Designing non-conventional 3-D coils

Compact devices for inductive energy and information transfer require the design of appropriate non-conventional 3-D induction coils. This is because only a small volume for placing the coil inside the device is available, and one is only interested in the near-field characteristics of the generated magnetic field. In our study we focus on design strategies for appropriate three-dimensional induction coils by exploiting an inverse methodology. A target field is specified over a certain region and an approximation of the current density through a Fourier series expansion is derived which generates the desired field. Because of the ill-posed nature of this problem a Tikhonov regularization with a penalty term is used to calculate the unknown parameters of the Fourier series expansion. In this contribution we discuss the effect of different penalty terms, i.e. a 2-norm term, a gradient and a laplace term on the resulting current densities. Based on this, we obtain the coil windings by calculating the maximum of a current density map and applying a stream function approach.