An Omnidirectional and Directional Pattern Switchable Antenna Using Characteristic Mode Analysis

In this paper, an omnidirectional and directional pattern switchable antenna operating at 2.5GHz is proposed. Characteristic mode analysis (CMA) is utilized to design the proposed antenna. Based on the CMA, certain kinds of modes can be excited to generate an omnidirectional pattern or a directional beam. To verify this, a ring patch antenna with four slots and four feeding ports is analyzed by the CMA. By changing the phase difference among the four ports, different modes are excited, resulting in varying radiation pattern. Simulation results demonstrate that the omnidirectional and directional pattern switchable characteristic is obtained by the proposed ring patch antenna. With this feature, the proposed antenna can be used in a multi-functional system.