th Internation-al Symposium on Advanced Research in AsynehronousCircuits and Systems.—45～51(EC)     

MEI系数循环卷积的快速解法

提出了一种用于减少不变量测试方程(MEI)法计算时间的快速算法,循环卷积和快速多极子(FMM)技术(CC-FMM)分别用于不同区域对应的MEI系数,可以加速建立不变量测试方程所需系数的计算.由于循环卷积和FMM的计算效率明显高于直接求和,故整个算法的计算时间明显减少.二维验算实例验证了这种算法的有效性和准确度.     

点对多点微波通信系统跳频同步的设计实现

跳频通信具有很强的抗干扰、抗衰落、抗截获能力,兼有能多址组网应用等诸多优点。跳频同步是跳频通信的技术关键,也是跳频通信系统开发的难点,只有实现了快速精确的同步,才能正确提取传递信息,发挥出跳频通信的优点。分析了点对多点微波传输及时分多址通信跳频同步的特点,结合工程中的时分多址跳频抗干扰通信技术,设计了一种基于TOD的同步方案,并利用FPGA技术实现,给出了应用过程中的跳频图案及其同步过程的详细设计。     

基于小波变换的跳频信号跳速盲估计算法研究

针对传统的语图测量方法在跳频信号跳速估计中跳变点定位存在的时间模糊现象,利用小波变换在奇异点检测方面的独优势,提出了一种基于小波变换的跳速盲估计的新方法,并给出了仿真试验,仿真结果表明该方法能够准确地提取跳频信号的跳速,并具有较高的抗信噪比性能。     

快速跳频频率合成

跳频通信具有抗干扰能力强,保密性好等优点,已被广泛地应用于通信、雷达、电子战等领域。此系统的关键是其快速跳频频率合成器,本文以跳频速度为中心,对实现快速跳频的频率合成方法进行了综合、分析、讨论,并提出了几种快速跳频频率合成方案。     

对相位编码信号的部分相关检测

根据二相编码信号在相位突跳点两侧具有反相特性,提出一种二相编码解调方法：利用构造的相位突跳点样本,对各突跳点完成相关检测,并可在此基础上对编码进行重构。相关处理所具有的增益使得该方法可应用于对信噪比较低的相位编码信号的侦察。     

步进式集成电子变阻器

提出一种新型的步进式集成电子变阻器.其电路输出的电阻或电位的变化是逐级平缓地进行,没有跳变现象.还以成功的应用实例介绍了该项技术在直流电动机调速系统中的具体应用,解决了生产实际中的一些问题,使用非常方便,在电子技术应用中有广阔的发展空间.     

一种空域可分级的自适应视频码流控制方法

在传统的CBR码流控制中,为防止缓冲器上溢,通常采用跳帧的方法来保持码率恒定。由于跳帧引起解码端运动补偿误差增大,客观上造成跳帧期间图像PSNR降低,图像失真度迅速增加,在主观上造成图像有跳跃感,画面不流畅。针对以上缺陷,该文基于H.263+的TMN8帧级码流控制算法,提出了一种空域可分级的自适应码流控制方法。该方法在编码端对原跳帧方法中不编码的帧进行自适应下采样编码,解码端通过上采样恢复。实验结果证明,该文提出的码流控制算法在低带宽条件下,图像质量较跳帧方法有较大提高。在低码率条件下,对于高运动图像该方法的平均PSNR值比采用跳帧的码流控制方法高0.3~0.8dB;比采用增大量化步长的方法高0.1~0.4dB,而对于跳帧阶段PSNR值,该算法比传统的跳帧方法高1~2dB左右。     

非相干扩频测量体制应答机的测距数据处理

介绍了一种非相干扩频测量体制的测距原理,分析了测距跳周问题对测距精度的影响,提出了一种测距数据处理算法.采用相位相差180°的双码钟采样法,对两个码计数和两个码相位进行采样和时差比对,判别出距离跳变的数值进行算法修正,有效消除了码计数对应的距离跳周问题,保证了系统的测距精度.该算法已经成功运用到多个实际工程中,系统测距精度完全满足指标要求.     

一种基于MJPEG2000的实时跳帧图像传输系统

介绍一种基于MJPEG2000格式的无线实时图像传输系统中跳帧视频传输的设计与实现,图像的压缩与解压缩利用专用硬件ADV202实现,通过FPGA实现跳帧与补帧,在信道速率受限的情况下,能有效提高传输图像质量.     

User adaptation to interactive advertising formats: The effect of previous exposure,habit and time urgency on ad skipping behaviors

Due to commercial information loss of efficacy, social media advertising introduced skippable formats as an interactive function to attract customers. This empowerment of users could also favor the development of their skills and strategies to deal with online advertising, which may result in a lower advertising effectiveness. A study with 286 YouTube users was carried out to investigate this adaptation process to an advertising format by focusing on pre-roll skippable video ads. In contrast to advertisers’ approach (e.g. improving the persuasiveness of the ad), our research deepens on the ad skipping phenomenon from a human and context based perspective. In favor of an ad avoidance training effect, the findings show that participants previously exposed to a skippable ad are faster in taking the decision to watch or skip a subsequent ad. Participants’ skipping habits and time urgency are also revealed as main determinants of different ad skipping behaviors. This innovative research provides empirical support for the adaptation process leading people’s interrelation with interactive advertising formats. Practical and theoretical consequences are discussed for advancing on this underexplored topic.     

高性能视频编码帧间预测的单元划分优化算法

新一代的高性能视频编码(HEVC)通过应用各种先进技术来大幅提高视频编码的性能,然而,这些方法也大大增加了整个编码过程,尤其是预测编码阶段的计算复杂度。该文提出一种应用于高性能视频编码帧间预测的快速单元划分算法。该算法基于HEVC灵活的四叉树结构,根据被编码单元的运动特性来确定所编码信息的阈值,并以此作为单元划分的提前终止条件,从而减少了不必要的单元划分操作和率失真代价的相关计算,达到节省编码时间和降低编码复杂度的目的。实验结果表明,在峰值信噪比(PSNR)损失仅为0.0418 dB的情况下,所提算法可以平均降低46.1%的编码时间。     

基于状态机控制的降压型开关电容DC-DC转换器

介绍一种基于状态机控制的多种增益模式转换的控制方法,采用增益跳变和跳周期调制技术,控制增益模式的切换和开关频率,使输出电压稳定,并使系统有较高的转换效率。基于csmc0.5 μm CMOS工艺进行spectreverilog[JP]仿真,结果表明能准确控制3种增益的切换和开关频率的变化,并可输出约1.8 V的稳定电压,纹波＜20 mV,达到了预期目的。     

Circular BIST with state skipping

Circular built-in self-test (BIST) is a "test per clock" scheme that offers many advantages compared with conventional BIST approaches in terms of low area overhead, simple control logic, and easy insertion. However, it has seen limited use because it does not reliably provide high fault coverage. This paper presents a systematic approach for achieving high fault coverage with circular BIST. The basic idea is to add a small amount of logic that causes the circular chain to skip to particular states. This "state skipping" logic can be used to break out of limit cycles, break correlations in the test patterns, and jump to states that detect random-pattern-resistant faults. The state skipping logic is added in the chain interconnect and not in the functional logic, so no delay is added on system paths. Results indicate that in many cases, this approach can boost the fault coverage of circular BIST to match that of conventional parallel BIST approaches while still maintaining a significant advantage in terms of hardware overhead and control complexity. Results are also shown for combining "state skipping" logic with observation point insertion to further reduce hardware overhead.     

A Computer Optimization of the Rayleigh-Ritz Method

A method has been developed to improve the use of the RayIeigh-Ritz procedure. A criterion is established, which is a measure of the cumulative improvement due to the addition of more and more terms in the series expansion. Without calculating the exact roots of determinantal equations, the convergence is accelerated by skipping unnecessary intermediate steps. The computation time is drastically reduced because the final result is obtained after only a few (not more than 5 to 7) values of determinants of increasing order. Inhomogeneneously loaded waveguides are chosen as an application because the exact solution is available to check the validity of the method. The results obtained with the method described in this paper are compared with other approximate procedures. The comparison shows a definite advantage for the suggested technique.     

Opportunistic Spectral Usage: Bounds and a Multi-Band CSMA/CA Protocol

In this paper, we study the gains from opportunistic spectrum usage when neither sender or receiver are aware of the current channel conditions in different frequency bands. Hence to select the best band for sending data, nodes first need to measure the channel in different bands which takes time away from sending actual data. We analyze the gains from opportunistic band selection by deriving an optimal skipping rule, which balances the throughput gain from finding a good quality band with the overhead of measuring multiple bands. We show that opportunistic band skipping is most beneficial in low signal to noise scenarios, which are typically the cases when the node throughput in single-band (no opportunism) system is the minimum. To study the impact of opportunism on network throughput, we devise a CSMA/CA protocol, multi-band opportunistic auto rate (MOAR), which implements the proposed skipping rule on a per node pair basis. The proposed protocol exploits both time and frequency diversity, and is shown to result in typical throughput gains of 20% or more over a protocol which only exploits time diversity, opportunistic auto rate (OAR).