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

A novel design for achieving a 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 degrees 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 a 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.