Performance of pin loaded microstrip patch antennas

There have been continuing attempts to reduce the size of patch antennas in applications such as mobile telephones and wireless communication. In this paper, we present both analytical and simulation studies of the main characteristics of a pin loaded microstrip patch antenna of a circular shape. On the analytical side, the cavity modal fields are derived and the modal equation is solved for the cavity resonant frequencies. It is shown that the dominant cavity mode of a pin-loaded patch achieves an area saving of 75 to 90% relative to the unloaded patch. However, the radiation efficiency of this mode is considerably reduced. Simulation results using Zealand´s IE3D software confirms such findings.