A circular mesh scheme for the non-orthogonal finite difference time domain method

Beam forming networks (BFN) are an important component of a complex satellite antenna system because they are used to provide accurate amplitude and phase excitation to the elements of the feed network. The need for handling high power and the need for a high degree of integrability, often leads one to choose square coaxial metal lines for constructing BFNs. BFNs usually require variable power dividers such as the rat-race (or ring) couplers with constant or variable divider ratios in order to deliver a prescribed amount of power to a certain element of an antenna array to steer the beam in a desired direction. However, modeling of such circular structures in square coaxial form is not an easy task. To account for the structure complexity and diversity requires a numerical method with a known flexibility, versatility, and accuracy. In the paper, it is shown that the finite difference time domain (FDTD) method equipped with a circular mesh generator is highly suited to handling these kinds of discontinuities.