Edward H. Newman

Electromagnetic modeling of composite wire and surface geometries

A moment method solution to the problem of radiation or scattering from geometries consisting of open or closed surfaces, wires, and wire/surface junctions is presented. The method is based on the sinusoidal reaction formulation. Several examples of input impedance calculations illustrate the versatility, accuracy, and computational efficiency of the method.

Two methods for the measurement of antenna efficiency

Two methods for measuring antenna efficiency are described. The two methods, referred to as the Wheeler method and the Q method, are used to find the efficiency of electrically small multiturn loop antennas. The principal advantage of both methods is that they can be quickly and easily applied. Further, both methods relate the antenna efficiency to the input impedance rather than a far-field pattern integration. Thus, the methods are applicable at VHF and frequencies below where the design of an antenna range or anechoic chamber becomes increasingly difficult and expensive.

Generation of wide-band data from the method of moments by interpolating the impedance matrix (EM problems)

The method of moments (MM) requires computation of the impedance matrix at each frequency. Since the computation can be a very time-consuming process, its performance over a wide frequency range can require a prohibitive amount of CPU time. A method is described whereby the impedance matrix is computed at relatively large frequency intervals and then interpolated to approximate its values at intermediate frequencies. Basically, the method trades reduced computer CPU time for increased storage. >

Analysis of microstrip antennas using moment methods

The method of moments is used to analyze microstrip antennas of rectangular and nonrectangular shape. Surface currents are used to model the microstrip patch and volume polarization currents for the dielectric slab. The method requires unusually precise computation of the impedance matrix but is capable of accurately predicting currents, impedance, and resonant frequency of the antenna.

Scattering by a multilayer chiral cylinder

An efficient recursive eigenfunction solution for the problem of scattering by a multilayer chiral circular cylinder, with or without a surface impedance center cylinder, is presented. For an M layer cylinder, the solution requires the multiplication of M4*4 matrices, versus the solution of a 4M*4M matrix equation in a standard approach. The problem of a transverse electric (TE) incident plane wave differs from that of a transverse magnetic (TM) wave only by a plus/minus sign at one step in the solution. The addition of the surface impedance center cylinder requires only one additional matrix multiplication. Numerical results, including echo width and internal fields, are presented for several sample cylinders. >

Scattering by a chiral cylinder of arbitrary cross section

An integral equation and method-of-moments (MM) solution to the problem of scattering by an inhomogeneous chiral cylinder of arbitrary cross section is presented. The volume equivalence theorem for chiral media is developed and used to formulate a set of coupled integral equations for the electric and magnetic volume polarization currents representing the chiral cylinder. These coupled integral equations are solved using a standard pulse basis and point-matching MM solution. Numerical results, including echo width and internal fields, are presented for the scattering by chiral slabs and circular cylinders. These results are compared to exact solutions when available. >

Small antenna location synthesis using characteristic modes

It is shown that the efficiency of a small antenna can be substantially increased by properly locating it on its support structure. Characteristic modes are used to determine the optimum location and frequency.

Considerations for efficient wire/surface modeling

The most significant aspects of a moment method surface patch/wire formulation are speed, accuracy, convergence, and versatility. Techniques for improving these parameters are discussed and applied to a solution based on the piecewise sinusoidal reaction formulation.

A microstrip line on a chiral substrate

Right and left circular vector potentials are developed and used in a spectral-domain solution for a microstrip transmission line on a chiral substrate. These vector potentials have properties similar to those of the usual magnetic and electric vector potentials, except that they result in circular rather than linearly polarized fields, thereby simplifying field expansions in chiral media. The chiral microstrip line does not have bifurcated modes like other chiral guided wave structures; however, the chiral substrate causes a significant asymmetry in both the fields and currents. >

Analysis of a monopole mounted near an edge or a vertex

The problem of a monopole mounted near the edge of a wedge or a vertex is considered. Three types of solutions-surface patch modeling, moment method/geometrical theory of diffraction (MM/GTD), and MM/eigenfunction-are presented, discussed, and compared with measurements. Results are in the form of input impedance and radiation patterns.