Pattern reconfigurable compact antenna

This paper presents a design of an compact antenna providing two diverse radiation patterns, which results from the excitation of two different modes. The antenna consists of a capacitively fed annular ring microstrip antenna, which can be shorted via shorting pins on its edges using pin diodes. Therefore, depending on the state of the pin diodes, the antenna operates in normal patch mode (TM₁₁) or unipolar wire-patch mode. The resonance frequencies of both modes are nearly the same and they have overlapping 10 dB impedance bandwidths. In this design, only a single feed point is needed for both excitations. Detail design considerations are described. Simulated and experimental results are also presented and discussed.