A tracking algorithm for the eigenvectors calculated with characteristic mode analysis

Characteristic mode analysis (CMA) is a useful design tool that enables antenna designers to follow a nonbrute force approach of systematically extracting the radiating properties of a structure. These properties are quantified with CMA in the form of eigenvalues and eigenvectors, i.e., the solutions of a generalised eigenvalue equation that is formulated from the Method-of-Moments (MoM) impedance matrix. One particular challenge to CMA, however, is the manner in which quantities such as eigenvalues are plotted as a function of frequency. At each discrete frequency sample, the eigenvalues are sorted according to modal significance, i.e., based on the efficiency with which they radiate. At higher frequencies, the ordering of modes may differ from that obtained at lower frequencies. To mitigate this problem, we have developed a tracking algorithm to keep the ordering of modes as consistent as possible over frequency.