Benjamin Beker

Calculation and experimental validation of induced currents on coupled wires in an arbitrary shaped cavity

An efficient numerical technique is presented for the calculation of induced electric currents on coupled wires and multiconductor bundles placed in an arbitrary shaped cavity and excited by an external incident plane wave. The method is based upon the finite-difference time-domain (FD-TD) formulation. The concept of equivalent radius is used to replace wire bundles with single wires in the FD-TD model. Then, the radius of the equivalent wire is accounted by a modified FD-TD time-stepping expression (based on a Faradays law contour-path formulation) for the looping magnetic fields adjacent to the wire. FD-TD computed fields at a virtual surface fully enclosing the equivalent wire are then obtained, permitting calculation of the currents on the wires of the original bundle using a standard electric field integral equation (EFIE). Substantial analytical and experimental validations are reported for both time-harmonic and broad-band excitations of wires in free space and in a high- Q metal cavity.

Numerical analysis and validation of the combined field surface integral equations for electromagnetic scattering by arbitrary shaped two-dimensional anisotropic objects

The numerical solution of coupled integral equations for arbitrarily shaped two-dimensional, homogeneous anisotropic scatterers is presented. The combined theoretical and numerical approach utilized in the solution of the integral equations is based on the combined field formulation and is specialized to both transverse electric (TE) and transverse magnetic (TM) polarizations. As opposed to the currently available methods for anisotropic scatterers, the present approach involves integration over the surface of the scatterer in order to determine the unknown surface electric and magnetic current distributions. The solution is facilitated by developing a numerical approach employing the method of moments. The various difficulties involved in the numerical effort are pointed out, and ways of overcoming them are discussed in detail. The results obtained for two canonical anisotropic structures, namely, a circular cylinder and a square cylinder, are given and validated by results obtained by alternative methods. >

Dispersion characteristics of open and shielded microstrip lines under a combined principal axes rotation of electrically and magnetically anisotropic substrates

This work examines the dispersion properties of microstrip transmission lines whose substrate permittivity and permeability tensors are rotated simultaneously. The analysis takes into account both shielded and open structures, including both single and coupled microstrip line geometries. The spectral-domain method is utilized to formulate the dyadic impedance Greens function, and Galerkins method is applied to find the propagation constants. Numerical studies are performed when the angular difference between the principal axes of ( epsilon ) and ( mu ) tensors is fixed, but both are rotated from 0 to 90 degrees . The dispersion characteristics for all structures are computed over a wide frequency band that ranges from 0.1-100 GHz. The study indicates that propagation properties of microwave integrated circuits (MICs) with dielectrically and magnetically anisotropic substrates (such as composites) can be changed considerably by the misalignment of material and structure coordinates systems. >

Analysis of single and coupled microstrip lines on anisotropic substrates using differential matrix operators and the spectral-domain method

A differential matrix operator technique is presented to simplify the formulation of boundary-value problems for open millimeter-wave integrated circuits that use anisotropic substrates. The spectral-domain method is applied to analyze the propagation characteristics of single and coupled microstrip lines printed on anisotropic substrates whose properties are described by both ( in ) and ( mu ) tensors. In addition to considering the permittivity and permeability as a uniaxial or biaxial tensor, the effects of coordinate misalignment between the principal axes of ( in ) and those of the structure in the transverse plane are also included. It is shown that the misalignment in ( in ) and the presence of the ( mu ) tensor have a significant effect on the dispersive properties of these two structures. >

Analysis of microwave capacitors and IC packages

This paper presents quasi-static electromagnetic (EM) models for analysis and design of microwave capacitors and integrated circuit (IC) packages. The theoretical background for modeling of open 3-D boundaries with finite difference method (FDM) is reviewed and the use of current simulation method (CSM) for inductance computation is proposed. Computed data for the capacitance and inductance of capacitors with complex three-dimensional geometries are verified both numerically and experimentally, validating the proposed quasi-static models. Numerical results for practical devices and IC packages are also given. >

Spectral-domain analysis of shielded microstrip lines on biaxially anisotropic substrates

The spectral-domain technique is extended to the study of shielded microstrip lines on biaxial substrates. The analysis simultaneously includes dielectric and magnetic anisotropy effects. A fourth-order formulation leads to the determination of the appropriate Greens function for the structure. The characteristic equation is formed through the application of the Galerkin method to the equations resulting from the boundary conditions on the strip. Numerical results calculated by this method for isotropic as well as dielectrically anisotropic substrates are compared with the existing data, and in both cases a very good agreement is observed. New data on the propagation constant of the shielded microstrip with different substrate permittivities and permeabilities are presented to illustrate the effects of the material parameters on the characteristics of the microstrip line. >

An application-enhanced approach to introductory electromagnetics

This paper describes an application-enhanced approach to teaching fundamental concepts in electromagnetics at the introductory undergraduate level. A numerical tool with interactive visualization is used to aid in the presentation of engineering applications that are used to motivate basic electromagnetic concepts. The goals are to exploit design automation tools as a supplementary instructional aid, and to illustrate to students the use of theory in practice.

Frequency-dependent characteristics of shielded broadside coupled microstrip lines on anisotropic substrates

A spectral-domain technique is applied to compute the propagation characteristics of a shielded broadside coupled microstrip line printed on homogeneous uniaxial and biaxial substrates. The formulation derives the Greens functions for even and odd modes of the guiding structure via the transformed fourth-order differential equations. The analysis includes anisotropic substrates which are simultaneously characterized by both ( epsilon ) and ( mu ) tensors. This rigorous full-wave approach to the solution of the problem is shown to yield results agreeing well with the existing data. The propagation characteristics are studied with respect to different line width/thickness ratios as well as to the material substrate parameters. >

ANALYSIS OF ELECTROMAGNETIC SCATTERING BY ARBITRARILY SHAPED TWO-DIMENSIONAL ANISOTROPIC OBJECTS: COMBINED FIELD SURFACE INTEGRAL EQUATION FORMULATION

ABSTRACT An analysis of electromagnetic scattering by an arbitrarily shaped anisotropic, but homogeneous material structure utilizing combined field surface integral equation formulation is presented. Derivation of the appropriate electromagnetic potentials for the time harmonic Maxwells equations is also undertaken. The medium in this study is characterized by its permittivity and permeability tensors, and the mathematical formulation is specialized to the two-dimensional anisotropic scatterer of arbitrary shape excited by a plane wave at normal incidence. The derived potentials along with their appropriate gauges are used to represent the fields in the medium. Subsequently, these field representations are utilized in the derivation of a set of coupled integral equations with the help of the equivalence principle. Rigorous analysis approach is developed for the two-dimensional objects, both for the TM and the TE polarizations.

Unified matrix presentation of Maxwell's and wave equations using generalized differential matrix operators [EM engineering education]

In this paper, the authors introduce the concept of generalized differential matrix operators (GDMOs) that are useful for the formulation of electromagnetic boundary value problems in arbitrary orthogonal coordinate systems, e.g., Cartesian, cylindrical and spherical. The most significant attribute of the GDMO approach is that their use helps to simplify the complicated manipulation of vector differential equations, especially in problems dealing with an anisotropic media. They show that the use of the GDMOs enable one to replace, for most problems in electromagnetics, the complicated vector differential operations with manipulation of 3/spl times/3 matrices. In addition, they demonstrate GDMOs are convenient for deriving many differentiation identities and integral theorems which find extensive applications in electromagnetics.