Publications

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The model for penetration of a wire braid is rigorously formulated. Integral formulas are developed from energy principles and reciprocity for both self and transfer immittances in terms of potentials for the fields. The detailed boundary value problem for the wire braid is also setup in a very efficient manner; the braid wires act as sources for the potentials in the form of a sequence of line multipoles with unknown coefficients that are determined by means of conditions arising from the wire surface boundary conditions. Approximations are introduced to relate the local properties of the braid wires to a simplified infinite periodic planar geometry. This is used in a simplified application of reciprocity to be able to treat nonuniform coaxial geometries including eccentric interior coaxial arrangements and an exterior ground plane.

In this article, a negative-index metamaterial prism based on a composite unit cell containing a split-ring resonator and a z-dipole is designed and simulated. The design approach combines simulations of a single unit cell to identify the appropriate cell design (yielding the desired negative-index behavior) together with subcell modeling (which simplifies the mesh representation of the resonator geometry and allows for a larger number of resonator cells to be handled). In addition to describing the methodology used to design a n = -1 refractive index prism, results including the effective-medium parameters, the far-field scattered patterns, and the near-zone field distributions corresponding to a normally incident plane-wave excitation of the prism are presented.

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This report presents analytic transmission line models for calculating the shielding effectiveness of two common calibration standard cables. The two cables have different canonical aperture types, which produce the same low frequency coupling but different responses at resonance. The dominant damping mechanism is produced by the current probe loads at the ends of the cables, which are characterized through adaptor measurements. The model predictions for the cables are compared with experimental measurements and good agreement between the results is demonstrated. This setup constitutes a nice repeatable geometry that nevertheless exhibits some of the challenges involved in modeling non-radio frequency geometries.

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This report estimates inductively-coupled energy to a low-impedance load in a loop-to-loop arrangement. Both analytical models and full-wave numerical simulations are used and the resulting fields, coupled powers and energies are compared. The energies are simply estimated from the coupled powers through approximations to the energy theorem. The transmitter loop is taken to be either a circular geometry or a rectangular-loop (stripline-type) geometry that was used in an experimental setup. Simple magnetic field models are constructed and used to estimate the mutual inductance to the receiving loop, which is taken to be circular with one or several turns. Circuit elements are estimated and used to determine the coupled current and power (an equivalent antenna picture is also given). These results are compared to an electromagnetic simulation of the transmitter geometry. Simple approximate relations are also given to estimate coupled energy from the power. The effect of additional loads in the form of attached leads, forming transmission lines, are considered. The results are summarized in a set of susceptibility-type curves. Finally, we also consider drives to the cables themselves and the resulting common-to-differential mode currents in the load.

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In this paper a simple effective-media analysis (including higher-order multipoles) is used to design a single-resonator, negative-index design based on a metal-core, dielectric-shell (MCDS) unit cell. In addition to comparing the performance of the MCDS design to other core-shell negative-index designs, performance trade-offs resulting from the relative positioning of the electric and magnetic modal resonances in the MCDS design are also discussed. © 2011 IEEE.

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This paper presents a mixed-potential integral-equation formulation for analyzing 1-D periodic leaky-wave antennas in layered media. The structures are periodic in one dimension and finite in the other two dimensions. The unit cell consists of an arbitrary-shaped metallic/dielectric structure. The formulation has been implemented in the EIGER™ code in order to obtain the real and complex propagation wavenumbers of the bound and leaky modes of such structures. Validation results presented here include a 1-D periodic planar leaky-wave antenna and a fully 3-D waveguide test case. ©2010 IEEE.

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