Polarisation reconfigurable ultra wideband antenna for cognitive radio devices

A novel compact planar ultra wideband monopole antenna with reconfigurable polarisation capability is presented. By adding two rectangular slots near the edges of the patch, the antenna can be switched from linear polarisation (LP) to right hand circular polarisation (RHCP) or left hand circular polarisation (LHCP). The frequency band at which the antenna is radiating circular polarisation (CP) can also be controlled by carefully changing the lengths of the etched slots embedded in the patch using RF switches. The simulated and measured results of the reflection coefficient and axial ratio verified the effectiveness of the proposed antenna configuration. The proposed antenna demonstrates suitable candidate for cognitive radio (CR) systems by adding the benefits of polarisation diversity.