Divergence-free basis for full-wave solutions involving inhomogenous package structures

A standard approach for calculating the propagation in or radiation from package structures that involve finite-size dielectrics is to use electric currents to represent the three-dimensional polarization effects. Such volume formulations may employ any of a number of different basis functions to represent the polarization current, such as the tetrahedral, 3D rooftop, 3D pulse, and 2D rooftop functions [1-7]. Each basis function offers different advantages, and usually there is some trade-off between program complexity, accuracy, and the number of current elements required. Independent of the choice of basis, the volume formulation's advantage is that only free-space Greens functions are needed, and arbitrary shape, though often in a Cartesian sense, can be handled.