Development of polarisation reconfigurable omnidirectional antennas using crossed dipoles

A new method for the development of polarisation reconfigurable omnidirectional antennas is presented. Four crossed-dipole elements around a cylinder are used to construct an omnidirectional antenna. By switching on/off four PIN diodes for each crossed-dipole element, three types of polarisation reconfigurable omnidirectional antennas are realised, including vertical or horizontal polarisation (VP/HP), ±45° slant polarisation (SP), and left-handed circular polarisation or right-handed circular polarisation (LHCP/RHCP). The VP/HP, ±45° SP, and LHCP/RHCP reconfigurable omnidirectional antennas are simulated, fabricated, and measured, respectively. Simulated and measured results show that all the three reconfigurable omnidirectional antennas feature good omnidirectional patterns with gain variations of <;2 dB in the horizontal plane.