Emerging reconfigurable antenna elements for broadband wireless communication systems

This paper introduces several emerging reconfigurable antenna elements for modern broadband wireless communication systems. Firstly, we will present a broadband uni-directional circular polarization (CP) reconfigurable antenna consisting of four planar monopole radiators and an broadband output phase reconfigurable feeding network. Switchable left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP) are realized by controlling the rotating direction of the currents (J_m1, J_m2, J_m3 and J_m4) on the four monopoles. Secondly, beside of realizing the polarization switching of uni-directional radiation pattern, we designed a broadband omni-directional CP reconfigurable antenna with a conical-beam pattern. The idea is to combine a broadband center-fed monopolar patch working as an electric dipole (E-dipole) and eight reconfigurable coupling loop stub radiators as the magnetic dipoles (M-dipole) together to generate the reconfigurable CP conical-beam radiation. Above two designs have the polarization reconfigurable characteristics. In addition, we also realized a broadband pattern reconfigurable CP antenna by exciting a quadrifilar helical antenna (QHA) with the same reconfigurable feeding network as in the first design. Broadside and backfire CP radiation patterns are switchable by controlling the output phases of the four excitations. These proposed antennas are good candidate for many modern wireless communication systems as navigation and geostationary satellite systems, RFID, or other systems requiring CP radiations.