A four beam-switched planar array antenna for mobile terminals

Low-profile beam-switched antennas are effective for mobile terminals to reduce the interference such as multipath fading, co-channel interference or near-far problem. A four beam-switched antenna consisting of four monopoles and corner reflectors was proposed for antenna pattern diversity by Ikegami et al. (1986); however, it was not suitable for practical usage. For the flat four-beam switched antenna, we require a cardioid pattern in the vertical plane with 90/spl deg/ of the half power beam width in the horizontal plane. A flat array antenna concept using four magnetic line currents and hybrid couplers proposed by Arai et al. (1990) was realized by a low profile trapezoidal cavity antenna element. However, this element had narrow band width due to the element configuration, and was not suitable for practical use. Therefore we need to develop a wide band beam-switched flat antenna. In this paper, we propose a modified flat array concept and a low profile element for wide band four-beam switched array antenna. The characteristics of the antenna element are evaluated by a cavity resonator model and finite element method (FEM), which are verified by experiments.