A Method for Tracking Characteristic Numbers and Vectors

A new method for tracking characteristic numbers and vectors appearing in the Characteristic Mode Theory is presented in this paper. The challenge here is that the spectral decomposition of the moment impedance-matrix doesn't always produce well ordered eigenmodes. This issue is addressed particularly to flnite numerical accuracy and slight nonsymmetry of the frequency- dependent matrix. At speciflc frequencies, the decomposition problem might be ill-posed and non-uniquely deflned as well. Hence an advanced tracking procedure has been developed to deal with noisy modes, non-continuous behavior of eigenvalues, mode swapping etc. Proposed method has been successfully implemented into our in-house Characteristic Mode software tool for the design of microstrip patch antennas and tested for some interesting examples.

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