Analysis of parallel plate mode in slot‐coupled microstrip antenna

Hisao Iwasaki, Hiroki Shoki, Kazuaki Kawabatas

Research output: Contribution to journalArticle


In the electromagnetic slot‐coupled microstrip antenna in which a triplate transmission line is used and a patch antenna is fed via a slot on the ground plane, a parallel plate mode (TEM wave) propagating between the ground planes is excited so that a power leakage causes unwanted coupling and radiation. This paper studies the Poynting power and the electric field of this parallel plate mode. The amount of the parallel plate mode generated and the propagation behavior are investigated analytically by means of the Spatial Network Method. The method for installing shorting pins known for their suppression of the parallel plate mode is studied in its relationship to the generation of the parallel plate mode. A method for placing pins with a least number of pins is proposed. The relationship between the resonance of the parallel plate mode and the external dimensions of the dielectric substrate comprising the triplate transmission line is studied experimentally. It is found that the resonance of the parallel plate mode coincides with that of an open resonator with its dimensions identical to a finite dielectric substrate comprising the triplate transmission line.

Original languageEnglish
Pages (from-to)40-49
Number of pages10
JournalElectronics and Communications in Japan (Part I: Communications)
Issue number2
Publication statusPublished - 1993



  • Microstrip antenna
  • parallel plate mode
  • slot coupled antenna
  • spatial network method
  • suppression method

ASJC Scopus subject areas

  • Computer Networks and Communications
  • Electrical and Electronic Engineering

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