A Fast Algorithm for Computation of Electromagnetic Wave Propagation in Half-Space

A new frequency-domain algorithm, the planar Taylor expansion through the fast Fourier transform (FFT) method, has been developed to speed the computation of the Green's function related formulas in the half-space scenario for both the near-field (NF) and the far-field (FF). Two types of Taylor-FFT algorithms are presented in this paper: the spatial Taylor-FFT and the spectral Taylor-FFT. The former is for the computation of the NF and the latter is for the computation of the FF or the Fourier spectrum. The planar Taylor-FFT algorithm has a computational complexity of ${O(N^{2} log _{2} N^{2})}$ for an ${Ntimes N}$ computational grid, comparable to the multilevel fast multipole method (MLFMM). What's more important is that, the narrowband property of many electromagnetic fields allows the Taylor-FFT algorithm to use larger sampling spacing, which is limited by the transverse wave number. In addition, the algorithm is free of singularities. An accuracy of $-50~{rm dB}$ for the planar Taylor-FFT algorithm is easily obtained and an accuracy of $-80~{rm dB}$ is possible when the algorithm is optimized. The algorithm works particularly well for narrowband fields and quasi-planar geometries.      

A Fast Computation Technique for RF Performances in Broadband Millimeter Wave Helix TWTs

A computation technique for gain, efficiency and output power in broadband millimeter wave helix TWTs from their dimensions is described. The computed results by modeling are good agreement with experimental measurements. It is shown that the method is fast and useful accuracy. It can be used as engineering design for MMW TWTs.     

毫米波段连续波雷达天线隔离度设计

收发系统间信号隔离度是连续波雷达天线设计的关键指标,它主导着连续波雷达系统的性能。针对本连续波雷达收发天线间具体的信号耦合通道,本文在收发天线间加装扼流槽,铺设微波吸波材料以及安装具有滤波功能的微波光子晶体结构等隔离措施,提高了收发天线间的隔离度。     

Calculation of the Parameters for Ring-loop Traveling Wave Tube in MMW

The feature of the ring-loop slow wave structure is high coupling impedance and low harmonic wave components. Therefore ring-loop traveling wave tube (TWT) has advantages of high gain, small dimension, higher operating voltage and less danger of the backward wave oscillation. But calculation of the ring-loop is rather difficult. Here on basis of calculation of dispersion and impedance, a fast estimation of interaction efficiency, output power and saturated gain for Ka-band ring-loop TWT are given.     

Engineering Computation and Analysis of Enhancing Efficiency for Folded Waveguide TWT in MMW

Large signal operating equations in TWT have been solved by numerical solve method. The relations between interaction efficiency and design parameters in TWT are analyzed. A fast engineering design method of enhancing efficiency for folded waveguide TWT by velocity resynchronization is described. The computation is shown that the efficiency of Ka-band folded waveguide TWT with double taper can be enhanced over twice as original tube. This method of approach is very useful for tube designer.     

360 GHz返波管的研究

对采用齿状光栅结构的慢波电路进行了研究,该结构在电子束与光栅表面接近的情况下有一定的通过率。在求得最大耦合阻抗条件下,设计了一种工作在360 GHz的返波管,通过对互作用电路的耦合阻抗的分析,可以减小亚毫米波及太赫兹真空电子学辐射源对阴极发射电流密度的要求。当工作电压为19.5 kV,工作电流75 mA时,PIC模拟结果得到了8 W的平均功率输出,考虑阴极为脉冲工作时,该器件在360 GHz可以得到4 mW的平均功率输出。     

旋转椭球函数的数值计算

本文给出了计算旋转长椭球和扁椭球函数的程序流图和相应的有用数学公式，并讨论算法，所编ＦＯＲＴＲＡＮ程序具有适应参变量范围较宽和可获较高精度的数值结果。     

实现相息图快速计算的一种方法

建立一张物点位置和它在相息图上单位振幅波前分布关系的表格,采用查表的方法求物点在相息图样点上的波前分布,加快了计算输出相息图的速度。在保留重构图象细节的前提下,该方法的运算速度比平方根准确计算的方法提高5倍以上。     

A New Fast and Accurate Algorithm for the Computation of Microstrip Capacitances

A new algorithm is presented for the calculation of TEM parameters of microstrips, based on a lumped-circuit model of the microstrip transverse static field. The use of such an algorithm allows one to obtain either very high accuracies or very low computer times when ordinary accuracies are tolerated. Compared with the similar technique by Lennartsson, the analysis method presented here allows substantial reduction in computer time, storage, and errors.     

多小波预滤波器设计中初始滤波器的快速算法

针对多小波矢量预处理滤波器设计中计算初始滤波器Q(0)过程复杂的问题,文章提出了一种基于零空间的快速计算方法,只要给出多小波的尺度和小波滤波器的系数,就可快速准确地计算出Q(0)值.文中计算了对应GHM和CL多小波的Q(0)值,计算结果与传统方法相同,证明了方法的正确性.整个过程耗时不到0.03秒,并且避免了繁琐推导计算过程中可能出现的人为误差.     

Cutoff Angles of the Backward Spin Wave in a Tangentially Magnetized Ferrite Plate

The cutoff angles for the wave vector and the group velocity vector of a backward spin wave propagating in a tangentially magnetized ferrite plate are calculated. It is established that the expressions for these angles do not depend on the mode number and coincide with the analogous expressions for the corresponding cutoff angles of a spin wave in an unbounded ferromagnet. It is found that the regions corresponding to all possible orientations of the wave vector for the backward and surface spin waves in a ferrite slab and for a spin wave in an unbounded ferromagnet are adjacent and nonintersecting. It is shown that, if the isofrequency dependence of the wave has inflection points, then the range of all possible orientations of the group velocity vector of the wave can be wider than the angular interval enclosed between the cutoff angles for the group velocity vector.     

Hardware Efficient Fast Computation of the Discrete Fourier Transform

In this paper, a new systolic array for prime N-length DFT is first proposed, and then combined with Winograd Fourier Transform algorithm (WFTA) to control the increase of the hardware cost when the transform length is large. The proposed new DFT design is both fast and hardware efficient. Compared with the recently reported DFT design with computational complexity of O(log N), the proposed design saves the average number of required multiplications by 30 to 60% and reduces the average computation time by more than 2 times, when the transform length changes from 16 to 2048. Chao Cheng received his MSEE degree from Huazhong University of Science and Technology, Wuhan, China, in 2001. With three years industrial experience as a digital communication engineer from VIA Technologies, he is now pursuing his Ph.D. degree at the University of Minnesota, Twin Cities, MN. His present research interest is in VLSI digital signal processing algorithms and their implementation. Keshab K. Parhi received his B.Tech., MSEE, and Ph.D. degrees from the Indian Institute of Technology, Kharagpur, the University of Pennsylvania, Philadelphia, and the University of California at Berkeley, in 1982, 1984, and 1988, respectively. He has been with the University of Minnesota, Minneapolis, since 1988, where he is currently Distinguished McKnight University Professor in the Department of Electrical and Computer Engineering. His research addresses VLSI architecture design and implementation of physical layer aspects of broadband communications systems. He is currently working on error control coders and cryptography architectures, high-speed transceivers, and ultra wideband systems. He has published over 400 papers, has authored the text book VLSI Digital Signal Processing Systems (Wiley, 1999) and coedited the reference book Digital Signal Processing for Multimedia Systems (Marcel Dekker, 1999). Dr. Parhi is the recipient of numerous awards including the 2004 F.E. Terman award by the American Society of Engineering Education, the 2003 IEEE Kiyo Tomiyasu Technical Field Award, the 2001 IEEE W.R.G. Baker prize paper award, and a Golden Jubilee award from the IEEE Circuits and Systems Society in 1999. He has served on the editorial boards of the IEEE TRANSACTIONS ON CAS, CAS-II, VLSI Systems, Signal Processing, Signal Processing Letters, and Signal Processing Magazine, and currently serves as the Editor-in-Chief of the IEEE Trans. on Circuits and Systems---I (2004--2005 term), and serves on the Editorial Board of the Journal of VLSI Signal Processing. He has served as technical program cochair of the 1995 IEEE VLSI Signal Processing workshop and the 1996 ASAP conference, and as the general chair of the 2002 IEEE Workshop on Signal Processing Systems. He was a distinguished lecturer for the IEEE Circuits and Systems society during 1996--1998. He is a Fellow of IEEE (1996). An erratum to this article is available at .     

Fast Likelihood Computation in Speech Recognition using Matrices

Acoustic modeling using mixtures of multivariate Gaussians is the prevalent approach for many speech processing problems. Computing likelihoods against a large set of Gaussians is required as a part of many speech processing systems and it is the computationally dominant phase for Large Vocabulary Continuous Speech Recognition (LVCSR) systems. We express the likelihood computation as a multiplication of matrices representing augmented feature vectors and Gaussian parameters. The computational gain of this approach over traditional methods is by exploiting the structure of these matrices and efficient implementation of their multiplication. In particular, we explore direct low-rank approximation of the Gaussian parameter matrix and indirect derivation of low-rank factors of the Gaussian parameter matrix by optimum approximation of the likelihood matrix. We show that both the methods lead to similar speedups but the latter leads to far lesser impact on the recognition accuracy. Experiments on 1,138 work vocabulary RM1 task and 6,224 word vocabulary TIMIT task using Sphinx 3.7 system show that, for a typical case the matrix multiplication based approach leads to overall speedup of 46 % on RM1 task and 115 % for TIMIT task. Our low-rank approximation methods provide a way for trading off recognition accuracy for a further increase in computational performance extending overall speedups up to 61 % for RM1 and 119 % for TIMIT for an increase of word error rate (WER) from 3.2 to 3.5 % for RM1 and for no increase in WER for TIMIT. We also express pairwise Euclidean distance computation phase in Dynamic Time Warping (DTW) in terms of matrix multiplication leading to saving of approximately ${1} \over {3}$ of computational operations. In our experiments using efficient implementation of matrix multiplication, this leads to a speedup of 5.6 in computing the pairwise Euclidean distances and overall speedup up to 3.25 for DTW.     

X波段相对论返波管卡诺枪设计

设计了一种用于X波段相对论返波管的电子枪,利用粒子模拟软件对整管进行测试,结果表明,这种电子枪能产生电流为4kA电压为550kV电子注,且具有使用寿命长,整管真空度高,性能好,可获得高重复频率输出等优点。获得了频率为10．34GHz,微波峰值功率1．5GW,转化效率为20％的微波输出。     

A Fast Finite Element Analysis of Millimeter Wave Waveguide Filters

The multifrontal method is applied for solving a large system of linear equations resulting from the use of edge-based finite element method (FEM). The finite element method combined with the perfectly matched layers (PML) is given for simulation of microwave filters and the algorithm of multifrontal method is described in detail. The reflection and insertion losses of millimeter wave filter are analyzed as the examples and the obtained results are compared with those obtained from literature. In order to demonstrate the efficiency of the multifrontal method, the computational time is compared with that of both symmetric successive overrelaxation (SSOR) preconditioned conjugate gradient (PCG) and conjugate gradient methods (CG) for the thick-iris waveguide bandpass filer.     

一种新颖的快速启动零温度系数电流基准

基于三极管BE结电压的负温度特性原理,提出了一种零温度系数电流基准电路.该电路具有结构简单、无需带隙基准单元、静态功耗低、启动快速、对电源电压不敏感等优点,实用性高.在0.5 μm标准CMOS工艺下,Hspice模拟结果显示,在25℃、1.8～5.5 V范围内,基准电流变化0.019μA;在1.8 V、-40℃～125℃范围内,基准电流变化0.09μA.该新方案可用于无需电压基准、低功耗、需要快速启动的混合信号系统设计.     

Velocity Sorting Detection in Backward Wave Autodyne Reception (Correspondence)

An electronically tunable microwave receiver which uses an oscillating backward wave amplifier driving a crystal detector has been described previously. This receiver has the advantages of large dynamic range and good rejection of unwanted signals, but has the disadvantage that its frequency response can be no better than that of its crystal detector. Since a variation in sensitivity of greater than 3 db over the tuning range of 8 to 12 kmc would seriously lower its usefulness as a spectrum display device, the restrictions on the crystal detector performance are quite severe.     

Computation of the Para-Pseudoinverse for Oversampled Filter Banks: Forward and Backward Greville Formulas

Frames and oversampled filter banks have been extensively studied over the past few years due to their increased design freedom and improved error resilience. In frame expansions, the least square signal reconstruction operator is called the dual frame, which can be obtained by choosing the synthesis filter bank as the para-pseudoinverse of the analysis bank. In this paper, we study the computation of the dual frame by exploiting the Greville formula, which was originally derived in 1960 to compute the pseudoinverse of a matrix when a new row is appended. Here, we first develop the backward Greville formula to handle the case of row deletion. Based on the forward Greville formula, we then study the computation of para-pseudoinverse for extended filter banks and Laplacian pyramids. Through the backward Greville formula, we investigate the frame-based error resilient transmission over erasure channels. The necessary and sufficient condition for an oversampled filter bank to be robust to one erasure channel is derived. A postfiltering structure is also presented to implement the para-pseudoinverse when the transform coefficients in one subband are completely lost.      

爬行波电流传播常数及幅度的计算

本文提出了一种计算金属圆柱表面爬行波电流传播常数和幅度的新方法。该方法在获得金属柱表面爬行波电流的精确数值解后，应用Ｐｒｏｎｙ方法得了金属表面爬行波电流各个模的传播常数和幅度，避开了传统方法解时冗长、繁锁的数学推导过程。经比较，本文方法的计算结果比几何绕射理论的计算结果更为精确。