LAUSR

A low-profile broadband quad-polarization reconfigurable omnidirectional antenna is presented. The quad-polarization antenna consists of a circular loop for horizontal polarization (HP) and a top-loaded monopole for vertical polarization (VP). The circular loop is composed of four arc dipoles excited by a broadband feeding network. The left-handed circular polarization (LHCP) is obtained by simultaneously feeding the circular loop and the top-loaded monopole with different phases. Two $\lambda $ g/2 phase shifters are introduced for the right-handed circular polarization (RHCP). The 12 p-i-n diodes are employed in the feeding network to realize the quad-polarization reconfiguration. It is shown that the bandwidth of the quad-polarization reconfigurable omnidirectional antenna overlapped for HP, VP, LHCP, and RHCP is about 28.6% (1.65–2.2 GHz) with good omnidirectional patterns. The total height of the antenna is about $0.09\lambda _{0}$ .