Characteristic Comparison between Electric Currents on Upper and Lower Surfaces of Patch Conductor in a Microstrip Antenna

Takafumi FUJIMOTO  Kazumasa TANAKA  Mitsuo TAGUCHI  

Publication
IEICE TRANSACTIONS on Communications   Vol.E88-B    No.2    pp.729-736
Publication Date: 2005/02/01
Online ISSN: 
DOI: 10.1093/ietcom/e88-b.2.729
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Antennas and Propagation
Keyword: 
microstrip antenna,  integral equation method,  Green's function in layered medium,  electric currents,  input impedance,  

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Summary: 
The electric currents on the upper, lower and side surfaces of the patch conductor in a circular microstrip antenna are calculated by using the integral equation method and the characteristic between the electric currents on the upper and lower surfaces is compared. The integral equation is derived from the boundary condition that the tangential component of the total electric field due to the electric currents on the upper, lower and side surfaces of the patch conductor vanishes on the upper, lower and side surfaces of the patch conductor. The electric fields are derived by using Green's functions in a layered medium due to a horizontal and a vertical electric dipole on those surfaces. The result of numerical calculation shows that the electric current on the lower surface is much bigger than that on the upper surface and the input impedance of microstrip antenna depends on the electric current on the lower surface.