Theory and Experiment of Spherical Aperture-Coupled Antennas

Rigorous mathematical method of moments (MoM) for analyzing spherical microstrip aperture-coupled antennas is presented in this paper by using dyadic Green´s functions (DGF) in conjunction with magnetic field integral equation (MFIE) and electric field integral equation (EFIE) formulations. With the aid of linear Rao-Wilton-Glisson (RWG) triangular basis functions, spherical three-layer aperture-coupled patch antennas are analyzed. The effect of mutual coupling between slot and patch antenna is developed and the input impedance and radiation patterns of such an antenna are presented. A prototype of a spherical aperture-coupled antenna is fabricated and tested. The measurement results are compared to the results of the proposed method and a good agreement between the results is achieved. The measured efficiency and gain of this antenna at 3.15 GHz are 85% and 5.23 dB, respectively.