A Fast Algorithm for Wave Propagation from a Plane or a Cylindrical Surface

The newly developed Taylor-Interpolation-FFT (TI-FFT) algorithm dramatically increases the computational speeds for millimeter wave propagation from a planar (cylindrical) surface onto a “quasi-planar” (“quasi-cylindrical”) surface. Two different scenarios are considered in this article: the planar TI-FFT is for the computation of the wave propagation from a plane onto a “quasi-planar” surface and the cylindrical TI-FFT is for the computation of wave propagation from a cylindrical surface onto a “quasi-cylindrical” surface. Due to the use of the FFT, the TI-FFT algorithm has a computational complexity of O(N ²?log₂? N ²) for an N?×?N computational grid, instead of N ⁴ for the direct integration method. The TI-FFT algorithm has a low sampling rate according to the Nyquist sampling theorem. The algorithm has accuracy down to ?80 dB and it works particularly well for narrow-band fields and “quasi-planar” (“quasi-cylindrical”) surfaces.     

迭代不变性测试方程法在城市微小区电波传播预测中的应用

本文建立了基于不变性测试方程法的二维城市微小区电波传播预测模型。该模型考虑了地面反射和建筑物墙面的二维散射,利用ＭＥＩ方法在每个建筑物表面建立共形差分网格形成差分方程,并用迭代方法模拟电波在建筑物之间的多次散射。所得结果与实测值ＧＴＤ,ＦＤＴＤ的预测结果进行了比较。     

Electromagnetic Wave Propagation in Lossy Ferrites

The square of the complex transverse propagation constant in a lossy, magnetized ferrite is found to be described approximately by a circle in the complex plane when the magnetic field is varied. A graphical method for obtaining approximate values for the transverse propagation constant when the wave number in the direction of the applied field is given and real is derived here. This method is used to find The power absorbed from an incident plane wave by A semi-infinite ferrite as a function of the magnetizing field amplitude.     

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.     

Electromagnetic Wave Propagation in Twisted Anisotropic Media

The complete solution of the differential equation describing the propagation of plane uniform TEM waves along the twist axis of a twisted anisotropic medium with a constant rate of twist is shown to be of exponential type, consisting of two identical pairs of independent propagation modes, each pair being associated with a particular direction of energy flow. Knowledge of the complete solution is used to solve the boundary value problem relative to wave penetration into a twisted medium at normal incidence, a numerical example being given illustrating the polarization transformation properties of the medium near the short wavelength limit. Analysis of mode properties reveals circnlar birefringence should occur in twisted media at long wavelengths. A link power, as shown by certain crystalline substances provided by the theory.     

Electromagnetic Wave Propagation Through Chaff Clouds

The computation of electromagnetic wave scattering by clouds of dipoles is straightforward when the dipole density is small. For higher density clouds, the coupling effects between the dipoles and their attenuation effects on the wave must be considered. This is accomplished herein by replacing the randomly distributed dipoles in the cloud by a conducting continuum. The conductivity of this continuum is determined by requiring that the radar cross section (RCS) of an infinitesimally thin slab of the continuum be the same as that of a similar portion of the dipole cloud. The thinness of this reference dipole cloud eliminates the necessity to consider inter-dipole coupling. The reflection and transmission characteristics of the cloud are then obtained using standard methods for propagation through the effective conductor. RCS results are shown to agree with coupled numerical integral equation solutions for scattering from a closely spaced system of wires. Simple formulas are derived for the attenuation effects of the dipole cloud. For most cases of interest, the wave with wave length lambda attenuates through a cloud of half wave dipoles of density p at the rate of 0.655 (plambda³) dB per lambda.     

矿井电磁环境及电波传播特性的研究

文中对矿井中电缆漏泄、电火花、电网电压波动以及大型设备的启停等所产生的电磁干扰进行了分类研究。通过对矿井的巷道结构,电波在矿井中传播所遵循的帐篷定律,巷道中收发天线所处的位置,煤层与巷道支护材料电特性,粉尘水汽雾滴等电磁散射特性的讨论,分析了电磁波传播过程中的时延、衰落和损耗,并结合电磁波折射理论,就不同频率及水平极化和垂直极化两种方式的电磁波,在矿井中的传播特性进行了综合的研究分析发现,电波频率越高,损耗越大,水平极化的电波损耗要小于垂直极化的电波损耗,矿井中收发天线放置在与巷道壁一定距离的中上部位置为最佳。     

电磁波在海水中的传播特性研究

利用电磁场传播所满足的MaxWell方程组,计算和分析了电磁波在海水中传播时的参数及特征,并分析了海水中电磁波的能量特征,为海水中通信、信号探测、导航等方面工作提供了理论依据.     

电磁波在铁电材料中的传输理论

本文从波动方程出发,系统地阐明了铁电材料中,电磁波与各种模式的耦合,包括下面三个方面:纵向光学模式与弹性波的耦合;电磁耦子与纵向弹性波的耦合以及表面耦子和B-G波的耦合,给出了每种情况下的耦合波的色散特征和基本模式。     

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.     

一种分析电磁散射问题的快速算法

将基于特征谱的双步预处理方法与多分辨预处理方法结合,用来快速分析电磁散射问题。特征谱双步预处理方法有效地利用了多分辨预处理方法的等级特性,计算实例证实它有很高的计算效率。     

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。     

Nonreciprocal Electromagnetic Wave Propagation in Ionized Gaseous Media

The nonreciprocal propagation of electromagnetic waves in ionized gaseous media is discussed, and experimental observations are reported in this paper. The classical Faraday experiment in the optics of anisotropic media has suggested an analogous phenomenon at microwave frequencies. The anisotropic behavior of the free electron gas which is immersed in a magnetic field and subjected to an incident electromagnetic wave is determined. Guided microwave experiments were performed which confirm the theoretical predictions of nonreciprocal wave propagation in such ionized gases.     

Transient Electromagnetic Guided Wave Propagation in Moving Media

An analytical study of the influence of moving media on the propagation of transient electromagnetic modal waves in dispersive waveguides is presented. The response to impulsive excitation is determined in exact closed form and used to demonstrate that the nature of the pulse distortion differs in each of the three cases, 1) 0 < u < c /spl equiv/ (/spl epsi//spl mu/)/sup -1/2/, 2) v = c, and 3) c < v < c/sub 0/ /spl equiv/ (/spl epsi//sub 0//spl mu//sub 0/)/sup -1/2/ (v = speed of the medium). An expression is derived from which the pulse waveform generated by an input of arbitrary form can be readily determined when 0 < v < c if the transient response to a similar input is known for v = 0. An untabulated Laplace transform pair is derived and used to determine the unusual pulse distortion in case 3) which shows a markedIy discontinuous change from the pulse distortion in case 2). The theory illuminates a singular circumstance in which the Lorentz transformation is consistent with the "speed of light" differing from one inertial reference frame to another.     

Theoretical Investigation of the Electromagnetic Wave Propagation Tool

A theoretical investigation of the electromagnetic wave propagation tool (EPT)? is presented. An asymptotic analysis, using contour integration, was utilized to derive approximations for the waves at the receivers of the EPT tool. The waves at the receivers are decomposed into a guided wave and a lateral wave. When the mudcake layer is thin, the lateral wave nearly satisfies the guidance condition of the mudcake layer, and its algebraic decay is diminished from the negative of the three-halves power with distance (thick mudcake) to the negative one-half power with distance. In this case, the guided wave and the lateral wave both propagate with a wave number close to the wave number of the invaded zone. Indeed, plots of the directional dependence of the transmitted wave in the invaded zone demonstrate that more power is directed along the planar boundary in the invaded zone when the mudcake layer is thin. Plots of the total magnetic field and the magnetic field from the guided wave at the receiver locations are presented as a function of mudcake thickness. These plots show the dominance of the guided wave for increasing mudcake thickness. Travel times are also computed, using both asymptotic approximations and a plane-wave assumption. These results are then compared with the results of Freedman and Vogiatzis. Excellent agreement with the plane wave assumption is found for a thin mudcake layer. This analysis validates the schemes used by Schlumberger for interpreting the EPT tool log.     

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.     

海上蒸发波导条件下电波传播的分析

抛物方程方法已经被广泛地应用于电磁波传播的研究,并成为解决电磁波传播问题主要的工具。应用抛物方程和电波传播的基本理论,计算了电磁波在蒸发波导和标准大气中的传输损耗,得到了电波的空间传播损耗图,与射线理论的射线描迹技术得到的结论是一致的,但是抛物方程方法求解速度快,具有很好的实时计算特性,并且能弥补目前射线描迹技术尚不能精确描述空间场分布的缺点,因此更具有实用价值。     

A Fast Computation of the Start-Oscillation Current of Backward Wave in MMW HTWT's

Backward wave oscillation can be troublesome in high power helix TWT, especially millimeter wave helix traveling wave tubes (MMW HTWT's). To suppress these oscillations, start-oscillation current of backward wave has to know when MMW HTWT's are designed. A fast computation of the start-oscillation current for MMW HTWT's is presented. It is shown that the computed values are agreed with the experimental results in Ka band.     

Electromagnetic Wave Propagation Along a Ferrite Loaded Wire

The dispersion relation for axially symmetric modes propagating on a surface waveguide composed of a central conductor surrounded by an axially magnetized ferrite tube has been obtained. Tuning curves for an open boundary post resonator are calculated and compared with experimental results for an X-band tunable filter. The modes of circulation of a three-port waveguide circulator utilizing this geometry have also been studied and experimentally verified.     

电磁波传播聚焦特性的仿真研究

从基本电磁理论出发 ,推导轴对称条件下电磁波的波动方程 ,给出求解此类波动方程的数值仿真方法。分析比较不同发射口面分布下的电磁波的传播规律 ,得出满足聚焦条件的一种口面分布。其仿真模拟方法不仅可用于电磁波传播研究 ,还可用于高功率微波波束的传输特性分析。