Directivity and Diversity Dual-Mode Stacked Antenna Array Using Directors of Yagi–Uda Antenna as Monopole Antennas

A dual-mode stacked antenna array is presented for 2.4-GHz applications. It provides two modes, a directivity mode and a diversity mode. The stacked Yagi-Uda antenna supports a directivity mode. In addition, three directors of the Yagi-Uda antenna are working as monopole antennas that provide a pattern diversity mode. Dimensions for circular patches and their distances are chosen to have the highest gain in the directivity mode. In order to achieve good isolation between each directional antenna and diversity antennas, bent feeding lines were designed. A novel hybrid microstrip-line/coplanar-waveguide (MSL/CPW) feeding line technique is used to achieve good performances in both directivity and diversity modes. The performance of the proposed dual-mode stacked antenna array is demonstrated from simulation and measurement results.