天线与天线系统

0609122高功率微波在等离子体填充波导中的传播特性〔刊,中〕/傅文杰//强激光与粒子束.—2005,17(12).—1852-1856(E)在考虑有质动力情况下对高功率微波在等离子体填充波导中的传播特性进行了理论分析和数值计算,研究了高功率微波在等离子体中的传播特性和微波场强与等离子密度之间的关系。结构表明高功率微波的有质动力将影响波色散特性,使微波场强分布偏离Bessel分布,并对等离子体有排开作用,当场强足够大时可将波导中心处等离子体排空形成低密度通道。参90609123一种高精度微波辐射计天线伺服系统〔刊,中〕/王振收//雷达科学与技术.—20…     

天线与天线系统

Y2002.63088·187 0215353交换报合磁系统滞后行为模拟用的局部优化=b父al叩自‘翻‘阅咖ulating hysteretie behe训or of exchanse目喇目功娜,.CS”t~〔会,英〕/sUn,M,&Fuji-,阴比‘H.// PrOC以泪in,of the 33rd与utheastems帅po-址切.的S外tem Theo口一187一192(PE)砚002.63088·193 D215354采用具有透明吸收边界的FDTD技术计算特殊吸收率=SAR司e己ation using FDTD tec俪que袱th trans-p~.卜扣rbing boundary〔会,英〕/卜砧msup,N.//P。-cee庄n,of the 33rd豁以heasterns卿卿iurn on SystemTheo叮一193一195(PE)Y2O02·631…     

天线与天线系统

0210897阻抗加载天线的计算机辅助分析〔刊〕/陈海涛//现代通信技术.—2001,(4).—20～23(C) 本文讨论了用矩量法对线天线的阻抗加载进行计算机辅助分析的问题。详细阐述了阻抗加载天线各种电气指标的计算方法,最后给出了一些计算结果,并与实验测量结果进行了比较,证明本文所介绍的算法是有效可行的。参3     

天线与天线系统

Y98-61450-331 9913402超宽合成孔径雷达的特征天线测量=Antenna mea-sures of merit for ultra-wide synthetic aperture radar[会,英]/Ayers,E.L.& Ralston,J.//1998 IEEE RadarConference.—331～336 (HG)     

天线与天线系统

0100427补偿型 Fresnel 区平板天线[刊,译,英]/李小林//中国邮电高校学报.—2000,7(3).—44～47(E)介绍了一新型补偿 Fresnel 区域平板反射器天线(FZPA)。FZPA 相位修正区是椭圆型的。依据物理光学方法对反射器聚焦特性进行了分析。对新型 FZPA与环型 FZPA、MawzonesFZPA 进行了比较。参60100428测试状态下天线重力产生的变形的确定[刊]//电子机械工程.—2000,(5).—27～29(C)     

天线与天线系统

Y2001-62725-614 0118665健壮波束成形的神经子分量分析=Neural MCA for ro-bust beamforming[会,英]/Fiori,S.& Piazza,F.//2000 IEEE International Symposium on Circuits and Sys-tems,Vol.3.—614～617(HC)本文目的是给出关于神经子分量分析调用的新结果及其对部分自适应阵滤波的应用,使用了约束波束成形仪功率最佳原理,通过强调白噪声灵敏性控制和     

天线与天线系统

Y90-62009-313 0003939标准增益天线与具有等孔径维数的测试天线的增益传送法精度=Accuracy of the gain-transfer method for astandard gain antenna and a test antenna with equal aper-ture dimensions[会,英]/Mayhew-Ridgers,G.& Oden-daal,J W.//Proceedings of the 1998 South AfricanSymposium on Communications and Signal Processing(COMSIG’98).—313～314(PC)     

天线与天线系统

IELDVD069:9880 0600767 2005年IEEE天线技术:小天线和新型元材料会议录 =2005 IEEE International Workshop on Antenna Technology: Small Antennas and Novel Metamaterials[会, 英]／Institute for Information Research．-p．568(E) 本会议录收集了会上发表的174篇论文,内容涉及电子带隙天线,光子晶体,开槽天线,微带天线阵,宽带天线,补片天线,UWB系统天线,单极天线,透镜天线,双圾天线,漏波天线,双波段天线,天线馈源,喇叭     

天线与天线系统

Y2002-63465-377 0327997健壮产生旁瓣对消的频域有效实现=Efficient frequen-cy-domain realization of robust generalized sidelobe can-cellers[会,英]/Herbordt,W.& Kellermann,W.//2001 IEEE Fourth Workshop on Multimedia Signal Pro-     

天线与天线系统

0623126新型短波通讯天线的计算机仿真[刊,中]/杨毅//西华大学学报(自然科学版)．一2006,26(1)．—90-93(G)作者研究了一种通讯短波宽带共形线天线,并利用时域有限差分算法(FDTD)仿真计算,经过优化和匹配电路的加载,得出天线在短波10～90MHZ频率下的反射系数、输入阻抗、电压驻波比、辐射方向图。在决定匹配电路参量过程中使用了最优搜索法和梯度法。该天线具有小型宽带、平面共形特点,可加载于车辆、低速飞机等移动载体上。参7 0623127衰落相关对分布式MIMO信道容量的影响[刊,中]/倪振文//湖南科技大学学报(自然科学版)．—2006,21 (2)．—29-33(C)     

Precoder Distribution and Adaptive Codebook in Wideband Precoding

Based on wideband precoding (WBP) in the multiple‐input multiple‐output orthogonal frequency division multiplexing system, an adaptive nonuniform codebook is presented in this paper. The relationship between the precoder distribution and spatial correlation is analyzed at first. A closed‐form expression based on overlapped isosceles triangles is proposed as an approximation of the precoder distribution. Then, the adaptive codebook design is derived with the approximate distribution to minimize quantization errors. The capacity and bit error rate performance demonstrate that the adaptive codebook with WBP outperforms the conventional fixed uniform codebook.     

用增益精确值和归一化波形码书改进G.728

分析研究了增益、波形乘积码书结构的缺陷，设计了归一化波形码书和精确表示增益的LD-CELP方案。采用自适应预测和自适应量化对增益的精确值进行量化，在3bit和4bit自适应量化时比G．728固定量化增益分别提高0．5dB和6dB。采用4bit自适应量化和64波形码书比G.728SNR提高约1dB。将G．728综合滤波器由50阶减少到30阶，信噪比不变而算法复杂性降低约20%。     

基于矢量线性运算的自适应球帽差分反馈算法

信道时间相关多输入多输出(MIMO)系统中一种重要有限反馈策略为差分反馈,该文提出一种适用于单用户多输入单输出(SU-MISO)系统的自适应球帽差分反馈算法。首先,运用相邻时刻信道间的扰动规律设计自适应差分反馈策略;其次,不同于现有差分码本的非线性构造方法,提出一种基于矢量伸缩和合成的球帽差分码本算法;最后,联合球帽码本空间分布规律和时间相关信道的统计规律推导出球帽半径计算方法。仿真结果说明,该算法能准确跟踪信道并较现有算法有一定性能提高。     

基于ACELP的嵌入式语音编码算法

为实现对激励信号的精细描述,提出了一种基于ACELP模型的嵌入式语音编码算法,该算法通过逐层增加脉冲数以及采用一种新的自适应码书结构,能够保证各层编码的相对独立性以及编码器参数的最佳匹配。与以往基于ACELP模型的嵌入式编码算法相比,实现的编码器能够获得具有嵌入结构的码流,不仅能够保证核心层的合成语音质量,而且在增强层也取得了与对应速率的现有标准编码器相当的合成语音质量。     

一种MIMO系统自适应码本设计方法

提出一种基于码本旋转的自适应码本设计方法,在不改变现有的码本基础矩阵的基础上,根据误码率(BER)和信干噪比(SINR)的统计和估计结果,生成一组新的旋转矩阵码本,并结合反馈开销考虑与原来基础码本矩阵构成双码本矩阵,根据信道的实时变化及时地调整码本的精度,从而能够在有限反馈的情况下更加有效地提高预编码的性能。     

低延迟话音编码算法的增益优化与混合窗设计

G.728标准将增益滤波器的偏移不适当地处理成常数32dB,相当于将20～30ms内短时平稳的语音信号不适当地按整个时间轴上的平稳信号对待。对增益滤波器的改进必然涉及优化混合窗。该文提出一种估计平均分段信噪比的方法用来设计混合窗参数,并导出激励增益的精确表示。以此为基础,将Jayant的自适应量化与G.728的增益预测结合起来,提出一种适合于设计低时延码激励线性预测(LD-CELP)的增益码书的方案。用此方法,激励的精确值经自适应预测和量化后,3bit自适应量化和4bit自适应量化分别比G.728的固定量化有0.5dB和6dB的信噪比的改善。当采用4bit自适应量化和64码字的波形码书,比G.728复杂性降低20%,同时信噪比提高1dB。     

Distributed Jacobi eigen-beamforming for closed-loop MIMO systems

This work presents a novel eigen-beamforming technique suitable for tracking fading channels in multiple-input multiple-output (MIMO) systems employing low feedback rate, closed-loop feedback channels. The method uses a single unitary coordinate plane transformation to update the transmit antenna weights without requiring parameters that depend on fading rate, typically found in recursive methods. The computational complexity is fixed, in contrast with codebook solutions, whose operations count increases linearly with the codebook size. Simulations show that the new eigen-beamforming method reaches near optimal bit error probability performance in low mobility scenarios. Furthermore, by buffering the available feedback bits the proposed algorithm outperforms signed gradient methods for the same average feedback rate     

Adaptive edge-based side-match finite-state classified vectorquantization with quadtree map

Vector quantization (VQ) is an effective image coding technique at low bit rate. The side-match finite-state vector quantizer (SMVQ) exploits the correlations between neighboring blocks (vectors) to avoid large gray level transition across block boundaries. A new adaptive edge-based side-match finite-state classified vector quantizer (classified FSVQ) with a quadtree map has been proposed. In classified FSVQ, blocks are arranged into two main classes, edge blocks and nonedge blocks, to avoid selecting a wrong state codebook for an input block. In order to improve the image quality, edge vectors are reclassified into 16 classes. Each class uses a master codebook that is different from the codebooks of other classes. In our experiments, results are given and comparisons are made between the new scheme and ordinary SMVQ and VQ coding techniques. As is shown, the improvement over ordinary SMVQ is up to 1.16 dB at nearly the same bit rate, moreover, the improvement over ordinary VQ can be up to 2.08 dB at the same bit rate for the image, Lena. Further, block boundaries and edge degradation are less visible because of the edge-vector classification. Hence, the perceptual image quality of classified FSVQ is better than that of ordinary SMVQ.     

Efficient codebooks for vector quantization image compression withan adaptive tree search algorithm

This paper discusses some algorithms to be used for the generation of an efficient and robust codebook for vector quantization (VQ). Some of the algorithms reduce the required codebook size by 4 or even 8 b to achieve the same level of performance as some of the popular techniques. This helps in greatly reducing the complexity of codebook generation and encoding. We also present a new adaptive tree search algorithm which improves the performance of any product VQ structure. Our results show an improvement of nearly 3 dB over the fixed rate search algorithm at a bit rate of 0.75 b/pixel     

基于Hilbert填充曲线的自适应隐写

 自适应隐写用于将适量的消息比特嵌入到载体以取得感知质量和容量的最佳折衷.本文提出一种基于量化嵌入机制的自适应隐写方法,并基于该方法将秘密消息比特嵌入到由Hilbert填充曲线顺序构造的三像素组的两像素差中.由于充分利用图像本身的感知特性构造了量化嵌入使用的分割码本,所提算法在感知质量和容量上具有较好的综合性能.