A MODAL EXPANSION METHOD OF ANALYSIS AND MEASUREMENT ON APERTURE-COUPLED MICROSTRIP ANTENNA

Interest in the use of microstrip patches for array antennas has prompted investigations into numerous feed mechanisms. One of the interesting mechanisms that offers considerable advantages, especially for multilayered antenna configurations, is aperture coupling. In this paper, the coupling of a feedline to a rectangular patch through an aperture in the ground plane separating them is described using modal field analysis. The cavity model is used to describe the patch, the feedline is represented by a dynamic planar waveguide model, and the coupling is via a magnetic current in the aperture. Both theoretical and experimental results for the antenna performance are presented and design curves are generated. Very good agreement between theory and experiment was obtained. Results and design curves were obtained for antennas at 5 and 10 GHz, respectively.