A modal approach to tuning and bandwidth enhancement of an electrically small antenna

Jacob J. Adams, Jennifer T. Bernhard

Research output: Contribution to journalArticlepeer-review


We describe the physical phenomena that contribute to the behavior of an electrically small TM10 antenna using characteristic mode theory. The application of characteristic modes to antenna tuning and bandwidth enhancement serves as demonstration of the broad utility of the modal technique. A modal analysis of the TM10 antenna's impedance match yields several interesting observations as to the nature of resonances and antiresonances, which has implications for the impedance matching of small antennas in general. Furthermore, to overcome the bandwidth limitations inherent in small antennas, we determine that multiple resonances must be combined and use a conductance ratio as a figure of merit for design. We then investigate the TM10 antenna's potential for multiresonant operation by examining different candidate modes. Using the appropriate characteristic modes to form multiple resonances, we show how the bandwidth of the TM10 antenna can be designed to be nearly double that expected from the physical limit for a single resonance.

Original languageEnglish (US)
Article number5722973
Pages (from-to)1085-1092
Number of pages8
JournalIEEE Transactions on Antennas and Propagation
Issue number4
StatePublished - Apr 2011


  • Bandwidth
  • Q
  • characteristic modes
  • electrically small antenna
  • multimode
  • multiresonant
  • spherical antenna

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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