Full-wave Formulation Research Articles

DESIGN OF BROAD-BAND POLYGONAL PATCH ANTENNAS FOR MOBILE COMMUNICATIONS

A design of broad-band patch antennas for mobile communications is presented in this paper. The main idea of this work is based on the possibility of changing the electromagnetic properties of a standard rectangular patch antenna by the means of proper geometrical perturbations of its sides (slope, length, etc.). The final patch shape is a convex polygon, which can be analyzed in the spectral domain through a full-wave formulation and a Method of Moments (MoM) numerical code employing entire-domain basis functions. Some examples of practical UMTS antenna designs developed applying this method are then presented and compared with similar radiators already proposed in the literature, showing how a proper perturbation of the patch shape can significantly improve the antenna performances.

A full-wave model of wire structures with arbitrary cross sections

Transmission lines with rectangular cross sections are usually used in integrated circuit (IC) and computer chip problems. In this paper, a full-wave method is proposed based on an efficient wire model to analyze transmission-line circuits, where the cross sections of wires can be arbitrary. Comparing the existing wire models in the method of moments, it has been shown that the best performance occurs when the current is assumed to flow along the electrical axis of a wire and the testing is on the whole surface if two wires are very close. The physical significance of such modeling implies that the surface current on a wire is equivalent to a current filament along the electrical axis. For a single round wire, the electrical axis is exactly the same as its geometrical axis. For two parallel round wires, the electrical axis of each wire is located at the image position of the other wire. In this paper, a general wire model is proposed to determine electrical axes of wires with arbitrary cross sections by solving a static problem. Then, full-wave formulations are derived for wire structures with rectangular cross sections, which are the most important for IC and computer-chip problems. Numerical simulations are given to test the validity and accuracy of the proposed method.

Three-dimensional electromagnetic modeling of fiber-core effects on the coupling characteristics of weakly fused tapered fiber-optic couplers

Based on the full-wave formulations, which combine the finite element method add the boundary element technique, and the step-like approximation method, a three-dimensional (3-D) electromagnetic modeling approach is proposed in this work to investigate the fiber-core effects on the coupling characteristics of the weakly fused tapered couplers. We find the fiber cores have significant effects on the mode field patterns, coupling coefficients, and birefringence for the coupler with large normalized frequencies. The influence of the fiber cores on the coupling behavior for the real couplers, such as 3 dB power dividers, polarization beam splitters, and wavelength demultiplexing/multiplexing couplers, are also studied in 3-D view. It is found that the effects of fiber-cores in the weakly fused tapered couplers have to be considered for accurately modelling their coupling behavior, although the model with no core assumption can predict the trend of the coupling characteristics for the real couplers.

Finite element beam propagation method with perfectly matched layer boundary conditions for three-dimensional optical waveguides

The perfectly matched layer boundary condition is incorporated into the beam propagation method based on a finite element scheme for 3-D optical waveguides. Not only an approximate scalar formulation but a full-wave formulation is presented. Its effectiveness is verified by way of numerical examples. Copyright © 2000 John Wiley & Sons, Ltd.

Correction procedures for the numerical parasitic elements associated with lumped elements in global electromagnetic simulators

This paper presents a comparative study of the treatment of lumped elements in two different full-wave electromagnetic formulations: the finite-difference time-domain (FDTD) technique and the technique of integral equations. Although these two approaches are basically different, they are seen to exhibit the same kind of numerical troubles when lumped elements are involved. More precisely, lumped elements are systematically associated with numerical parasitic elements that can seriously alter the calculated results. As a solution, this paper proposes a general alternative formulation, which permits one to suppress these numerical parasites. This formulation is successfully applied to the FDTD technique. A simpler numerical deembedding procedure, which does not fundamentally transform the original formulation, is preferred for the integral-equation technique.

Hybrid electromagnetic modeling of noise interactions in packaged electronics based on the partial-element equivalent-circuit formulation

The partial-element equivalent-circuit (PEEC) method is used to develop a flexible, hierarchical electromagnetic modeling and simulation environment for the analysis of noise generation and signal degradation mechanisms in packaged electronic components and systems. The circuit-oriented approach used by the method for the development of the numerical approximation of the electric-field integral equation leads to SPICE-compatible, yet fully dynamic, discrete approximation of the electromagnetic problem. Contrary to other full-wave formulations, the proposed method has the important attribute of lending itself to a very systematic and physical model complexity reduction on the basis of the electrical size of the various portions of the system. Thus, a hybrid electromagnetic modeling and simulation environment is established for the analysis of complex structures which exhibit large variation in electrical size over their volume, using a combination of lumped-circuit elements, transmission lines, as well as three-dimensional (3-D) distributed electromagnetic models. These models may or may not account for retardation, depending on the electrical size of the part of the structure that is being modeled. These special attributes of the proposed electromagnetic-simulation environment are demonstrated through several examples from its application to the modeling of noise interactions in generic interconnect and package geometries.

Full-wave analysis of the effective relative permittivity of a coplanar waveguide printed inside a cylindrical substrate

The frequency-dependent dispersion characteristics of a coplanar wave-guide printed inside a cylindrical substrate are studied. A full-wave formulation incorporating the derived dyadic Green's function in a moment-method calculation is applied. The theoretical results are calculated and verified by the measurement, and the curvature effects on the dispersion characteristics of an inside cylindrical coplanar waveguide are discussed. © 1996 John Wiley & Sons, Inc.

A study of the transverse current contribution to the characteristics of a wide cylindrical microstrip line

By considering both the longitudinal and transverse components of the surface current on the microstrip line, the effective relative permittivity and the characteristic impedance of a wide cylindrical microstrip line are analyzed. Theoretical results are calculated with the use of a full-wave formulation and a moment-method computation. Experiments are also conducted to verify the calculated results, and the contribution of the transverse current component to the characteristics of a wide cylindrical microstrip line is discussed. © 1996 John Wiley & Sons, Inc.

Complex media microstrip ridge structures: formulation and basic characteristics of ferrite structures

Microstrip transmission lines residing on bianisotropic material ridges embedded in a multilayered environment are studied using a coupled set of integral equations (IE's). The full-wave IE formulation accounts for general linear media in the ridge region using equivalent polarization currents residing in a multilayered bianisotropic background. Numerical results showing basic propagation characteristics are presented for a variety of single and coupled ferrite ridge structures. It is shown that the use of finite width ferrite ridges as either substrates or superstrates can produce nonreciprocity while confining the ferrite material to a small area in the vicinity of the transmission line.

Propagation characteristics of microstrip transmission line on an anisotropic material ridge

A microstrip transmission line residing on an electrically anisotropic material ridge embedded in a multilayered environment is studied using a coupled set of integral equations (IE's). The full-wave IE formulation easily accommodates arbitrary material anisotropy and inhomogeneity in the finite ridge region using equivalent polarization currents residing in a multilayered isotropic background. New results are presented for uniaxially anisotropic ridge structures which show that the transmission line propagation constant is sensitive to anisotropy for certain ridge structures and insensitive for others, compared to the conventional line on an infinite substrate. Results are also presented for a transmission line printed on a nonreciprocal solid-state magnetoplasma ridge. The current distribution associated with the dominant microstrip mode is investigated, where it is found that the transverse component of current is much larger for the ridge geometry than for the infinite substrate case, although the transverse component is still small compared to the longitudinal component. >

Resonance in a cylindrical wraparound microstrip structure with superstrate

Analysis of the resonance problem of a cylindrical wraparound microstrip structure with superstrate is presented. In this study the rigorous full-wave formulation and Galerkin's method are used. The numerical convergence for the selected sinusoidal basis functions with edge singularity is also discussed. Numerical results of the superstrate loading effects on the real and imaginary parts of complex resonant frequency of the structure as a radiator at TE/sub 01/ mode and as a resonator at HE/sub 10/ mode are calculated and analyzed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A study on the coaxial aperture electromagnetic sensor and its application in material characterization

An open-ended coaxial line has been studied by many researchers in order to use it as an electromagnetic sensor for the characterization of materials. These studies include static as well as quasi-static formulations under various simplifying assumptions. In this paper, we use a full-wave formulation of the problem and solve an integral equation to evaluate the aperture field distribution. The electromagnetic field distributions in the material medium as well as the aperture admittance are evaluated subsequently. The effects of a conducting flange over the coaxial opening and the finite sample size are also studied. The results are compared with the experimental data as well as the data obtained by other approaches. An application of this coaxial sensor for the characterization of materials up to 40 GHz is demonstrated. >

Full-wave iterative variational formulation for multiple coupled microstrip lines

A novel variational formulation in terms of two formally decoupled potentials is derived for the full wave propagation constants of multiple coupled microstrip lines. At very low frequency limits, the present formulation is reduced directly to the conventional quasi-static formulation. The quasi-static solutions are then used as an initial guess to solve the high-frequency problem for each coupled mode by a generalized Newton-Raphson iterative scheme. Numerical results are presented for two and three coupled microstrip lines of identical or nonidentical widths with various spacings and frequencies. >

The RCS of a microstrip patch on an arbitrarily biased ferrite substrate

The radar cross section (RCS) of a rectangular microstrip patch on a lossy biased ferrite substrate is investigated. The analysis is based on a full-wave integral equation formulation in conjunction with the method of moments. In the analysis, the direction of the bias field is not prescribed. The RCS characteristics, especially the resonance behavior of a patch with various biasing conditions, are studied and compared to those for an unbiased ferrite. It is found that the resonant frequencies of a patch vary significantly with the change of the bias field, except for those resonant modes which have a dominant magnetic-field component in the direction of the bias field. This phenomenon is explained with a waveguide cavity model, and provides an independent check of the analysis. It is found that the magnetic loss affects the RCS at resonances significantly. >

A full-wave mixed potential mode-matching method for the analysis of planar or quasi-planar transmission lines

A full-wave mixed potential mode-matching method is presented for the analysis of planar and/or quasi-planar transmission lines. The transmission lines studied consist of layered (stratified) and nonlayered dielectric substrates and metal strips of finite thickness. The y-directed hybrid transverse electric (TE) and transverse-magnetic (TM) Hertzian potentials, perpendicular to the interfaces between each layered region, are employed in the layered regions. The nonlayered regions consist of dielectric step discontinuities that destroy the layered configuration in the horizontal plane, allowing a systematic and easy to handle full-wave formulation of the transmission line problem. The relative convergence criterion needs to be satisfied to obtain accurate electromagnetic field solutions. Theoretical results are in very good agreement with published data for various transmission line structures. Applications of the formulation to the proximity effects of microstrip and microslab lines are illustrated. >

Dispersion characteristics of optically excited coplanar striplines: comprehensive full-wave analysis

A comprehensive full-wave formulation to evaluate the dispersion and losses for coplanar striplines on substrates of finite and infinite thicknesses is presented. The loss mechanisms incorporated in the analysis are substrate losses and dielectric material losses. The method of N.K. Das and D.M. Pozar (1987) is generalized to include a complex propagation vector and can be used over a wide frequency range. A large range of line dimensions can also be handled, limits being set by the accuracy of the moment method. Metal losses can also be incorporated into this analysis by applying the appropriate boundary conditions for lossy metal. Analytically, the excitation of substrate modes is shown to correspond to the occurrence of the poles of the Green's function in the reaction integrals. Results of the full-wave analysis are in good agreement with those obtained by established theory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Surface-to-surface transition via electromagnetic coupling of microstrip and coplanar waveguide

A structure which forms a transition from coplanar waveguide on one substrate to microstrip on another is described. Energy is transferred via electromagnetic coupling rather than with wire bonds. A full-wave formulation along with the theory of asymmetrically coupled lines is used to analyze the transition. Two model transitions were built and tested. Theory and measurement show good agreement when the coupler length to width ratio is larger than 0.6.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>