Polarization reconfigurable omni-directional antenna combining monopole and loop radiators

A novel polarization reconfigurable omni-directional antenna is proposed in this paper. By adopting a coaxial probe which acts as the monopole and printed spoke-like metal strips fabricated on two substrates which act as the loop, the omni-directional circularly polarized (CP) wave can be generated in the azimuthal plane. To make the antenna polarization reconfigurable, 48 PIN diodes are placed on the two substrates to alter the current direction of the loop. An additional DC bias network is used to bias the diodes. The polarization status can be switched between RHCP and LHCP. The measured -10 dB impedance bandwidth is 25% and 26% and the average axial ratio (AR) is 2.33 dB and 2.45 dB for RHCP and LHCP in the azimuthal plane.