Guided Waves on a Planar Helix

Considered here is a planar structure comprising a pair of parallel arrays of periodically spaced conducting strips which conduct in different directions in the two arrays. The guiding properties of this planar structure are found to be similar, in one case, to those of circular tape helices. While in general, different dielectric media are assumed in the sandwiched and outer regions, the special cases studied are 1) the case in which air constitutes both the media, 2) the normal-helix case in which the inner medium is a solid dielectric and the outer medium is air, and 3) the "inverted-helix" case with the two media interchanged.     

Elastic Waves Guided by a Solid Layer Between Adjacent Substrates

The present investigation is motivated by the problem of coupling Rayleigh waves between adjacent substrates when either substrate is nonpiezoelectric, in which case it becomes necessary to resort to some mechanical means to achieve this coupling. The use of a fluid coupling layer has been investigated and experimentally demonstrated elsewhere, while the use of a solid layer, with its inherently greater mechanical stability, has also been proposed. In this work, the operating characteristics of a specific solid-layer structure are predicted on the basis of a theoretical analysis, which furnishes the propagation characteristics and field structure of the waves which may be guided by a solid layer between two identical solids.     

Waves Guided by Conductive Strips Above a Periodically Perforated Ground Plane

This paper considers the propagation of waves along an array of conductive strips situated above a periodically perforated conductive plane. Each conductor has zero thickness and finite sheet resistance, and the dielectric is homogeneous. The surface current density on the conductors is approximated by a finite number of current elements having rooftop spatial dependence. The transverse electric field is expressed in terms of the current, and the electric field boundary condition is satisfied in an integral sense over the conductors. This generates a matrix equation whose solution gives the dispersion curve relating the propagation constant to frequency, as well as the current distribution. The simulation results are used to obtain equivalent transmission-line parameters applicable to printed circuit boards found in high-performance computers. A characteristic impedance is defined and it is shown that, with proper interpretation, the uniform transmission-line equations for propagation constant and characteristic impedance apply to such computer packages. The coupling between adjacent strips is caculated, and the effect of finite resistivity discussed.     

Guided Waves in Moving Media

This paper contains a theoretical study of the guided waves in a moving isotropic medium. The normal modes which can exist in a circular or rectangular wave guides are found by solving the Maxwell-Minkowski Equations subject to the appropriate boundary conditions. By certain transformations of field vectors, it is possible to change the Maxwell-Minkowski Equations into familiar forms such that the method of vector potentials can be applied to derive complete expressions for the field vectors. The results demonstrate that expressions for the propagation constant and the transverse-wave impedance and admittance in stationary media are modified by terms independent of the guide geometry when the media are moving.     

Localized Spoof Surface Plasmon Skyrmions Excited by Guided Waves

Recently, skyrmions are constructed in the system of localized spoof surface plasmons (LSSPs), showing topological robustness and near-equidistant multi-resonant response. Guided wave excitation of the LSSP skyrmions plays an elementary role in large-scale planar integration and construction of complex networks. However, it is not investigated. In this study, the LSSP skyrmions are excited by guided waves supported by two kinds of widely used transmission lines, microstrip line and coplanar waveguide. Space-coiling meta-structures with different shapes that support LSSP skyrmions are etched on the ground planes as defected ground structures (DGSs). All structures including resonator, transmission line, input and output ports are in one plane. The structures are fabricated on printed circuit boards (PCBs) and the near-equidistant multi-resonant spectra of the LSSP skyrmions are measured. Moreover, to reduce the material loss, the structure is made on MgB₂ superconducting film, and the quality factor (Q-factor) is increased by seven times compared to the corresponding mode on PCB. This study paves the way for the massive planar integration of the LSSP skyrmions and the construction of complex networks with the LSSP skyrmions, and provides an idea for developing metasurfaces with low material loss in the microwave and terahertz bands.     

磁光薄膜波导中光导波的模式转换和衍射效率计算

根据耦合模理论,应用微扰方法分析了Ｂｉ：ＹＩＧ薄膜波导中斜向静磁场对静磁波与导波光相互作用的影响,计算了斯托克斯和反斯托克斯相互作用中导波光的模式转换效率和衍效率。     

Design of a Monopulse Antenna Using a Dual V-Type Linearly Tapered Slot Antenna (DVLTSA)

The dual V-type linearly tapered slot antenna (DVLTSA) is a modified version of the Vivaldi radiator and is first introduced here. It is much more compact and keeps the advantages of the conventional tapered slot antenna (TSA). Furthermore, this antenna is suitable for a monopulse antenna owing to its special configuration. Both the sum and difference beams can be generated only employing a single DVLTSA respectively through the multimode substrate integrated waveguide (SIW) feeding technology. With detailed theoretical analysis, a prototype of the monopulse antenna proposed at the center frequency of 36 GHz was integrated on a single substrate using the normal PCB process. Measured gain of the sum beam is 10.6dBi, while the zero depth of the difference beam is lower than $-35$ dB. It also has good cross-polar characteristics and can be applied over a broad bandwidth as well.      

斜向场双层波导中导波光模式转换和衍射效率

本文研究了斜向场下双层磁光薄膜波导中导波光与静磁正向体波之间的相互作用。在静磁波频率为1．9－3．4GHz的范围内,计算了不同磁场倾角下导波光的衍射效率和模式转换效率。结果表明,在相匹配条件下,通过改变磁场倾角、微带线的宽度和孔径,可以使导光的衍射效率得到较大的提高。斜向场下使用YIG材料制成的双层波导与单层波导相比,在增进导波光的衍射效率具有较大的优势和潜力。     

Radiation Fields of a Tapered Film and a Novel Film-to-Fiber Coupler

Light in a tapered thin-film optical waveguide radiates into the substrate because the waveguide mode in the taper becomes cut off. Our measurement of the radiation pattern shows that the light emerges from the taper as a narrow beam with an angular width of only 2/spl deg/-4/spl deg/. We have studied the problem based on ray optics and based on a wave theory of radiation modes. We also have demonstrated a film-to-fiber coupler in which an optical fiber collects all the light emerging from the taper.     

Guided Waves on a Flattened Sheath Helix (Letters)

The "flattened sheath helix" considered in this letter consists of a pair of parallel unidirectionally conducting screens conducting in different directions and having different dielectric media in the sandwiched and outer regions. Special cases are 1) the normal flattened helix in which the inner medium is a solid dielectric and the outer medium is air, and 2) the inverted flattened helix with the two media interchanged. The guiding properties of such structures are studied.     

Microwave Network Methods for Guided Elastic Waves

The possibility of obtaining true microminiaturization by the use of elastic wave circuitry on solids is hampered by the lack of knowledge regarding the behavior of the constituents of those circuits. Since boundary value problems involving elastic waves in solids are generally very intricate and difficult to solve, a direct frontal attack on those problems will in many cases lead to frustration. In this paper, a series of steps is outlined which avoids the frontal attack and lends itself to a systematic procedure for achieving the understanding sought. It involves the application of concepts and techniques of proven value in electromagnetic microwaves to corresponding categories of problems in elastic guided waves. To demonstrate the value of this approach, it is used to derive the properties of several well-known types of elastic wave on layered media, such as Rayleigh surface waves, leaky Rayleigh waves, Lamb waves, and Love waves. In the building-block approach employed, the results derived separately include transmission-line models for body waves in fluids and isotropic solids, with expressions for the characteristic impedances and the velocity and stress vector mode functions, and equivalent networks for several types of interface which are constituents of the layered media mentioned above. The propagation properties of the guided waves are then obtained by the use of the transverse resonance procedure in a systematic, simple, and direct fashion.     

Matched Representations and Filters for Guided Waves

We propose time-frequency methods to filter dispersive guided wave signals. Guided waves occur in acoustical propagation (oceanic waveguides), geophysics (layered medium), or optics (dielectric optical waveguides). In waveguides, signals can be decomposed into normal modes which contain information on environmental parameters and source localization. As modes present nonlinear time-frequency evolution, modal filtering is not possible with conventional tools. To overcome the difficulty presented by these nonlinearties, we have developed matched tools: matched frequency and time-frequency representations and the modal filterings associated with these representations. The tools developed are based on unitary equivalence principle. Performance and robustness of different proposed modal filters are evaluated and compared. All of these tools can be used for both source localization and environmental inversion.     

Guided Beam Waves Between Parallel Concave Reflectors

A new guided beam wave transmission system is proposed here, which is composed of two parallel concave reflectors. The principle is a combination of waveguide and beam wave transmission. The shape of the reflector cross section and the corresponding mode functions were obtained. Attenuation due to wall current and limited aperture of the reflectors were calculated. Experiments were made to confirm the modes and the attenuation. One of the remarkable features of this transmission system is its field distribution, which is concentrated into a belt-shaped space between reflectors. Considering this feature, this system seems to be effectively applied to the railways as a medium for obstacle detection and communication.     

On Guided Waves in Moving Anisotropic Media

Based upon the Maxwell-Minkowski theory, the equations governing the propagation of electromagnetic waves in a cylindrical waveguide of an arbitrary cross section filled with a moving anisotropic medium are derived. The governing equations are reducible to a pair of coupled wave equations in the axial components of the electric and magnetic fields, which in turn can be solved through the solution of a single second order scalar homogeneous Hehnholtz equation. For a general anisotropic medium no pure TM or TE modes can exist in the waveguide. However, if the moving medium is uniaxially anisotropic, TM and TE modes are possible. It is interesting to note that the cutoff frequencies are always lowered by a factor which depends upon the velocity of the medium and is independent of the guide geometry. The formulas for the characteristic wave impedance and power flow in a waveguide for a moving uniaxial medium, if expressed in terms of the new cutoff frequency, have the same forms as those for a moving isotropic medium. The propagation characteristics of waveguides of rectangular and circular cross sections filled with a moving uniaxial gyroelectric medium are discussed.     

Reflection of Magnetostatic Forward Volume Waves by a Shallow-Grooved Grating on a YIG Film

The magnetostatic forward volume wave (MSFVW) reflection characteristics of a uniform grating of shallow grooves etched on the planar surface of an epitaxial YIG film are treated using an approach which integrates field theory with the coupled-mode approach. The MSFVW reflectivity per groove is found to be comparable to the reflectivity of magnetostatic surface waves (MSSW's) and thus is found to be significantly large considering that the volume waves are reflected by surface-localized and shallow grooves.     

Coupling Between Guided Surface Waves, Lateral Waves, and the Radiation Fields by Rough Surfaces--Full-Wave Solutions

In this paper explicit expressions are presented for the guided surface waves and lateral waves that are excited when radiation fields are incident upon rough surfaces. Similarly, expressions are presented for the radiation fields scattered by rough surfaces that are excited by surface waves and lateral waves. In addition, coupling between the surface waves and the lateral waves due to surface irregularities is considered in detail. The solutions, which are based on a full-wave approach to the problem, are subject to the exact boundary conditions at the irregular interface. These are shown to be consistent with the reciprocity relationship in electromagnetic theory. The validity of the approximate impedance boundary condition is examined and consideration is given to excitation at the grazing incidence, the Brewster angle, and to waves incident at the critical angle for total internal reflection. Optimum conditions are determined for coupling between the radiation fields, the surface waves, and the Iateral waves incident upon irregular boundaries. Thus this work is applicable to problems of radio wave propagation near an irregular interface between two media and excitation of guided waves by irregular dielectric structures.     

无介质基片直线渐变式槽缝天线辐射特性的分析

根据电磁场的等效原理 ,基于半无限大导电平面上磁流元的并矢格林函数 ,给出了无介质基片直线渐变式槽缝天线 (TEM LTSA)远区辐射场的主极化及交叉极化分量的理论公式 ,各极化分量只需计算一维的数值积分。分析天线张角、天线长度的各种结构的TEM -LTSA的交叉极化辐射特性 ,给出了对角平面内辐射场主极化幅值电平与交叉极化幅值电平的关系曲线     

Effect of Nonuniform Magnetic Field That Magnetizes a Ferrite Film on the Measurement Accuracy for Characteristics of Spin Waves

Journal of Communications Technology and Electronics - A magnetic system is developed to generate a stationary uniform magnetic field in a relatively large region between the poles of a magnet that...     

板状材料中脉冲激光激发超声导波的数值分析

利用有限元法(FEM)对板状金属材料中脉冲激光激发的超声导波进行了理论研究。在考虑热弹激发的条件下,利用三维轴对称的有限元模型,计算了相同能量的分别具有不同聚焦半径以及脉冲宽度的脉冲激光光源直接作用于Al板表面激发出的声表面波信号的时域特征,并利用Wigner-Ville分布的时频分析工具得到了信号能量在频域上的分布特征。研究结果表明,激光单脉冲能量不变的情况下,超声导波信号的峰值幅度随着脉冲激光的聚焦半径的减小而逐渐增大;同时缩小聚焦半径也可以提高超声导波的频带宽度;然而脉冲宽度的变化却没有引起超声信号在时域及频域特征上的明显变化。