Scattering by an inhomogeneous dielectric/ferrite cylinder ofarbitrary cross-section shape-oblique incidence case

A moment method (MM) solution is developed for the fields scattered by an inhomogeneous dielectric/ferrite cylinder of arbitrary cross-section. The incident field is assumed to be a plane wave of arbitrary polarization with oblique incidence with respect to the axis of the cylinder. The total electric and magnetic fields are the unknown quantities in two coupled equations from which a system of linear equations is obtained. Once the total electric and magnetic fields within the cylinder are computed, the scattered fields at any other point in space can be calculated. It is noted that for the case of oblique incidence, the scattered field has TE_z and TM_z polarized fields regardless of the polarization of the incident field. The echo widths of cylinders and shells of circular, semicircular, and rectangular cross section are calculated for TE_z and TM_z polarized incident fields. It is shown that the results obtained for dielectric/ferrite cylinders and shells of circular cross section with the solutions developed here agree very well with the corresponding exact eigenfunction solutions     

High-Temperature Superconducting Homopolar Inductor Alternator for Marine Applications

This paper describes a high power density high-temperature superconducting (HTS) electric machine topology that is scalable for marine propulsion and power generation. The design, currently being pursued for airborne applications, is based on homopolar inductor alternator (HIA) technology, which is new within HTS applications. The basic machine design configuration of the HTS HIA is based on a stationary HTS field excitation coil, a solid rotor, and an advanced but conventional stator comprising liquid-cooled air-gap armature winding and an advanced iron core. High power density is obtained by the enhanced magneto-motive force capability of the HTS coil, the increased airgap flux density and armature current loading, and the high tip velocity of the rotor. Preliminary scaled up designs look attractive for three marine applications: propulsion drive, primary ship power generation, and power generation modules. The generators are driven directly by the turbines without the additional complexity of a clutch and gear system. A conceptual design study of a 36-MW 3600-r/min generator, a 4-MW 7000-r/min auxiliary generator, and a 36-MW 120-r/min and 4-MW 132-r/min propulsion motor are summarized.     

激光二极管端面抽运圆形截面Nd∶GdVO_4晶体的热形变

以解析分析理论为基础,研究圆截面Nd∶GdVO4激光晶体受到具有高斯分布半导体激光端面中心入射时,晶体温度场分布和抽运面热形变分布情况。通过对激光二极管(LD)端面入射晶体工作特点分析,建立了符合实际工作情况的热模型,利用热传导方程新求解方法,得出了圆形截面Nd∶GdVO4晶体温度场分布和端面热形变场通解表达式,对比分析了圆形截面和矩形截面Nd∶GdVO4晶体的热形变。研究结果表明,当使用输出功率为15 W激光二极管端面中心入射Nd∶GdVO4激光晶体时,在抽运端面中心获得187.5℃最高温升和1.313μm最大热形变量。两种截面晶体具有相同的热形变形状,当截面尺寸不太大时,如果圆形截面晶体的半径等于矩形截面晶体半边长,最大热形变量将减少4.1%。这种方法还可以应用到其他圆形截面晶体热问题研究中,为有效解决激光系统热问题提供了理论依据。     

A physical optics approach to near field RCS computations

The scattered field of a perfectly conducting body treated using a physical optics approach is obtained in near field in either the monostatic or bistatic case. This approach opens new prospects for a broad range of applications in the areas of radar cross section (rcs) and antennas. Numerical examples for simple shapes (circular and rectangular plates) are given. Remarkable phenomena are found and discussed.     

Current induced by TE excitation on a conducting cylinder located near the planar interface between two semi-infinite half-spaces

An analysis is presented for determining the current induced by a known transverse electric excitation on a perfectly conducting cylinder located near the planar interface separating two semi-infinite, homogeneous half-spaces of different electromagnetic properties. The conducting cylinder of general cross section is of infinite extent and the excitation is transverse electric to the cylinder axis. Two types of integral equations, the magnetic field integral equation and the electric field integral equation, are formulated, and the Green's functions for the integral equations are derived in an appendix. Numerical solution methods for solving the integral and integrodifferential equations are presented. For a strip parallel or perpendicular to the interface, a circular cylinder, and a rectangular cylinder, data are presented and discussed for selected parameters, including the case of a cylinder resting on the interface.     

TE- and TM-waves in waveguides of very general cross section

The waveguide of the general cross section is transformed into a waveguide of rectangular cross section by conformal transformation. The electric and magnetic field, the critical frequency, wall current, power transport and attenuation of the different TE-and TM-modes are calculated by a series approximation. Examples of numerical evaluation are given for five different cross sections.     

Approximate pattern calculation of a leaky waveguide

A method is described for calculating the patterns of leaky waveguides radiated from the aperture in the metal wall of a waveguide with a rectangular cross section, the waveguide and the aperture being assumed of infinite length along the axis, the tangential components of the electric field on the aperture being assumed to have been prescribed. This method is accomplished by substituting a well approved elliptic cylinder for a boundary with a rectangular cross section. Measurements have been made for the leakyHguide to verify the accuracy of this method.     

A novel LDMOS structure using P-trench for high performance applications

In this paper, we propose a new structure of silicon on insulator (SOI) lateral diffused metal oxide semiconductor (LDMOS) field effect transistors to improve the device performance. In the proposed structure, a trench is created in the buried oxide under the drift and drain regions and filled with p-type Si. We called the proposed structure as P-trench SOI-LDMOS (PT-LDMOS). Our simulations with two dimensional ATLAS simulator shows the unique features exhibited by the proposed structure in comparison with a conventional SOI-LDMOS (C-LDMOS). In the PT-LDMOS, the electric field is modified by producing a new additional peak at the electric field distribution, reducing the magnitude of electric field peak near the gate edge, removing of electric field crowding near the drift and drain junction at the bottom surface of the silicon layer, and making the surface electric field distribution more smooth. We optimize the doping concentration and the dimensions of the P-trench in the PT-LDMOS structure. Hence, the results illustrate the benefits of high performance PT-LDMOS over conventional one and expand the application of SOI-LDMOSs to high voltage.     

Transmission through dielectric-filled slots in a conductingcylindrical shell of arbitrary cross section: TE case

A simple moment solution is summarized for the problem of electromagnetic transmission through dielectric-filled slots in a conducting cylindrical shell of arbitrary cross section. The system is excited by a plane-wave polarized transverse electric (TE) to the axis of the shell. The equivalence principle is used to replace the shell and the dielectric by equivalent electric and magnetic surface currents radiating into an unbounded medium. Two different sets of coupled integral equations involving the surface currents are obtained by enforcing the boundary conditions on the tangential components of the total electric and magnetic fields. The method of moments is used to solve the integral equations. Pulses are used for both expansion and testing functions. Special attention is paid to circular and rectangular shells. Results for shell surface current, the internal field, and the aperture field are presented. For the case of air dielectric filling, the results computed using the electric field and/or the magnetic field formulation are in very good agreement with published data. In general, it is observed that the effect of filling a slot with a dielectric is not predictable from a simple theory     

发电机定子线棒在线监测系统的研制

大容量发电机是电网的心脏,为确保大型发电机安全、可靠地运行,对发电机定子线棒进行在线监测至关重要,为此,研发了一种新型的发电机定子线棒在线实时监测系统。通过新型的光纤加速度传感器检测发电机的汽端和励端的振动信号,进行了发电机定子线棒的振动特性的时域和频域分析;采用了虚拟仪器技术,实现了系统人机界面化,结合后台数据库,达到多功能、多状态的实时监测及报警、动态分析及历史查询、记录趋势并报表输出,达到诊断参数与数据共享,实现了远程监测与诊断技术。     

Scattering by a dielectric cylinder of arbitrary cross section shape

The theory and equations are developed for the scattering pattern of a dielectric cylinder of arbitrary cross section shape. The harmonic incident wave is assumed to have its electric vector parallel with the axis of the cylinder, and the field intensities are assumed to be independent of distance along the axis. Solutions are readily obtained for inhomogeneous cylinders when the permittivity is independent of distance along the cylinder axis. Although other investigators have approximated the field within the dielectric body by the incident field, we treat the total field as an unknown function which is determined by solving a system of linear equations. In the case of the dielectric cylindrical shell of circular cross section, this technique yields results which agree accurately with the exact classical solution. Scattering patterns are also presented in graphical form for a dielectric shell of semicircular cross section, a thin homogeneous plane dielectric sheet of finite width, and an inhomogeneous plane sheet. The effects of surface-wave excitation and mutual interaction among the various portions of the dielectric shell are included automatically in this solutiom     

End losses in a magnetohydrodynamic channel: Dc channel with fluid having large magnetic reynolds number

The Wiener-Hopf technique is used to solve for the electric field in a dc magnetohydrodynamic generator channel, under mixed boundary conditions. The ohmic losses are then evaluated. No restriction is made on the magnitude of the magnetic Reynolds number of the working fluid. Two problems of the semi-infinite generator section are solved, namely when the end region is at the channel entrance and when it is at the channel exit. Also the finite generator section problem is discussed.     

电子束轰击半导体偏转调制放大器带状层流电子束的设计

本文给出了用于电子束轰击半导体器件的带状层流电子束的设计考虑、计算机分析和实验结果。采用特殊校正透镜获得了截面为1×3mm~2的带状层流束。校正透镜的使用对于有限宽度带状束的实现是一个重要措施,可推广应用于其他场合。     

Equivalent circuit parameters of an aperture coupled open resonatorcavity

In this paper, we use modified form of Bethe's small hole coupling theory to compute equivalent circuit parameters of an aperture coupled open resonator cavity. The open resonator cavity is composed of spherical mirrors of circular cross section. The cavity is coupled to a rectangular waveguide by means of a common hole in the mirror and the shorted end wall of the rectangular waveguide. Closed form expressions have been obtained for the equivalent circuit parameters. Experiments conducted in the W-band frequency range show good agreement with theory when an experimentally estimated correction to the transmission coefficient is applied for the thickness of the coupling holes     

TE and TM Modes of Some Triangular Cross-Section Waveguides Using Superposition of Plane Waves (Short Paper)

Exact transverse electric and magnetic mode solutions of four triangular cross-section waveguides have been found via a new general method using Snell's law and superposition of plane waves. This paper presents results for 1) equilateral, 2) 30°, 30°, 120°, 3) isosceles right, and 4) 30°, 60° right triangular waveguides. The electric and magnetic field solutions form finite sums of separable rectangular harmonics and are the only waveguides of triangular cross section for which such solutions have been found.     

一种求解目标内谐振时散射截面的有效方法

众所周知,在内谐振频率点上,用矩量法求解电场或磁场表面积分方程将得到不正确的表面电流。文中应用奇异值分解和正交化方法对由电场积分方程计算出的表面电流进行修正,从而得到目标表面上产生散射场的真实电流分布。文中计算了一无限长理想导体圆柱内谐振时的散射截面,所得结果与解析解一致,并对一无限长理想导体正方柱的后向散射截面进行了计算,结果表明本文方法是有效和准确的。     

The Dominant Cutoff Wavelength of a Lunar Line

A method is presented for calculating the lowest cutoff wavelength of a new microwave transmission line, the "lunar line," which is formed by two eccentric circular metal tubes connected with a metal bar or tangential to each other. The lunar-shaped cross section is approximated by introducing a series of steps in the outer guide wall and by dividing the cross section into m fan-shape regions. Thus, the problem is reduced to one of a multiple-step waveguide and can be solved by introducing the angular parameter alpha/sub i/ for the individual regions. The radial boundary conditions require a combination of Bessel functions of noninteger order for each region. The common boundaries between regions give m integral equations that represent the total power in one region transferred into the next region. The integral equations are solved approximately by solving only the first terms of an infinite series expansion of the tangential electric field at the common boundary. The solution of the m-stepped waveguide results in a system of 2m equations containing 2m unknowns: the cutoff wave number beta/sub c/, the order of the Bessel function p/sub i/, and the angular parameter alpha/sub i/. A successive approximation method is applied to obtain the cutoff wavelength. The calculated value is in close agreement with experimental results.     

RCS of a partially open rectangular box in the resonant region

The radar cross section (RCS) of a partially open rectangular box in the resonant region is investigated. Two-dimensional numerical results are generated using the method-of-moments solution to the electric field integral equation. Resonance spikes are found in the RCS spectrum at frequencies which correspond to the resonant frequencies of the interior rectangular cavity. The dependence of the resonant behavior on the box dimension, aperture size, and incident polarization can be interpreted in terms of the field distribution inside the cavity. Experimental data for a three-dimensional box are also presented. They are consistent with the two-dimensional simulation     

Rectangular modes and dyadic Green's functions in a rectangularchirowaveguide. I. Theory

An analytic solution of electromagnetic-wave propagation in a rectangular chirowaveguide is represented in this paper in terms of spectral-domain dyadic Green's functions (DGF's) in a general form. The method used here is a combination of a wavefield decomposition method and DGF eigenfunction expansion technique. This DGF decomposition method avoids having to use the modified and normalized vector wave functions, which are found difficult to satisfy the boundary conditions of chirowaveguides in which the reconciliation of Dirichlet and Neumann conditions is impossible. On the other hand, this method can be generalized to a chirowaveguide of arbitrary cross section and is found reducible to a nonchiral case. It is observed that in a similar fashion to the conventional rectangular waveguide, the duality between the electric and magnetic types of DGF's in the rectangular chirowaveguide does not exist. To show the reducibility of the generalized DGF's for bi-isotropic media, we summarized the procedure of utilizing the formulas and proved in detail that the form of the DGF's can be reduced to that for chiral media and achiral (isotropic) media. Exactly the same DGF's are obtainable for the isotropic media by reducing the general formulas. The electric and magnetic fields in the rectangular chirowaveguide due to a point dipole excitation oriented in the y-direction are derived. The detailed numerical analysis includes the novel features of the dispersion relations, the effects of chirality on the novel features of the rectangular chirowaveguides, some newly discovered features, and vector field plots and contour plots of higher order modes of electric and magnetic fields     

Scattering by circular metallic disks

The eigenfunction solution for the far-field scattering by a thin, circular metallic disk is summarized. This solution yields both components of the scattered electric field for an incident plane wave of arbitrary polarization and arbitrary incidence directions. Sample amplitude, phase, and cross section results are presented.