The modeling of quasi-static optimization problems often involves divergence-free surface current densities. In this paper, a novel technique to implement these currents by using the boundary element method framework is presented. A locally-based characterization of the current density is employed, to render a fully geometry-independent formulation, so that it can be applied to arbitrary shapes. To illustrate the versatility of this approach, we employ it for the design of gradient coils for MRI, providing a solid mathematical framework for this type of problem.

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Abstruct-Cenetic algorithm (CA) are applied to the design of thin-wire antennas for Ground Penetrating Radar (GPR). The broadband characteristics of the antenna are achieved using resistive loading along the wires. In some cases also capacitive loading is considered. The geometries considered are straight thin-wire dipoles. V antennas and a thin-wire bow-tie antenna.lndex Terms-Broadband antennas, Genetic algorithms, Thin-wire antennas.

A n essential characteristic for the accurate simulation of wideband antenna systems is the modeling of their intricate geometrical details, including the feeding ports. In this article, we describe a leap-frog (LF) discontinuous Galerkin (DG) time-domain (TD) method combined with an efficient local time-stepping (LTS) strategy to deal with the high contrast in the element sizes for the electromagnetic modeling of these kinds of structures.The traditional delta-gap source model and a realistic coaxial port model are revisited. Numerical examples are presented and validated with measurements and commercial software simulations to demonstrate the applicability of the proposed approach.

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