Performance of the microstrip disk antenna with a shorting post

This study investigates the resonant frequency of microstrip disk antennas affected by a shorting post. Initially an analytic solution for the resonant frequencies of a microstrip disk antenna with a shorting post is presented. The solution is then specialized to the special cases of even and odd excitation. These excitations further the understanding of the shorting-post size and location effects on the resonant modes. The results agree well with experimental results and indicate that the location of the shorting post may be used to control the resonant frequency and polarizations, or to cancel the unwanted modes of a microstrip disk antenna. These properties provide a means for the electronic control of microstrip disk antennas.