Full-wave analysis of the annular-ring loaded spherical-circular microstrip antenna

In this paper, an annular-ring loaded (ARL) spherical-circular microstrip antenna is studied theoretically. The antenna is excited by a coaxial probe. The theoretical formulation is based on full-wave analysis in the spectral domain by using the vector Legendre transform and Galerkin's moment method is used for numerical calculation. Numerical results of the resonance frequencies, input impedance, voltage standing wave ratio (VSWR), and radiation characteristics are presented. It is shown that the impedance bandwidth of the spherical-circular microstrip antenna can be broadened by adding an annular-ring parasitic patch. By comparing to the single circular-patch case the spherical-circular microstrip antenna with an annular-ring parasitic patch has larger minor lobes and larger cross-polarization radiation.