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.     

均匀光纤光栅内部前向波与后向波动态特性研究

研究了前向波与后向波在均匀光纤光栅内的动态特性。结果表明:前、后向波的振幅 呈正弦震荡且震荡步调一致,极大值个数与波长阶数相同,极大值大小亦与波长阶数有关,而与在光栅中的位置无关,极大值周期分布于整个光栅长度;后向波振幅极小值为零。     

相对论返波振荡器的非线性理论

本文建立起分析相对论返波管注波互作用过程的自洽非线性工作方程组,理论模型中计及了正向波基波与电子注的异步互作用效应、电子注的空间电荷效应.运用四阶龙格一库塔法编制了数值求解工作方程组的Fortran程序,对均匀耦合阻抗型器件和耦合阻抗单阶跃变型器件的效率进行了仿真和优化.数值模拟结果表明正向波基波与同步波在慢波结构起始处的相差,正向波基波与电子注的异步互作用效应能显著地影响相对论返波管效率,均匀阻抗器件运行于最佳状态时,效率可达到27%,耦合阻抗单阶跃变型器件最优化效率可达到50%.     

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.     

一种新的Pseudo-Zernike矩的快速算法

Zernike矩因具有正交性和旋转不变性而广泛应用于模式识别、图像分析等领域.Pseudo-Zernike 矩具有与Zernike 矩相似的性质,但它较Zernike 矩具有更好的抗噪声性.由于pseudo-Zernike矩的复杂性,相关的快速算法的研究尚未得到很好的解决.本文根据pseudo-Zernike矩自身的特点,推导了一种快速有效的计算方法.     

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。     

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.     

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。     

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.     

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。     

毫米波行波管返波振荡的仿真研究

该文利用HFSS仿真了工作在Ka波段的螺旋线、反绕双螺旋线及耦合腔等慢波系统,通过傅里叶分析得到空间谐波,进而分析和比较了上述慢波系统的返波振荡特性.结果表明:螺旋线慢波系统中出现明显的角向谐波次数和轴向谐波次数不相等的窄问谐波分量,在π模附近,有产生返波振荡的危险:而反绕双螺旋线通过提高基波耦合阻抗及可工作的归一化频率来提高了抑制返波振荡的能力;为了避免返波振荡,耦合腔工作频带的选择应尽可能远离单腔相移为π,2π的频点.     

0.14 THz返波管器件数值模拟与实验研究

对有限引导磁场环形电子束的色散曲线作了理论推导,并利用该色散关系数值计算了正弦慢波结构的色散曲线。采用KARAT模拟程序对0.14 THz返波管进行了粒子模拟,并在RADAN303脉冲源上开展了初步的实验研究,实验获得频率大于0.14 THz、脉冲宽度为1 ns～2 ns、重复频率10 Hz和辐射功率大于1.45 MW太赫兹波输出。     

X 波段注入锁定相对论返波管设计

为实现X 波段的相干功率合成,提出了一种高功率的注入锁定相对论返波管模型。器件在结构上分为输入腔和 输出慢波结构：输入腔用于减少注入微波的泄漏,同时腔内的驻波电场可以有效调制电子束;输出慢波段实现调制电子 束的换能输出。模拟表明该结构在注入功率6 kW 的条件下,可以实现2.5 GW输出微波的相位控制。     

太赫兹返波振荡器的应用及研究进展

太赫兹返波振荡器是一种功率高、宽带可调谐、可在常温下连续波工作的辐射源。本文介绍了太赫兹返波振荡器在太赫兹技术研究中的应用需求及其发展现状,说明返波振荡器在太赫兹技术研究中的重要作用和前景,并对太赫兹返波振荡器的最新动态、技术难点进行了分析,可供该种管型研究的参考。     

0.22 THz折叠波导返波管设计

作为折叠波导家族的重要成员之一,折叠波导返波管无需种子微波源,具有可观的振荡功率输出,可在较宽频带内方便地进行电压调谐,在THz波段的紧凑型电真空器件中占有重要地位。介绍了中物院应用电子学研究所0.22 THz折叠波导的研究情况,并阐述整管设计的原理和理念。通过一维模型分析和三维宏粒子模拟校验,完成了调谐频宽10 GHz,带宽内输出功率为瓦级的折叠波导返波管的理论设计。     

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 .