Dual frequency patch antenna using partially shorted annular ring patch antenna

In this paper, a dual frequency patch antenna using partially shorted annular ring patch antenna is proposed. The resonant frequency can be controlled by adjusting the number or the radii of the shorted pin, without changing the radiator size itself. Design and experimental results have good agreement, and the effectiveness is confirmed. The proposed dual-frequency antenna has minimum size, and the ratio of the two operating frequencies is small.