Eigenvalue Crossing Avoidance in Characteristic Modes

Kurt R. Schab, John M. Outwater, Matthew W. Young, Jennifer T. Bernhard

Research output: Contribution to journalArticlepeer-review


The theory of characteristic modes (TCM) provides a set of eigenvalues and eigenvectors that are determined entirely by a structure's geometry at a particular frequency. When examining a design over a range of frequencies, consistent interpretation of the modal data is crucial. Here, we present a way of interpreting crossing avoidances observed when tracking characteristic-mode eigenvalue traces over frequency. Using the framework of coupled-mode theory, a method for decomposing a pair of characteristic modes into auxiliary modes is developed. The auxiliary modes have a degeneracy (eigenvalue crossing) and maintain continuity of modal current distributions through the coupling region of the original characteristic modes. We demonstrate several examples using our method on simple objects. Furthermore, we explore the effect of multiplicative noise and lumped reactive loading on induced crossing avoidance.

Original languageEnglish (US)
Article number7446294
Pages (from-to)2617-2627
Number of pages11
JournalIEEE Transactions on Antennas and Propagation
Issue number7
StatePublished - Jul 2016


  • Antenna theory
  • coupled-mode analysis
  • method of moments
  • modal analysis

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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