Wideband Horizontally Omnidirectional, Polarization-Reconfigurable, Cylindrical Antenna Based on Combined Common and Differential Modes

A novel design for achieving wideband horizontally omnidirectional, polarization-reconfigurable antenna based on the combination of common mode and differential mode is presented by utilizing a custom switching circuit system. Initially, a four-dipole antenna is designed to achieve horizontally omnidirectional horizontally-polarized radiation with differential-mode operation. Subsequently, another monopole antenna is designed to achieve horizontally omnidirectional vertically-polarized radiation with common-mode operation. Furthermore, owing to the inherent orthogonality and 90° phase difference between the common mode and differential mode, circularly-polarized radiation is obtained by combining two antennas to form a cylindrical antenna. A switching circuit system is developed to control the combined polarization-reconfigurable cylindrical antenna. Finally, a prototype is fabricated and measured. The polarization-reconfigurable cylindrical antenna prototype has an overlapping operating bandwidth of 34.5%, a gain variation with frequency of < 2.5 dB, and an out-of-roundness of < 1.9 dB, which shows excellent horizontally omnidirectional radiation performance across three polarization states.