This paper proposes planar antennas with quadri-polarization diversity using a pair of orthogonal linear polarizations and a pair of orthogonal circular polarizations (CP). A novel feeding network with four input ports and four output ports is presented, allowing antenna polarization diversity by selecting different input ports, which can generate right-handed CP, left-handed CP, horizontal linear polarization, and vertical linear polarization. The first design uses two square patch resonators to synthesize the four polarizations; the second design comprises four circularly polarized patches to synthesize the four polarizations with an improved axial-ratio (the ratio of orthogonal components of an E-field) bandwidth. The proposed designs do not require for embedding PIN diodes and DC-biasing circuits, making them suitable for use in higher-frequency applications where using lump elements would be difficult. The novel antennas provide potential polarization diversity features which can be used for many applications. Details of the antenna design are shown, and the measurement and simulation results are also provided to validate the proposed concept.
International Journal of Microwave and Wireless Technologies 8(2), p.385-394