Quasi-TEM modes in parallel-line transmission structures withconductors embedded in dielectrics

A transmission structure of many parallel conductors is capable of propagating many distinct quasi-TEM modes. A field theory of such modes was developed for a theoretically infinite number of very thin conductors placed on a dielectric substrate. The current paper extends this work to include a large number of thin parallel conductors embedded within finite dielectric slabs. The theory is illustrated by the following three structures: a large number of parallel wires embedded in dielectric slabs with substrates of infinite width, both with and without a ground plane; and a large number of thin wires embedded in a finite dielectric slab without a ground plane. This extension to a finite dielectric structure is obtained using a superposition method where both vertical and horizontal surfaces are considered infinite in turn. A major application of the derived formulation is the investigation of velocity distributions and crosstalk within these structures. Comparison of these structures with ones where the conductors are on the substrate (as opposed to embedded) indicates how the placement and structure of the conducting channel affects the modal velocities and crosstalk     

Multiconductor Transmission Lines In Multilayered Dielectric Media

A method for computing the capacitance matrix and inductance matrix for a multiconductor transmission line in a multilayered dielectric region is presented. The number of conductors and the number of dielectric layers are arbitrary. Some of the conductors may be of finite cross section and others may be infinitesimally thin. The conductors are either above a single ground plane or between two parallel ground planes. The formulation is obtained by rising a free-space Green's function in conjunction with total charge on the conductor-to-dielectric interfaces and polarization charge on the dielectric-to-dielectric interfaces. The solution is effected by the method of moments using pulses for expansion and point matching for testing. Computed results are given for some cases where all conducting lines are of finite cross section and other cases where they are infinitesimally thin.     

The Electrostatic Field of Conducting Bodies in Multiple Dielectric Media

A method for computing the electrostatic fields and the capacitance matrix for a multiconductor system in a multiple dielectric region is presented. The number of conductors and the number of dielectrics in this analysis are arbitrary. Some of the conductors maybe of finite volume and others may be infinitesimally thin. The conductors can be either above a single ground plane or between two parallel ground planes. The formulation is obtained by using a free-space Green's function in conjunction with total charge on the conductor-to-dielectric interfaces and polarization charge on the dielectric-to-dielectric interfaces. The solution is effected by the method of moments using triangular subdomains with piecewise constant expansion functions and point matching for testing. Computed results are given for some finite-length conducting lines, compared to previous results obtained by two-dimensional analysis.     

Analysis of coupled microstrip lines on a layered substrate containing a metal ferromagnetic film

A method is described for the numerical analysis of the fundamental electromagnetic waves in an open planar multiconductor transmission line on a layered substrate containing a thin metal ferromagnetic film. Matrices of the inductance and capacitance per unit length of the strip conductors are obtained via rigorous solution of 2D magnetostatic and electrostatic boundary-value problems. Formulas for calculation of the phase velocities of quasi-TEM modes and corresponding amplitudes of currents and voltages on the strip conductors are derived.     

Modal analysis of multi-connected waveguides

A general analysis for the modal characterization of multiconnected uniform, hollow, conducting waveguides is presented. It is relevant to waveguides with an `outer' conductor for which analytical Green's functions are known and `inner' conductors described by integral equations. The transverse electromagnetic (TEM)-mode space is analyzed, and singularities of the integral equations are studied to determine the higher-order modes. The cases of parallel wires into rectangular waveguides and above a ground plane are addressed in detail; experimental results about a complex multiwire line are reported. Mixed coaxial and circular offset coaxial waveguides are also analyzed. Spurious solutions arise due to the structure of the integral equations for multiconnected waveguides. Criteria to discard such modes are presented     

Scattering of a plane electromagnetic wave by a structure consisting of a dielectric ellipsoid and a plane lattice of three thin conductors

A structure consisting of a dielectric ellipsoid and a plane lattice of three thin conductors is considered. Scattering of a plane electromagnetic wave by this structure in the resonance frequency range is analyzed with the use of the auxiliary source method. The developed computer code is described. The effect of the lattice on the radar cross sections of the ellipsoid is illustrated numerically. Results characterizing the current distributions along the conductors of the lattice and the influence of deviations of the dielectric body’s shape from the axisymmetric geometry on the bistatic cross sections of the structure are presented.     

High-Order Mode Cutoff In Rectangular Striplines (Short Papers)

The higher order mode cutoff characteristics of rectangular stripline structures, with thin center conductors, are discussed. Data are given, using an alternative method of presentation, on the normalized cutoff of the first eleven higher order modes. Discussions are included on the physical reasons why cutoff is aftered for some modes, relative to that in rectangular waveguides, but not for others.     

Susceptance computation of a meander-line polarizer layer

The solution to the problem of scattering of a plane wave by an infinite periodic array of meander-line thin conductors on a dielectric sheet is considered. Numerical results on perpendicular and parallel polarization susceptances are given as well as a comparison with experimental data over a large frequency range. Results showing variations of array's susceptances with respect to constitutive parameters are also presented.     

Shielding properties of an ensemble of thin, infinitely long,parallel wires over a lossy half space

A determination of the total electric field produced by an ensemble of thin, infinitely long, parallel wire scatterers over a flat lossy half space illuminated by a plane wave whose polarization is parallel to both the wires and the interface is presented. By invoking the thin wire idealization, a matrix equation is obtained for determining the currents on each wire, from which the total electric field is obtained. Several plots are given to show how the wires' radii, the earth's conductivity, the incident angle, and the total number of wires affect the shielding for a semicircular shell. In many cases, it is demonstrated that the shielding effectiveness can be as much as 70 dB; for other cases, when the structure is of resonant dimensions, the shielding can be degraded to 20 dB. It is also shown that a wire grid model can give shielding results similar to those of a continuous perfectly conducting structure of similar dimensions     

Characteristic Impedances of Multiconductor Strip Transmission Lines

The design of certain log-periodic microwave circuit elements requires a knowledge of the characteristic impedances of a system of four-coupled strip transmission lines. The system of four strip conductors between parallel ground planes is capable of supporting four different TEM modes which have different characteristic impedances. In this paper, the characteristic impedances of the four modes are determined by a variational method. The variational solution is an upper bound to the exact characteristic impedance of the line. In general, the coplanar strip conductors are located at an arbitrary (but identical) displacement from the parallel ground planes. When the separation between the broadside-coupled strips is precisely one-half the spacing between the parallel ground planes, two of the mode impedances may be determined exactly by means of conformal mapping. The variational solutions are compared to the exact solutions for this special case. Because of the "cell image" principle which holds for the problem, the mode solutions presented here also apply to various single- and two-conductor strip transmission lines with arbitrary displacements. As a result, solutions for the following strip line configurations are available from the analysis: a single strip conductor in a trough, or between parallel ground planes; two coplanar strips between ground planes; two broadside-coupled strips in a trough, or between parallel ground planes. An extensive set of curves are presented which show the characteristic impedances of the four modes as a function of the relative dimensions of the strip transmission line.     

Nondegenerate Surface-Wave Mode Coupling Between Dielectric Waveguides

A new variational derivation of the coupling coefficient is given for the problem of nondegenerate surface-wave modes on parallel dielectric waveguides. The results coincide with those of a number of different methods in the literature on the degenerate case, but all give distinct results in the nondegenerate case. These differences are examined and compared with the exact solution, whereby the approximations involved can be evaluated for the case of two parallel slab waveguides.     

Selective screening of waveguide modes by a system of two grids with square cells

The problem of selective screening of waveguide modes with the help of a filter consisting of two metal grids with square cells is analyzed. The filter has perfect contacts at conductors’ crosses. The investigation is performed by means of the method of averaged boundary conditions. The general expressions are obtained for the mode reflection and transmission coefficients. Examples of filtering of various modes are presented for the case of a circular waveguide. The method is shown to be especially efficient for extraction of higher order modes. It is noted that, in such filters, grids with very thin conductors are the most promising.     

Reduction of mutual coupling using perfectly conducting fences

A theoretical and experimental study of the use of thin perfectly conducting fences to reduce the mutual coupling of two parallel-plane waveguides radiating through a ground plane is described. The two cases which are studied areE-plane coupling of parallel planes with transverse electromagnetic mode propagation andH-plane coupling of parallel planes with the fundamental transverse electric mode propagation. The analysis presented accounts for a number of higher order modes in the waveguide apertures and uses a Fourier series approximation to the fence currents. Close agreement with experimental results is demonstrated.     

邻域图像处理机中的新型邻域功能流水线结构

本文介绍了邻域图像处理机原理,提出了邻域图像处理中新型的收缩型和级联型邻域功能流水线结构.这两种邻域功能流水线的流水线作业是以独立的图像处理算法为基础进行的,可以实时(甚至超实时)地完成多个独立的图像处理算法,高度体现了并行处理机数据并行、处理并行的原则,体现了多个算法的有机集成,因此特别适合于实际问题对综合算法的需求.这种邻域功能流水线结构不仅大大提高了图像处理的速度,而且增强了系统的灵活性.本文论述了收缩型和级联型邻域功能流水线的结构,给出了多个图像处理功能的组合.     

Subwavelength Grating-Mirror VCSEL With a Thin Oxide Gap

A new vertical-cavity surface-emitting laser (VCSEL) structure based on a subwavelength grating mirror and a thin oxide gap is suggested and numerically investigated. The structure is shown to exhibit similar threshold gain, suppression of higher order transverse modes, and polarization stability as a grating-mirror VCSEL reported in the literature based on a thick air gap. The thin oxide gap structure has a number of advantages including easier fabrication, better mechanical stability, and very strong single-mode properties.     

Coaxial feed in uniaxial substrate between two finite parallel conductors

A coaxial feed located in a uniaxial substrate between two finite parallel conductors is reduced analytically into a finite number of voltage sources over the coaxial probe. The procedure used is the same as originally developed for an isotropic substrate. The resulting expressions for both the new sources and the separated admittance component are interpreted by comparison with the isotropic case.<>     

Radio frequency transmission via a trolley wire in a tunnel with a rail return

An analysis is given for the transmission of electromagnetic waves along a circular tunnel in the presence of axial conductors. One of these conductors is an idealization of a trolley wire with its bonded feeder line that may be located anywhere in the tunnel. The other is a metal rail that is located within the homogeneous rock medium at a finite distance from the tunnel wall. A mode equation for the propagation modes is obtained that is used to obtain numerical results for the attenuation rate in the frequency range 50 to 800 kHz. It is shown that the attenuation rate is only weakly dependent on the burial depth of the rail conductor, at least in the range up to 50 cm. Also, it is found that the rail conductor for the model adopted carries an appreciable fraction of the total return current when typical rock conductivities are assumed. A thin layer of insulation on the rail appears to have a negligible effect. In fact, there is little change even if the rail is within the tunnel and just above the tunnel floor.     

Correct determination of TE and TM cutoff wavenumbers intransmission lines with circular outer conductors and eccentric circularinner conductors

The cutoff wavenumbers of TE and TM modes (higher order modes) in transmission lines with circular outer conductors and eccentric circular inner conductors are carefully evaluated. The correctness of Kuttler's bounds is confirmed and the reason why some of the values obtained lie outside the bounds and why some of the modes could not be found in the work of A. Vishen et al. (1986) is given. A reliable technique for accurately determining the roots of an analytical function is proposed for finding cutoff wavenumbers in such a way as to avoid missing any modes     

A Network Analogue Method for Computing the TEM Characteristics of Planar Transmission Lines

A network analogue method for calculation of the capacitance matrix of certain two-dimensional multiconductor systems is presented. The system is contained in a finite or infinite conducting rectangular boundary. An arbitrary number of parallel dielectric layers can be present, and the conductors consist of an arbitrary number of conducting strips at one or more of the dielectric interfaces. The strips are assumed to have zero thickness.     

Magnetostatic Surface-Wave Propagation in Ferrite Thin Films with Arbitrary Variations of the Magnetization Through the Film Thickness

A variational formulation for the magnetostatic problem in an anisotropic and inhomogeneous region bounded by perfect conductors is described. The method is applied to the special case of magnetostatic surface-wave (MSSW) modes propagating in a ferrite thin film with arbitrary variations of the saturation magnetization through the film thickness. Methods for calculating dispersion relations, delay characteristics, and magnetostatic potential functions are discussed. The functional that is minimized is interpreted in terms of contributions to the mode energy. Also, concepts pertaining to homogeneous films such as mode bandwidth and dimensional scaling effects are extended to the general inhomogeneous case. Calculations for a two-layer film with a gradual transition region and an ion-implanted film are presented as numerical examples.