Steven P. Castillo

Coupling through narrow slot apertures to thin-wire structures

Electromagnetic coupling through a narrow slot aperture in an infinite ground plane is considered when a thin wire is present in the coupled half-space. The effect of the wire on coupling is determined. The slot has width and depth. The method of moments is applied to determine equivalent aperture currents and wire currents. Then coupling is calculated from the resulting fields. Results are presented for high and low Q slots and on and off resonance.

A new finite-difference time-domain algorithm for the accurate modeling of wide-band electromagnetic phenomena

A finite-difference-time-domain (FDTD) method for the efficient solution of wideband electromagnetic phenomena is described. The algorithm uses a second-order Lax-Wendroff finite-difference algorithm in conjunction with the method of flux-corrected transport (FCT) to suppress problems with dispersion that occur when solving Maxwells equations using the standard second-order Yee FDTD algorithm. Results comparing the accuracy of the Lax-Wendroff/FCT method and the Yee algorithm for propagating pulsed-type plane waves are given. >

Electromagnetic coupling into complex cavities through narrow slot apertures having depth and losses

We present results for coupling through narrow slot apertures into a variety of cavity configurations. The effects of slot geometry, slot material, cavity geometry, cavity wall losses and dielectric inhomogeneities within the cavity are considered. All results include both the calculated and experimental data to verify the validity of the numerical simulations. The equations are solved with a hybrid finite element method/moment method.

Experimental study of narrow slot, cavity-backed apertures with finite wall conductivity

The authors present results showing the effects of varying conductivity and surface preparations for half-space coupling as well as different loadings of the narrow slot apertures. The coupling through narrow slot apertures having depth was measured for a variety of resonant cavity loadings. The loadings were chosen such that the cavity resonant frequencies were above, near, and below the resonant peak of the half-space coupling curve. Measurements were made in the 2-4-GHz band with vertical polarization. Two cases were considered: the slot radiating into a half-space and a cavity-backed aperture. The half-space coupling was reduced when the slot width decreased and/or the depth was increased. For very narrow slots, the wall loss dominates and this lowers the Q of the aperture. A decrease in Q was observed for a corresponding reduction in conductivity. It was observed that the cavity fields measured were quite large when a resonant structure loaded the aperture.<<ETX>>

Open-region, electromagnetic finite-element scattering calculations in anisotropic media on parallel computers

Open-region scattering calculations for complex, electrically large scatterers remains a difficult modeling and simulation problem. The finite-element method (FEM) has been shown to be a viable approach to solving such problems. However, conventional methods on serial computers limit the size which can be tackled with the FEM. In this paper, we demonstrate the use of both a PML boundary condition along with a parallel solver for tackling large, complex problems containing scatterers which are inhomogeneous and anisotropic.

Solution of Large, Sparse, Irregular Systems on a Massively Parallel Computer

A set of tools is introduced which allow engineers and scientists to obtain solutions to large finite-element problems by utilizing multiple-instruction, multiple-data (MIMD) parallel computers. The finite-element mesh is decomposed so that each resulting sub-domain is connected to at most two other subdomains. The node-numbering of the decomposed mesh is such that the resulting set of finite element equations will have a border-block diagonal structure. A parallel algorithm is used to assemble, factor and solve the set of simultaneous algebraic equations that result from the finite-element method (FEM). In this paper, we demonstrate the method on a message passing parallel computer for two- and three-dimensional electrostatic problems, governed by Laplaces equation. Results and performance data for the algorithm as applied to electrostatics problems are given. The current work is an extension of the algorithm described and implemented in Reference [1].

A hybrid MoM/FEM model of coupling to thin-wire structures in complex cavities

Electromagnetic coupling through a narrow-slot aperture to a region containing a thin-wire structure is computed as a characterization of electromagnetic compatibility and interference (EMC/EMI) issues. Results are presented for coupling through a narrow slot to multiple, thin, straight segments of wire in a cavity. The slot has width and depth and the wires have arbitrary position and orientation within the coupled region. By varying the wires/slot geometries the interaction of the respective resonance structures is examined. Results for a coupled half-space as well as results for a complex cavity enclosure containing multiple thin-wire scatterers are presented. The objective of this work is to compute coupling through a narrow slot to a complex cavity containing thin-wire scatterers with arbitrary position and orientation within the cavity, accounting for slot depth, wall losses, and dielectrics in the slot region. Previously, results have been presented that were limited to half-space coupling. The full wires/slot/cavity coupling is now incorporated into the model.

Electromagnetic coupling to thin-wire structures in complex cavities

Electromagnetic coupling through a narrow-slot aperture to a region containing a thin-wire structure is computed as a characterization of electromagnetic compatibility and interference (EMC/EMI) issues. Results are presented for coupling through a narrow slot to a single, thin, straight segment of wire in a cavity. The slot has width and depth and the wire has arbitrary position and orientation within the coupled region. By varying the wire/slot geometries the interaction of the respective resonance structures is examined. Results for a coupled half-space as well as results for a complex cavity enclosure are presented.

The application of flux corrected transport to transient electromagnetic phenomena

The authors describe the application of flux-corrected transport (FCT), a scheme which allows the accurate numerical analysis of waveshapes that have steep leading or trailing edges. The idea behind the method is to use both a lower-order and, separately, a higher-order approximation to the spatial derivative. The solutions are then combined node by node using a nonlinear weighting scheme that does not allow new maxima or minima to form. The method of FCT is discussed in the context of applications to time-dependent electromagnetic problems. The results indicate a drastic improvement in the solution in regions where steep gradients appear as in pulse propagation. The results of the addition of FCT to the original Lax-Wendroff algorithm are presented. It can be seen that the wavefront is maintained without the additional burden of ripples in the solution.<<ETX>>

Panel Session - Effective Strategies to Diversify Engineering Faculty

What role do department chairs and deans play in ensuring faculty diversity? This panel presents strategies developed in several contexts including those that were the focus of a year-long collaborative project on increasing the diversity of engineering faculty. While there are many guides to diversity, quite often these guides are prescriptions written by diversity consultants and rarely by academics within science and engineering. The panelists discuss strategies that they have employed and their personal assessments of the effectiveness of these strategies. Panelists encouraged to share both those that were successful as well as those strategies that were not in order to develop better methods of recruiting, retaining, and advancing a diverse professoriate. Proposed panelists are from institutions of different types in the Southwest, therefore a focus was both on improving gender diversity and ethnic diversity among engineering faculty