Theoretical and measured electric field distributions within an annular phased array: Consideration of source antennas

A detailed calculation of sources and electric fields associated with a prototype annular phased array for clinical hyperthermia is presented. Two antenna current distributions are used as field sources. One is based on a linear dipole model. The second models the thin strip antenna elements in detail, and the current is derived using the theory of a microstrip transmission line. These currents are then used to calculate the magnetic vector potential and the electric field. To verify the theoretical simulations, the magnitude of the electric field is measured under the same conditions as those used in the theoretical simulations. The comparison between measured and calculated fields demonstrates better convergence of theory and experiment when the antenna sources are modeled in detail. Thus, the use of these results for an improved incident-scatter model that will allow more general calculations of E fields in inhomogeneous media with irregular geometries is anticipated.