Analysis of the spherical-circular microstrip antenna with an annular-ring parasitic patch

Various characteristics of a single spherical microstrip antenna have been rigorously analyzed using a full-wave approach. The coupling problem between two spherical microstrip antennas, however, is not addressed. A novel geometry of a spherical-circular microstrip antenna gap-coupled with an annular-ring parasitic patch is studied. By choosing a gap spacing between the circular disk and the annular-ring patch to be about one substrate thickness or less, it is expected that the antenna bandwidth of the spherical-circular microstrip antenna can be increased. To study this problem, a rigorous Green´s function formulation in the spectral domain and a Galerkin´s moment method calculation are applied. The input impedance at the driven circular disk is formulated and calculated, and the results for the voltage standing wave ratio (VSWR) are presented. The antenna bandwidth determined by a VSWR /spl les/2.0, is then discussed.