A decoupling method in characteristic modes tracking

The theory of characteristic modes (TCM) is a powerful tool for antenna designers to analyze the radiators systematically, which provides a set of orthogonal eigenmodes and corresponding eigenvalues determined entirely by a structure's geometry and a particular frequency. So tracking the CMs at discrete frequency points over a frequency range is necessary for any wideband modal analysis of complex structure. However, it is still a challenge to track the modes when their eigenvalues are in close proximity. The degeneracy (close eigenvalue) of these modes always leads to an inaccurate eigenvalue tracking result and an unsmooth modal excitation coefficient curve for existing tracking algorithms, especially when frequency increment step is reduced. In this paper, we propose a decoupling method to alleviate the problem by decomposing a pair of degenerated modes into two new modes with consistent evolution of surface current distributions, accurate eigenvalue tracking results and smooth curves of modal excitation coefficients.