On Observation of Surface Electromagnetic Waves in Enclosed Spaces

An experiment on the study of waveguide propagation of surface electromagnetic waves with a frequency of 1 GHz in an enclosed space on free curved metal–dielectric interface was conducted. The distribution of the field of the electromagnetic wave along the propagation path was obtained for two cases: when a metallized tape was placed between radiating and receiving antennas and without the tape. It has been found that the field strength in the presence of the metallized tape is higher than the field strength without the tape.     

基于FEM/BEM方法的表面声场体波模式数值研究

采用有限元/边界元法(FEM/BEM),分析了有限长叉指换能器在半无限大压电晶体128°YX-LiNbO3中激发的表面波和体波在晶体表面上的分布情况。通过对频域内表面声场的分析,得到了表面上三个位移场分量含有的声波模式,对相应时域内各场分量的体波脉冲振幅进行处理,详细分析了各个模式的体波脉冲振幅随时间的分布关系。结果表明,除Rayleigh型表面波外,各场分量中还包含不同成分和比例的体波模式;在场分量1和场分量3中占主要成分的准纵波,以及在场分量2中占主要成分的准慢切变波,在表面上其传播损耗以指数衰减。     

On computation of electromagnetic fields on planar surfaces from fields specified on nearby surfaces

A technique is presented for solution of the inverse problem of calculating the electric field on a planar surface from the electric field specified on a nearby surface. An integral equation is derived that relates two orthogonal components of the electric field on the nearby surface to the respective components of the plane wave spectrum of the planar electric field. The integral equation is solved by an iterative technique, and the planar near field is calculated by an inverse Fourier transform of the plane wave spectrum.     

Analysis of lightning-radiated electromagnetic fields in the vicinity of lossy ground

An antenna theory (AT) approach in the frequency domain is presented to compute electromagnetic fields radiated by a lightning return stroke. The lightning channel is modeled as a lossy-wire monopole antenna (a wire antenna with distributed resistance) energized by a current source at its base, and the ground is modeled as a lossy half-space. The method of moments is used for solving the governing electric field integral equation (EFIE) in the frequency domain. The resultant current distribution along the channel is used to calculate electromagnetic fields at different distances from the channel. All field components are evaluated using a rapid but accurate procedure based on a new approximation of Sommerfeld integrals. In contrast with the previous models, the approach proposed here is characterized by a self-consistent treatment of different field components in air or on the surface of a lossy half-space. It is shown that the omission of surface wave terms in the general field equations, as done in the perfect-ground approximation, can strongly affect model-predicted field components.     

一种具有新型分立介质支撑的翼片加载螺旋带慢 波结构的研究

本文研究了一种具有新型分立介质支撑的翼片加载螺旋带慢波系统,该种慢波系统具有较高的功率容量和较宽的带宽.通过用切比雪夫多项式来展开螺旋带上的面电流,用真空层来模拟螺旋带的厚度,用均匀分层介质来等效新型分立介质支撑,考虑到过渡连接金属块的影响,用场论的方法得到了非常实用的色散方程和耦合阻抗的表达式,同时进行了HFSS模拟,发现用场论的方法所得出的结果与用HFSS模拟的结果吻合良好.本文的结果对这种新型慢波结构的设计具有指导意义.     

On the Condition for Transformation of a Fast Surface Wave into a Slow Surface Wave

Surface plasmons (polaritons) along the boundary between vacuum and a dissipative half-space with given complex permittivity, including the case of placing an electrically thin dielectric layer (system of layers) on the boundary, are considered. Conditions for transformation of a fast gliding Zenneck surface wave (polariton) into a slow wave (slow surface plasmon) are considered. The behavior of the group velocity and the energy velocity of motion (transfer) in such structures are analyzed. The reflection coefficient of the Zenneck wave along the sea for the ice pack of a given thickness is determined. It has been shown that rigorous solution of the Sommerfeld problem by means of numerical calculation of integrals in the near zone allows obtaining the solution of the inverse problem of the structure of the surface region on the basis of redundant experimental data on components of the electromagnetic field on the surface at different ranges from the antenna.     

Electromagnetic waves and oscillations in the layered semiconductor-dielectric-semiconductor structure

Theoretical and numerical studies of the electromagnetic properties of the layered semiconductor — dielectric — semiconductor (SDS) structure was carried out. It was shown that the weak damping guide and surface waves may exist in this structure and retardation of surface waves may be several times more than for the semiconductor — dielectric (SD) interface. If this structure contains reflections it leads to the formation of high Q-factor resonance oscillations. It was found that at the beginning of intermode coupling of two surface oscillations in the studied resonance structure, hybrid surface oscillations with near resonance frequencies are formed. Their electromagnetic field components along the wave propagation direction are orthogonal to each other and modulated along the SD interface by orthogonal envelopes.     

The Radiation Properties of a Parallel-Plane Waveguide in a Transversely Magnetized, Homogeneous Plasma

The Wiener-Hopf technique is used to study the radiation from a parallel-plane waveguide embedded in a homogeneous anisotropic plasma in which the external magnetic field is perpendicular to the direction of propagation and parallel to the perfectly conducting planes of the guide. The incident field in the guide is a TEM wave, which propagates in the positive z direction. The parallel-plane guide terminates at z = 0, causing a reflected field in the waveguide, a radiation field, and a surface wave that is guided along the outer surface of one of the perfect conductors. Expressions are found for these field components, and the results are discussed for the different frequency ranges.     

Radar reflectivity of the ocean surface for circular polarization

If one transmits an electromagnetic wave, an electric field is set up in space. The earth's surface modifies the field and an interference pattern results. To calculate such a pattern one must know the reflection characteristics of the surface for the polarization of the incident wave. These are known for linear polarizations. Since a circularly polarized wave is a combination of the two linear polarizations, we can compute the reflection coefficient for circular polarizations by proper combination of the two linear reflection coefficients. This reflection coefficient is known for smooth sea conditions. In this paper the vector model of reflectivity for a rough sea is extended to include circular polarization. Reflection coefficients for the rough sea case are derived. Analytical expressions are given for the total received signal including the coherent and incoherent components. Receiver antenna polarizations of the same and opposite senses to that of the transmitter are considered.     

Characteristics of the electromagnetic radiation resulting from arbitrarily directed propagation of magnetostatic surface waves in an increasing transverse magnetic field

Radiation of the electromagnetic waves accompanying propagation of a magnetostatic surface wave with nonparallel directions of the phase and group velocities in a ferrite slab magnetized in its plane by a transverse linearly increasing magnetic field is analyzed using the model of accelerated motion of magnetic charges. It is shown that, at each point of the space surrounding the ferrite slab, the shape of the radiation pattern strongly depends on the angle between the direction perpendicular to the direction of propagation of the magnetic field and the direction of the wave vector of the magnetostatic surface wave.     

Disk scattering at edge-on incidence

As part of a general study of the backscattering from thin plates illuminated by a plane wave at glancing incidence, measurements have been made of the surface and far fields of circular disks. Some results of the surface field probing are presented and interpreted in terms of optics and creeping wave components analogous to those appropriate to the surface of a cylinder. Analytic forms for the components are then determined, and an expression for the backscattered field deduced therefrom. The result is compared with measured far-field data for electrically thin disks, and the effects of increasing the electrical thickness, either uniformly or nonuniformly, are also discussed.     

Excitation of a grounded dielectric slab by a horizontal dipole

The structure consisting of a horizontal electric dipole above a grounded dielectric slab is examined, primarily from the standpoint of power distribution among the two power-carrying wave components, i.e., surface and space waves. It is shown that surface wave propagation is always in the form of two distinct modes characterized by the same cutoff properties. Also, surface wave excitation efficiency curves are given for a range of parameter variation.     

Scattering cross sections for composite rough surfaces using the unified full wave approach

The full wave approach is used to derive a unified formulation for the like and cross polarized scattering cross sections of composite rough surfaces for all angles of incidence. Earlier solutions for electromagnetic scattering by composite random rough surfaces are based on two-scale models of the rough surface. Thus, on applying a hybrid approach physical optics theory is used to account for specular scattering associated with a filtered surface (consisting of the large sonic spectral components of the surface) while perturbation theory is used to account for Bragg scattering associated with the surface consisting of the small scale spectral components. Since the full wave approach accounts for both specular point scattering and Bragg scattering in a self-consistent manner, the two-scale model of the rough surface is not adopted in this work. These unified full wave solutions are compared with the earlier solutions and the simplifying assumptions that are common to all the earlier solutions are examined. It is shown that while the full wave solutions for the like polarized scattering cross sections based on the two-scale model are in reasonably good agreement with the unified full wave solutions, the two solutions for the cross polarized cross sections differ very significantly.     

A two-dimensional model of propagation of long and medium waves above inhomogeneous paths

A 2D model of a radio path for the field of a vertical electric dipole over the Earth surface is considered. The field components on the interface of the media satisfy the Leontovich boundary conditions. A quadrature formula taking into account irregularities of the path within the first several Fresnel zones is proposed for calculating the attenuation function of the surface wave field.     

The structure of high-frequency fields of a surface spin wave in a tangentially magnetized ferrite plate

Vector lines of the high-frequency magnetic field, magnetic induction, and magnetization of a surface spin wave in a tangentially magnetized ferrite plate are calculated. It is found that the magnetic induction vector lines form contrariwise directed curls that are localized near the opposite surfaces of the plate. It is shown that the structure of the magnetic induction of a spin wave and the change of its electric field are interdependent: in the ferrite layer, there is a plane on which the electric field amplitude is zero and which is simultaneously a boundary between the curls of the magnetic induction. It is found out that the directions of the magnetic field and wave magnetic induction vectors are substantially different in the ferrite plate, although these vectors coincide in the half-spaces surrounding the plate.     

Diffraction of a cylindrical surface wave by a discontinuity in surface reactance

This scattering problem is essentially two-dimensional due to the circular symmetry of the incident TM mode, and is solved exactly by the Wiener-Hopf technique. As stated, the incident wave is the symmetrical TM axial surface wave, traveling in the positive x direction and guided by a reactive surface at r = a. The normal surface reactance is X1for x < 0 and X2for x > 0, where X1and X2are positive and real. The discontinuity produces transmitted, reflected, and radiated fields whose amplitudes are given in terms of integrals which are evaluated in specific cases by quadrature formulas. It is shown that the derived field components reduce to those of Kay [1] or Barlow and Brown multiplied by a constant coefficient, for the case of a plane surface, if the radius a is allowed to become very large. Coefficients of transmitted, reflected and radiated power, relative to the incident power are calculated in certain cases, with conservation of energy being verified.     

Example of the generalised-function validity of the Rayleigh hypothesis

The electromagnetic field scattered by a conducting circular cylinder is expressed as an outward-going wave expansion in an eccentrically placed polar-co-ordinate system. It is shown that the expansion is always valid on the cylinder surface in the generalised-function sense but not in the conventional-function sense.     

Influence of mobile ion in organic material used in semiconductor devices

Kapton tape is often used for co-planarity of inner metal lead frame parts in the packaging of semiconductor components. It is made of organic material known as high temperature insulating tape. In this paper, the increment of leakage current in a packaged component that is caused by a Kapton tape was studied. The leakage measurement on Kapton tape was done using simple testing instruments such as source meter, micro prober and temperature controlled hot plate. The different leakage current characteristics were investigated on high temperature, test duration and length of the Kapton tape. According to the measured leakage current on various dependencies, it is suggested the leakage is due to mobile ion in Kapton tape. Various analysis techniques were able to identify the mobile ion was Sodium ions in the glue of the Kapton tape. Based on the observation, a model explaining the Sodium mobile ions failure mechanism in the Kapton tape was established. The deployment of leakage test can be applied to test incoming lead frame material. The test set up did not require expensive tester equipment and manufactured devices. It could also be transferred as new outgoing quality check mainly for lead frame suppliers.     

Computations of scattering cross sections for composite surfaces and the specification of the wavenumber where spectral splitting occurs

The scattering cross sections for composite random rough surfaces are evaluated using the full wave approach. They are compared with earlier solutions based on a combination of perturbation theory which accounts for Bragg scattering, and physical optics which accounts for specular point theory. The full wave solutions which account for both Bragg scattering and specular point scattering in a self-consistent manner are expressed as a weighted sum of two cross sections. The first is associated with a filtered surface, consisting of the larger scale spectral components, and the second is associated with the surface consisting of the smaller scale spectral components. The specification of the surface wavenumber that separates the surface with the larger spectral components from the surface with the smaller spectral components is dealt with in detail. Since the full wave approach is not restricted by the limitations of perturbation theory, it is possible to examine the sensitivity of the computed values for the backscatter cross sections to large variations in the value of the wavenumber where spectral splitting is assumed to occur.     

Construction of heuristic diffraction coefficients in the analytical solutions to the problems in which wave fields of different physical nature are scattered by polygonal flat plates with complex boundary conditions

The heuristic diffraction coefficients of the problem in which the wave field of an arbitrary physical nature is scattered by a polygonal flat plate with complex boundary conditions are determined. Diffraction coefficients are constructed with the help of the geometric optics coefficients of wave field reflection from an infinite plane surface by analogy with the known solution to the electrodynamic problem of diffraction by a perfectly conducting scatterer. It is established that the new approach makes it possible to derive simple formulas for diffraction coefficients. Their accuracy exceeds that of the formulas of the known heuristic analytical methods and tends to the accuracy of rigorous solutions. It is demonstrated that the derived results can be used in both electrodynamics and the other areas of physics, e.g., in calculations of the seismic wave diffraction.