Extraction of Via-Plate Capacitance of an Eccentric Via by an Integral Approximation Method

An integral approximation method is proposed to extract the via-plate capacitance of an eccentric via in the via hole (anti-pad). An analytical formula is derived for the coaxial capacitance part, which is used as a benchmark to validate the integral approximation method. Furthermore, numerical simulations are also used to validate the method. It is shown that small eccentricity results in only a few percentage increase of the via-plate capacitance, which is helpful in specifying the manufacturing tolerance of via designs.      

Temperature Compensation of Coaxial Cavities

This paper describes a technique for temperature compensation of coaxial cavities by controlling the capacitance between the end of the center conductor and an end plate across the outer conductor. A formula is derived for this capacitance which is verified experimentally. Supplemental design data are also obtained experimentally.     

Characteristic Impedance of a Rectangular Coaxial Line with Offset Inner Conductor

The singular-integral-equation technique is used to derive the capacitance and, hence, characteristic impedance of a rectangular coaxial line with a zero-thickness inner conductor. The position of the inner conductor is arbitrary, but its orientation is assumed to be parallel to the top and bottom walls of the outer conductor. Simple yet very accurate formulas for the capacitance and characteristic impedance are found in terms of complete elliptic integrals.     

Electromagnetic scattering from anisotropic plasma-coated perfect electromagnetic conductor cylinders

The scattering of electromagnetic waves by a perfect electromagnetic conductor (PEMC) cylinder coated with a homogeneous plasma anisotropic material is studied in this paper. Both of the transverse electric and the transverse magnetic polarizations of the incident waves have been analyzed and formulated. The presented analysis and formulations are general for any perfect conductor cylinder (PEC, PMC, or PEMC) with general isotropic/anisotropic material coatings that include plasma and metamaterials. The co-polarized and the cross-polarized components of the scattered fields are computed for different cases of the anisotropic plasma coated PEMC cylinders and for an anisotropic plasma column. Bistatic echo widths for the cases of PEMC, PEC (perfect electric conductor) and PMC (perfect magnetic conductor) cores have been computed and compared. The behavior of the monostatic echo width with the variation of the admittance parameter for the co-polarized and the cross polarized fields is also investigated. The comparisons of the computed results of the presented formulations with the published results of some special cases confirm the accuracy of the presented analysis.     

Image theory for electromagnetic sources in chiral medium above thesoft and hard boundary

The classical image theory valid for electromagnetic (EM) sources in an isotropic medium above a planar perfect electric conductor (PEC) or perfect magnetic conductor (PMC) surface was extended to involve the planar soft-and-hard surface (SHS) boundary that can be realized with tuned corrugations. The image principle is now generalized to EM sources in isotropic chiral medium above an SHS boundary. The problem is solved by two consecutive decompositions of the sources reducing the problem to four classical ones involving electric and magnetic sources above PEC and PMC boundaries; each involving an isotropic nonchiral medium and possessing a known image solution. One of the decompositions is based on the fact that the two eigenwaves of a chiral medium do not couple at a soft-and-hard surface; and, the other one, on the eigenpolarizations of the reflection dyadic     

A technique for approximating the location of surface- and leaky-wave poles for a lossy dielectric slab

An approximation technique for locating the surface- and leaky-wave poles for a lossy dielectric slab is presented. The problem is reduced to the simultaneous solution of two transcendental equations (for each of the perfect magnetic conductor (PMC) and perfect electric conductor (PEC) cases) which is shown to yield a simple approximate solution for the poles, and which can subsequently be refined using numerical optimization. The technique yields both surface-wave and leaky-wave poles, and results are presented for a typical example to demonstrate the approach. The greatest approximation accuracy was observed for surface-wave and leaky-wave poles well removed from the spectral gap. For poles either within or in close proximity to the spectral gap, an alternative iterative technique is proposed. Expressions for the number of proper plus improper surface-wave poles in a given problem are also derived.     

Array Antenna With Increased Element Separation Based on a Fabry–PÉrot Resonant Cavity With AMC Walls

A new method is presented for increasing the separation between the radiating elements of a 1-D array antenna by incorporating it into a Fabry-Perot type resonant cavity with artificial magnetic conductor (AMC) walls. The AMC walls create a more uniform distribution of field within the cavity and, moreover, eliminate diffracted fields. The concept is demonstrated via 3-D full-wave simulations as well as experimental measurements for a prototype antenna. Comparison between an antenna with AMC walls and an identical reference antenna, without walls, shows a reduction in the sidelobe level. An array element separation of 2lambda is achieved whilst maintaining good radiation performance. The performance of the proposed structure is also compared to that of an antenna incorporating PEC walls. Finally, the effect of the sidewall and central AMC walls are considered separately in order to isolate their corresponding effect on the antenna performance.     

A Numerical Calculation of the Capacitance for the Rectangular Coaxial Line with Offset Inner Conductor Having an Anisotropic Dielectric

The capacitances of the rectangular coaxial lines with an offset zero-thickness inner conductor having a sapphire dielectric are presented by using an expanded charge simulation method, In order to apply the method to an anisotropic region, we propose an electric potential formula for a two-dimensional system consisting of a line charge and an infinite plate conductor which are arbitrarily situated in the region. The potential formula is anatyticafly derived by means of an affine transformation, a confomal mapping technique, and the method of images. The capacitance calculated using this method is in good agreement with those of other available methods.     

Approximate Determination of the Characteristic Impedance of the Coaxial System Consisting of an Irregular Outer Conductor and a Circular Inner Conductor

An elementary formula is presented for the determination of the characteristic impedance of a coaxial transmission line consisting of a circular inner conductor and an irregular outer conductor. In this approach, the irregular outer conductor is replaced by an eccentric circular enter conductor which has the same "shield factor" as an irregular one at the extreme of a small wire, and the same formnla is adapted for outer conductors of different shapes by determining values of eccentricity of the equivalent eccentric coaxial lines. The validity of the formula is confirmed by numerical results.     

A multipole analysis of a dielectric loaded coaxial rectangularwaveguide

A multipole analysis of a coaxial rectangular waveguide whose inner conductor is circular is made in order to determine the TE and TM modes of the system. The analysis is based on using multipole (dipole, quadrupole etc.) electric and magnetic current sources to generate field solutions in the waveguide. These solutions are used to match the electromagnetic boundary condition in a homogeneous coaxial rectangular waveguide and to determine the TE and TM eigenvalues of the waveguide system. Eigenvalue results are compared with results of the generalized spectral domain method and to eigenvalue results for a ridged waveguide. Propagation in a coaxial rectangular waveguide is also studied when the coaxial rectangular waveguide is loaded with lossy inhomogeneous dielectric material. A variational formula is used to relate the TEM, TE, and TM modes of an empty coaxial rectangular waveguide to the propagation in the loaded inhomogeneous dielectric waveguide     

Losses in the PEMC Boundary

Perfect electromagnetic conductor (PEMC) was recently introduced to generalize both the perfect electric conductor (PEC) and the perfect magnetic conductor (PMC), which are used as boundary material. In this paper, an extension of PEMC boundary conditions is made to a more realistic model with small losses (“good electromagnetic conductor”). It is shown that the antisymmetric boundary impedance dyadic defining the ideal PEMC boundary cannot alone carry any losses and a symmetric component must be added that actually dominates the lossy behavior of the boundary. As an example, a slab of low-loss gyrotropic wave-guiding material is studied and shown to represent the lossy counterpart of the PEMC boundary. The effect of losses is demonstrated by considering plane-wave reflection from an imperfect PEMC plane.     

Lightning-Induced Transients on Buried Shielded Transmission Lines

This paper is primarily concerned with the analysis of induced transient current and voltage surges on buried shielded transmission lines due to earth-conduction effects of nearby lightning discharges. An analytical method is presented in this paper to model the conductive coupling mechanisms in the earth and to determine the amount of coupling between a lightning discharge to ground and an earth-return transmission line. The transmission line is assumed to be a long straight horizontal coaxial cable with an inner shield and an outer armor, terminated on both ends with typical communication-equipment load impedances. The general case is considered here, in which the outermost conductor is not necessarily in perfect contact with the conducting earth, but has a contact impedance with the earth, as in cables with an outer dielectric covering for corrosion or water protection. Average lightning-channel conditions and a representative buriedcable geometry are examined. The results are conveniently displayed via several graphs of the time histories of the resulting transient current and voltage surges.     

Application of an anisotropic perfectly matched layer absorber for open boundary truncation in the multiresolution time domain scheme

We apply an anisotropic perfectly matched layer (APML) absorber for open boundary truncation in implementation of the multiresolution time domain (MRTD) scheme. We develop an APML update algorithm to handle a general APML region in the MRTD formulations with the content of the leapfrog algorithm applied in the conventional finite-difference time-domain method. We also discuss the boundary truncations for both perfectly electric conductor (PEC) and perfectly magnetic conductor (PMC) walls using the image techniques. We validate the algorithm by analyzing various guided wave and antenna structures. It is found that the APML performs well for absorbing electromagnetic waves in the MRTD algorithm.     

The Magnetic Field Distributions and Beam Propagation Properties of the Hybrid Coaxial Wiggler

In this paper a novel coaxial wiggler, the hybrid coaxial wiggler, is proposed. The analytical formula for magnetic field of the wiggler is derived, and the beam propagation properties are investigated numerically. The results show that the hybrid coaxial wiggler is scalable to small periods with high field amplitude, high beam current acceptance, and excellent transverse focusing properties.     

Theory of the Slotted Coaxial Cable

The electromagnetic problem of the coaxial cable with a continuous slot along the outer conductor is solved taking into account the dielectric constant of tbe cable insulation. Cylindrical harmonics expansions for the inner and outer space are used. The basic difficulty is to express boundary conditions on a part of the period in Fourier series. It appears that the singularity of the fields at the edge of the outer conductor plays a key role in the uniqueness of the result. The propagation constants of the monofilar and coaxial modes are obtained with a good accuracy. It is shown that these modes have different transfer inductances.     

Mode coupling in coaxial waveguides with varying-radius center andouter conductors

The mode conversion process in a coaxial waveguide with varying-radius center and outer conductors is shown to be described by a system of first-order differential equations-the coupled mode equations. The nondiagonal coefficients of this system are called the coupling coefficients. In this paper, we derive the explicit expressions for the coupling coefficients in a varying-radius coaxial waveguide and discuss some of their important features. These coefficients can be used in determining model conversion in a coaxial cavity with slowly varying walls or designing and analyzing coaxial waveguide tapers and mode converters. Some experimental results of the coupling coefficients for the case of azimuthally symmetric modes, TE_0n modes, are also given     

Efficient Methods for Determining the Coupling to Wires in Circular Cavities

The electromagnetic field coupling to a loaded thin wire in a cylindrical/coaxial cavity is investigated. Computationally efficient methods are presented for determining the coupling to a thin wire located near a cavity wall in a system of cascaded and/or overlapping coaxial and circular cylindrical cavity sections, and the accuracy and limitations of these methods are established. The sections are coupled through apertures and conducting elements common to more than one section, which may have different axial and radial dimensions and which may be filled with material having different magnetic and electric properties. The loaded thin wire is close to the outer wall of a cavity section and may represent a cable or, perhaps, a conducting tube. The coupling of the cavity field to the wire is determined from an analysis of a distributed voltage and current source model based on transmission line theory as well as via coupled integral equations techniques. The accuracy of the results obtained from these analyses is supported by experimental data measured on a laboratory model of the cavity-wire structure.     

An antenna system using a plasma column having a central conductor and excited by a co-axial line†

The radiation pattern of an open-ended co-axial line excited in the TEM mode in a plasma column having a central conductor along the axis is studied. The field distribution at the open-end cross-section of the co-axial line is assumed to be equivalent to the vector sum of magnetic current rings of various radii, ranging from the outer radius of the inner conductor to the inner radius of the outer conductor of the co-axial line at the open end. The radiation field is obtained as a vector sum of field components duo to individual rings of magnetic current. This type of configuration gives rise to a veil-enhanced radiation peak near and before the critical angle. The amplitude of the radiation peak depends upon the dimensions of the plasma column, the diameter of the central conductor and the inner diameter of the outer conductor of the coaxial line at the open end. Its direction can be changed by changing the plasma density. Based upon these results it is proposed to develop an electronically scannable narrow-beam plasma antenna system.     

圆形外导体-复杂形状内导体同轴传输线特性阻抗的计算

本文由Meleontiev方法将任意复杂形状的单连通区域的外部变换为单位圆的外部,利用多项式变换函数的性质和复杂形状内导体边界的等效圆半径变化的一般规律,给出了具有圆形外导体-复杂形状内导体一类传输线的解。通过与文献中准确值的比较,证实了本文方法的准确性和实用性。     

Upward travelling current wave excitation of overhead cable

We carry out a self-consistent analysis of the excitation of current on an overhead cable by a vertical current source. The ground plane is assumed to be a perfect conductor, but otherwise the solution obtained is quite general. It is shown, for the cable model adopted, two dominant modes are excited; one is the expected transmission line mode between the cable and the ground plane and the other is the coaxial mode between the center conductor and sheath. When generalized, results for the traveling wave source can simulate lightning, but this task is left for the future